paper on slump variation

Study of variation of concrete constituents for

varied design slump: an experimental approach

Ankur M. Tripathi VIII Sem, Civil Engineering,Dept.

G.H. Raisoni College of Engg.Nagpur, India.

[email protected]

Rohit V. Morghade VIII Sem, Civil Engineering,Dept.


[email protected]

Nikhil A. Maske Asst. Professor, Civil Engineering,Dept.


[email protected]

Abstract— In this paper an approach to study the variation of various concrete constituents for different design slumps for the same grade of concrete. In Ready-Mix Concrete Plants, the concrete mix design is altered everytime according to the workability requirements of clients as well as the distance to be covered by transit mixer along with the temperature of surroundings. The choice of correct design slump results in efficient utilisation of constituent materials and prove to be economical. This paper compares the variation of constituent material, basically cementious material, fine and coarse aggregate. The workability test used for this investigation was slump test.Slump is a relative measurement in concrete consistency.

Index Terms—Workability, Ready-Mix Concrete, Aggregate, Slump Introduction.

I. INTRODUCTION

Concrete is most vital material in modern construc-

tion. It has versatile properties like easy mouldability, high

compressive strength and long lasting durability. In addition to

normal concrete, other varieties in use are, high strength and

high performance concrete, self-compacting, light weight,

high density, fiber reinforced, polymer, coloured concrete etc.

The making of concrete is an art as well as a science.-

Science because all the ingredients are proportioned as per the

standard codes of practice to get the targeted strength & dura-

bility, and an art because in addition to accurate proportioning,

quality of concrete depends on the way it is mixed, placed,

compacted, finished, cured and protected. Ready mix Concrete

(RMC) technology results in a perfect blend of the Art and

Science.

American Concrete Institute (ACI) Standard 116R-90 (ACI

1990b) defines workability as “that property of freshly mixed

concrete which determines the ease and homogeneity with

which it can be mixed, placed, consolidated, and finished.”

For this study, workability is considered to increase or

improve as the ease of placement, consolidation, and finishing

of a concrete increase. In common practice, an assumption is

made that the standard test for slump of concrete indicates

workability. In fact, it correlates well with one component of

workability. Aggregates influence the workability of the

concrete by the amount of aggregate, the relative proportions

of fine and coarse aggregate, and the different aggregate

properties.

Factors affecting workability:

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mailto:[email protected]

Water-Cement Ratio: More the water cement ratio more will

be the workability of concrete. Since by simply adding water

the inter-particle lubrication is increased. High water content

results in a higher fluidity and greater workability. Increased

water content also results in bleeding. Another effect of higher

water content can be escape of cement slurry through joints of

formwork.

Amount and type of Aggregate: Since larger aggregate sizes

have relatively smaller surface areas for cement paste to coat

and less water means less cement, it is usually suggested to

use larger aggregate size particles and stiffest practical mix. In

case of Ready-Mix Concrete, the cement-aggregate ratio is so

selected so as to achieve the best workable concrete at site

which is usually after 90 to 120 minutes after the addition of

water to the mix. A fine aggregate deficiency results in a

mixture that is harsh, prone to segregation, and difficult to

finish. On the contrary, an excess of fine aggregate will lead to

some extent more permeable and less economical concrete,

although the mixture will be easily workable.

Temperature: If the temperature is high, evaporation

increases which causes considerable decrease in the

workability of the concrete. It is therefore very important to

keep a watch on the temperature while preparing mix design.

Admixtures: Admixtures form an essential part of the

Concrete especially in the Ready-Mix Concrete Sector as they

can increase the workability. Air entraining agents produce air

bubbles which act as ball- bearing between particles and

increase mobility and hence workability.

Slump: Slump is a relative measurement in concrete

consistency. It is not an indicator of quality of the material.

The slump of a mix with the same aggregate, cement and

water can vary significantly by adding an admixture. The

admixture does not reduce the quality of the material.

II. CURRENT SCENARIO

In all the developed as well as most of the developing

nations, use of RMC for construction has made it possible to

achieve speed and quality. The advent of commercial RMC in

India is about a decade old, but in recent years it has become

the preferred choice of architects, engineers and consumers.

The acceptance of a freshly mixed concrete depends

on concrete quality control test results. If the results indicate

that the concrete does not meet the specification, mix design

adjustment must be made. Concrete mix design and

adjustment are complicated and time-consuming tasks

performed best by experienced persons.

India is the second largest producer of cement in the

world. In 2003, India produced 115 million metric tons (Mt)

of cement, behind China (750 Mt), but ahead of the U.S. (93

Mt) and Japan (72 Mt) (UNESCAP, 2004; van Oss, 2004).

India’s cement industry – both installed capacity and actual

production – has grown significantly over the past three

decades, with production increasing at an average rate of 8.1%

per year between 1981 and 2003.

With infrastructure development growing and the

housing sector booming,, there has been a rapid increase in the

demand for Ready-Mix Concrete due to its convenience and

rapid concreting facilities. It is, therefore, very important to

maintain both quality as well as economic aspects.

Major Ready-Mix Concrete plants use fly ash as 30%

to 50% of the total cementious content of the mix design. This

has again proved to be economical for the companies.

Fly ash is an industrial waste product. The cost

incurred is mainly that of transportation from the power plant

to the construction site. Cost of fly ash within 200 km from a

thermal power plant is as low as 10% to 20% of the cost of

cement. This offers a certain economic advantage.

III. LITERATURE REVIEW

Overview

Concrete is the most widely used man made

construction material in the world, and is the most utilized

substance on the planet. Concrete is “a composite material that

consists essentially of a binding medium within which are

embedded particles or fragments of aggregate, usually a

combination of fine aggregate and coarse aggregate”. The

mixture when placed in forms and allowed to cure hardens

into a rock like mass. The hardening is caused by chemical

reaction between water and cement and it continues for a long

time and consequently the concrete grows stronger with age.

In a concrete mix cementious material and Fly Ash Concrete

applies to engineered concrete systems in which have fly ash

as a partial replacement of cement. This type of concrete often

requires the use of a super plasticizer in order to achieve the

desired workability. The fly ash quantity is optimized through

judicious selection of materials, mixture proportioning and the

use of chemical admixtures. The ingredients of fly ash

concrete are, fly ash, cement, sand, coarse aggregate and

water. The allowable percentage of fly ash in cement ranges

from 55 to 60% coats the surface of the fine and coarse

aggregates and binds them together as it cures, thereby

cementing the particles of aggregates together in a compact

mass. water form a paste called cement-water paste which in

addition to filling the voids of the fine aggregate The strength,

durability and other characteristics of the concrete depend

upon the properties of its ingredients, on the proportions of

mix, the method of compaction and other controls during

placing, compaction and curing. The popularity of the

concrete is due to the fact that from the common ingredients, it

is possible to tailor the properties of concrete to meet the

demands of any particular situation. The key to producing a

strong, durable and uniform concrete, i.e. high performance

concrete lies in the careful control of its basic and process

components which are cement, aggregates, water and

admixtures.

IV. EXPERIMENTAL PROGRAMME

SR.NO. TEST RESULT

1. Fineness of the cement 10%

2. The standard consistency 35 %

3. Initial setting time of the cement 45 minutes

4. The specific gravity of an aggregate 2.76

5.The fineness modulus of the coarse

aggregate8.84

6.The fineness modulus of the fine

aggregate2.48

7. The bulking of sand 10 %

8. Moisture Content 2 %

9. The bulk density of aggregate1725.925

kg/m3

The following test procedures were followed:

Sieve analysis:

The primary sieve analysis of the constituent elements of

concrete namely 10mm aggregate, 20mm aggregate, river

sand was been carried out before batching them. The samples

were air dried or preheated at 100-110°C before sieving. It

was ensured that the sieves were clean before sieving of any

of the constituents. After carrying out all these preliminary

procedures the sieve analysis was been carried out in

accordance with IS: 2386 (Part 1) – 1963.

Specific Gravity and Water absorption:

The specific gravity and water absorption of the aggregates

was found before the batching of the trial mix. These results

played a crucial role in the mix design. The respective samples

were soaked in clean water for 24 ± ½ hrs at 22°C to 32°C.

After this the samples were oven dried at 100°C to 110°C for

24 ± 1/2 hrs. The specific gravity and the water absorption

values of the aggregate were calculated in accordance with IS:

2386 (Part 3) – 1963.

Mix design:

The mix design was calculated using the test results on the

aggregate and the procedure described in IS: 10262 - 2009.

The materials were batched by weight for a quantity of

0.035m3 and then dry mixed in the mixer. The quantity of

water calculated in the mix then was added along with the

admixture. The constituents were thoroughly mixed. It was

ensured that no lumps were remaining in the bottom of the

mixer to get a uniform mix.

Mix calculations:-The sample mix calculations per unit volume of concrete shall

be as follows:a) Volume of concrete = 1m3

b) Volume of cement = ((Mass of cement*1) / (specific gravity of cement))*100

= 0.085m3

c) Volume of fly ash = ((Mass of fly ash*1)/ (specific gravity of water))*100

= 0.066m3

d) Volume of water = ((Mass of water*1) / (specific gravity of water))*100

= 0.177m3

e) Volume of admixture = ((Mass of water*1) / (specific gravity of water))*100

= 0.0041m3

f) Volume of all in aggregate = = [a-{b+c+d+e}]

= 0.672 m3

g) Mass of Coarse Aggregate 10mm = (f * volume of coarse aggregate) X 1000(S.G of 10mm aggregate *

%age of 10mm)= 358 Kg

h) Mass of coarse aggregate 20mm = (f * volume of coarse aggregate) X 1000(S.G of 20mm aggregate *

%age of 20mm)= 644 Kg

i) Mass of fine aggregate = (f * volume of fine aggregate) X 1000 (S.G of fine aggregate * %age of fine aggregate)

= 710 Kg

Slump cone test:

After mixing, the slump cone test was been carried out. Initial

slump was taken just after mixing the trial, after which the

slump cone test was carried out at regular intervals of 30min,

60min, 90min, 120min, and 180 min.

V. TEST RESULTS

MIX DESIGN

M20 WITHOUT

ADMIXTURE (150-

175MM)

M20 WITHOUT

ADMIXTURE (125-

150MM)

M20 WITHOUT

ADMIXTURE (100-125MM)

CEMENT 278 271 264

FLYASH 150 146 142

20MM 644 654 664

10MM 358 363 369RIVER SAND 710 721 732

WATER 214 208 203

TABLE 1. Mix design M-20 without admixture

MIX DESIGN

M20 WITH ADMIXTURE (150-175MM)



CEMENT 236 230 224FLYASH 127 124 121

20MM 701 709 71710MM 389 394 399

RIVER SAND 772 782 791ADMIXTURE 1% 1% 1%

WATER 182 177 172

TABLE 2. Mix design M-20 with admixture

MIX DESIGN

M25 WITHOUT


M25 WITHOUT


M25 WITHOUT


CEMENT 278 236 269FLYASH 150 149 145

20MM 644 653 66310MM 358 363 368

RIVER SAND 710 714 725ADMIXTURE 0% 0% 0%

WATER 214 208 203




MIX DESIGNM30 WITH



CEMENT 268 260FLYASH 144 140

20MM 692 70110MM 384 389

RIVER SAND 752 762ADMIXTURE 1% 1%

WATER 177 172


MIX DESIGNM35 WITH



CEMENT 281 273

FLYASH 151 147

20MM 700 709

10MM 389 394

RIVER SAND 722 732

ADMIXTURE 1% 1%

WATER 177 172


MIX DESIGNM40 WITH



CEMENT 310 302

FLYASH 133 129

20MM 701 710

10MM 289 395

RIVER SAND 718 728

ADMIXTURE 1% 1.2%

WATER 177 172


DISCUSSION & CONCLUSION

From the above observations, following conclusions regarding

workability of concrete mix and its constituents can be made.

1. As the design slump goes on decreasing, the cemen-

tious content was observed to decline as compared to

the initial value.

2. Also, a fall in water content /m3 of concrete was ob-

served as we decreased the design slump value.

3. However, keeping the primary consideration as work-

ability, it was required to keep the mix blended

enough to ensure pumping. Therefore an increase in

the volume of aggregate (coarse as well as fine) is ob-

served after conducting the trials.

MIX DESIGN




CEMENT 236 235 229FLYASH 127 126 123

20MM 701 709 71710MM 389 394 398RIVER SAND 772 776 785

ADMIXTURE 1% 1% 1%

WATER 182 177 172

MIX DESIGN

M30 WITHOUT


M30 WITHOUT ADMIXTURE (100-

125MM)

CEMENT 315 306FLYASH 170 165

20MM 632 64310MM 351 357

RIVER SAND 687 699ADMIXTURE 0% 0%

WATER 208 203

4. Workability ensures a proper pump able mix to meet

user-end requirements.

5. Hence, keeping the final strength unaffected by the

variation of constituents it was made a point to change

the required slump according to the requirement.

6. Comparison of various constituents can be easily

studied for each and every mix design.

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