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CHAPTER 1

1.1 INTRODUCTION

Today the civil engineering industries grows very rapidly the use of new material on

construction is a very important need because it saves our environment and natural resources.

Most of the construction in now days are done with cement sand aggregate and water mix

commonly called concrete. Concrete is a very versatile material it has very important

properties which makes it the best constructional material used for making any structure

which posses enough strength. The main properties of concrete are its compressive strength it

is the property of material which makes it strong to resist adequate load under certain

conditions. In now a days most of the structures are made with concrete due to its

engineering properties. In most of the world high rise structures are made with concrete,

because it gives them enough strength and age to resist the different loads. Today big and tall

structures like dams bridges towers nuclear power plant etc is made with concrete just

because of its strength to resist load, but every structure has a life after which it is not enough

capable to resist load it is because in its useful life it resist various natural/artificial loads

which reduces its strength then the time come to destroy the structure and make the new one

in place of it. When the structure is destroyed a huge amount of waste is produced which

include waste from bricks masonry iron bars etc and a huge amount of concrete this concrete

can be termed as demolisioned waste obtained demolishing the structure. We know that

while making the fresh concrete a huge amount of natural resources are used which we

cannot we get back once we use them so there was a problem faced by the engineer to first to

dispose the demolished material because it require a huge amount of land which we cannot

used again after dumping the waste and second to full fill the demand of raw material like

sand aggregate etc, which are used to make concrete. In both the conditions such that to full

fill the requirement of material for new construction and also the disposal of waste material

makes a huge amount of burden on our environment so as to reduce the amount of burden

from our environment there is a new concept is utilised which provides us a solution to this

problem and the solution is that to use the material obtained from waste. This is not a new

idea our ancestor’s knows that all the material available in the earth has a limit after that it

gets ends. So they develop the idea of utilisaing the material reusing is a process in which the

raw material which is used is obtained from the parent material. After proper studying the

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properties of material it can be used again because all the material posses adequate amount of

strength to make it workable. Concrete is the premier construction material across the world

and the most widely used in all types of civil engineering works, including infrastructure, low

and high-rise buildings, defence installations, environment protection and local/domestic

developments. Concrete is a manufactured product, essentially consisting of cement,

aggregates, water and admixture(s). Among these, aggregates, i.e. inert granular materials

such as sand, crushed stone or gravel form the major part. Traditionally aggregates have been

readily available at economic price. However, in recent years the wisdom of our continued

wholesale extraction and use of aggregates from natural resources has been questioned at an

international level. This is mainly because of the depletion of quality primary aggregates and

greater awareness of environmental protection. In light of this, the availability of natural

resources to future generations has also been realized. Given this background, the concept of

sustainable development put forward almost a decade ago, at the 1992 Earth Summit in Rio

de Janeiro, and it has now become a guiding principle for the construction industry

worldwide. In fact many governments throughout the world have now introduced various

measures aimed at reducing the use of primary aggregates and increasing reuse and

recycling, where it is technically, economically, or environmentally acceptable. For example,

the UK government has introduced a number of policies to encourage wider use of secondary

and as an alternative to naturally occurring primary aggregates. These include landfill and

future extraction taxes to improve economic viability, support to relevant research and

development work. In now a days recycling of concrete is done on a large scale because

natural resources are reduces day by day and we have to conserve them. Recycling of

concrete is not a new idea it is first it is used after the second world war. Material obtained

from Construction and Demolishing waste commonly called as (C&D) waste it is normally

constitute rubble masonry iron bars, masonry bricks and tiles sand and dust and a large

portion of concrete. This demolished concrete can be used again after proper treatments in

making different structures it can be shows that crushed rubble concrete when carefully

sieved and separated from parent demolished structure can be used as natural course

aggregate in making concrete or as a sub base and base layer in making pavements this type

of material obtained from waste is called recycle material or Granite concrete there

utilisation of waste material is the only way to reduce it after second world war there are

many countries shows interest in recycling of material because it gives them enough material

for new construction and enough space of land for use them.

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Many countries like Japan, China Russia, London, Europe, Nietherlands Hongkong

Spain, Belgium etc were shoes interest in Recycling of Concrete due to increasing the land

prices in the recent years the cost of dumping is also increased in recent years so the persons

found that is more useful to recycled material as compared to dumping it. Various standards

are established to make good quality material from the demolished material to promote the

recycling of material proper guidelines are given to contractors to installing recycling plants

in urban places and permitted them to use recycled material in place of natural aggregate.

Recycling of material provide us higher efficiency in its useful lifecycle and its consistency

with the natural environment. When the useful life of material is completed it becomes waste

and can be transformed in to new material to make new structures which have new life and

also new strength as well. Due to large scale decrease of natural aggregates and significant

increase in demolisioned aggregate going to land fill sites.

The use of Granite Course Aggregates trend growing globally and use of granite

aggregate. These aggregates shows similar strength to concrete with similar performance to

characteristics to natural aggregate. The research project is completed with the study of

equipments which are used for making Granite Course Aggregate from granite waste in this

context it is well known how they are made. There is a significant processes followed by

different countries for making concrete. Aggregate particularly in Netherlands waste

products are used as aggregate for unbound layers in road construction because natural

aggregate in Netherlands is very scare. Similarly Dutch followed a well defined process to

produce good quality of Granite Course Aggregate s. While the recycling plants of Europe

and Britain are less well equipped when compared to Netherlands with cleaning and

shortening devices which make good quality of Granite Course Aggregates the recycled

products obtained from recycling plants are carefully examined and their physical properties

are carefully compared with natural aggregates. with the end of this century environmental

protection and sustainable development is the key role of society and we have to work hard

for this. It is very important for our environment to make it clean by different methods like

by reduction pollution emission conservation of natural resources especially for the civil

industry. In this context main problems faced by the industry are:

Natural aggregate depletion. High production and consumption of Portland cement due

to this there is a high emission of carbon dioxide Large amount of production of construction

and demolition waste and fill land space depletion. It is very big problem in European

countries. It is known that 1m3

of concrete contains about 1m3

of aggregates. here the

properties of concrete made from Granite concrete using granite waste aggregate as course

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aggregate is replaced by natural aggregate. Some proposals are made for the construction

industries to use recycles aggregate in making different structures particularly in road sub

base layer and production from masonry units. But in practice Granite Course Aggregate is

not commonly used in production of fresh concrete. The main reason is that Portland cement

is made to produce structure which meet high strength and durability requirement. Extensive

research is required to use know the properties of waste material before it can be adopted in

industry. The main aim of this research is to find the adequate strength parameters for making

high performance concrete made with granite course aggregate. By studying the various

strength properties it can be suitably used in industry.

1.2 MOTIVATION AND PURPOSE OF STUDY

Use of Granite Course Aggregate in making Concrete is the recent development in Concrete. It

has been more popular these days and is being used in many prestigious projects. There are

different mineral admixtures such as fly ash, silica fume, etc are more commonly used in

development of high performance concrete. Course aggregate and fine aggregate are the main

constituent in making concrete. The most commonly used fine aggregate is river sand is obtained

from the river bed, and course aggregate is obtained from the natural stones. With the growth of

the construction industry the consumption of the natural aggregate increased due to extensive use

of concrete the demand of the natural aggregate is increased continuously, in particular the

demand of the natural aggregate is quite high in developed countries owing to the infrastructural

growth.

The non availability of the sufficient quantity of ordinary natural aggregate for making

concrete is affecting the growth of the construction industry in many parts of the country.

Recently in Madhya Pradesh government has imposed the restrictions on aggregate stone

quarrying due to unsafe impact threatening on many parts of the state. On the other hand Granite

Course Aggregate generated by the industry has accumulated over the years. The main aim of

this research is to fine adequate strength parameters and the optimum percentages of the Granite

Course Aggregate used in making concrete. So by using this granite waste we can reduce the

consumption of the natural aggregate in making concrete thus for saving the environment.

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1.3 AIM & OBJECTIVE OF STUDY

My research has following eight main aims:

(a) To determine the changes in compressive strength of cement concrete.

(b) To determine the changes in compressive strength of cement concrete at various

percentages of Granite Course Aggregate (GCA are to total the volume of course

aggregate ) into cement concrete at 7 & 28 days compressive strength test.

(c) To determine the increasing the dead weight of cement concrete samples at various

percentages of Granite Course Aggregate GCA.

(d) To determine the bulk & dry density of cement concrete at various percent of Granite

Course Aggregate in cement concrete.

(e) To determine the maximum safe percentage of Granite Course Aggregate into cement

concrete to get maximum compressive strength.

(f) To find out suitable aspect ratio of Granite Course Aggregate in cement concrete.

(g) To design high strength cement concrete (M-25 Grade of cement concrete) with Granite

Course Aggregate .

(h) Corrections & changes in the Mix design of M-25 Grade of concrete due to use of

Granite Course Aggregate in cement concrete as course aggregate.

1.4 THE STRUCTURE OF THE DISSERTATION

The outline structure of dissertation is as follows:

CHAPTER 1: INTRODUCTION

This chapter described the background and motivation for the study. The approach to use of

Granite Course Aggregate (GCA) into cement concrete is briefly outlined and concerns are

highlighted. The objective, aim, purpose of the dissertation is also outlined in this chapter.

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CHAPTER 2: LITERATURE REVIEW

This chapter described the research works in the field of Granite Course Aggregate concrete

which had already done & discussed what we wanted to do new, innovative with Granite

Course Aggregate and importance of Granite Course Aggregate in cement concrete.

CHAPTER 3: CEMENT CONCRETE

This chapter detailed the all about cement concrete such as history of concrete, its historical

uses, its importance in world, microstructure of concrete, its ingredients microstructure,

physical properties of concrete and many more important points related to concrete all are

cover in detail under this chapter.

CHAPTER 4: RESEARCH PROCEDURE

In this chapter, general procedures used to collect, process and present the different types of

data are described and explain how testing of various material can done and what result can

obtain by these tests of concrete. Along with this the mix design of M- 25 grade of concrete.

It explains whole design step by step and explains how corrections and adjustments are made

in various proportions of ingredient materials of cement concrete as per design change due to

lab tests of ingredient materials of concrete.

CHAPTER 5: RESULTS & DISCUSSIONS

Results obtained from the processing of the various testing data are presented. The way the

data was analyzed to get the information is described in detail. The information obtain from

the result is discussed in terms of the set objectives, findings from the literature.

5.1 INTRODUCTION

In this chapter results obtained by Mix design of M-25 Grade of concrete from chapter

4.Cement concrete cubes prepared and casted as per chapter 4.

5.2 CONCLUSION

Remarks are made based on the results and discussion.

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CHAPTER 2

LITERATURE REVIEW

2.1 GRANITE CONCRETE AGGREGATE

2.1.1 General

In recent years certain countries have considered the reutilization of construction and

demolition waste as a new construction material as being one of the main objectives

with respect to sustainable construction activities.

The literature review presents the current state of knowledge and examples of successful uses

of alternative materials in concrete technology, and in particular the use of Granite concrete

(GCA) aggregate as a coarse aggregate fraction in non- structural and structural concrete.

Many researchers have dedicated their work to describe the properties of these kinds of

aggregate, the minimum requirements for their utilization in concrete and the properties

of concretes made with waste aggregates. It also presents a review of available literature

on physical, mechanical and durability properties of GCA aggregates, and mechanical,

durability and structural properties of GCA concrete. However, minor attention has been paid

to the structural behavior granite aggregate concrete slabs. This thesis focuses on utilization

of granite waste as an aggregate in structural concrete in flexure and punching shear.

2.1.2 Constituent Materials in Concrete

Modern concrete is a sophisticated composited material which is constantly undergoing

improvements and modifications. However, the basic constituents of conventional Ordinary

Portland Cement (OPC) concrete such as fine and coarse aggregate, cement and water

remain same. There are other materials such as chemical admixtures including

superplasticisers, water reducers and air-entertainers’ that can be used to modify the

characteristics of OPC concrete. There is also an increase in the use of pozzolanic materials

like fly ash, metakoline, granulated blast-furnace slag and silica fume. Over the last few

decades, the uses of various alternative fine and coarse aggregates in the production of

concrete have been investigated, including the use of GCA aggregates.

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Properties of Granite Course Aggregate

Raw materials for production of the natural aggregates and GCA aggregate contribute to

some differences and variations of aggregate properties. Granite concrete aggregates have

approximately same physical properties as the natural aggregates. Relative amounts of these

components, as well as grading, affect aggregate properties and classify the aggregate as suitable

for production of concrete. There is a general consensus that the amount of cement paste has a

significant influence on the quality, and the physical, mechanical and chemical properties of the

aggregates and as such has potential influence on the properties of GCA concrete.

Physical

The various physical properties of Granite Course Aggregate are presented below.

.

Aggregate Fineness Modulus Density kg/m3 Specific Gravity

Fine aggregate 2.77 1752 2.60

Course aggregate 4.086 1805.62 2.65

Granite Course

Aggregate

4.476 1660.44 2.68

Table 1(a): Various properties of Natural & Granite Course Aggregate .

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Bulk density

The bulk density or unit weight of an aggregate gives valuable information

regarding the shape and grading of the aggregates. For a given specific gravity the

angular aggregates shows a lower bulk density. Bulk density of aggregates is of interest

when deal with light weight aggregates and heavy weight aggregates. It depends on

the strength of original concrete and size of original aggregates.

It is concluded that the Granite Course Aggregate which obtained from granite waste

is of higher strength had higher density and also the saturated surface density depends

on the kind of crushing machine employed and the energy used. The density changes

with the size of the aggregate The density of Granite Course Aggregate concrete

reduces with smaller size of aggregates. Granite Course Aggregate concrete shows

high dense than conventional concrete. Further more it is concluded that by addition of

silica fume to the Granite Course Aggregate concrete and conventional concrete,

reduces the density.

Specific gravity

It is investigated that the specific gravity decreases from 4.5 to 7.6% when

compared with specific gravity of natural aggregate. The specific gravity of

Waste Concrete Aggregates (WCA) was lower than normal crushed aggregates.

The reason for this was thought to be the fact that there was a certain proportion of

mortar over these aggregates. It is noted that the specific gravity of demolished

concrete aggregates is lower than that of natural aggregate. The average specific

gravity of aggregate usually varies from 2.6 to 2.8

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When I studied the following research papers I found that no work has been done in

the replacement of waste granite aggregate, only granite fines has been replaced and

then the various studied are done.

1. Journal of Civil Engineering Research 2014, 4(2A): 1-6 DOI:

10.5923/c.jce.201401.01 Strength and Durability Properties of Granite Powder

Concrete, A. Arivumangai1,T. Felixkala2, The main parameter investigated in

this study is M30 grade concrete with replacement of sand by granite powder by 0,

25 and 50% and cement was partial replacement with silica fume, fly ash, slag and

super plasticizer. This paper presents a detailed experimental study on compressive

strength, split tensile strength 28, 56 and 90 days. Durability study on chloride

attack was also studied and percentage of weight loss is compared with normal

concrete. Test results indicate that use of granite powder and admixtures in concrete

has improved the performance of concrete in strength as well as in durability aspect.

2. IRACST – Engineering Science and Technology: An International Journal

(ESTIJ), ISSN: 2250-3498,Vol.3, No.1, February 2013,Dr.G.Prince Arulraj,

Mr.A.Adin and Mr.T.Suresh Kannan, This granite powder waste can be utilized

for the preparation of concrete as partial replacement of sand. In order to explore the

possibility of utilizing the granite powder as partial replacement to sand, an

experimental investigation has-been carried out. The percentages of granite powder

added by weight to replace sand by weight were 0, 5, 10, 15, 20 and 25. To improve

the workability of concrete 0.5% Super plasticiser was added. This attempt has been

done due to the exorbitant hike in the price of fine aggregate and its limited

availability due to the restriction imposed by the government of Tamil Nadu. Fifty

four cubes and 36 cylinders were cast. Compressive strength and split tensile

strength were found. The test results indicate that granites replacement sand with

granite powder has beneficial effect on the mechanical properties such as

compressive strength and split tensile strength of concrete.

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3. International Journal of Advanced Engineering Research and Studies E-

ISSN2249–8974, Experimental Investigation On Behaviour Of Concrete With

The Use Of Granite Fines, Divakar.Y, Manjunath.S and Dr. M.U. Aswath, In this

paper an attempt is made experimentally to investigate the Strength Behaviour of

Concrete with the use of Granite Fines as an additive. Concrete is prepared with

granite fines as a replacement of fine aggregate in 5 different proportions namely 5%,

15%, 25%,35% and 50% and various tests such as compressive strength, Split tensile

strength and Flexural strength are investigated and these values are compared with the

conventional concrete without granite fines.

4. Indian Journal of Science and Technology Vol. 3 No. 3 (Mar 2010) ISSN: 0974-

6846, Granite powder concrete T. Felixkala and P. Partheeban, This paper

examines the possibility of using granite powder as replacement of sand and partial

replacement of cement with fly ash, silica fume, slag and super plasticiser in concrete.

The percentage of granite powder added by weight was 0, 25, 50, 75 and 100 as a

replacement of sand used in concrete and cement was replaced with 7.5% silica fume,

10% fly ash, 10% slag and 1% super plasticiser. The effects of water pounding

temperatures at 26oC and 38

oC with 0.4 water-to-binder (w/b) ratios on mechanical

properties, plastic and drying shrinkage strain of the concrete were studied and

compared with natural fine aggregate concrete. The test results obtained indicate that

granite powder of marginal quantity as partial sand replacement has beneficial effect

on the mechanical properties such as compressive strength, split tensile strength,

modulus of elasticity. Furthermore, the test results indicated that the values of both

plastic and drying shrinkage of concrete in the granite powder concrete specimens

were nominal than those of ordinary concrete specimens.

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5. Research Inventy: International Journal Of Engineering And Science Vol.2,

Issue 12 (May 2013), Pp 36-50 Issn(e): 2278-4721, Issn(p):2319-6483, Effect of

Granite Powder on Strength Properties of Concrete , Dr.T. Felix Kala, This paper

focuses on the experimental study of using locally available granite powder as fine

aggregate and partial replacement of cement with admixtures in the production of

HPC with 28 days strength to the maximum of 60 MPa. The influence of water

cement ratio and curing days on mechanical properties for the new concrete mixes

were premeditated. The percentage of granite powder added by weight was 0, 25, 50,

75 and 100% as a replacement of sand used in concrete and cement was replaced with

7.5 % silica fume, 10% fly ash, 10% slag and the dosage of superplasticiser added 1%

by weight of cement. The test results show clearly that granite powder of marginal

quantity, as partial sand replacement has beneficial effect on the above properties.

The highest strength has been achieved in samples containing 25% granite powder

together with admixtures. Based on the results presented in this paper, it can be

concluded that concrete mixture can be prepared with granite powder as an additive

together with admixtures to improve the strength of concrete structure.

As per I concern more researches are required to find the better workability and the

mixing methods are developed to gain maximum benefit. Due to higher construction

cost of the new material I was motivated to find the material which can be use d

again and which has good engineering properties. These research papers were

motivated me to find out compressive strength of cement concrete cubes at various

percentage of Granite Course Aggregate . In this dissertation work I find out 7 days

& 28 days compressive strength of M-25(High strength concrete) grade of concrete

& also find out optimum percentage of Granite Course Aggregate into cement

concrete for getting maximum compressive strength of cement concrete. In this

dissertation, I worked on the changes of Bulk Density & Dry Density of cement

concrete (M-25 Grade) at various percentage of Granite Course Aggregate which

may lead to reduction of dead weight of structure which is directly related to saving

of funds or economy.

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No paper was focus on waste granite aggregate strength parameter which is new and

innovative in this dissertation work.

The aim of my research is to find the possibility of using low cost Granite Course

Aggregate as an alternative material to course aggregate in structural concrete and

also the optimum percentage of Granite Course Aggregate as a partial replacing of

natural aggregate in concrete, for saving the cost of construction and the natural

aggregates.

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CHAPTER 3

CEMENT CONCRETE

3.1 INTRODUCTION

Concrete is a composite material composed mainly of water, aggregate, and

cement. Often, additives and reinforcements (such as rebar) are included in the

mixture to achieve the desired physical properties of the finished material. When

these ingredients are mixed together, they form a fluid mass that is easily moulded

into shape. Over time, the cement forms a hard matrix which binds the rest of the

ingredients together into a durable stone-like material with many uses.

It is believed that in the ancient time a Romanian scientist to be the first who

know about the chemistry of the cementations material mainly the lime. The most

notable example of the Romanian work is the work in Pantheon. It is a very big

dome which have 43.43m span. The calcareous material used in its construction is

made by either composed of suitable lime stones which are burned in kilns or with

a mixture of lime stone or volcanic dust combining it in to a hardened material or in

to a hard concrete

Famous concrete structures include the Hoover Dam, the Panama Canal and

the Roman Pantheon. The earliest large-scale users of concrete technology were the

ancient Romans, and concrete was widely used in the Roman Empire. The Coliseum

in Rome was built largely of concrete, and the concrete dome of the Pantheon is the

world’s largest unreinforced concrete dome.

After the Roman Empire collapsed, use of concrete became rare until the

technology was re pioneered in the mid-18th century. Today, concrete is the most

widely used man-made material (measured by tonnage).

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3.2 HISTORY

The word concrete comes from the Latin word "concretes" (meaning

compact or condensed), the perfect passive participle of "concrescere", from "con"

(together) and "crescere" (to grow).

Perhaps the earliest known occurrence of cement was twelve million years

ago. A deposit of cement was formed after an occurrence of oil shale located

adjacent to a bed of limestone burned due to natural causes. These ancient deposits

were investigated in the 1960s and 1970s.

On a human time-scale, small usages of concrete go back for thousands of

years. The ancient Nabataea culture was using materials roughly analogous to

concrete at least eight thousand years ago, some structures of which survive to this

day.

German archaeologists Heinrich Schliemann found concrete floors, which

were made of lime and pebbles, in the royal palace of Tiryns, Greece, which dates

roughly to 1400-1200 BC. Lime mortars were used in Greece, Crete, and Cyprus in

800 BC.

The Assyrian Jerwan Aqueduct (688 BC) made use of fully waterproof

concrete. Concrete was used for construction in many ancient structures.

The Romans used concrete extensively from 300 BC to 476 AD, a span of

more than seven hundred years. During the Roman Empire, Roman concrete (or opus

caementicium) was made from quicklime, pozzolana and an aggregate of pumice. Its

widespread use in many Roman structures, a key event in the history of architecture

termed the Roman Architectural Revolution, freed Roman construction from the

restrictions of stone and brick material and allowed for revolutionary new designs in

terms of both structural complexity and dimension.

Concrete, as the Romans knew it, was a new and revolutionary material. Laid

in the shape of arches, vaults and domes, it quickly hardened into a rigid mass, free

from many of the internal thrusts and strains that troubled the builders of similar

structures in stone or brick.

Modern tests show that opus caementicium had as much compressive

strength as modern Portland-cement concrete (ca. 200 kg/cm2). However, due to the

absence of reinforcement, its tensile strength was far lower than modern reinforced

concrete, and its mode of application was also different.

Modern structural concrete differs from Roman concrete in two important

details. First, its mix consistency is fluid and homogeneous, allowing it to be poured

into forms rather than requiring hand-layering together with the placement of

aggregate, which, in Roman practice, often consisted of rubble. Second, integral

reinforcing steel gives modern concrete assemblies great strength in tension, whereas

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Roman concrete could depend only upon the strength of the concrete bonding to

resist tension.

The widespread use of concrete in many Roman structures ensured that many

survive to the present day. The Baths of Caracalla in Rome are just one example.

Many Roman aqueducts and bridges such as the magnificent Pont du Grad have

masonry cladding on a concrete core, as does the dome of the Pantheon.

After the Roman Empire, the use of burned lime and pozzolana was greatly

reduced until the technique was all but forgotten between 500 AD and the 1300s.

Between the 1300s until the mid-1700s, the use of cement gradually returned. The

Canal du Midi was built using concrete in 1670, and there are concrete structures in

Finland that date from the 16th century.

Perhaps the greatest driver behind the modern usage of concrete was the third

Eddystone Lighthouse in Devon, England shown in figure 1. To create this

structure, between 1756 and 1793, British engineer John Smeaton pioneered the use

of hydraulic lime in concrete, using pebbles and powdered brick as aggregate.

Fig. 1 : EddystoneLighthouse inDevon,England

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The most Vitruvius work was conducted by M. Vicat of France. The first

person who introduce cement was Joseph Aspedin or Yorkshire of united kingdom

he was the first who introduce Portland cement in 1824 formed by heating a mixture

of lime stone and finely divided clay in to a high temperature furnace up to a

temperature high enough to drive of the carbonic acid gas . in the year 1845, Sir

Isaac . Johnson invented the cement by increasing the temperature at which the ixture

of lime stone and clay were sufficiently burned to form clinker. This cement was the

basic model for the prototype of the modern Portland cement.

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Fig. 2 : The Colosseum of Rome

Top View Front View

Fig. 3 : Pantheon of Rome

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3.2.1 ANCIENT ADDITIVE

Concrete like materials were used since 6500BC by the Nabataea

traders or Bedouins who occupied and controlled a series of oases and

developed a small empire in the regions of southern Syria and northern

Jordan. They discovered the advantages of hydraulic lime, with some self-

cementing properties by 700 BC. They built kilns to supply mortar for the

construction of rubble-wall houses, concrete floors, and underground

waterproof cisterns. The cisterns were kept secret and were one of the

reasons the Nabataea were able to thrive in the desert. In both Roman and

Egyptian times it was rediscovered that adding volcanic ash to the mix

allowed it to set underwater. Similarly, the Romans knew that adding horse

hair made concrete less liable to crack while it hardened, and adding blood

made it more frost-resistant.

3.2.2 MODERN ADDITIVE

In modern times, researchers have experimented with the addition of

other materials to create concrete with improved properties, such as higher

strength, electrical conductivity, or resistance to damages through spillage.

3.3 TYPES OF CONCRETE

Based on unit weight, concrete can be classified into three broad categories.

Concrete containing natural sand and gravel or crushed-rock aggregates,

generally weighing about 2400 kg/m3 (4000 lb/yd

3), is called normal weight

concrete, and it is the most commonly used concrete for structural purposes. For

application where a higher strength-to-weight ratio is desired, it is possible to

reduce the unit weight of concrete by using natural or pyro-processed aggregate

with lower bulk density. The term lightweight concrete is used for concrete that

weighs less than about 1800 kg/m3 (3000 lb/yd

3). Heavy weight concrete, used

for radiation shielding, is a concrete produced from high-density aggregate and

generally weighs more than 3200 kg/m3 (5300 lb/yd

3).

Strength grading of cements and concrete is prevalent in Europe and many

other countries but is not practiced in the United States. However, from

standpoint of distinct differences in the microstructure-property relationship is

useful to divide concrete into three general categories based on compressive

strength:

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Low-strength concrete: less than 20 MPa (3000 psi)

Moderate-strength concrete: 20 to 40 MPa (3000 to 6000 psi)

High-strength concrete: more than 40 MPa (6000 psi).

Moderate-strength concrete, also referred as ordinary or normal

concrete, is used for most structural work. High-strength concrete is used for special

application. There are numerous modified concretes which are appropriately named:

for example, fibber-reinforced concrete, expansive-cement concrete, latex-modified

concrete, etc.

3.4 MICROSTRUCTURE OF CONCRETE

3.4.1 PREVIEW

Microstructure-property relationships are at the heart of modern

material science. Concrete has a highly heterogeneous and complex microstructure.

Therefore, it is very difficult to constitute realistic models of its microstructure from

which the behaviour of the material can be reliably predicted. However, knowledge

of the microstructure and properties of the individual components of concrete and

their relationship to each other is useful for exercising control on the properties.

3.4.2 DEFINITION

The type, amount, size, shape, and distribution of phase present in a

solid constituent its microstructure. The gross elements of the microstructure of a

material can readily be seen from a cross section of the material, whereas the finer

elements are usually resolved with the help of a microscope. The term

macrostructure is generally used for the gross microstructure visible to the human

eye; the limit of resolution of the unaided human eye is approximately one-fifth of a

millimetre (200 µm). The term microstructure is used for the microscopically

magnified portion of a macrostructure. The magnification capability of modern

electron microscope is of the order of 105

times. Therefore, application of

transmission and scanning electron microscopy techniques has made it possible to

resolve the microstructure of materials to a fraction of one micrometer.

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3.4.3 SIGNIFICANCE

Progress in the field of materials has resulted primarily from recognition of the

principle that the properties originate from the internal microstructure, in other

words, properties can be modified by making suitable changes in the microstructure

of a material. Although concrete is the most widely used structural material, its

microstructure is heterogeneous and highly complex. The microstructure-property

relationships in concrete are not yet fully developed; however, some understanding

of the essential elements of the microstructure would be helpful before discussing the

factors influencing the important engineering properties of concrete, such as

strength, elasticity, shrinkage, creep, cracking, and durability.

3.4.4 COMPLEXITIES

Form examination of a cross section of concrete (Fig.: 4), the two phases that

can easily be distinguished are aggregate particles of varying size and shape, and the

binding medium composed of an incoherent mass of the hydrated cement paste.

Fig. 4 : Polished section from a concrete specimen

{Macrostructure is the gross structure of a material that is visible to the unaided human eye. In the

macrostructure of concrete two phases are readily distinguished: aggregate of varying shapes and size, and the

binding medium, which consists of an incoherent mass of the hydrated cement paste. }

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At the macroscopic level, therefore, concrete may be considered as a two-phase

material, consisting of aggregate particles dispersed in a matrix of cement concrete

paste.

At the microscopic level, the complexities of the concrete microstructure are

evident. It becomes obvious that the two phases of the microstructure are neither

homogeneously distributed with respect to each other, nor are they themselves

homogeneous. For instance, in some area the hydrated cement paste mass appears to

be as dense as the aggregate, while in others it is highly porous (Fig. : 5). Also if

several specimens of concrete containing the same amount of cement but different

amounts of water are examined at various time intervals, it will be seen that, in

general, the volume of capillary voids in the Hydrated cement paste decreases with

decreasing water-cement ratio or with increasing age of hydration. For a well-

hydrated cement paste, the inhomogeneous distribution of solids and voids alone can

perhaps be ignored when modelling the behaviour of the material. However,

microstructure studies have shown that this cannot be done for the hydrated cement

paste present in concrete. In the presence of aggregate, the microstructure of

hydrated cement paste in the vicinity of large aggregate particles is usually very

different from the microstructure of bulk paste of mortar in the system. In fact many

aspects of concrete behaviour under stress can be explained only when the cement

paste-aggregate interface is treated as a third phase of the concrete microstructure.

Thus the unique feature of the concrete microstructure can be summarized as

follows: First there is the interfacial transition zone, which represents a small region

next to the particles of coarse aggregate. Existing as a thin shell, typically 10 to 50

µm thick around large aggregate, the interfacial transition zone is generally weaker

than either of the two main components of concrete, namely the aggregate and the

bulk hydrated cement paste; therefore, it exercises a far greater influence on the

mechanical behaviour of concrete than is reflected by its size. Second, each

aggregate particle may contain several minerals in addition to micro cracks and

voids. Similarly, both the bulk hydrated cement paste and the interfacial transition

zone generally contain a heterogeneous distribution of different types and amount of

solid phases, pores and micro cracks, as will be described. Third, unlike other

engineering materials, the microstructure of concrete is not an intrinsic characteristic

of the material because the two components of the microstructure, namely the

hydrated cement paste and the interfacial transition zone, are subjected to change

with time, environmental humidity, and temperature.

The highly heterogeneous and dynamic nature of the microstructure of

concrete are the primary reason why the theoretical microstructure-properties

relationship models, that are generally so helpful for predicting the behaviour of

engineering material, are not of much practice use in the case of concrete. A broad

knowledge of the important feature of the microstructure of each of the three phases

of concrete, as provided below, is nevertheless essential for understanding and

control of properties of the composite material.

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Fig. 5 : Microstructure of a hydrated cement paste

{ Microstructure is the subtle structure of a material that is resolved with the help of microscope. A low-

magnification (200×) electron micrograph of a hydrated cement paste show the structure is not homogeneous;

while some areas are dense, the individual hydrated phases by using higher magnifications. For example, massive

crystals of calcium hydroxide, long and slender needles of ettringite, and aggregate of small fibrous crystals of

calcium silicate hydrate can be seen at 2000 × and 5000 × magnifications.}

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3.4.5 MICROSTRUCTURE OF THE AGGREGATE PHASE

The aggregate phase is predominantly responsible for the unit weight, elastic

modulus, and dimensional stability of concrete. These properties of concrete depend

to a large extend on the bulk density and strength of the aggregate, which in turn are

determine by physical rather than chemical characteristics of the aggregate. In other

works, the chemical or the mineralogical composition of the solid phases in

aggregate is usually less important than the physical characteristics, such as volume,

size, and distribution of pores.

Fig. 6 : (a) Diagrammatic representation of bleeding in freshly

deposited concrete; (b) Shear-bond failure in a concrete

specimen tested in uniaxial compression.

{ Internal bleed water tends to accumulate in the vicinity of elongated, flat, and large pieces of aggregate. In

these locations, the aggregate-cement paste interfacial transition zone tends to be weak and easily prone to

microcracking. This phenomenon is responsible for the shear-bond failure at the surface of the aggregate particle

marked in the photograph.}

In addition to porosity, the shape and texture of the coarse aggregate also

affect the properties of concrete. Natural gravel has a rounded shape and a smooth

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surface texture. Crushed equipment, the crushed aggregate may contain a

considerable proportion of flat or elongated particles that adversely affect many

properties of concrete. Lightweight aggregate particles from pumice, which is highly

cellular, are also angular and have a round texture, but those from expanded clay or

shale are generally rounded and smooth.

Being stronger than the other two phases of concrete, the aggregate phases

has usually no direct influence on the strength of normal concrete except in the case

of some highly porous and weak aggregate, such as pumice. The size and the shape

of coarse aggregate can, however affect the strength of concrete in an indirect way. It

is obvious that from Fig. : 6 that the size of aggregate in concrete and the higher the

proportion of elongated and flat particles, the greater will be the tendency for water

film to accumulate next to the aggregate surface, thus weakening the interfacial

transition zone. This phenomenon is known as bleeding.

3.4.6 MICROSTRUCTURE OF THE HYDRATED CEMENT

PASTE

The term hydrated cement paste as used here refers to pastes made from

Portland cement. The microstructure of the hydrated cement paste develops as a

result of chemical reactions between Portland-cement compounds and water.

Anhydrous Portland cement is a gray powder composed of angular particles

typically in the size range from 1 to 50 µm. It is produced by pulverizing a clinker

with a small amount of calcium sulphate, the clinker being a heterogeneous mixture

of several compounds produced by high-temperature reactions between calcium

oxide and silica, alumina, and iron oxide. The chemical composition of the principal

clinker compounds corresponds approximately to C3S, C2S, C3A and C4AF. In

ordinary Portland cement their respective amounts usually range between 45 and 60,

15 and 30, 6 and 12, and 6 and 8 percent.

When Portland cement is dispersed in water, the calcium sulphate and the high-

temperature compounds of calcium begin to go into solution, and the liquid phase

gets rapidly saturated with various ionic species. As a result of interaction between

calcium, sulphate, aluminates, and hydroxyl ions within a few minutes of cement

hydration, the needle-shaped crystals of calcium trisulfoaluminate hydrate, called

ettringite first make their appearance. A few hours later, large prismatic crystals of

calcium hydroxide and very small fibrous crystals of calcium silicate hydrates begin

to fill the empty space formerly occupied by water and the dissolving cement

particles. After some days, depending on the alumina-to-sulphate ratio of the

Portland cement, ettringite may become unstable and will decompose to form

monosulfoaluminate hydrate, which has hexagonal-plate morphology. Hexagonal-

plate morphology is also the characteristic of calcium aluminates hydrates that are

Page | 26

formed in the hydrated pastes of either under sulphated or high-C3A Portland

cements. A scanning electron micrograph illustrating the typical morphology of

phases prepared by mixing a calcium aluminates solution with calcium sulphate

solution is shown in Fig.: 7

Fig. 7 : Scanning electron micrograph of typical hexagonal crystals

of monosulfate hydrate and needlelike crystals of ettringite formed

by mixing calcium aluminates and calcium sulfate solutions.

Page | 27

A model of the essential phases present in the microstructure of a well-hydrated

Portland cement paste is shown in Fig.: 8

Fig. 8 : Model of a well-hydrated Portland cement paste.

{“A” represents aggregation of poorly crystalline C-S-H particles which have at least one colloidal dimension (1

to 100 nm). Inter-particle spacing within an aggregation is 0.5 to 3.0 nm (avg. 1.5 nm) “H”represents hexagonal

crystalline products such as CH=C4AH19=C4ASH18. They form large crystals, typically 1 µm wide.

“C”represents capillary cavities or voids which exist when the spaces originally occupied with water do not get

completely filed with the hydration products of cement. The size of capillary voids ranges from 10 nm to 1 µm,

but in well-hydrated pastes with low water/cement, they are less than 100 nm.}

From the micro structural model of the hydrated cement paste shown in Fig. 8, it

may be noted that the various phases are neither uniformly distributed nor are they

uniform in size and morphology. In solids, micro structural in homogeneities can

lead to serious effects on strength and other related mechanical properties because

these properties are controlled by the micro structural extremes, not by the average

microstructure. Thus, in addition to the evolution of the microstructure as a result of

the chemical changes, which occur after cement comes in contact with water,

attention has to be paid to certain rheological properties of freshly mixed cement

paste that also influence the microstructure of the hardened paste. For instance, the

anhydrous particles of cement have a tendency to attach each other and form flocks,

which entrap large quantities of mixing water. Obviously, local variations in water-

cement ratio would be the primary sources of evolution of the heterogeneous

Page | 28

microstructure. With a highly flocculated cement paste system, not only the size and

shape of pores but also the crystalline products of hydration would be different when

compared to a well-dispersed system.

3.4.6.1 SOLIDS IN THE HYDRATED CEMENT PASTE

The types, amounts, and characteristics of the four principle solids phases in the

hydrated cement paste that can be resolved by an electron microscopic are as

follows:

Calcium Silicate Hydrate. The calcium silicate hydrated phase, abbreviated as C-

S-H, makes up to 50 to 60 percentage of the volume of solids in a completely

hydrated Portland cement paste and is, the most important phase determining the

properties of the paste. The fact that the term C-S-H is hyphenated signifies that C-S-

H is not a well-defined compound; the C/S ratio varies between 1.5 and 2.0 and the

structural water content varies even more. The morphology of C-S-H also varies

from poorly crystalline fibres to reticular network. Due to their colloidal dimensions

and a tendency to cluster, C-S-H crystals could only be resolved with the advent of

electron microscopy. In older literature, the material is often referred to as C-S-H

gel. The internal crystal structure of C-S-H also remains unresolved; previously it

was assumed to resemble the natural mineral tobermorite and that is why C-S-H was

sometimes called tobermorite gel.

Although the exact structure of C-S-H is not known, several model have been

proposed to explain the properties of the materials. According to the Powers-

Brunauer model, the material has a layer structure with a very high surface area.

Depending on the measurement technique, surface areas on the order of 100 to 700

m2/g have been proposed for C-S-H, and the strength of the material is attributed

mainly to vander Waals’ force. The size of gel pores, or the solid-to-solid distance, is

reported to be about 18Å. The Feldman-Sereda model visualizes the C-S-H structure

as being composed of an irregular or kinked array of layers which are randomly

arranged to create interlayer spaced of different shapes and sizes (5 to 25Å).

Calcium Hydroxide. Calcium hydroxide crystals (also called portlandite) constitute

20 to 25 percent of the volume of solids in the hydrated paste. In contrast to the C-S-

H, calcium hydroxide is a compound with a definite stoichiometry, Ca(OH)2. It tends

to form large crystals with a distinctive hexagonal-prism morphology. The

morphology usually varies from nondescript to stacks of large plates, and is affected

by the available space, temperature of hydration, and impurities present in the

system. Compared with C-S-H, the strength-contribution potential of calcium

hydroxide is limited as a result of considerably lower surface area.

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Calcium Sulfoaluminates Hydrates. Calcium Sulfoaluminates hydrates occupy 15

to 20 percent of the volume in the hydrated paste and, therefore play only a minor

role in the microstructure-property relationships. It has already been stated that

during the early stages of hydration the sulfate/alumina ionic ratio of the solution

phase generally favours the formation of trisulfate hydrate, C6AṤ3H32, also called

ettringite, which forms needle-shaped prismatic crystals. In pastes of ordinary

Portland cement, ettringite eventually transforms to the monosulfate hydrate,

C6AṤ3H32, which forms hexagonal-plate crystals. The presence of the monosulfate

hydrate in Portland cement concrete makes the concrete vulnerable to sulphate

attack. It should be noted that both laterite and the monosulfate contain small amount

of iron, which can substitute for the aluminium iron in the crystal structure.

Unhydrated clinker grains. Depending on the particle size distribution of the

anhydrous cement and the degree of hydration, some unhydrated clinker grains may

be found in the microstructure of hydrated cement paste, even long after hydration.

As stated earlier, the clinker particles in modern Portland cement generally conform

to the size range 1 to 50 µm. with the progress of the hydration process, the smaller

particles dissolve first and disappears from the system, then the larger particles

become smaller. Because of the limited available space between the particles, the

hydration product tend to crystallize in close proximity to the hydration clinker

particles, which gives the appearance of a coating formation around them. At later

ages, due to the lack of available space, in situ hydration of clinker particles results

in the formation of a very dense hydration product, the morphology of which may

resemble the original clinker particle.

3.4.6.2 VOIDS IN THE HYDRATED CEMENT PASTE

In addition to solids, the hydrated cement paste contains several types of voids which

have an important influence on its properties. The typical sizes of both the solid

phases and the voids in hydrated cement paste are illustrated in Fig 9a. the various

types of voids and their amount and significance are discussed, just for information

the size range of several objects ranging from human height to Mars’s diameter is

shown in Fig 9b.

Interlayer space in C-S-H. Powes assumed the widht of the interlayer space

within the C-S-H structure to be 18 Å and determined that it accounts for 28

peGCAent porosity in solid C-S-H; however, Feldman and Sereda suggested the the

space may vary form 5 to 25 Å. This void size is too small to have an adverse effect

on the strength and permeability of the hydrated cement paste. However, as

disscussed below, water in these small voids can be held by hydrogen bonding, and

its removal under certain condition may contribute to drying shrinkage and creep.

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Capillary Voids. Capillary void represents the space not filled by the solid

components of the hydrated cement paste. The total volume of a typical cement-

water mixture remains essentially unchanged during the hydration process. The

average bulk density of the hydration products is considerably lower than the density

of anhydrous, requires about 2 cm3 of space to accommodate the products of

hydration. Thus, cement hydration may be looked upon as a process during which

the space originally occupied by cement and water is being replace more and more

by the space filled by hydration products. The space not taken up by the cement or

the hydration products consists of capillary voids, the volume and size of the

capillary voids being determined by the original distance between the anhydrous

cement particles in the freshly mixed cement paste (i.e., water-cement ratio), and the

degree of cement hydration. A method of calculating the total volume of capillary

voids, popularly known as porosity, in Portland cement pastes having either different

water-cement ratios or different degrees of hydration.

In well-hydrated, low water-cement ratio pastes, the capillary voids may range from

10 to 50 nm; in high water cement ratio pastes, at early ages of hydration, the

capillary void may be as large as 3 to 5µm. typical pore size distribution plots of

several hydrated cement paste specimens tested by the mercury intrusion technique

are shown in Fig. 10. It has been suggested that the pore size distribution, not the

total capillary porosity, is a better criterion for evaluating the characteristics of a

hydrated cement paste. Capillary voids larger than 50 nm, referred to as macrospores

in modern literature, are probably more influential in determining the strength and

impermeability characteristics, whereas voids smaller than 50 nm, referred to as

microspores, play an important part in drying shrinkage and creep.

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Fig. : 9a & 9b

Page | 32

Fig. 10: Pore size distribution in hydrated cement pastes.

{ It is not the total porosity but the pore size distribution that actually controls the strength,

permeability, and volume changed in a hardened cement paste. Pore size distributions are affected by

water-cement ratio, and the age (degree) of cement hydration. Large pores influence mostly the

compressive strength and permeability; small pore influence mostly the drying shrinkage and creep. }

Air voids. Whereas capillary voids are irregular in shape, air voids are generally

spherical. A small amount of air usually gets trapped in the cement paste during

Page | 33

concrete mixing. For various reasons, admixtures may be added to concrete to

entrain purposely tiny air voids. Entrapped air voids may be as large as 3 mm;

entrained air voids usually range from 50 to 200 µm. therefore, both the entrapped

and entrained air voids in the hydrated cement paste are much bigger than the

capillary voids, and are capable of adversely affecting the strength.

3.4.6.3 WATER IN THE HYDRATED CEMENT PASTE

Under electron microscopic examination, voids in the hydrated cement paste appear

to be empty. This is because the specimen preparation technique calls for drying

the specimen under high vacuum. Actually, depending on the environmental

humidity and the porosity of the paste, the untreated cement paste is capable of

holding a large amount of water. Water can exist in the hydrated cement paste in

many forms. The classification of water into several types is based on the degree of

difficulty or ease with which it can be removed from the hydrated cement paste

when the relative humidity of the environment is reduced; the dividing line

between the different states of water is not rigid. In spite of this, the classification is

useful for understanding the properties of the hydrated cement paste. In addition to

vapour in empty or partially water-filled voids, water exists in the hydrated cement

paste in the following states:

Capillary water. This is the water present in voids larger than about 50 Å. It may

be pictured as the bulk water that is free from the influence of the attractive forces

exerted by the solids surface. Actually, from the standpoint of the behaviour of

capillary water is the hydrated cement paste, is desirable to divide the capillary

water into two categories: the water in large voids of the order of >50 nm (0.05

µm), which may be called free water (because its removal does not cause any

volume change), and the water held by capillary tension in small capillaries (5 to

50 nm), the removal of which may cause shrinkage of the system.

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Fig. 11: Diagrammatic model of the types of water associated

with the calcium silicate hydrate.

Adsorbed water. This is the water that is close to the solid surface. Under the

influence of attractive forces, water molecules are physically adsorbed onto the

surface of solids in the hydrated cement paste. It has been suggested that up to six

molecular layers of water (15 Å) can be physically held by hydrogen bonding.

Because the bond energies of the individual water molecules decreases with distance

from the solid surface, a major portion of the adsorbed water can be lost when

hydrated cement paste is dried to 30 percent relative humidity. The loss of adsorbed

water is responsible for the shrinkage of the hydrated cement paste.

Interlayer water. This is the water associated with the C-S-H structure. It has been

suggested that a monomolecular water layer between the layers of C-S-H is strongly

held by hydrogen bonding. The interlayer water is lost only on strong drying (i.e.,

below 11 percent relative humidity). The C-S-H structure shrinks considerably when

the interlayer water is lost.

Page | 35

Chemically combined water. This is the water that is an integral part of the

microstructure of various cement hydration products. This water is not lost on

drying; it is evolved when the hydrates decompose on heating. Based on the

Feldman-Sereda model, different types of water associated with the C-S-H are

illustrated in Fig. 11.

3.5 IMPACT OF MODERN CONCRETE USE

Concrete is widely used for making architectural structures, foundations, brick/block

walls, pavements, bridges/overpasses, highways, runways, parking structures, dams,

pools/reservoirs, pipes, footings for gates, fences and poles and even boats. Concrete

is used in large quantities almost everywhere mankind has a need for infrastructure.

The amount of concrete used worldwide, ton for ton, is twice that of steel, wood,

plastics, and aluminum combined. Concrete’s use in the modern world is exceeded

only by that of naturally occurring water.

Concrete is also the basis of a large commercial industry. Globally, the ready mix

concrete industry, the largest segment of the concrete market, is projected to exceed

$100 billion in revenue by 2015. In the United States alone, concrete production is a

$30-billion-per-year industry, considering only the value of the ready-mixed

concrete sold each year. Given the size of the concrete industry, and the fundamental

way concrete is used to shape the infrastructure of the modern world, it is difficult to

overstate the role this material plays today.

3.5.6 ENVIRONMENTAL & HEALTH

The manufacture and use of concrete produce a wide range of environmental and

social consequences. Some are harmful, some welcome, and some both, depending

on circumstances.

A major component of concrete is cement, which similarly exerts environmental and

social effects. The cement industry is one of the three primary producers of carbon

dioxide, a major greenhouse gas (the other two being the energy production and

transportation industries). As of 2001, the production of Portland cement contributed

7% to global anthropogenic CO2 emissions, largely due to the sintering of limestone

and clay at 1,500°C (2,730 °F).

Page | 36

Fig 12 : Concrete mixing plant in Birmingham, Alabama in 1936

Concrete is used to create hard surfaces that contribute to surface runoff, which can

cause heavy soil erosion, water pollution, and flooding, but conversely can be used

to divert, dam, and control flooding.

Concrete is a primary contributor to the urban heat island effect, though less so than

asphalt. Workers who cut, grind or polish concrete are at risk of inhaling airborne

silica, which can lead to silicosis. Concrete dust released by building demolition and

natural disasters can be a major sources of dangerous air pollution.

The presence of some substances in concrete, including useful and unwanted

additives, can cause health concerns due to toxicity and radioactivity. Wet concrete

is highly alkaline and must be handled with proper protective equipment.

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Fig 13: Recycled crushed concrete, to be reused as granular fill, is

loaded into a semi-dump truck

3.5.7 CONCRETE RECYCLING

Concrete recycling is an increasingly common method of disposing of concrete

structures. Concrete debris was once routinely shipped to landfills for disposal, but

recycling is increasing due to improved environmental awareness, governmental

laws and economic benefits.

Concrete, which must be free of trash, wood, paper and other such materials, is

collected from demolition sites and put through a crushing machine, often along

with asphalt, bricks and rocks.

Reinforced concrete contains rebar and other metallic reinforcements, which are

removed with magnets and recycled elsewhere. The remaining aggregate chunks

are sorted by size. Larger chunks may go through the crusher again. Smaller pieces

of concrete are used as gravel for new construction projects. Aggregate base gravel

Page | 38

is laid down as the lowest layer in a road, with fresh concrete or asphalt placed over

it.

Crushed Granite concrete can sometimes be used as the dry aggregate for brand

new concrete if it is free of contaminants, though the use of re- cycled concrete

limits strength and is not allowed in many jurisdictions. On 3 March 1983, a

government-funded research team (the VIRL research codes) estimated that almost

17% of worldwide landfill was by-products of concrete based waste. Recycled

crushed concrete is shown in figure 13.

3.6 COMPOSITION OF CEMENT CONCRETE

There are many types of concrete available, created by varying the proportions of

the main ingredients below. In this way or by substitution for the cementations and

aggregate phases, the finished product can be tailored to its application with

varying strength, density, or chemical and thermal resistance properties.

"Aggregate" consists of large chunks of material in a concrete mix, generally a

coarse gravel or crushed rocks such as limestone, or granite, along with finer

materials such as sand.

"Cement", most commonly Portland cement is associated with the general term

“concrete.” A range of materials can be used as the cement in concrete. One of the

most familiar of these alternative cements is asphalt. Other cementations materials

such as fly ash and slag cement are sometimes added to Portland cement and

become a part of the binder for the aggregate. Water is then mixed with this dry

composite, which produces a semi-liquid that workers can shape (typically by

pouring it into a form). The concrete solidifies and hardens through a chemical

process called hydration. The water reacts with the cement, which bonds the other

components together, creating a robust stone-like material.

"Chemical admixtures" are added to achieve varied properties. These ingredients

may speed or slow down the rate at which the concrete hardens, and impart many

other useful properties including increased tensile strength and water resistance.

"Reinforcements" are often added to concrete. Concrete can be formulated with

high compressive strength, but always has lower tensile strength. For this reason it

is usually reinforced with materials that are strong in tension (often steel).

"Mineral admixtures" are becoming more popular in re- cent decades. The use of

recycled materials as concrete ingredients has been gaining popularity because of

increasingly stringent environmental legislation, and the discovery that such

materials often have complementary and valuable properties. The most

conspicuous of these are fly ash, a by-product of coal-fired power plants, and silica

fume, a by-product of industrial electric furnaces. The use of these materials in

concrete reduces the amount of resources required, as the ash and fume act as a

cement replacement.

Page | 39

Fig 14 (a) : Aggregate Fig 14 (b) : Cement

Fig 14 (c) : Fly Ash Fig 14 (d) : Blast Furnace Slag

Fig 14 (e) : OPC, PFA &Silica Fume

Page | 40

This displaces some cement production, an energetically expensive and

environmentally problematic process, while reducing the amount of industrial waste

that must be disposed off.

The mix design depends on the type of structure being built, how the concrete is

mixed and delivered, and how it is placed to form the structure.

3.6.6 CEMENT

Portland cement is the most common type of cement in general usage. It is a

basic ingredient of concrete, mortar and plaster. English masonry worker Joseph

Aspdin patented Portland cement in 1824. It was named because of the similarity of

its colour to Portland limestone, quarried from the English Isle of Portland and used

extensively in London architecture. It consists of a mixture of oxides of calcium,

silicon and aluminium. Portland cement and similar materials are made by heating

limestone (a sources of calcium) with clay and grinding this product (called

clinker) with a source of sulphate (most commonly gypsum).

In modern cement kilns many advanced features are used to lower the fuel

consumption per ton of clinker produced. Cement kilns are extremely large,

complex, and inherently dusty industrial installations, and have emissions which

must be controlled of the various ingredients used in concrete the cement is the

most energetically expensive. Even complex and efficient kilns require 3.3 to 3.6

gigajoules of energy to produce a ton of clinker and then grind it into cement.

Many kilns can be fueled with difficult to dispose of wastes; the most common

being used tires. The extremely high temperatures and long periods of time at those

temperatures allow cement kilns too efficiently and completely burn even difficult-

to-use fuels.

3.6.7 WATER

Cement paste by the process of hydration. The cement paste glues the

aggregate together, fills voids within it, and makes it flow more freely.

A lower water-to-cement ratio yields a stronger, more durable concrete,

whereas more water gives a free- flowing concrete with a higher slump. Impure

water used to make concrete can cause problems when setting or in causing

premature failure of the structure.

Hydration involves many different reactions, often occurring at the same

time. As the reactions proceed, the products of the cement hydration process

gradually bond together the individual sand and gravel particles and other

components of the concrete to form a solid mass.

Page | 41

Reactions :

Cementchemistnotation:C3S+H→C-S-H +CH

Standard notation:

Ca3SiO5+ H2O →(CaO)·(SiO2)·(H2O)(gel)+Ca(OH)2

Balanced:

2Ca3SiO5 + 7H2O →3(CaO)·2(SiO2)·4(H2O)(gel) + 3Ca(OH)2

3.6.8 AGGREGATES

Fine and coarse aggregates make up the bulk of a concrete mixture. Sand,

natural gravel and crushed stone are used mainly for this purpose. Granite Course

Aggregate s (from construction, demolition, and excavation waste) are increasingly

used as partial replacements of natural aggregates, while a number of manufactured

aggregates, including air-cooled blast furnace slag and bottom ash are also

permitted.

The presence of aggregate greatly increases the durability of concrete above

that of cement, which is a brittle material in its pure state. Thus concrete is a true

composite material.

Redistribution of aggregates after compaction often creates in homogeneity

due to the influence of vibration. This can lead to strength gradients.

Decorative stones such as quartzite, small river stones or crushed glass are

sometimes added to the surface of concrete for a decorative “exposed aggregate”

finish, popular among landscape designers. In addition to being decorative,

exposed aggregate adds robustness to a concrete driveway.

3.6.9 REINFORCEMENT

Concrete is strong in compression, as the aggregate efficiently carries the

compression load. However, it is weak in tension as the cement holding the

aggregate in place can crack, allowing the structure to fail. Reinforced concrete

adds steel reinforcing bars, steel fibres, glass fibbers, or plastic fibbers to carry

tensile loads.

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Fig 15: Constructing a rebar cage. This cage will be permanently

embedded in poured concrete to create a reinforced concrete structure.

3.6.10 CHEMICAL ADMIXTURES

Chemical admixtures are materials in the form of powder or fluids that are added

to the concrete to give it certain characteristics not obtainable with plain concrete

mixes. In normal use, admixture dosages are less than 5% by mass of cement and are

added to the concrete at the time of batching/mixing. The common types of

admixtures are as follows.

Accelerators speed up the hydration (hardening) of the concrete. Typical

materials used are CaCl2 , Ca(NO3)2 and NaNO3. However, use of chlorides may

cause corrosion in steel reinforcing and is prohibited in some countries, so that

nitrates may be favoured. Accelerating admixtures are especially useful for

modifying the properties of concrete in cold weather.

Retarders slow the hydration of concrete and are used in large or difficult

pours where partial setting before the pour is complete is undesirable. Typical

retarders are sugar, sucrose, sodium glaciate, glucose, citric acid, and tartaric acid.

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Air entrainments add and entrain tiny air bubbles in the concrete, which

reduces damage during freeze- thaw cycles, increasing durability. However,

entrained air entails a trade off with strength, as each 1% of air may decrease

compressive strength 5%. If too much air becomes trapped in the concrete as a result

of the mixing process, Deformers can be used to encourage the air bubble to

agglomerate, rise to the surface of the wet concrete and then disperse.

Plasticizers increase the workability of plastic or “fresh” concrete, allowing it

be placed more easily, with less consolidating effort. A typical plasticizer is

lignosulfonate. Plasticizers can be used to reduce the water content of a concrete

while maintaining workability and are sometimes called water-reducers due to this

use. Such treatment improves its strength and durability characteristics. Super

plasticizers (also called high-range water- reducers) are a class of plasticizers that

have fewer deleterious effects and can be used to increase workability more than is

practical with traditional plasticizers. Compounds used as super plasticizers include

suffocated naphthalene formaldehyde condensate, suffocated melamine

formaldehyde condensate, acetone formaldehyde condensate and polycar-boxylate

ethers.

Pigments can be used to change the colour of concrete, for aesthetics.

corrosion inhibitors are used to minimize the corrosion of steel and steel bars

in concrete.

Bonding agents are used to create a bond between old and new concrete

(typically a type of polymer) with wide temperature tolerance and corrosion

resistance.

Pumping aids improve pump ability, thicken the paste and reduce separation

and bleeding.

3.6.11 MINERAL ADMIXTURES & BLENDED CEMENTS

Inorganic materials that have pozzolanic or latent hydraulic properties, these very

fine-grained materials are added to the concrete mix to improve the properties of

concrete (mineral admixtures), or as a replacement for Portland cement (blended

cements). Products which incorporate limestone, fly ash, blast furnace slag, and

other useful materials with pozzolanic properties into the mix,

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are being tested and used. This development is due to cement production being one

of the largest producers (at about 5 to 10%) of global greenhouse gas emissions, as

well as lowering costs, improving concrete properties, and recycling wastes.

Fly ash: A by-product of coal-fired electric generating plants; it is used to

partially replace Portland cement (by up to 60% by mass). The properties of fly ash

depend on the type of coal burnt. In general, siliceous fly ash is pozzolanic, while

calcareous fly ash has latent hydraulic properties.

Ground granulated blast furnace slag (GGBFS or GGBS): A by-product of

steel production is used to partially replace Portland cement (by up to 80% by mass).

It has latent hydraulic properties.

Silica fume: A by-product of the production of silicon and ferrosilicon alloys.

Silica fume is similar to fly ash, but has a particle size 100 times smaller. This results

in a higher surface-to-volume ratio and a much faster pozzolanic reaction. Silica

fume is used to increase strength and durability of concrete, but generally requires

the use of super plasticizers for workability.

High reactivity Metakaolin (HRM): Metakaolin produces concrete with

strength and durability similar to concrete made with silica fume. While silica fume

is usually dark gray or black in color, high- reactivity metakaolin is usually bright

white in color, making it the preferred choice for architectural concrete where

appearance is important.

3.7 CONCRETE PRODUCTION

Concrete production is the process of mixing together the various ingredients

water, aggregate, cement, and any additives to produce concrete. Concrete

production is time-sensitive. Once the ingredients are mixed, workers must put the

concrete in place before it hardens. In modern usage, most concrete production takes

place in a large type of industrial facility called a concrete plant, or often a batch

plant.

In general usage, concrete plants come in two main types, ready mix plants

and central mix plants. A ready mix plant mixes all the ingredients except water,

while a central mix plant mixes all the ingredients including water. A central mix

plant offers more accurate control of the concrete quality through better

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measurements of the amount of water added, but must be placed closer to the work

site where the concrete will be used, since hydration begins at the plant.

Modern concrete is usually prepared as a viscous fluid, so that it may be poured into

forms, which are containers erected in the field to give the concrete its desired shape.

There are many different ways in which concrete formwork can be prepared, such as

Slip forming and Steel plate construction. Alternatively, concrete can be mixed into

dryer, non-fluid forms and used in factory settings to manufacture precast concrete

products.

There is a wide variety of equipment for processing concrete, from hand tools

to heavy industrial machinery. Whichever equipment builder’s use, however, the

objective is to produce the desired building material; ingredients must be properly

mixed, placed, shaped, and retained within time constraints. Once the mix is where it

should be, the curing process must be controlled to ensure that the concrete attains

the desired attributes. During concrete preparation, various technical details may

affect the quality and nature of the product.

When initially mixed, Portland cement and water rapidly form a gel of tangled

chains of interlocking crystals, and components of the gel continue to react over

time. Initially the gel is fluid, which improves workability and aids in placement of

the material, but as the concrete sets, the chains of crystals join into a rigid structure,

counteracting the fluidity of the gel and fixing the particles of aggregate in place.

During curing, the cement continues to react with the residual water in a process of

hydration. In properly formulated concrete, once this curing process has terminated

the product has the desired physical and chemical properties. Among the qualities

typically desired, are mechanical strength, low moisture permeability, and chemical

and volumetric stability.

3.7.6 MIXING OF CONCRETE

Thorough mixing is essential for the production of uniform, high-quality concrete.

For this reason equipment and methods should be capable of effectively mixing

concrete materials containing the largest specified aggregate to produce uniform

mixtures of the lowest slump practical for the work.

Separate paste mixing has shown that the mixing of cement and water into a paste

before combining these materials with aggregates can increase the compressive

strength of the resulting concrete. The paste is generally mixed in a high-speed,

shear-type mixer at a w/cm (water to cement ratio) of 0.30 to 0.45 by mass. The

cement paste premix may include admixtures such as accelerators or retarders, super

plasticizers, pigments, or silica fume. The premixed paste is then blended with

aggregates and any remaining batch water and final mixing is completed in

conventional concrete mixing equipment.

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Nano concrete is created by High-energy mixing (HEM) of cement, sand and water

using a specific consumed power of 30 - 600 watt/kg for a net specific energy

consumption of at least 5 kJ/kg of the mix. A plasticizer or a super plasticizer is then

added to the activated mixture which can later be mixed with aggregates in a

conventional concrete mixer. In the HEM process sand provides dissipation of energy

and increases shear stresses on the surface of cement particles.

Fig 16 (a) : Concrete plant facility showing a Fig 16 (c) : Pouring and smoothing

Concrete mixer being filled from out concrete at Palisades

the ingredient silos. Park in Washington DC

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Fig 16 (d) : A Concrete Slab & Concrete Cubes Ponded while Curing

The quasi-laminar flow of the mixture characterized with Reynolds

number less than 800 is necessary to provide more effective energy

absorption. This results in the increased volume of water interacting with

cement and acceleration of Calcium Silicate Hydrate (C-S-H) colloid

creation. The initial natural process of cement hydration with formation of

colloidal globules about 5 nm in diameter after 3-5 min of HEM spreads out

over the entire volume of cement – water matrix. HEM is the “bottom-up”

approach in Nanotechnology of concrete. The liquid activated mixture is

used by itself for casting small architectural details and decorative items, or

foamed (expanded) for lightweight concrete. HEM Nano concrete hardens in

low and subzero temperature conditions and possesses an increased volume

of gel, which drastically reduces capillarity in solid and porous materials.

3.7.7 WORKABILITY

Workability is the ability of a fresh (plastic) concrete mix to fill the form/mold

properly with the desired work (vibration) and without reducing the concrete’s

quality. Workability depends on water content, aggregate (shape and size

distribution), cementations content and age (level of hydration) and can be

modified by adding chemical admixtures, like super plasticizer. Raising the water

content or adding chemical admixtures increases concrete workability. Excessive

water leads to increased bleeding (surface water) and/or segregation of aggregates

(when the cement and aggregates start to separate), with the resulting concrete

having reduced quality. The use of an aggregate with an undesirable gradation can

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result in a very harsh mix design with a very low slump, which cannot readily be

made more workable by addition of reasonable amounts of water.

Workability can be measured by the concrete slump test, a simplistic measure of

the plasticity of a fresh batch of concrete following the ASTM C 143 or EN

12350-2 test standards. Slump is normally measured by filling an "Abrams cone"

with a sample from a fresh batch of concrete. The cone is placed with the wide

end down onto a level, non-absorptive surface. It is then filled in three layers of

equal volume, with each layer being tamped with a steel rod to consolidate the

layer. When the cone is carefully lifted off, the enclosed material slumps a certain

amount, owing to gravity. A relatively dry sample slumps very little, having a

slump value of one or two inches (25 or 50 mm) out of one foot (305 mm). A

relatively wet concrete sample may slump as much as eight inches. Workability

can also be measured by the flow table test.

Slump can be increased by addition of chemical admixtures such as plasticizer

or super plasticizer without changing the water-cement ratio. Some other

admixtures, especially air-entraining admixture, can increase the slump of a mix.

High-flow concrete, like self-consolidating concrete, is tested by other flow-

measuring methods. One of these methods includes placing the cone on the

narrow end and observing how the mix flows through the cone while it is

gradually lifted. After mixing, concrete is a fluid and can be pumped to the

location where needed.

3.7.8 CURING

In all but the least critical applications, care must be taken to properly cure

concrete, to achieve best strength and hardness. This happens after the concrete

has been placed. Cement requires a moist, controlled environment to gain strength

and harden fully. The cement paste hardens over time, initially setting and

becoming rigid though very weak and gaining in strength in the weeks following.

In around 4 weeks, typically over 90% of the final strength is reached, though

strengthening may continue for decades. The conversion of calcium hydroxide in

the concrete into calcium carbonate from absorption of CO2 over several decades

further strengthens the concrete and makes it more resistant to damage. However,

this reaction, called carbonation, lowers the pH of the cement pore solution and

can cause the reinforcement bars to corrode.

Hydration and hardening of concrete during the first three days is critical.

Abnormally fast drying and shrinkage due to factors such as evaporation from

wind during placement may lead to increased tensile stresses at a time when it has

not yet gained sufficient strength, resulting in greater shrinkage cracking. The

early strength of the concrete can be increased if it is kept damp during the curing

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process. Minimizing stress prior to curing minimizes cracking. High-early-

strength concrete is designed to hydrate faster, often by increased use of cement

that increases shrinkage and cracking. The strength of concrete changes

(increases) for up to three years. It depends on cross-section dimension of

elements and conditions of structure exploitation.

During this period concrete must be kept under controlled temperature and humid

atmosphere. In practice, this is achieved by spraying or pounding the concrete

surface with water, thereby protecting the concrete mass from ill effects of

ambient conditions. The picture to the right shows one of many ways to achieve

this, ponding – submerging setting concrete in water and wrapping in plastic to

contain the water in the mix. Additional common curing methods include wet

burlap and/or plastic sheeting covering the fresh concrete, or by spraying on a

water- impermeable temporary curing membrane.

Properly curing concrete leads to increased strength and lower permeability and

avoids cracking where the surface dries out prematurely. Care must also be taken

to avoid freezing or overheating due to the exothermic setting of cement.

Improper curing can cause scaling, reduced strength, poor abrasion resistance and

cracking.

3.8 PROPERTIES OF HARDENED CONCRETE

There are two states of concrete (i) plastic state, and (ii) hardened state.

Plastic state refers to the state of concrete before it has set and hardened. During

this state, concrete is placed in a form work and compacted. It should be workable

so that it can be easily mixed, placed, compacted and finished at the surface.

After concrete has been placed in the form work, it hardens and gains strength.

Hardened concrete should be durable. Impermeable and should have adequate

strength.

The properties of hardened concrete are as follows:

3.8.6 IMPERMEABILITY

Impermeability is the resistance of concrete to the flow of water into it. The

water flows into the pore spaces in the concrete which are formed due to the

evaporation of superfluous water that does not combine with cement. In addition

to these water occupied voids, there are air voids. The impermeability of concrete

increases with the reduction such pore spaces. It increases the durability by

increasing its resistance of weathering, chemical attack and corrosion.

Impermeable concrete can be obtained by adopting low water to cement ratio

and by proper compaction so that water occupied voids and air voids are

minimum. Also, well graded aggregate and adequate curing ensures proper

hydration and improves the impermeability of concrete.

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3.8.7 STRENGTH

The strength of concrete is the property most valued by designers and quality

control engineers. In solids, there exists a fundamental inverse relationship

between porosity (volume fraction of voids) and strength. Consequently, in

multiphase materials such as concrete, the porosity of each component of the

microstructure can become strength-limiting. Natural aggregates are generally

dense and strong; therefore, it is the porosity of the cement pate matrix as well as

the interfacial transition zone between the matrix and coarse aggregate, which

usually determines the strength characteristics of natural-weight concrete.

Although the water-cement ratio is important in determining the porosity of both

the matrix and the interfacial transition zone and hence the strength of concrete,

factors such as compaction and curing condition (degree of cement hydration),

aggregate size and mineralogy. Admixtures types, specimen geometry and

moisture condition, types of stress, and rate of loading can also have an important

effect on strength.

3.8.7.1 DEFINITION

The strength of material is defined as the ability to resist stress without

failure. Failure is sometimes identified with the appearance of cracks. However,

micro structural investigations of ordinary concrete show that unlike most

structural materials concrete contains many fine cracks even before it is subjected

to external stresses. In concrete, therefore, strength is related to the stress required

to cause failure and it is defined as the maximum stress the concrete sample can

withstand. In tension testing, the fracture of the test piece usually signifies failure.

In compression the test piece is considered to have failed even when no signs of

external fracture are visible; however, the internal cracking has reached such an

advanced state that the specimen is unable to carry a higher load.

3.8.7.2 SIGNIFICANCE

In concrete design and quality control, strength is the property generally

specified. This is because, compared to most other properties, testing of strength

is relatively easy. Furthermore, many properties of concrete, such as elastic

modulus, water tightness or impermeability, and resistance to weathering agents

including aggregate water, are believed to be dependent on strength and many

therefore be deduced from the strength data. The compressive strength of concrete

is several times greater than other types of strength; therefore a majority of

concrete elements are designed to take advantage of higher compressive strength

of the material. Although in practice most concrete is subjected simultaneously to

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a combination of compressive, shearing, and tensile stresses in two or more

directions, the un axial compressive tests are the easiest to perform in laboratory,

and the 28-days compressive strength of concrete determined by a standard un

axial compression test is accepted universally as a general index of the concrete

strength.

3.8.7.3 STRENGTH-POROSITY RELATIONSHIP

In general, there exists a fundamental inverse relationship between porosity

and strength of solids. For simple homogeneous materials, it can be described by

the expression

S = S0 e –kp

……………. (1)

where S = strength of the material which has a given porosity p

S0 = intrinsic strength at zero porosity

k = constant

For many materials the ratio S/S0 plotted against porosity follows the same

cured. For instance, the data in Fig. 17arepresent normally-curved cements,

autoclaved cements, and a variety of aggregates. Actually, the same strength-

porosity relationship is applicable to a very wide range of materials, such as iron,

plaster of paris, sintered alumina, ammonia (Fig. 17b).

Powers found that the 28-days compressive strength fc of three different mortar

mixtures was related to the gel/space ratio between the solid hydration products in

the system and the total space:

fc = ax3

……………. (2)

where a is the intrinsic strength of the material at zero porosity p, and x the

solid/space ratio or the amount of solid fraction in the system, which is therefore

equal to 1– p. powers data are shown in Fig. 17c; he found the value of a to be

234 MPa (34,000 psi). The similarity of the three curves in Fig. 17 confirms the

general validity of the strength-porosity relationship in solids.

Whereas in hardened cement paste or mortar the porosity can be related to

strength, with concrete the situation is not simple. The presence of micro-cracks

in the interfacial transition zone between the coarse aggregate and the matrix

makes concrete too complex a material for prediction of strength by precise

strength-porosity relations. The general validity of strength-porosity relation,

however, must be respected because porosities of the component phases of

concrete, including the interfacial transition zone, indeed become strength-

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limiting. With concrete containing the conventional low-porosity or high-strength

aggregate, the strength of the material will be governed both by the strength of the

matrix and the strength of the interfacial transition zone.

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3.8.7.4 FAILURE MODES IN CONCRETE

With a material such as concrete, which contains void spaces of various size

and shape in the matrix and micro cracks at the interfacial transition zone, the

failure modes under stress are very complex and vary with the type of stress. A

brief review of the failure modes, however, will be useful in understanding and

control of the factors that influence concrete strength.

Under uni-axial tension, relatively less energy is needed for the initiation and

growth of cracks in the matrix. Rapid propagation and interlink age of the crack

system, consisting of pre-existing cracks at the interfacial transition zone and

newly formed cracks in matrix, account for the brittle failure. In compression, the

failure mode is less brittle because considerably more energy is needed to form

and to extend cracks in the matrix. It is generally agreed that, in uni-axial

compression test on medium or low strength concrete, no cracks are initiated in

the matrix up to about 50 percent of the failure stress; at this stage a stable system

of cracks, called shear bond cracks, already exists in the vicinity of coarse

aggregate. At higher stress levels, cracks are initiated within the matrix; their

number and size increases progressively with increasing stress levels. The cracks

in the matrix and the interfacial transition zone (shear-bond cracks) eventually

join up, and generally a failure surface develops at about 20º to 30º from the

direction of the load.

3.8.7.5 COMPRESSIVE STRENGTH & FACTORS

AFFECTING IT

The response of concrete to applied stress depends not only on the stress type

but also on how a combination of various factors affected porosity of the different

structure components of concrete. The factors include properties and proportions

of materials that make up the concrete mixture, degree of compaction, and

condition of curing. From the standpoint of strength, the relationship between

water-cement ratio and porosity is undoubtedly the most important factor

because, independent of other factor, it affects the porosity of both the cement

mortar and the interfacial transition zone between the matrix and the coarse

aggregate.

Direct determination of porosity of the individual structure component of

concrete–the matrix and the interfacial transition zone–is impractical, and

therefore precise models of predicting concrete strength cannot be developed.

However, over a period of time many useful empirical relations have been found,

which, for practical use, provide enough indirect information about the influence

of numerous factors on compressive strength (compressive strength being widely

used as an index of all other types of strength). Although the actual response of

concrete to applied stress is a result of complex interactions between various

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factors, to facilitate a clear understanding of characteristics and proportions of

materials, curing condition of concrete.

3.8.7.6 CHARACTERISTICS & PROPORTIONS OF

MATERIALS

Before making a concrete mixture, the selection of proper component

materials and their proportions is the first step toward obtaining a product that

would meet the specified strength. It should be emphasized that, many mix design

parameters are interdependent, and therefore their influence cannot really be

separated.

3.8.7.6.1 WATER-CEMENT RATIO

In 1918, as a result of extensive testing at the Lewis Institute, University of

Illinois, Duff Abrams found that a relation existed between water-cement ratio

and concrete strength. Popularly known as Abrams’ water-cement ratio rule, this

inverse relation is represented by the expression

fc =

where w/c represents the water-cement ratio of the concrete mixture and k1 and k2

are empirical constants. From an understanding of the factors responsible for the

strength of hydrated cement paste and the effect of increasing the water cement

ratio on porosity at a given degree of cement hydration, the w/c- strength

relationship in concrete can easily be explained as the natural consequences of a

progressive weakening of the matrix caused by increased porosity with increase in

the water-cement ratio. The explanation, however, does not consider the influence

of the water-cement ratio on the strength of the interfacial transition zone. In low

and medium strength concrete made with normal aggregate, both the interfacial

transition zone

porosity and the matrix porosity determine the strength, and a direct relation

between the water-cement ratio and the concrete strength holds. This seems no

longer to be the case in high-strength (i.e., very low water-cement ratio) concrete

mixtures. For water-cement ratio under 0.3 disproportionately high increases in

the compressive strength can be achieved with very small reductions in water-

cement ratio. The phenomenon is attributed mainly to a significant improvement

in the strength of the interfacial transition zone at very low water-cement ratio.

Furthermore, with low water-cement ratio the crystal size of the hydration

products is much smaller and the surface area is corresponding higher.

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3.8.7.6.2 AIR ENTRAINMENT

For the most part, it is the water-cement ratio that determines the porosity of

the cement paste matrix at a given degree of hydration; however, when air voids

are incorporated into the system, either as a result of inadequate compaction or

through the use of an air-entraining admixture, they also have the effect of

increasing the porosity and decreasing the strength of the system. At a given

water-cement ratio, the effect on the compressive strength of concrete of

increasing the volume of entrained air. It has been observed that the extent of

strength loss as a result of entrained air dependent not only on the water-cement

ratio of the concrete mixture, but also on the cement content. In short, as a first

approximation, the strength loss due to air entrainment can be related to the

general level of concrete strength. At a given water-cement ratio, high-strength

concretes (containing a high cement content) suffer a considerable strength loss

with increasing amounts of entrained air, whereas low-strength loss or may

actually gain some strength as a result of air entrainment. This point is of great

significance in the design of mass-concrete mixtures.

The influence of the water-cement ratio and cement content on the response

of concrete to applied stress can be explained from the two opposing effects

caused by incorporation of air into concrete. By increasing the porosity of the

matrix, entrained air will have an adverse effect on the strength of the interfacial

transition zone (especially in mixture with very low water and cement contents)

and thus improves the strength of concrete. It seems that with concrete mixtures

of low cement content, when air entrainment is accompanied by a significant

reduction in the water content, the adverse effect of air entrainment on the

strength of the matrix is more than compensated by the beneficial effect on the

interfacial transition zone.

3.8.7.6.3 CEMENT TYPE

The degree of cement hydration has a direct effect on porosity and

consequently on strength. At ordinary temperature ASTM Type III Portland

cement, which has a higher fineness, hydrates more rapidly than other types;

therefore, at early ages of hydration (e.g., 1,3, and 7 days) and a given water-

cement ratio, a concrete containing Type III Portland cement will have a lower

porosity and correspondingly a higher strength. On the other hand, compared to

ASTM Type I, Type II, and Type IV and Type V Portland cements, and with

Portland-slag and Portland-pozzolan cement are slower up to 28 days; however

the differences usually disappear thereafter when they have achieved a similar

degree of hydration.

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3.8.7.6.4 AGGREGATE

In concrete technology, on overemphasis on the relationship between water-

cement ratio and strength has caused some problems. For instance, the influence

of aggregate on concrete strength is not generally appreciated. It is true that

aggregate strength is usually not a factor in normal strength concrete because,

with the exception of lightweight aggregates, the aggregate particle is several

times stronger than the matrix and the interfacial transition zone in concrete. In

other words, with most natural aggregates the strength of the aggregate is hardly

utilized because the failure is determined by the other two phases.

There are, however, aggregate characteristics other than strength, such as the

size, shape, surface, texture, grading (particle size distribution), and mineralogy,

which are known to affect concrete strength in varying degrees. Frequently the

effect of aggregate characteristics on concrete strength can be traced to a change

of water-cement ratio. But there is sufficient evidence in the published literature

that this is not always the case. Also, from theoretical considerations it may be

anticipated that, independent of the water-cement ratio, the size, shape, surface

texture, and mineralogy of aggregate particles would influence the characteristics

of the interfacial transition zone and therefore affect concrete strength.

A change in the maximum size of well-graded coarse aggregate of a given

mineralogy can have two opposing effects on the strength of concrete. With the

same cement content and consistency, concrete mixtures containing larger

aggregate particles require less mixing water than those containing smaller

aggregate. On the contrary, larger aggregate tend to form weaker interfacial

transition zone containing more micro cracks. The net effect will vary with the

water-cement ratio of the concrete and the type of applied stress. The effect of

increasing maximum aggregate size on the 28-days compressive strengths of the

concrete was more pronounced with a high-strength (0.4 water-cement ratio) and

a moderate-strength (0.55 water-cement ratio) concrete than with a low-strength

concrete (0.7 water-cement ratio). This is because at lower water-cement ratios

the reduced porosity of the interfacial transition zone begins to play an important

role in the concrete strength. Furthermore, since the interfacial transition zone

characteristics have more effect on the tensile strength of concrete compared to

the compressive strength, it is to be expected that with a given concrete mixture

any changes in the coarse aggregate properties would influence the tensile-

compressive strength ratio of the material. For instance a decrease in the size of

coarse aggregate, at a given water-cement ratio, will increase the tensile-

compressive strength ratio.

A change in the aggregate grading without any change in the maximum size

of coarse aggregate, and with water-cement ratio held constant, can influence the

concrete strength when this change causes a corresponding change in the

consistency and bleeding characteristics of the concrete mixture. In a laboratory

experiment, with a constant water-cement ratio of 0.6, when the coarse/fine

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aggregate proportion and the cement content of a concrete mixture were

progressively raised to increase the consistency from 50 to 150 mm of slump

there was about 12 percent decrease in the average 7-days compressive strength.

It has been observed that a concrete mixture containing a rough-textured or

crushed aggregate would show somewhat higher strength (especially tensile

strength) at early ages than corresponding concrete containing smooth or naturally

weathered aggregate of similar mineralogy. A stronger physical bond between the

aggregate and the hydrated cement paste is assumed to be responsible for this.

At later ages, when chemical interaction between the aggregate and the

cement paste begins to take effect, the influence of the surface texture of

aggregate on strength may be reduced. From the standpoint of the physical bond

with cement paste, it may be noted that a smooth-looking particle of weathered

gravel, when observed under a microscope would appear to possess adequate

roughness and surface area. Also, with given cement content, somewhat more

mixing water is usually needed to obtain the desired workability in a concrete

mixture containing rough-textured aggregates; thus the small advantage due to a

better physical bonding may be lost as far as overall strength is concerned.

Differences in the mineralogical composition of aggregate are also known to

affect the concrete strength. Reports show that, with identical mix proportions, the

substitution of a calcareous for a siliceous aggregate can result in strength

improvement.

3.8.7.6.5 MIXING WATER

Impurities in water used for mixing concrete, when excessive, may affect not

only the concrete strength but also setting time, efflorescence (deposits of white

salts on the surface of concrete), and the corrosion of reinforcing and prestressing

steel. In general, mixing water is rarely a factor in concrete strength, because

many specifications for making concrete mixtures require that the quality of water

used should be fit for drinking, and municipal drinking waters seldom contain

dissolved solids in excess of 1000 ppm (parts per million). As a rule, water that is

unsuitable for drinking may not necessarily be unfit for mixing concrete. Slightly

acidic, alkaline, salty, brackish, colour, or foul-smelling water should be rejected

outright, this is important because of the water shortage in many areas of the

world. Also, recycled waters from cities, mining, and many industrial operations

can be safely used as mixing waters for concrete. The best way to determine the

suitability of a water of unknown performance for making concrete is to compare

the setting time of cement and the strength of mortar cubes made with the

unknown water with reference water that is clean. The cubes made with the

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questionable water should have 7 and 28-days compressive strength equal to or at

least 90 percent of the strength of reference specimens made with clean water;

also the quality of mixing water should not affect the setting time of cement to an

unacceptable degree.

Seawater, which contains about 35,000 ppm dissolved salts, is not harmful to

the strength of plain concrete. However, with reinforced and pre-stressed concrete

it increases the risk of steel corrosion; therefore, the use of seawater as concrete-

mixing water should be avoided under these circumstances. As a general

guideline, from standpoint of the concrete strength, the presence of excessive

amount of algae, oil, salt, or sugar in the mixing water should send a warning

signal.

3.8.7.6.6 ADMIXTURES

The water-reducing admixtures can enhance both the early and the ultimate

strength of concrete. At a given water-cement ratio, the presence of water-

reducing admixtures in concrete generally has a positive influence on the rates of

cement hydration and early strength development. Admixtures capable of

accelerating or retarding cement hydrate obviously would have a great influence

on the rate of strength gain; however, the ultimate strength may not be

significantly affected. Many researchers have pointed out the tendency toward a

higher ultimate strength of concrete when the rate of strength gain at early ages

was retarded.

For ecological and economic reasons, the use of pozzolanic and

cementations by product as mineral admixtures in concrete is gradually

increasing. When used as a partial replacement for Portland cement, mineral

admixtures usually have a retarding effect on the strength at early ages. However,

the ability of a mineral admixture to react at normal temperatures with calcium

hydroxide (present in the hydrated Portland cement paste) and to form additional

calcium silicate hydrate can lead to significant reduction in porosity of both the

matrix and the interfacial transition zone. Consequently, considerable

improvements in the ultimate strength and water tightness of concrete are

achievable by incorporation of mineral admixtures. It should be noted that

mineral admixtures are especially effective in increasing the tensile strength of

concrete.

Page | 59

3.8.8 DURABILITY

Designers of concrete structures have been interested in the strength

characteristics of the material; for a variety of reasons, they must now become

durability-conscious. Whereas property constituted, placed and cured concrete

can be durable under most natural and industrial environments, cases of

premature deterioration of concrete structure do occur and they provide valuable

lessons for control of factors responsible for the lack of durability.

Water is generally involved in form of deterioration and, with porous solids the

ease of penetration of water into the solid usually determines its rate of

deterioration. Physical effects that adversely influence the durability of concrete

include surface wear, cracking due to crystallization of salts in pores, and

exposure to temperature extremes such as during frost action or fire. Deleterious

chemical effects include leaching of the cement paste by acidic solution, and

corrosion of the embedded steel in concrete.

Special attention is given to performance of concrete in sea water. As numerous

physical and chemical causes of deterioration occur simultaneously when a

concrete is exposed to seawater, the study of the behaviour of concrete in sea

water provides an excellent opportunity to appreciate the complexity of durability

problems that usually occurs with concrete infield practice.

3.8.8.1 DEFINITION

A long service life is consideration synonymous with durability. As

durability under one set of conditions does not necessarily mean durability under

another, it is customary to include a general reference to the environment when

defining durability. According to ACI Committee 201, durability of Portland

cement concrete is defined as its ability to resist weathering action, chemical

attacks, abrasion, or any other process of deterioration. In other words, a durable

concrete will retain its original form, quality, and serviceability when exposed to

its intended service environment.

No material is inherently durable. As a result of environmental interactions

the microstructure and consequently the properties changes with time. A material

is assumed to reach the end of service life when its properties, under given

conditions of use, have deteriorated to an extent that its continued use is ruled

either unsafe or uneconomical.

Page | 60

3.8.8.2 SIGNIFICANCE

For a variety of reasons, there is a general awareness now that designers of

structures must evaluate the durability characteristics of the construction materials

under consideration as carefully as other aspects, such as mechanical properties

and initial cost. First, there is a better appreciation of the socioeconomic

implications of durability. Increasingly, repair and replacements costs of

structures arising from materials failure have become a substantial portion of the

total construction budget. For example, it is estimated that, in industrially

developed countries, about 40 percent of the total resources of the construction

industry are being applied to repair and maintenance of existing structures and

only 60 percent to new installations. The escalation in replacement costs of

structures and growing emphasis on the life-cycle cost rather than the first cost are

forcing engineers to pay serious attention to durability issues. Next, there is a

realization that a close relation exists between durability of materials and ecology.

Conservation of natural resources by making the construction materials last

longer is therefore an ecological step. Failure of offshore steel structures in

Norway, Newfoundland, and other parts of world has shown that both the human

and economic costs associated with sudden failure of the material of construction

can be very high. Therefore, the uses of concrete are being extended increasingly

to severe environments, such as offshore platforms in the North Sea, and concrete

containers for handling liquefied gases at cryogenic temperatures.

3.8.8.3 GENERAL OBSERVATION

Before a discussion of important aspect of durability of concrete, a few

general remarks on the subject will be helpful. First, water, which is the primary

agent of both creation and destruction of many natural materials, happens to be

central to most durability problems in concrete. In porous solids, water is known

to be the cause of many types of physical processes of degradation. As a vehicle

for transport of aggressive ions, water can be also be a source of chemical

processes of degradation. Second, the physical-chemical phenomena associated

with water transport in porous solids are controlled by the permeability of the

solid. For instance, the rate of chemical deterioration is dependent on whether

chemical attack is confined to the surface of concrete, or whether it is also

happening inside the material. Third, the rate of deterioration is affected by the

type and the concentration of ions present in water, and by the chemical

composition of the solid. Unlike natural rocks and minerals, concrete is

essentially an alkaline material because all of the calcium compounds that

constitute the hydration product of Portland cement are alkaline. Therefore, acidic

waters are particularly harmful to concrete.

Page | 61

Most of our knowledge of physical-chemical processes responsible for

concrete deterioration is derived from case histories of structures in the field; it is

difficult in the laboratory to simulate the combination of long-term conditions

normally present in real life. In practice, deterioration of concrete is seldom due to

a single cause. Usually, at an advanced stage of a material’s degradation more

than one deleterious phenomenon is at work. In general, the physical and

chemical causes of deterioration are so closely intertwined and mutually

reinforcing that separation of the causes from their effects often becomes

impossible. Therefore, a classification of concrete deterioration processes into

neat categories should be treated with some caution. The purpose of such a

classification is to explain systematically and individually the various phenomena.

However, one must not overlook the interactions that occur when several

phenomena are present simultaneously.

3.8.8.4 WATER AS AN AGENT OF DETERIORATION

Concrete is not the only material vulnerable to physical and chemical

processes of deterioration associated with water. Therefore it is desirable to

review, in general, the characteristics of water that make it the principal agent of

destruction of solid materials.

Water in its forms, such as seawater, groundwater, river water, lake water,

snow, ice, and vapour, is undoubtedly the most abundant fluid in nature. Water

molecules are very small and, therefore, are able to penetrate into extremely fine

pores or cavities. As a solvent, water is noted for its ability to dissolve more

substances than any other known liquid. This property accounts for the presence

of many ions and gases in some water which, in turn, become instrumental in

causing chemical decomposition of solid materials. Also, water has the highest

heat of vaporization among the common liquids; therefore, at ordinary

temperatures it has a tendency to exist in the liquid state in porous materials,

rather than vaporizing and leaving the material dry. Furthermore, with porous

solids, internal moisture movements and structural transformations of water are

known to cause disruptive volume changes of many types. For example, freezing

of water into ice, formation of an ordered structure of water inside the fine pores,

development of osmotic pressure due to differences in ionic concentration, and

hydrostatic pressure build-up by differential vapour pressure can lead to high

internal stresses.

Page | 62

3.8.8.5 PERMEABILITY

In concrete, the role of water has to be seen in a proper perspective because,

as a necessary ingredient for the cement hydration reactions and as an agent that

facilitates the mixing of the components of concrete, water is present from the

beginning. Gradually, depending on the ambient conditions and the thickness of a

concrete element, most of the evaporable water in concrete (all the capillary water

and a part of the adsorbed water) is lost, leaving the pores empty or unsaturated.

As it is the evaporable water that is free able and also free for internal movement,

a concrete will not be vulnerable to water-related destructive phenomena if there

is a little or no evaporable water left after drying, and if sub-sequent exposure of

that concrete to the environment does not cause restoration of the pores. The

latter, to a large extent, depends on the hydraulic conductivity, which is also

known as the coefficient of permeability (K). Note that, in concrete technology, it

is a common practice to drop the adjective and refer to K simply as the

permeability.

Garboczi reviewed several theories that attempt to relate the micro structural

parameters of cements products with either infusibility (the rate of diffusion of

ions through water-filled pores) or permeability (the rate of viscous flow of fluids

under pressure through the pore structure). For materials like concrete with

numerous micro cracks, a satisfactory fluid transport property factor is difficult to

determine because of the effect of unpredictable changes in the pore structure

upon penetration of a fluid from outside. Note that the fluid transport property of

the material is changing continuously because of cycles of narrowing and

widening of the pores and micro cracks due to ongoing physical-chemical

interactions between the penetrating fluid and the minerals of the cement paste.

According to Garboczi, the diffusivity predictions need more development and

validation before their practical usefulness can be proven. Therefore, the

discussion in this will be limited to permeability of concrete. However, it is

implied that the term, in a crude sense, refers to the overall fluid transport

property of the material.

Page | 63

Permeability is defined as the property that governs the rate of flow of a fluid

into a porous solid. For steady-state flow, the coefficient of permeability (K) is

determined form DaGCAy’s expression:

Where

= rate of fluid flow

µ = viscosity of the fluid

∆H = pressure gradient

A = surface area

L = thickness of the solid

The coefficient of permeability of a concrete to gases and water vapor is much

lower than the coefficient for liquid water; therefore, tests for measurement of

permeability are generally carried out using water that has no dissolved air.

Unless otherwise stated, the data in this chapter pertain to permeability of

concrete to pure water. Due to their interaction with cement paste, the

permeability values for solutions containing ions would be different from the

water permeability.

3.8.8.6 CLASSIFICATION OF THE CAUSES OF

CONCRETE DETERIORATION

The physical causes of concrete deterioration grouped into two categories: (a)

surface wear or loss of mass due to abrasion, erosion, and cavitations; (b)

cracking due to normal temperature and humidity gradients, crystallization of

salts in pores, structural loading, and exposure to temperature extremes such as

freezing of fire. The chemical cause of deterioration into three categories: (1)

hydrolysis of the cement paste components by soft water; (2) cat ion-exchange

reactions between aggressive fluids and the cement paste; and (3) reactions

leading to formation of expansive products, such as in the case of sulphate attack,

alkali-aggregate reaction, and corrosion of reinforcing steel in concrete.

It should be emphasized again that the distinction between the physical and

chemical causes of deterioration is purely arbitrary; in practice, the two are

frequently superimposed on each other. For example, loss of mass by surface

wear and cracking increases the permeability of concrete, which then becomes the

Page | 64

primary cause of one or more processes of chemical deterioration. Similarly, the

detrimental effects of the chemical phenomena are physical; for instance, leaching

of the components of hardened cement paste by soft water or acidic fluids would

increase the porosity of concrete, thus making the material more vulnerable to

abrasion and erosion.

Page | 65

CHAPTER 4

RESEARCH PROCEDURE

4.1 INTRODUCTION

For designing of M-25 Grade of concrete. It was necessary that to performed

various types of tests on cement concrete and their ingredient materials. To obtain

cement concrete and its ingredients actual testing values (available in our laboratory)

I was perform tests on cement concrete, fine aggregates, coarse aggregates, cement,

and on Granite Course Aggregate s. I performed lab tests of cement to get actual

values of fineness modulus of cement, consistency of cement, Initial & final setting

time of cement and compressive strength of cement. For fine aggregates, I performed

tests like specific gravity of fine aggregate, moisture content, silt content, water

absorption of fine aggregate, bulking of fine aggregate, fineness modulus of fine

aggregate similarly for coarse aggregate, I performed tests like specific gravity of

coarse aggregate, moisture content, silt content, water absorption and fineness

modulus of coarse aggregate. After lab testing of ingredients materials of concrete I

performed workability test on concrete which was done with the help of Vee-Bee

apparatus or slump cone apparatus. This test was performed to know either concrete

was workable or non-workable in laboratory conditions as well as in field

conditions.

Laboratory Tests results were help me to design M-25 grade of Mix with the

help of IS 10262:2009. After designed M-25 grade of cement concrete, I got the

value of cement, fine aggregates, coarse aggregates, Granite Course Aggregates, and

water for making of one cubic meter of cement concrete. With the help of these

values I casted cement concrete cubes of size 15×15×15 cm3at various percentage of

granite course aggregates (GCA as total volume of course aggregates), then I was

left those cement concrete cube specimens for submerge curing of 7 days & 28 days

in soft water. After curing I was take dry weight of cubes to know the difference in

bulk and dry density of cubes due to change of percents of Granite Course Aggregate

into concrete.

In compressive strength test I tested various percentage of GCA cubes such

as 00%, 10%,20%,30%,40% of GCA(GCA as total volume of natural course

aggregates)to know its compressive strength behavior either it was increasing or

decreasing.

Page | 66

4.2 CEMENT TESTS

4.2.1 SPECIFICATION OF CEMENT

In testing I was used Portland-Pozzolana Cement with the following qualities

as per IS 1489 (part 1) : 1991 which are as :

(a) Fineness. When tested by the air permeability method as per IS 4031 (part 2)

: 1988, the specific surface of Portland-pozzolana cement shall be not less than 300

m3/kg.

(b) Soundness. When tested by “Le-chateliers” method and autoclave test as per

IS 4031 (part 3) : 1988, underrated Portland-pozzolana cement shall not have an

expansion of more than 10 mm and 0.8 percent respectively.

(c) Setting Time. The setting time of Portland-pozzolana cement, when tested

by the vicat apparatus method as per IS 4031 (part 5) : 1988, shall be as follows:

Initial setting time 30 min, Min

Final setting time 600 min, Max

(d) Compressive Strength. The average compressive strength of not less than

three mortar cubes (area of face 50 cm3) composed of one part of cement, three parts

of standard sand by mass, and p/4 + 3.0 percent (of combined mass of cement and

sand) water, and prepared, stored and tested in the manner as per IS 4031 (part 6) :

1988 shall be as follows:

a. At 72 ± 1 h 16 MPa, Min

b. At 168 ± 2 h 22 MPa, Min

c. At 672 ± 4 h 33 MPa, Min

NOTES

1. P is the percentage of water required to produce a paste of standard consistency.

2. Standard sand shall be conform to IS 650 : 1966.

(e) Drying Shrinkage. The average drying shrinkage of mortar bars prepared

and tested in accordance with IS 4031 (part 10) : 1988 shall not be more than 0.15

percent.

Page | 67

4.2.2 FINENESS TEST (DRY SIEVING METHOD)

Procedure:(a)Take IS 90 micron sieve and find out empty weight (W1)

(b) Take known weight of dry cement (say W gm).

(c) Put the cement on a IS Sieve 90 micron in size.

(d) Sieve about 10 minutes.

(e) Take the weight of the sieve with residue (W2).

(f) Calculate fineness as

× 100%

Results: Weight of 90 micron sieve = 217 grams

Weight of cement = 100 grams

Weight of cement retain on sieve = 2 grams

Fineness =

× 100%

Fineness = 4%

Hence percentage of total residue on 90 Micron IS sieve is less than 10% of total

mass of cement taken for test so this sample of cement is OK for further testing

purpose.

4.2.3 CONSISTENCY OF CEMENT

Procedure: (a) Prepare a paste of weighed quantity of cement (approx. 400 gms) with

weighed quantity of water (start from 20%–25%) taking care that mixing (gauging)

remains between 3 to 5 minutes and mixing shall be completed before any signs of

setting becomes visible.

(b) Fill the Vicat mould with the paste, mould should rest on non-porous base.

Page | 68

(c) Place the mould under Vicat’s apparatus. The plunger attached to a movable rod

is gently lowered on the paste.

(d) Settlement of plunger is noted, penetration from bottom is equal to the difference

of mould height and settlement of plunger. If penetration of the plunger is within 5-

7mm from bottom, then water added is correct. Otherwise, water is added and

process is repeated

.

Results: Weight of total cement taken for test= 400 gms

S.N. Parentage Water

(%)

Penetration from

bottom (mm)

1. 25% 32

2. 30% 25

3. 31% 18

4. 32% 12

5. 33% 7

Table 2: Reading values of Standard Consistency

From table number 5 the penetration of 5 to 7 mm was got on 33% or 132 ml of

water by weight of total mass of cement sample (400 gms).

4.2.4 INITIAL SETTING TIME

Procedure: (a)Take approx. 400 gms of dry cement and add 0.85P where P is the weight

of water for standard consistency to make paste.

(b) Fill the mould with paste, attach square needle to moving rod of apparatus.

(c) The needle is quickly released and is allowed to penetrate cement paste.

(d) Note down the time and penetration from bottom.

(e) Find Initial setting time (minutes) when penetration of needle (from bottom) is

within 5±0.5 mm.

Page | 69

Result: Consistency of water (P) = 132 ml

As per Formula (IS 4031(part 5):1988) = 0.85×P = 0.85×132 = 112.2 ml

S.N. Time

(min.)

Penetration from bottom

(mm)

1. 00 00

2. 10 01

3. 20 02

4. 30 02

5. 35 03

6. 40 04

7. 45 04

8 50 05

Table 3: Initial Setting Time

From Table number 6 the value of penetration of needle (from bottom) was 5 mm

(as per IS 4031(part 5):1988) at time of 45 minutes so the value of initial setting time

for cement paste was 45 min.

4.2.5 COMPRESSIVE STRENGTH OF CEMENT

Procedure:

(a) Take 185 grams of cement and 555 grams of standard sand (ratio of cement to

sand is 1:3) and mix them dry thoroughly.

(b) Add water quantity (P/4 + 3.0) % (P is the percentage of water required to

produce a paste of standard consistency determined) of combined weight of cement

and sand. Mix the three ingredients thoroughly for a minimum of 3 minutes and

maximum of 4 minutes to obtain a mix of uniform colour.

(c) Fill the mould with entire quantity of mortar using a suitable hopper attached to

the top of the mould for facility of filling and vibrate it for 2 minutes at a specified

speed of 12000 ± 400 per minutes to achieve full compaction.

(d) Remove the mould from the machine and keep it in a place with temp of 27 ±

2°C and relative humidity of 90% for 24 hours.

(e) Prepare at least 6 cubes. At the end of 24 hours remove the cube from the mould

and immediately submerge in fresh clean water. The cube shall be taken out of the

water only at the times of testing.

Page | 70

(f) Take the cube out of water at the end of three days with dry cloth. Measure the

dimension of the surface (A) in which the load is to be applied. Let be ‘L’ and ‘B’

dimensions respectively.

(g) Place the cube in compressive testing machine and apply the load uniformly.

Note the load at which the cubes fail, let it be ‘P’, therefore compressive strength

F = P/A (N/mm2).

Result: Amount of Cement (passing from 90 micron IS Sieve) = 185 gms

Amount of Standard sand (passing form 4.75 mm IS sieve & retaining on 90

micron IS Sieve) = 555 gms

Percentage of Water = [ P/4 + 3 ] = [32/4 + 3] = 11.25%

Total weight of sample = 740 gms

Total weight of water require for mixing of cement & sand = 81.4 ml

REFERANCE TESTING MATERIAL FOR GRANITE COARSE

AGGREGATE

Table 4: Compressive strength of Cement cube

Note: Average Value of 28 days compressive strength was used in Mix design to

select Water-cement ratio of design mix which was design by IS 10262 : 1982.

S.N. 7 Days 28 Days

Load

(N)

Comp. Strength

(N/mm2)

Load (N) Comp. Strength

(N/mm2)

1. 96000 19.2 191000 31.7

2. 95000 19.0 189000 31.9

3. 97000 19.4 193000 31 .6

Avg. Comp. Strength 19.2N/mm2 Avg. Comp. Strength 31.64N/mm

2

Page | 71

Fig 17(a): Casting of Cement Cubes Fig 17(b): Dry Cement

Cubes

.

Fig 17(c): Cement Cube Vibrator Machine

Page | 72

Fig 17(d): Cement Cubes Testing in Compression Testing Machine

4.3 FINE AGGREGATE TESTS

4.3.1 BULKING OF FINE AGGREGATE

Procedure: (a) Put sufficient quantity of the sand into a container until it is about

one-third full.

(b) Level off the sand and measure the height (h1) by pushing a steel rule vertically

down through the sand at the middle to the bottom. Measure the weight of the soil.

(c) Add 4% of water; mix it thoroughly in the container. Smooth and level the top

surface measure the height (h2) of soil. Find the height percentage increment.

(d) Repeat the same procedure with increasing amount of water by 2% until

percentage increment of sand height is reduced.

Result: Initial height of sand (h1) = 145 mm

Final height of sand (h2) = 200 mm

Percentage of Bulking =

– × 100

Percentage of Bulking =

– × 100

Percentage of Bulking = 37.94%

Page | 73

4.3.2 SPECIFIC GRAVITY OF FINE AGGREGATE

Procedure: (a) Take a clean, dry pycnometer, and find its weight with its cap and

washer (W1).

(b) Put about 200 g to 400 g of sand in the pycnometer, and find its weight (W2).

(c) Fill the Pycnometer and fill in sand with distilled water and measure its weight

(W3).

(d) Empty the pycnometer, clean it thoroughly, and fill it with clean water only to

the hole of the conical cap, and find its weight (W4).

(e) Repeat the same procedure at least for three different samples.

Result:Dry pycnometer weight with cap and washer(W1) = 303 gms

S

.

N

.

Wt

. of

em

pty

Py

cn.

(W

1)

(g)

Wt.

of

Pycn.

+ dry

aggre

gate

(W2)

(g)

Wt.

of

Pycn.

+ dry

aggre

gate

+

water

(W3)

(g)

Wt.

of

Pyc

n.

+w

ater

(W

4)

(g)

Specific

Gravity of fine

Aggregate

1. 303 503 1324 1202 2.645

2. 303 503 1321 1202 2.622

3. 303 503 1326 1202 2.632

Average S.G. = 2.62

Table 5: Specific Gravity of Fine Aggregate

Page | 74

4.3.3 FINENESS MODULUS OF FINE AGGREGATE

Procedure: (a) The sample shall be brought to an air-dried condition before

weight and sieving.

(b) Measure 500 grams of fine aggregate.

(c) Arrange sieve in descending order of size from the top.

(d) Put the fine aggregate in sieve 4.75 mm, and shake for 10 minutes. Material shall

not be forced though the sieve by hand pressure.

(e) After 10 minutes stop the shaker and separate the sieve 4.75 mm from the

apparatus, then with the help of balance measure the weight of retained particles,

note this weight in the table.

(f) Measure the weight of the particles retained in each sieve and notes them in the

table.

(g) Calculate the percentage of weight retained on each sieve.

(h) Find the percentage of the weight which has passed through each sieve.

Result: Total weight of Fine Aggregate sample taken = 500 grams

S.N

.

IS

Sieve

Size

(mm

& µ)

(1)

Weight

retained

(gms)

(2)

Cumulativ

e weight

retained

(gms)

(3)

Cumulativ

e

percentage

weight

retained

(4)= 100-

col(3)

Percentage

finer

1. 4.75

mm

00 00 0.0 % 100 %

2. 2.36

mm

22 22 4.4 % 95.6 %

3. 1.18

mm

70 92 18.4 % 81.6 %

4. 600 µ 74 166 33.2 % 66.8 %

5. 300 µ 90 256 51.2 % 48.8 %

6. 150 µ 100 356 71.2 % 28.8 %

7. 75 µ 104 460 92.0 % 8 %

8. PAN 40 500 100.00 % 0 %

Page | 75

Table 9: Fineness Modulus of Fine Aggregate

Fineness Modulus =

Fineness Modulus =

Fineness Modulus = 2.57

Note: Value of fineness Modulus is equal to 2.57 conforming to zone III for this

type of fine Aggregate (by IS 383 : 1970, page-11

4.3.4 MOISTURE CONTENT OF FINE AGGREGATE

Procedure: (a) Taking 500 gms (W1) of fine aggregate or sand sample, wash

thoroughly to remove dust.

(b)Then place the sample in a container, put in hot air oven for 24 hours, at a

temperature of 100 to 110°C. After 24 hours, measure the weight of air dried sample

(W2).

(c) Put the Values of W1 and W2 into formula of moisture content.

Moisture Content =

× 100%

Result: Before washed fine aggregate Sample weight (W1) = 500 gms

After washed oven dried fine aggregate sample weight (W2 = 496.5 gms

Moisture Content =

× 100%

Moisture Content =

× 100%

Moisture Content = 0.6 %

Hence Moisture content is in permissible limit as per IS 2386 (part 3) : 2002 so this

fine aggregate is suitable for further tests.

Page | 76

4.3.5 WATER ABSORPTION OF FINE AGGREGATE

Procedure: (a) Taking 500 gms of fine aggregate or sand sample, wash

thoroughly to remove dust. Then place the sample in a container, put in hot air oven

for 24 hours, at a temperature of 100 to 110°C.

(b) Take out oven dried aggregate and immerse in water for 24 hours at a

temperature between 22°C and 32°C with a cover of at least 5 cm of water above the

top of the basket.

(c) Take out the immersed aggregate and place in a dry cloth. It shall then be spread

out, and best exposed to the atmosphere away from direct sunlight or any other

source of heat for not less than 10 minutes, or until it appears to be completely

surface dry. Measure the weight of aggregate (W1).

(d) The aggregate shall then be placed in the oven in the shallow tray, at a

temperature of 100°C to 110°C and maintained at this temperature for 24 hours.

After 24 hours, it shall then be removed from the oven, cooled in the airlight

container and weight (W2).

Results: Washed fine aggregate oven dried sample weight (W1) = 500 gms

Oven dried, air cooled fine aggregate sample weight (W2) = 498 gms

Water Absorption =

× 100%

Water Absorption =

× 100%

Water Absorption = 1.25 %

4.4 COARSE AGGREGATE

4.4.1 SPECIFIC GRAVITY OF COARSE AGGREGATE

Procedure: (a) A sample of not less than 2000 g of the aggregate shall be tested.

Aggregates which have been artificially heated shall not normally be used. If such

material is used the fact shall be stated in the report.

(b) The sample shall be thoroughly washed to remove finer particles and dust,

drained and then placed in the wire basket (mesh not more than 6.3 mm) and

immersed in distilled water at a temperature between 22°C and 32°C with a cover of

at least 5 cm of water above the top of the basket.

Page | 77

(c) Immediately after immersion the entrapped air shall be removed from the sample

by lifting the basket containing it 25 mm above the base of the tank and allowing it

to drop 25 times at the rate of about one drop per second. The basket and aggregate

shall remain completely immersed during the operation and for a period of 24 ± ½

hours afterwards.

(d) The basket and the sample shall then be jolted and weighted in water at a

temperature of 22°C to 32°C, if it is necessary for them to times as described above

in the new tank before weighting (weight A1).

(e) The basket and the aggregate shall then be removed from the water and allowed

to drain for a few minutes, after which the aggregate shall be gently emptied from

the basket on to one of the dry clothes, and the empty basket shall be returned to the

water, jolted 25 times and weighted in water (A2).

(f)The aggregate placed on the dry cloth shall be gently surface dried with the cloth,

transferring it to the second dry cloth when the first will remove no further moisture.

It shall them be spread out not more than one stone deep on the second cloth, and lest

exposed to the atmosphere away from direct sunlight or any other source of heat for

not less than 10 minutes, or until it appears to be completely surface dry (which with

some aggregate may take on hour or more). The aggregate shall be turned over at

least once during this period and a gentle current of unheated air may be used after

the first ten minutes to accelerate the drying of difficult aggregates. The aggregate

shall then be weighed (Weight B).

(g)The aggregate shall then be placed in the oven in the shallow tray, at a

temperature of 100°C to 110°C and maintained at this temperature for 24 ± ½ hours.

It shall then be removed from the oven, cooled in the airtight container and weighed

(weight C).

Result: Weight of saturated aggregate in water ({A1 – A2} = A) = 1314 gms.

Weight of saturated surface dried Aggregate in air (B) = 2010 gms.

Weight of oven-dried aggregate in air (C) = 2000 gms.

Specific Gravity =

Specific Gravity =

Specific Gravity = 2.65

NOTE: Testing of Specific Gravity of Coarse Aggregate was done as per IS 2386

(part 3):2002. Tests of Specific Gravity of coarse aggregate were repeated for three

samples, in these samples values were same as above value of S.G. (±0.009).

Page | 78

4.4.2 FINENESS MODULUS OF COARSE AGGREGATE

Procedure: (a) The sample shall be brought to an air-dried condition before

weight and sieving.

(b) Measure 8000 grams of coarse aggregate.

(c) Arrange sieve in descending order of size from the top.

(d) Put the coarse aggregate in sieve 40 mm, and shake for 10 minutes. Material

shall not be forced though the sieve by hand pressure.

(e) After 10 minutes stop the shaker and separate the sieve 40 mm from the

apparatus, then with the help of balance measure the weight of retained particles,

note this weight in the table.

(f) Measure the weight of the particles retained in each sieve and notes them in the

table.

(g) Calculate the percentage of weight retained on each sieve.

(h) Find the percentage of the weight which has passed through each sieve.

Result: Total weight of Fine Aggregate sample taken = 8000 grams

S.N. IS

Sieve

Size

(mm

)

(1)

Weight

retained

(gms)

(2)

Cumulativ

e weight

retained

(gms)

(3)

Cumulative

percentage

weight

retained

(4)= 100-

col(3)

Percentage

finer

1. 40

mm

6400 6400 80% 100 %

2. 20

mm

240 6640 83% 44.5 %

3. 16

mm

160 6800 85% 33.37 %

4. 12.5

mm

160 6960 87% 26.94 %

5. 10

mm

480 7440 93% 13.5 %

6. 4.75

mm

480 7920 99% 0.125 %

7. PAN 80 8000 100 % 00 %

Table 10: Fineness Modulus of Coarse Aggregate

Page | 79

Fineness Modulus =

Fineness Modulus =

Fineness Modulus = 6.30

Note: Value of fineness Modulus is equal to 4.82 conforming to All in Aggregate

(by IS 383 : 1970, page-11).

4.4.3 WATER ABSORPTION OF COARSE AGGREGATE

Procedure: (a) Taking 1000 grams of coarse aggregate or sand sample, wash

thoroughly to remove dust. Then place the sample in a container, put in hot air oven

for 24 hours, at a temperature of 100 to 110°C.

(b) Take out oven dried aggregate and immerse in water for 24 hours at a

temperature between 22°C and 32°C with a cover of at least 5 cm of water above the

top of the basket.

(c) Take out the immersed aggregate and place in a dry cloth. It shall then be spread

out, and best exposed to the atmosphere away from direct sunlight or any other

source of heat for not less than 10 minutes, or until it appears to be completely

surface dry. Measure the weight of aggregate (W1).

(d) The aggregate shall then be placed in the oven in the shallow tray, at a

temperature of 100°C to 110°C and maintained at this temperature for 24 hours.

After 24 hours, it shall then be removed from the oven, cooled in the air light

container and weight (W2).

Page | 80

Results: Washed coarse aggregate oven dried sample weight (W1) = 1000 gms

Oven dried, air cooled coarse aggregate sample weight (W2) = 995 gms

Water Absorption =

× 100%

Water Absorption =

× 100%

Water Absorption = 0.52%

4.4.4 MOISTURE CONTENT OF COARSE AGGREGATE

Procedure: (a) Taking 1000 gms (W1) of coarse aggregate or sand sample, wash

thoroughly to remove dust.

(b)Then place the sample in a container, put in hot air oven for 24 hours, at a

temperature of 100 to 110°C. After 24 hours, measure the weight of air dried sample

(W2).

(c) Put the Values of W1 and W2 into formula of moisture content.

Moisture Content =

× 100%

Result: Before washed coarse aggregate Sample weight (W1) = 1000 gms

After washed oven dried coarse aggregate sample weight (W2) = 994 gms

Moisture Content =

× 100%

Moisture Content =

× 100%

Moisture Content = 0.6 %

Hence Moisture content is in permissible limit as per IS 2386 (part 3) : 2002 so this

coarse aggregate is suitable for further tests.

Page | 81

4.5 CEMENT CONCRETE

4.5.1 WORKABILITY TEST

Procedure:

(a) Take Mix proportion by weight as per mix design; use water cement ratio as per

mix design.

(b) Clean the internal surface of the mould thoroughly and it should be freed from

superfluous moisture.

(c) Place the mould on a smooth, horizontal, rigid and non-absorbent surface, such as

a carefully leveled metal plate, and fixed it.

(d) Fill the mould with freshly prepared concrete in four layers and compact each

layer by temping with twenty five stokes of temping rod. After the top layer has been

rodded, struck off the excess concrete, make level with a trowel or tamping rod.

(e) Carefully lift the mould vertically upwards, so as not disturb the concrete cone.

(f) Determine the level difference between the height of the mould and the highest

point of the subsided concrete.

(g) Height difference in mm is taken as Slump of concrete.

Result: Mix Proportion of M-25 grade of concrete for 1 m3

quantity of cement

concrete.

Water Cement Fine aggregate Coarse

aggregate

202.4 446.00 632 1151

0.454 1 1.417 2.581

Height of Slumps: (i) First sample of M-25 grade of concrete = 84 mm

(ii) Second sample M-25 grade of concrete = 78 mm

(iii) Third sample M-25 grade of concrete = 75 mm

Average Value of slump = 79.00 mm

Hence this Mix design is OK for casting of cement concrete cubes with Granite Course

Aggregate ..

Page | 82

4.5.2 COMPRESSIVE STRENGTH OF CONCRETE CUBE

Procedure:

(a) Take five cube moulds for each GCA mix. Assemble the mould

with base plate so that it is rigidly held together. Clean the inside of the mould and see

that joints (at the edges) are perfectly tight.

(b)Pour properly mixed concrete for the given mix to the cube moulds.

(c) Compaction was done with the help of Vibrating Table.

(d) Level the concrete at the top of the mould by means of trowel and give proper

identification mark of the specimen.

(e) Keep the cubes in laboratory for 24 hours cover by wet gunny bags.

(f) After 24 hours, dismantle the plates of cube mould and take out the hardened concrete

cubes carefully so that edges of specimens are not damaged.

(g) Provide the submerged curing to cement concrete cubes at duration or period of 7

days and 28 days.

(h)Test the Cube into computerized compression testing machine of various percentage

of GCA at 7 days and 28 days.

Fig. 18 (a) Fig. 18 (b) Fig. 18 (c)

Fig. 18 (a) : Weight Machine, Cement

Fig. 18 (b) : Fine aggregate

Fig. 18 (c) : Coarse Aggregate

Page | 83

Fig. 18 (d) Fig. 18 (e) Fig. 18 (f)

Fig. 18(d) : Tightening of Mould

Fig. 18 (e) : Compacting concrete by Vibrating Table

Fig. 18(f) : Marking on casted cubes

Fig. 19 (a) : Freshly Casted Cement Concrete Cubes

Page | 84

Fig. 19 (c) Fig. 19 (d)

Fig. 19 (c) : Air Dried Cement Concrete Cubes

Fig. 19 (d) : Computerized Compression Testing Machine

Results: Compressive strength testing results with Graphs and tables are shown in

Chapter 5 in detail.

Page | 85

Amount of raw material require for concrete cubes casting are as follows in

Table Number: - 6 (a) to 6 (e).

S.N.

1.

0.00% G.C.A

Name of Material Material require for

casting one cube

(gms)

Material require for

casting six cubes

(gms)

Cement 2,286 13716

Fine Aggregate 3,360 20160

Coarse Aggregate 5371.44 32228.64

Water 982ml 5897ml

GCA 00 00

Total 12000 72000

Table 6 (a): Calculated Material for 00% of GCA

S.N.

2.

10% G.C.A.

Name of Material Material require for

casting one cube

(gms)

Material require for

casting six cubes

(gms)

Cement 2286 13716

Fine Aggregate 3360 20160

Coarse Aggregate 4834 29004

Water 982.8ml 5897ml

GCA 537 3222

Total 12,000 72,000

Table 6 (b): Calculated Material for 10% of GCA

S.N.

3.

20% G.C.A

Name of Material Material require for

casting one cube

(gms)

Material require for

casting six cubes

(gms)

Cement 2286 5897

Fine Aggregate 3360 20160

Coarse Aggregate 4297 26,622

Water 982.8ml 5897ml

GCA 1074 6444

Total 12000 72000

Page | 86

Table 6 (c): Calculated Material for 20% of GCA

S.N.

4.

30% G.C.A

Name of Material Material require for

casting one cube

(gms)

Material require for

casting six cubes

(gms)

Cement 2286 13716

Fine Aggregate 3360 20160

Coarse Aggregate 3760 22560

Water 982.8 5897

GCA. 1611 9666

Total 12000 72000

Table 6 (d): Calculated Material for 30% of GCA

S.N.

5.

40% G.C.A.

Name of Material Material require for

casting one cube

(gms)

Material require for

casting six cubes

(gms)

Cement 2286 13716

Fine Aggregate 3360 20160

Coarse Aggregate 3224 26,622

Water 982.8ml 5897ml

GCA 2148 12888

Total 12000 72000

Table 6 (e): Calculated Material for 40% of GCA

Page | 87

4.5.3 MIX DESIGN FOR M-30 GRADE OF CONCRETE

4.5.3.1 TARGET MEAN STRENGTH

fck' = fck + 1.65s

Where,

fck' = Target mean compressive strength at 28 days in N/mm2

fck = Characteristics compressive strength at 28 days in N/mm2

s = Standard Deviation

fck' = 25 + (1.65 x 4)

fck' = 31.6 N/mm2

4.5.3.2 SELECTION OF WATER CEMENT RATIO

From fig 2 of IS 10262:1982 the target mean strength of 31.6 N/mm2

which

is for C line. It gives water cement ratio of 0.43 which is less than 0.45

prescribed for severe exposure condition in IS 456:2000.

4.5.3.3 SELECTION OF WATER & SAND CONTENT

Form table 4 for 20mm nominal maximum size of aggregate & sand

conforming to grading zone III, water for per cubic meter of concrete 186 Kg

& sand content as percentage of total aggregate by absolute volume of 35

Percentage.

Page | 88

For changing in value of water cement ratio & compaction factor,

sand belong to zone III the following adjustment require (From Table 6 of IS

10262:1982) :-

Serial

No.

Change in condition Adjustment

Water

content

Percentage of

sand in total

aggregate

1. For decrease in water cement ratio 0.6 to 0.43 - -3.4%

2. For increase in compaction factor 0.8 to 0.9 +3% -

3. For sand conforming to zone III of table 4 of IS383

:1970

- -1.5%

TOTAL +3% -4.9%

...Require sand content as percentage of total aggregate by absolute volume = 35% - 4.9%

...Require sand content as percentage of total aggregate by absolute volume= 30.1%

... Require water content = 186 + [(186 x 3) / 100]

... Require water content = 186 + 5.58

... Require water content = 191.6 L/m

3

4.5.3.4 DETERMINATION OF CEMENT CONTENT

Where :- water cement ratio = 0.43

water content = 191.6 L/m3

Page | 89

Cement content = 445.58 Kg/m3

From IS 456:2000 for M-25 (table 5) minimum cement content for R.C.C. in severe

exposure was 320 Kg/m3.

445.58 > 320 Kg/m3

Hence O.K

4.5.3.5 DETERMINATION OF COARSE AGGREGATES & FINE

AGGREGATES

Form IS 10262:1982 Table Number 3 the entrapped air in 20 mm maximum

size of aggregate in wet concrete is 2%. In mix taking this into account.

Where V = Absolute volume of fresh concrete which is equal to gross

volume (m3) minus the volume of entrapped air.

W = Mass of water (Kg) per m3 of concrete

C = Mass of cement (Kg) per m3 of concrete

Sc = Specific Gravity of cement

p = Ratio of fine aggregate to total aggregate by absolute volume

fa , Ca =Total mass of fine aggregates & coarse aggregates (Kg) per m3 of

concrete respectively.

Page | 90

Sfa , Sca = specific gravity of saturated surface dry fine aggregate & coarse

aggregate respectively.

or fa = 499.44 Kg/m3

Ca = 1299.07 Kg/m3

The Mix proportion then become

Water Cement Fine aggregate Coarse

aggregate

191.6 446.00 500 1300

0.43 1 1.211 2.920

4.5.3.6 CORRECTION OF WATER

In this mix Design I used Granite Course Aggregate and natural course aggregate

which

give approx. water absorption of 0.6% of its total weight in both cases.

For 1 m3

quantity:-

Amount of water absorbed by fine aggregate in percentage = 0.6% x 500

Amount of water absorbed by fine aggregate in percentage = 0.006 x 500

Amount of water absorbed by fine aggregate in percentage = 3 Kg

Amount of water absorbed by coarse aggregate in percentage = 0.6% x 1300

Amount of water absorbed by coarse aggregate in percentage = 0.006 x 1300

Amount of water absorbed by coarse aggregate in percentage = 7.8 Kg

Total amount of water absorbed by fine aggregate & coarse aggregate= 10.8

Kg

Page | 91

Actual water quantity require for M-30 Mix = 191.6+10.8 = 202.4 Kg/m3

4.5.3.7 CORRECTIONS IN MIX DESIGN

As I used Granite Course Aggregate concrete so I need to increase fine aggregate

upto 8.0% of total amount of aggregate.

Absolute volume of fine aggregate = 30.1%

Absolute volume after adding fine aggregate = 30.1%+08% = 38.1%

Actual quantities of Coarse Aggregates & Fine Aggregates

fa = 655 Kg/m3

Ca = 1048 Kg/m3

Page | 92

MIX PROPORTION

The designed proportion by mass on the basis of proportion of the available ingredient of

concrete is as follows:-

GRADE M 25

INGRADIENT WATER CEMENT FINE

AGGREGATE

COARSE

AGGREGATE

PROPORTION

BY MASS

0.40 1.00 1.45 2.95

PROPORTION

BY WEIGHT

419 167 607.55 1240

Following quantities of different material are required for one cum of concrete.

Cement 50 kg

Water 20 kg

Fine aggregate 72.5 kg (Saturated surface dry)

Course aggregate 147.5 kg (Saturated surface dry)

INGRADIENT WATER CEMENT FINE

AGGREGATE

COARSE

AGGREGATE

PROPORTION

BY MASS

0.40 1.00 1.45 2.95

PROPORTION

BY WEIGHT

419 167 607.55 1240

Page | 93

There mixing 10 % GA By volume of total coarse aggregate .The volume of required

aggregate is 104.8kg.For requiring 20 % of the total volume of coarse aggregate is

209.6 Kg. For replacement of 30% of coarse aggregate the volume of required

aggregate 314.4 kg. For requiring 40% replacement the volume of required aggregate is

419.2 kg.

Page | 94

CHAPTER 5

RESULT AND DISCUSSION

5.1 INTRODUCTION

In this chapter results obtained by Mix design of M-25 Grade of concrete from

chapter 4.Cement concrete cubes prepared and casted as per chapter 4 (process of

cube casting was mention in chapter 4).Results and values of chapter 4 presented and

discussed in the following section:

Decrease of dead weight of cement concrete samples of various percentages

of Granite coarse aggregate (GCA amount by total volume of cement in

design mix).

Decrease in Bulk density and Dry density of cement concrete due to Granite

concrete aggregate in cement concrete.

The increase of compressive strength of cement concrete at various

percentages of Granite coarse aggregate in cement concrete at 7 & 28 days

cube test.

Maximum safe percentage of Granite coarse aggregate in cement concrete.

In this chapter result obtained by mix design of M25 grade of concrete.

Cement concrete cube are prepared and casted.

Result and values are represented here.

Workability

Workability for all the mixes are same however. The water requirement for

all the mixes is different and specially for the mix with Granite Course

Aggregate coarse the water once mix start absorbing water by Granite

Course Aggregate and slump goes reducing with time however super

plasticizer can be used .

Compressive strength

The important aspect the designing and its getting accepted is the

compressive strength. In the given set of mixes and attempt was made to

check the acceptability of Granite Course Aggregate for M25 grade of

concrete. The table show the value of compressive strength of various mix.

The compressive strength rate of natural aggregate is higher than that of

Granite Course Aggregate. However Reason of decrease of the strength is

due to surface of Granite Course Aggregate .When the water absorbed by the

aggregate more space left by the water being absorbed can be occupied by

aggregate in a unit volume hence the density of Granite concrete is lower.

Page | 95

The table shows the result of compressive strength of concrete with

replacement of 0%, 10%,20%,30% and 40% Replacement of Granite coarse

aggregate. From the result compressive strength of concrete with replacement

of 30% is highest. The compressive strength of Granite concrete with 30%

replacement of GCA is close proximity with that of the control concrete.

5.2 Increase of the compressive strength of cement concrete at

various percentage of Granite course aggregate.

In cement concrete characteristics compressive strength is a very important

parameter to access characteristics properties of concrete. As I know that

concrete is strong in compression but very weak in tension, so I performed

concrete’s compressive strength test on M-25 Grade of concrete. In

compressive strength test I preparedM-25 grade of cement concrete cubes of

various percentages of Granite course aggregate for testing of 7 days and 28

days concrete cubes test after curing. Total thirty specimen cubes of M-25

grade of concrete were casted to perform 7 days and 28 days test. For conduct

this test I prepared cubes of various percentages of granite course aggregate

such as 00% GCA, 10% GCA, 20% GCA, 30% GCA, 40% GCA. Three

cubes of each of sample of different amount of GCA were prepared and cured

then tested for7 & 28 days compression strength test by computerized

compression testing machine. Results of various percentages of granite

course aggregate to total volume of natural aggregate are as follows:-

Page | 96

(a) All test results data for 7 days testing.

S.N % of

GCA

in

conc.

Cube

name

Date of

Manufacturing

of concrete

cubes

Date of

Testing of

concrete

cubes

Crushing

load

(KN)

Stress

(N/mm2)

Average

Stress

(N/mm2)

Percentage

of increase

in strength

1.

0.00 %

C1 15/Apr/2015 22/Apr/2015 450 20.00

19.95

Increase of

00 %

Strength

C2 15/Apr/2015 22/Apr/2015 447 19.956

C3 15/Apr/2015 22/Apr/2015 449 19.86

2.

10%

C1 15/Apr/2015 22/Apr/2015 462 20.53

20.5

Increase of

1.92 %

Strength

C2 15/Apr/2015 22/Apr/2015 463 20.58

C3 15/Apr/2015 22/Apr/2015 461 20.52

3.

20% C1 15/Apr/2015 22/Apr/2015 491 21.82

21.75

Increase of

2.92 %

Strength

C2 15/Apr/2015 22/Apr/2015 488 21.73

C3 15/Apr/2015 22/Apr/2015 489 21.69

4.

30% C1 15/Apr/2015 22/Apr/2015 503 22.36

22.36

Increase of

3.80 %

Strength

C2 15/Apr/2015 22/Apr/2015 502 22.40

C3 15/Apr/2015 22/Apr/2015 504 22.31

5.

40% C1 15/Apr/2015 22/Apr/2015 485 21.56

21.54

Decrease

of 1.66 %

Strength

C2 15/Apr/2015 22/Apr/2015 484 21.54

C3 15/Apr/2015 22/Apr/2015 485 21.51

Table 7: 7 Days GCA(M-25 Grade concrete) cubes, Crushing value,

Stress in concrete, average stress in concrete and percentage of increase or

decrease in Compressive strength of M-25 grade concrete.

Page | 97

Graph 1 : 07 Days Stress Value for M-25 Grade of Concrete

Graph 1 (a): M-25 Concrete Cubes Graph 1 (b): M-25 ConcreteCubes

at 0% G.C.A at 10% GCA

Graph 1 (c): M-25 Concrete Cubes Graph 1 (d): M-25 Concrete Cubes

at 20% G.C.A at 30% G.C.A

19.75

19.8

19.85

19.9

19.95

20

Cube 1

Cube 2

Cube 3

0.00 %G.C.A 20 19.86 19.95

Stre

ss (

N/m

m2

)

7 days Values of Stress

20.44

20.46

20.48

20.5

20.52

20.54

20.56

20.58

Cube 1

Cube 2

Cube 3

10 % G.C.A 20.53 20.58 20.49

Stre

ss (

N/m

m2

)

7 days Values of Stress

21.6

21.65

21.7

21.75

21.8

21.85

Cube 1

Cube 2

Cube 3

20 % G.C.A 21.82 21.69 21.73

Stre

ss in

7 days Values of Stress

22.26 22.28

22.3 22.32 22.34 22.36 22.38

22.4

Cube 1

Cube 2

Cube 3

30 % G.C.A 22.36 22.314 22.4

Axi

s Ti

tle

7 days value of stress

Page | 98

Graph 1 (e): M-30 Concrete Cubes

At 40% G.C.A

Graph 2: Values of 7 days average Stress at different amount of G.C.A in

M-25 Grade of Concrete

21.48

21.49

21.5

21.51

21.52

21.53

21.54

21.55

21.56

Cube 1 Cube 2 Cube 3

40 % G.C.A 21.56 21.51 21.56

Axi

s Ti

tle

7 days Values of Stress

18.5

19

19.5

20

20.5

21

21.5

22

22.5

0.0% G.C.A

10% G.C.A

20% G.C.A

30% G.C.A

40% G.C.A

Avg. Values of 3 cubes 19.95 20.53 21.75 22.36 21.54

Stre

ss (

N/m

m2

)

3 Cubes (at same G.C.A) Average Values of stress for Different amount of Granite Course

Aggregate

Page | 99

(b) All test results data for 28 days testing.

S.N % of

RCA

in

conc.

Cube

name

Date of

Manufacturing

of concrete

cubes

Date of

Testing of

concrete

cubes

Crushing

load

(KN)

Stress

(N/mm2)

Average

Stress

(N/mm2)

Percentage

of increase

in strength

1.

0.00 %

C1 15/Apr/2015 14/May/2015 639 28.40 28.44 Increase of

00%

Strength

C2 15/Apr/2015 14/May/2015 640 28.44

C3 15/Apr/2015 14/May/2015 641 28.49

2.

10%

C1 15/Apr/2015 14/May/2015 674 29.96 29.94 Increase of

1.27%

Strength

C2 15/Apr/2015 14/May/2015 674 29.96

C3 15/Apr/2015 14/May/2015 673 29.91

3.

20% C1 15/Apr/2015 14/May/2015 714 31.73 31.62 Increase of

2.63%

Strength

C2 15/Apr/2015 14/May/2015 712 31.64

C3 15/Apr/2015 14/May/2015 710 31.51

4.

30% C1 15/Apr/2015 14/May/2015 737 32.76 32.75 Increase of

03.57%

Strength

C2 15/Apr/2015 14/May/2015 738 32.80

C3 15/Apr/2015 14/May/2015 736 32.71

5.

40% C1 15/Apr/2015 14/May/2015 702 32.20 31.42 Decrease

of 1.76%

Strength

C2 15/Apr/2015 14/May/2015 703 31.24

C3 15/Apr/2015 14/May/2015 716 31.82

Table 8: 28 Days G.C.A (M-25 Grade concrete) cubes, Crushing value,

Stress in concrete, average stress in concrete and percentage of increase or

decrease in Compressive strength of M-25 grade concrete.

Page | 100

Graph 2 : 28 Days Stress Value for M-25 Grade of Concrete

Graph 3 (a): M-25 Concrete Cubes Graph 3 (b): M-25 Concrete Cubes

At 0% G.C.A at 10% G.C.A

Graph 3(c): M-25 Concrete Cubes Graph 3 (d): M-25 Concrete Cubes

at 20% G.C.A at 30% G.C.A

28.38

28.39

28.4

28.41

28.42

28.43

28.44

Cube 1

Cube 2

Cube 3

0 % G.C.A 28.4 28.44 28.42

Axi

s Ti

tle

28 days value of

stress

29.88

29.9

29.92

29.94

29.96

Cube 1

Cube 2

Cube 3

10 % G.C.A 29.96 29.94 29.91

Stre

ss (

N/m

m2

)

28 days Values of Stress

31.4 31.45

31.5 31.55

31.6 31.65

31.7 31.75

Cube 1

Cube 2

Cube 3

20 % G.C.A 31.73 31.64 31.51

Stre

ss (

N/m

m2

)

28 days Values of Stress

32.66 32.68

32.7 32.72 32.74 32.76 32.78

32.8

Cube 1

Cube 2

Cube 3

30 % G.C.A 32.76 32.8 32.71

Stre

ss (

N/m

m2

)

28 days Values of Stress

Page | 101

Graph 3 (e): M-30 Concrete Cubes

at 40% G.C.A

Graph 4 : Values of 28days Stress at different amount of G.C.A in M-25

Grade of Concrete.

30.8

31

31.2

31.4

31.6

31.8

32

Cube 1

Cube 2

Cube 3

40 % G.C.A 31.2 31.24 31.82

Stre

ss (

N/m

m2

) 28 days Values of Stress

26

27

28

29

30

31

32

33

00 % G.C.A

10 % G.C.A

20% G.C.A

30% G.C.A

40% G.C.A

Avg. Values of 3 cubes 28.44 29.94 31.62 32.75 31.42

Stre

ss (

N/m

m2

)

3 Cubes (at same G.C.A) Average Values of stress for Different amount of Granite Corse

Aggregate

Page | 102

From 28 days test result the strength is increased up to 30% replacement of G.C.A and then

after it was slightly decreased when the replacement is done up to 40 %. So I found that the

optimum replacement is done up to 30% the strength of the concrete is safe at the

replacement up to 30%. We can use the granite aggregate as a partial replacement of coarse

aggregate. The result of the compressive strength test for the testing of the concrete samples

is shown above. The above result shows the result of the testing of the 7 days and 28 days

respectively of the three specimens. It is observed that from the waste granite material good

quantity of material can be obtained which can be used for making aggregates.

These aggregates posses good engineering properties and adequate

strength. I found that at 7 days strength is increased when that granite course aggregate is

replaced by 10% the increase in strength is increased to 2.92% as compared to 0%

replacement, when the replacement is increased to 20% the strength is increased to 3.42%

when compared to 0% replacement, when the replacement is done to 30% the strength is

increased to 4.40%, further when the replacement is increased to 40% the strength is

decreased by 1.66%. the loss of the strength is due to higher workability of the concrete and

the high value of slump. The target compressive strength (31.6N/mm2) is achieved for 30%

replacement.

Both the test result of 7 days and 28 days shows that the optimum amount of

granite waste which can be used for making concrete is up to 30% replacement of natural

aggregate after it the strength decreased by a certain percent this may be due to lower water

absorption of granite aggregate. Further if the good treatment processes are applied such as

use of superplasticiser’s and curing processes may be lead to increase in strength. I found

that 30% is the safer limit to which it can be used this will help in reduction of the

consumption of the natural aggregate. The compressive strength is particularly higher in all

the ages is higher when compared to reference mix(G.A 0%), there was increase in strength

when the days of curing is increased. The compressive strength of GCA30% yielded higher

values than any other.

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5.2 Conclusion

Research on the usage of the waste constructional material is very important,

because, constructional waste material is gradually increased with the increasing

population and also increasing urban development. The reason is that many

investigation and analysis are done on granite fines as partial replacement of fine

aggregate, because a high amount of granite fines are available in factories where

the cutting of granite is done these fines also posses good properties so that they

can be used my focussed is that a larger amount of granite stones is available

which can be used for making aggregate after proper grading. Granite aggregate is

easy to obtain and their cost is also lower than the natural aggregate.

The main aim of this research is to determine strength

and durability characteristics of granite waste for the potential application in high

concrete structural concrete. The study shows that:-

1.When the percentage of the granite waste aggregate is increased upto 30% the

strength is increased. After 40% it was slightly decreased. However it can be

minimised by adjusting water cement ratio.

2.The target compressive strength is achieved at 30% to 40% of granite course

aggregate. This is classified as concrete strength and can be used in making

structural component.

3. The compression test result indicate that an increasing trend of compressive

strength up to 40% replacement of Granite course aggregate then it was slightly

decreased.

4. Hence granite course aggregate can be used up to 30% replacement of natural

aggregate.

5.3 Future scope

My work is done on the granite aggregate only as partial replacement of natural

course aggregate, I found that 30% replacement is the acceptance limit of the

aggregate to which it can be used,, future studies and researches are must done

also with the combination of granite fine aggregate and granite course aggregate

then the strength characteristics are determined in order to find higher

compressive strength, when the replacement is done with the combination of

granite fines and the granite aggregate. We can use or conserve the natural

resources as good as possible.

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