study on durability of concrete when blended with micro silica and flyash

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International Journal of Research and Innovation (IJRI)

International Journal of Research and Innovation (IJRI)STUDY ON DURABILITY OF CONCRETE WHEN BLENDED WITH

MICRO SILICA AND FLYASH

R.nandini 1, K. Mythili2

1 Research Scholar, Department Of Civil Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India2 Associate Professor, Department Of Civil Engineering, Aurora's Scientific Technological & Research Academy,Hyderabad, India

*Corresponding Author: R.nandini, Research Scholar, Department of CIVIL Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India Published: October 29, 2014Review Type: peer reviewedVolume: I, Issue : II

Citation:R.nandini,(2014) Durability Of Concrete When Blended With Micro Silica And Fly Ash

INTRODUCTIONGENERAL

Concrete is one of the most extensively use con-struction materials in the world, with about two billion tons of utilization worldwide each year. It is attractive in many applications because it offers considerable strength at a relatively low cost. Con-crete can generally be produced of locally available constituents, can be cast in to wide variety of struc-tural configurations, and requires minimal mainte-nance during service. However, environmental con-cerns, stemming from high-energy expense and CO2 emission associated with cement manufacture, have brought pressures to reduce consumption through the use of supplementary materials.In general concrete is said to be a very durable one.

But when reinforced concrete structure subjected to severe environmental conditions its properties are affected adversely depending on the type of ex-posure. Durability is one the most important prop-erties to be considered in the design of reinforced concrete structures exposed to aggressive environ-ments can be described by two stages: the initiation and the propagation period. For the exposed to sea water or deicing salts, the initiation period is defined by the time taken from initial exposure to the aggressive environment un-til a concentration of reinforcement able to initiate corrosion, has been reached. However, even though corrosion of the reinforcement is in progress the structure still meet the service requirements for several years without high maintenance costs. The largest economic benefits are obtained by prolong-ing the initiation period through proper concrete mix selection, smart structural design and proper on-site placement of the concrete among others.

In both developed and developing countries recent researchers amide at the energy conservation in the cement and concrete industry, focused on the use of less energy intensive materials such as Fly-ash, slag and natural pozzlolanas. Later some attention has been given to the use of pozzolana, Micro silica as partial replacement to Portland cement. Unlike natural pozzolanas and fly ash, the silica reaction

Abstract

The environment in some concrete structures can become very acidic due to formation of sulphuric acid con-verted from hydrogen sulphide by bacterial action. Significant deteriation of concrete in such harsh environments has been reported world wide. Deteriotation of sewer system may result in serious problem such as the loss of ability to transport sewerage, contamaniation of ground and ground water, excessive ground settelements.

Very high costs are involved with the repair of deteriorated concrete structures. In the USA, sulphuric acid is responsible for billoins of dollars of damage to concrete waste water collection and treatment systems. In the state of south Australia alone an estimated budjet for maintaining the existing waste water infra structure is A $ 48 million per anum. Although it has been reported that some new materials can be more acid resistant such as concretes using melted sulphur as the binder or high proportions of polymer modified binders, these materials are too expansive for most practical applications. Therefore, the research into improvement of acid resistance of normal concretes is still attractive. Over the past 20 years the use supplementary cementitious materials (SCM) in concrete has become very com-mon due to their technological, economical and environmental benefits. The use of SCM such as Micro silica and fly ash in concretes has been found to improve the resistance of concrete sulphuric acid attack because of the reduced pres-ence of calcium hydroxide, which is most vunerable to acid attack. Using Micro silica in binary cement system as partial replacement of ordinary portland cement was found to be effective in reduciton of acid attack.

In the present investigation, 5% Micro Silica and 15 % Fly Ash is added by the weight of the cement as additional ingre-dients in concrete with different water/ binder ratios 0.55, 0.45 and 0.35 of Ordinary concrete and Ternary concrete mix . The behaviour of this Ordinary concrete and Ternary concrete mix studied for durablity properties like % Weight loss, % Loss of Compressive strength and Durability Factors by the immersion concrete specimens in 5% H2SO4 and 5 % HCl solution for 28 days,90 days and 180 days.

1401-1402

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involving Micro silica is rapid and therefore, a long curing period is not necessary.

Pozzolonic Materials:

Pozzolonic materials are finely divided siliceous and aluminous materials and have little or no cementa-tious value and in the presence of moisture at or-dinary temperature, chemically react with calcium hydroxide liberated during hydration, to form com-pounds possessing cementatious properties. The engineering benefits likely to be derived from the use of pozzolonas in concrete include improved re-sistance to thermal cracking because of lower heat of hydration, enhancement of ultimate strength and impermeability due to pore refinement, a better du-rability to chemical attacks such as acid, sulphate, water and alkali-aggregate expansion.

Types Of Pozzolonas:

Pozzolonic materials can be divided in to two Types

1.Natural pozzolonas 2.Artificial pozzolonas. Natural pozzolonas such as clay and shale, diato-maceous earth etc are processed involving crush-ing, grinding and size preparation, including ther-mal activation if necessary. The natural pozzolonas have lost their popularity in view of the availability of more active pozzolonas available as industrial by products.

Artificial pozzolonas such as fly ash, blast furnace slag, micro silica, rice husk ash, metakaoline are major industrial by products.

Advantages of Pozzolonas:

Generally concrete fails due to combined action of various detrimental agencies. Durability of concrete depends on many factors including volume change of concrete. Physical effects that adversely influ-ence the durability of concrete include surface wear, cracking due to crystallization, pressure of salts in pores and exposure to extreme temperatures, del-eterious chemical effects including leaching of the cement paste by acidic solutions and expansive re-actions involving alkali-aggregate attack, sulphate attack and corrosion of embedded steel in concrete. The aspect of progressive hydration of cement is connected with the volume change of gel and conse-quently in interior space. The unsoundness of con-stituent materials such as cement, reactive aggre-gates containing unsound mineral fractions causes volume changes and hence affects durability.

Fly Ash:

Fly ash is divided into three classes depending on its calcium content, in recognition of the difference in behavior between low and high lime fly ashes. These classes are as follows:

Type F, low calcium, 8% CaOType CI, intermediate calcium, 8–20% CaOType CH, high calcium, .20% CaO

Advantage of fly Ash in concrete:

The technical benefits of using fly ash in concrete are numerous. The various advantages found by dif-ferent investigators in India are summarized bellow 1. Superior pozzalonic action 2. Reduced water demand (for fly ash low carbon content and high fineness) 3. Improved workability 4. More effective action of water reducing admix-tures5. Reduced segregation and bleeding 6. increases setting time but remains within limits 7. Less heat of hydration 8. Less drying shrinkage 9. Higher ultimate compressive strength, tensile, flexural and bond strength 11. Higher ultimate modulus of elasticity.12. Reduced alkali-aggregate reaction 13. Improved freezing and thawing

Micro Silica:

During the last three decades, some new Pozzolan materials have emerged in the building industry as an off shoot of research aimed at energy conser-vation and strict enforcement of pollution control measures to stop dispersing the materials into the atmosphere. Micro Silica (other names have been used are silica dust, condensed silica fume) is one such Pozzolan, which has been used as a partial replacement of Portland cement due to its versatile properties. The availability of high range water-re-ducing admixtures (superplasticizers) has opened up new ideas for the use of Micro Silica as part of the cementing material in concrete to produce very high strength cement (> 100 Mpa/15,000 psi).

Ternary Blended System (Ternary cement sys-tem):

It means Micro Silica or other cement replacement additives are to be used with OPC only. That is not strictly true and ternary mixtures comprise efficient -systems. The primary incentive of adding limited amount Micro Silica –for example 5 percent with Fly-ash cement mixes was to ensure high early strength research has however, shown that Ternary mixtures of OPC, Micro Silica and Fly-ash result in synergic action to improve the micro structure and performance of concrete. When both Micro Silica and Fly-ash are used, the resultant enhancement of strength or pozzolanic activity was greater than super position of contributions of each, for the re-spective proportions. Such synergic effect results from strengthening the weak transition zone in ag-gregate cement interface, as well as segmentation and blocking of pores.

Depending upon the service environment in which

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it is to operate, the concrete structure may have to encounter different load and exposure regimes. In order to satisfy the performance requirements, different ternary compounds required. Such as ce-ment, fly-ash, silica fume. Greater varieties are in-troduced by the corporation of additives like poz-zolana, granulated slag are inert fillers this leads to different specifications of cements in national or international.

Effects of Ternary cement system:

The combination of Micro Silica and Fly ash in a Ternary cement system (i.e., portland cement being the third component) should result in a number of synergistic effects, some of which are obvious or in-tuitive, as follows:• Micro Silica compensates for low early strength of concrete with low CaO fly ash.• Fly ash increases long-term strength devel-opment of Micro Silica concrete.• Fly ash offsets increased water demand of silica fume.• Micro Silica reduces the normally high levels of high CaO fly ash required for sulphate resist-ance and ASR prevention.• Very high resistance to chloride ion penetra-tion can be obtained with ternary blends.• Fly ash due to presence of spherical particles that easily rollovers one another reducing inter par-tial friction (call bearing effects) leads to improved workability and reduction in water demand.

Durability advantage:

Since industrial wastes are relatively lesser-known materials than cement, it possible to have ques-tions on their long-term effects on concrete. Doubts about effects of Fly ash and Micro Silica on durabil-ity of concrete had initially inhibited their full use in structural concrete. However, experience over the years and continuous research has actually re-vealed positive effects on durability. Corrosion of re-inforcement, sulphate attack, heat of hydration and alkali silica reaction (ASR) in concrete are the ma-jor issues of durability. Use of Fly ash, Micro Silica is known to be beneficial in all such cases. These are supported by well-documented case studies and performance records reported from foreign sources. Data and case studies on Indian experiences with indigenous materials have been presented earlier, hence only the salient trends are enumerated.

Aim of the Present Study:

The environment in some concrete structures can become very acidic due to formation of sulphuric acid converted from hydrogen sulphide by bacterial action. Significant deteriation of concrete in such harsh environments has been reported world wide. Deteriotation of sewer system may result in serious problem such as the loss of ability to transport sew-erage, contamaniation of ground and ground water, excessive ground settelements.

Very high costs are involved with the repair of dete-riorated concrete structures. In the USA, sulphuric acid is responsible for billoins of dollars of damage to concrete waste water collection and treatment systems. In the state of south Australia alone an estimated budjet for maintaining the existing waste water infra structure is A $ 48 million per anum. Although it has been reported that some new mate-rials can be more acid resistant such as concretes using melted sulphur as the binder or high propor-tions of polymer modified binders, these materials are too expansive for most practical applications. Therefore, the research into improvement of acid re-sistance of normal concretes is still attractive.

Over the past 20 years the use supplementary ce-mentitious materials (SCM) in concrete has become very common due to their technological, economical and environmental benefits. The use of SCM such as Micro silica and fly ash in concretes has been found to improve the resistance of concrete sulphu-ric acid attack because of the reduced presence of calcium hydroxide, which is most vunerable to acid attack. Using Micro silica in binary cement system as partial replacement of ordinary portland cement was found to be effective in reduciton of acid attack.

In the present investigation, 5% Micro Silica and 15 % Fly Ash is added by the weight of the cement as additional ingredients in concrete with different wa-ter/ binder ratios 0.55, 0.45 and 0.35 of Ordinary concrete and Ternary concrete mix . The behaviour of this Ordinary concrete and Ternary concrete mix studied for durablity properties like % Weight loss, % Loss of Compressive strength and Durability Fac-tors by the immersion concrete specimens in 5% H2SO4 and 5 % HCl solution for 28 days,90 days and 180 days.

EXPERMENTAL INVESTIGATION

Introduction:

The present investigations are aimed at to study durability of Ternary Blended concrete, having 5% Silica fume and 15% Fly Ash by weight of cement with different W/B ratios 0.55, 0.45and 0.35. In the laboratory after the age of 28 Days, 90 Days and 180 Days.

MATERIALS

Cement

Locally available 53 grade of Ordinary Portland Ce-ment (Ultra Tech Brand.) confirming to IS: 12269 was used in the investigations. Table 4.1 gives the physical properties of OPC used in the present in-vestigation and they conform to IS specifications.

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Photomicrograph of Portland cement (Curtsy Micro Silica Manual)

Fly Ash:

The fly ash obtained from Hyderabad Industries, Andhra Pradesh is used in the present experimental work.

Table 4.4.1 gives properties of flyash. The chemical composition of flyash is rich in silica content which react with calcium hydroxide to form C-S-H gel. This gel is responsible for the strength mortar or concrete. The fly ash used to the specification of grade 1 flyash

Photomicrograph of Fly ash (Curtsy Aci Jurnal)

Micro Silica:

The Micro Silica obtained from ‘ Oriental Trexim Pvt Ltd ‘. Micro Silica conforming to a standard approved by the deciding authority may be used as part replacement of cement provided uniform blending with the cement is ensured. The Micro Silica (very fine non-crystalline silicon dioxide) is a by-product of the manufacture of silicon, ferrosilicon or the like, from quartz and carbon in electric arc furnace.

Table 4.5.1 gives properties of Micro Silica. The chemical composition of Micro Silica is rich in silica.

Micrograph showing: Micro Silica (Curtsy by Micro Silica Manual)

AGGREGATE:

The size, shape and gradation of the aggregate play an important role in achieving a proper concrete. The flaky and elongated particles will lead to blocking problems in confined zones. The sizes of aggregates will depend upon the size of rebar spacing.

The coarse aggregate chosen for Ternary Blended Concrete is typically angular in shape, is well graded, and smaller in maximum size that suited for conventional concrete; typical conventional concrete should have a maximum aggregate size of 20mm. Gradation is an important factor in choosing a coarse aggregate, especially in typical uses of Ternary Blended. Gap-graded coarse aggregate promotes segregation to a greater degree than the well graded coarse aggregate.

Fine Aggregates:

The locally available sand is used as fine aggregate in the present investigation. The sand is free from clayey matter, salt and organic impurities. The sand is tested for various properties like specific gravity, bulk density etc., and in accordance with IS 2386-1963. The fine aggregate is conforming to standard specifications.

Coarse Aggregates:

Machine crushed angular granite metal of 20mm nominal size from the local source is used as coarse aggregate. It is free from impurities such as dust, clay particles and organic matter etc. The course aggregate is also tested for its various properties. The specific gravity, bulk density and fineness modules of coarse aggregate are found to be 2.70, 1560 kg/cum and 7.1 respectively.

Water:

Locally available water used for mixing and curing which is potable, shall be clean and free from injurious amounts of oils, acids, alkalis, salts, sugar, organic materials or other substances that may be deleterious to concrete or steel.

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Superplasticizer:

Superplasticizer CONPLAST 430 of Fosroc Chemical India Ltd. Was used as water reducing admixture. It increases workability

Mix Proportion in the Laboratory:

The proportion used in preparation of mix is calculated as per BIS Method.

The ratio between F.A and C.A is p: (1-p )

Illustrative Example for Mix Design Mix Design for W/C ratio = 0.55

i. Text data for materials Specific gravity of cement =2.95 Specific gravity of Coarse Aggregate =2.70 Specific gravity of Fine Aggregate =2.53

ii. Selecting W/B ratio =0.55iii. Determination of cement content Water =178 Ltrs. Cement =323.6 Kgs.

iv. Determination of F.A and C.A

Fine Aggregate0.98= [178+ (323.6/2.95)+ (1/0.42)*(F.A/2.53)]*1/100=736 Kgs.

Coarse Aggregate0.98= [178+ (323.6/2.95)+ (1/1-0.42)*(C.A/1-2.2.7)]*1/100= 1084 Kgs.

v. Mix Proportion = 1.00:2.27:3.34:0.55

Similarly Mix proportions for other W/B are obtained and are as follows;For W/B ratio 0.55 Ternary Blended Concrete mix proportion is 1.00:2.27:3.34:0.55 For W/C ratio 0.45 Ordinary Concrete mix proportion is 1.00:1.78:2.73:0.45For W/B ratio 0.45 Ternary Blended Concrete mix proportion is 1.00:1.78:2.73:0.45For W/C ratio 0.35 Ordinary Concrete mix proportion is 1.00:1.26:2.11:3.55

For W/B ratio 0.35 Ternary Blended Concrete mix proportion is 1.00:1.26:2.11:3.55

PREPARATION OF TEST SPECIMENS:

Mixing:

Mixing of ingredients is done in a rotating drum. Thorough mixing by hand, using trowels is adopted.

The cementitious materials are thoroughly blended with hand and then the aggregate is added and mixed followed by gradual addition of water and mixing. Wet mixing is done until a mixture of uniform color and consistency are achieved which is then ready for casting. Before casting the specimens, workability of the mixes was found by compaction factor test.

The concrete mix design using the data obtained from the test on its ingredients. The mix proportions with different W/B ratios are shown in the table 4.6.1, 4.6.2 and 4.6.3 of Ordinary concrete and Ternary Blended Concrete. The adopted is BIS method.

Workability Test:

Immediately after mixing each of concrete, was tested for workability by compaction factor apparatus in the laboratory. Table 4.7 gives the Compaction Factor value for different mixes, and the Degree of Workability of mixes is medium for W/B 0.55, 0.45 and 0.35 of Ordinary and Ternary Blended Concrete

Compaction:

All the specimens were compacted by using pin vibrator.

Casting of Specimens:

The cast iron moulds are cleaned of dust particles and applied with mineral oil on all sides before concrete is poured in the moulds.

The moulds are of size 100mm x 100mm for cubes .The moulds are placed on a level platform. The well mixed green concrete is filled in to the moulds by vibration with needle vibrator. Excess concrete was removed with trowel and top surface is finished level and smooth.

Curing of the Specimens:

The specimens are left in the moulds undisturbed at room temperature for about 24 hours after casting. The specimens are then removed from the moulds and immediately transferred to the curing pond containing clean and fresh water.

Testing of Specimens:

A time schedule for testing of specimens is maintained to ensure their proper testing on the

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due date and time. The cast specimens are tested as per standard procedures, immediately after they are removed from curing pond and wiped off the surface water. The test results are tabulated carefully

Description of Compression Testing Machine:

The compression testing machine (Microprocessor based) used for testing the cube specimens is of standard make. The capacity of the testing machine is 200 Tonnes or 2000 KN. The machine has an ideal gauge on which the load applied can be read directly. The oil level is checked, the MS plates are cleaned and the machine is kept ready for testing specimens.

Testing Arrangements:

The specimens are removed from the curing pond just before testing on the specified due date and time and cleaned to wipe off the surface water. The cube specimen is placed on the lower platen such that the load is applied centrally on the faces other than top and bottom faces of casting.

TESTS CONDUCTED:

Compressive strength of Concrete Specimens:

The compressive strength of control concrete (ordinary concrete) and Ternary Blended concrete contain 5% Micro Silica and 15% Fly ash concrete specimens having W/B 0.55, W/B 0.45 and W/B 0.35 were tested.

Durability Studies of Ordinary and Ternary Blended Concrete:

In addition to strength durability property is also important for concrete, when concrete is exposed to aggressive environment consisting of chlorides and sulphates it should not be subjected to deterioration. Pozzolanic admixtures are replacements for cement in concrete are known to enhance the durability property of the concrete. To study the effect of Fly ash and Micro Silica replacement on durability, acid resistance test have been conducted in the laboratory.

DURABILITY OF CONCRETE:

The durability of Control concrete and Ternary blended concrete was tested for resistance against mineral and organic acids such as Sulphuric acid, hydrochloric acid and chlorides etc. The effect of chemical attack on plain (ordinary concrete) concrete and Ternary concretes was studied by physical observation and loss in weight.

Acid pond test:

Acid solution for immersion test. The method was modified for testing concrete in this investigation. A H2SO4 (Sulphuric) acid and HCl (Hydro chloride

Acid) of 5% concentration was chosen for this accelerated laboratory investigation to simulate the aggressive environment of some sewer structures. All the concrete cubes of 100mmx100mm size were continuously immersed in weekly refreshed 5% H2SO4 and HCl acid during the test period.

Visual inspection of concrete samples:

During the immersion period in 5% H2SO4 (Sulphuric) acid and HCl (Hydro chloride Acid) solution, the concrete cube samples were periodically retrieved from the acid solution for visual inspection of the surface appearance. Photographs were also taken of cubes samples after immersion in the acid over different time periods to record changes in surface appearance.

Mass changes of cubes over immersion time:

The mass change of the cubes of each concrete with the immersion time in 5% H2SO4 (Sulphuric) acid and HCl (Hydro Chloride Acid) solution.

EXPERIMENTAL RESULTS

Cement:

Physical Properties of Ordinary Portland Cement

S.No. Property Test Results1 Normal Consistency 32%2 Initial Setting time 90 min3 Final Setting time 250 min4 Specific Gravity of Ce-

ment2.95

5 Compressive Strength (at 28 days)

56.3 N/mm2

Fine Aggregate:

Physical Properties:

S.No Property Test Results1 Fineness

modulus2.48

2 Specific gravity 2.533 Bulk density

a).Looseb). Com-pacted

1600 kg/m3

1720 kg/m3

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Sieve analysis: Sample 1000 gms

S.No. I.S Sieve Size

Wt. Retained (gms.)

Cumu-lative Wt. Re-tained (gms.)

Cumula-tive % of wt Retained

% Pass-ing

1 4.75 mm

0.61 0.61 0.061 99.939

2 2.36 mm

2.6 3.21 0.321 99.679

3 1.18 mm

40 43.21 4.32 95.68

4 600µ 463 506.21 50.62 49.38

5 300µ 432 938.21 93.82 6.18

6 150µ 59.8 998.01 99.8 0.2

7 <150µ 2 1000 100 0

Total 1000 -- 248.94 --

Fineness modulus = 248.94/100 = 2.48

Coarse Aggregate:

Physical Properties

S.No Property Test Results1 Fineness modulus 7.172 Specific gravity 2.703 Bulk density

a).Looseb). Dense

1390 kg/m31560 kg/m3

4 Flakiness index 2.41%5 Elongation index 12.80%

Sieve analysis of 20mm aggregate: Sample 5000 gms

S.No IS Sieves size

Wt. Re-tained (gms.)

Cumula-tive wt. Retained (gms)

Cumula-tive % of wt. Re-tained

% Passing

1 40 mm 0 0 0 100

2 20 mm 915 915 18.30 100

3 10 mm 3994 4909 99.09 81.70

4 4.75mm 45 4954 100 0.92

5 2.36 mm

0 5000 100 0

6 1.18 mm

0 5000 100 0

7 600 µ 0 5000 100 0

8 300 µ 0 5000 100 0

9 150 µ 0 5000 100 0

Total 5000 717.38

Fineness modulus of Coarse aggregate = 717.8/100 = 7.17

Mix Design:

Percentages Mineral Ingredients of Ordinary Concrete and Ternary Blended Concrete Mixes:

Mix Type W/C % of Ce-ment

% of Micro Silica

% of Fly ash

Ordinary Concrete Mixes

0.55 100 - -

0.45 100 - -

0.35 100 - -

Ternary Blended Concrete Mixes (5%Micro Silica-15% Fly ash)

0.55 80 5 15

0.45 80 5 15

0.35 80 5 15

W/BType of Con-crete

5% H2SO¬4 Solution 5% HCl Solution

Sr N M D.F Sr N M D.F

0.55 Ordi-nary Con-crete

65.80

28 180 10.23 90.62 28 180 14.03

45.37

90 180 22.68 80.40 90 180 40.20

31.70

180 180 31.70 74.89 180 180 74.89

Ter-nary Blend-ed Con-crete

68.01

28 180 10.57 91.61 28 180 14.25

47.84

90 180 23.92 85.99 90 180 42.99

33.08

180 180 33.08 77.39 180 180 77.39


71.89

28 180 11.18 92.44 28 180 14.37

51.08

90 180 25.54 87.58 90 180 43.79

36.06

180 180 36.06 80.09 180 180 80.09


74.35

28 180 11.56 93.58 28 180 14.55

53.34

90 180 26.67 88.10 90 180 44.05

41.41

180 180 41.41 81.75 180 180 81.75


75.89

28 180 11.80 94.66 28 180 14.72

56.80

90 180 28.40 89.50 90 180 44.75

43.92

180 180 43.92 83.77 180 180 83.77


77.80

28 180 12.10 95.49 28 180 14.85

59.45

90 180 29.72 91.45 90 180 45.72

46.67

180 180 46.67 84.84 180 180 84.84

Sr=Relative strength at N days (%),

N=Number of days at which the durability factor is needed,

M= Number of days at which exposure is to be ter-minated,

D.F= Durability Factor.

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GRAPHS

Percentage of weight loss vs. Age in Days for W/B 0.55 Immersed in 5%H2SO4 Solution at 28 days, 90 days and 180 days.



Percentage of weight loss vs. Age in Days for W/B 0.55 Immersed in 5%HCl Solution at 28 days, 90 days and 180 days.

Percentage of weight loss vs. Age in Days for W/B 0.45 Immersed in 5%HCl Solution at 28 days, 90 days and 180 days.

Percent age of weight loss vs. Age in Days for W/B 0.35 Immersed in 5%HCl Solution at 28 days, 90 days and 180 days.

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Combined Graph Percentage of weight loss vs. Age in Days for W/B 0.55, 0.45 and 0.35 Immersed in 5% H2SO4 Solution at 28 days, 90 days and 180 days.

Combined Graph Percentage of weight loss vs. Age in Days for W/B 0.55, 0.45 and 0.35 Immersed in 5%HCl Solution at 28 days, 90 days and 180 days.

Percentage Loss of Compressive strength of after immersed in 5% H2SO4 Solution at 28 days, 90 days and 180 days.

Percentage Loss of Compressive strength of after immersed in 5% HCl Solution at 28 days, 90 days and 180 days.

DISCUSSION OF TEST RESULTS

Durability Studies on Ternary Blended Concrete

In addition to the strength, durability properties are also important for concrete. When concrete is exposed to aggressive environment consisting of sulphate, acids, chlorides. It should not be subjected to deterioration. Pozzolonic admixtures as replacement for cement in concrete are known to enhance the durability property of concrete. To study the test of Ternary Blended Concrete on durability acid resistance test and Rapid Chloride Permeability Test have been conducted in the laboratory.

Concrete specimens of size 100X100X100 mm are cured for 28 days and are immersed in 5% HCL , 5% H2SO4 for the period of 28 days , 90 days and 180 days of different water binder ratios of 0.55 , 0.45, and 0.35. All types of experiments are conducted for comparison of Ordinary Concrete and Ternary Blended Concrete in respect of acid resistance.

Studies on Loss of weight of Ordinary concrete and Ternary Blended concrete in different solutions

Loss of weight of specimens after immersing in 5% H2SO4 solution

Table 4.8.1 gives the percentage weight loss of W/C ratios 0.55, 0.45 and 0.35 of ordinary concrete after immersing in 5% H¬2 SO4 solution ranges from 4.87% to 2.12% for 28 days, 13.17% to 8.95% for 90 days, 17.16 % to 11.29% for 180 days respectively.

Table 4.8.2 gives the percentage weight loss of W/B ratios 0.55, 0.45 and 0.35 of Ternary Blended Concrete after immersing in 5% H¬2 SO4 solution ranges from 3.43 to 1.84% for 28 days, 11.71 to 6.50for 90 days, 15.21% to 9.54% for 180 days respectively.

The percentage weight loss of W/B ratio 0.55, 0.45 and 0.35 of ordinary concrete and Ternary Blended Concrete after immersing in 5% H¬2 SO4 solution increases corresponding to the time.

Loss of Weight of specimens after immersing in 5% HCl solution Table 4.9.1 gives the percentage weight loss of W/C ratios 0.55, 0.45 and 0.35 of ordinary concrete after immersing in 5% H¬Cl solution ranges from 3.52% to 1.33% for 28 days, 9.46% to 5.13% for 90 days, and 12.41% to 7.8 for 180 days respectively.

Table 4.9.2 gives the percentage weight loss of W/B ratios 0.55, 0.45 and 0.35 of Ternary Blended Concrete after immersing in 5% H¬Cl solution ranges from 2.87% to 1.10% for 28 days, 7.38% to 2.79% for 90 days, 10.21% to 4.64% for 180 days respectively.

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The percentage weight loss of W/B ratio 0.55, 0.45 and 0.35 of ordinary concrete and ternary concrete after immersing in 5% Hcl solution increases corresponding to the time.

Studies on Loss of Compressive strength of Ordinary and Ternary Blended Concrete Loss of Compressive strength of specimens after immersing in 5% H¬2 SO4 solution

Table 4.11.1 gives the percentage Loss of Compressive strength of W/C ratios 0.55, 0.45 and 0.35 of ordinary concrete after immersing in 5% H¬2 SO4 solution ranges from 34.20% to 24.11% for 28 days, 54.63% to 43.20% for 90 days, and 68.83 % to 56.92% for 180 days respectively.

Table 4.11.1 gives the percentage Loss of compressive strength of W/B ratios 0.55, 0.45 and 0.35 of Ternary Blended Concrete after immersing in 5% H¬2 SO4 solution ranges from 31.99% to 22.20% for 28 days, 5.63% to 40.55% for 90 days, 66.92% to 58.33% for 180 days respectively.

The Loss of compressive strength of W/B ratio 0.55, 0.45 and 0.35 of ordinary concrete and Ternary Blended Concrete after immersing in 5% H¬2 SO4 solution increases corresponding to the time.

Under Sulfuric acid attack, calcium sulphate formed, can continue to react with calcium aluminate phase in cement to form Calcium Sulphoaluminate, which on crystallization can cause expansion and disruption of conctete.

Loss of Compressive strength of specimens after immersing in 5% HCl solution

Table 4.11.2 gives the percentage Loss of Compressive strength of W/C ratios 0.55, 0.45 and 0.35 of ordinary concrete after immersing in 5% HCl solution ranges from 9.37% to 5.34% for 28 days, 19.60% to 10.50% for 90 days, 25.11% to 16.23% for 180 days respectively.

Table 4.11.2 gives the percentage Loss of Compressive strength of W/B ratios 0.55, 0.45 and 0.35 of Ternary Blended Concrete after immersing in 5% HCl solution ranges from 8.37% to 4.51% for 28 days, 14.01% to 8.55% for 90 days, 22.61% to 15.16% for 180 days respectively.

The percentage Loss of Compressive strength of W/B ratio 0.55, 0.45 and 0.35 of ordinary concrete and Ternary Blended Concrete after immersing in 5% HCl solution increases corresponding to the time.

Studies on Durability Factors of Ordinary and Ternary Blended concrete

Durability Factors of Ordinary and Ternary Blended concrete specimens after immersing in

5% H¬2 SO4 solution

Table 4.12 gives Durability Factors of W/C ratios 0.55, 0.45 and 0.35 of ordinary concrete after immersing in 5% H¬2 SO4 solution. These values are observed to be ranges from 10.23 to 11.80 for 28 days, 22.68 to 28.4 for 90 days, and 31.70 to 43.92 for 180 days respectively.

Table 4.12 gives the percentage Loss of Compressive strength of W/B ratios 0.55, 0.45 and 0.35 of Ternary Blended Concrete after immersing in 5% H¬2 SO4 solution. These values are observed to be ranges from 10.57 to 12.10 for 28 days, 23.92 to 29.72 for 90 days, 33.08 to 46.67 for 180 days respectively.

Durability Factors of Ordinary and Ternary Blended concrete specimens after immersing in 5% HCl solution

Table 4.12 gives Durability Factors of W/C ratios 0.55, 0.45 and 0.35 of ordinary concrete after immersing in 5% H¬Cl solution. These values are observed to be ranges from 14.03 to 14.72 for 28 days, 40.20 to 44.75 for 90 days, and 74.89 to 83.77 for 180 days respectively.

Table 4.12 gives the percentage Loss of Compressive strength of various W/B ratios 0.55, 0.45 and 0.35 of Ternary Blended Concrete after immersing in 5% H¬Cl solution. These values are observed to be ranges from 14.25 to 14.85 for 28 days, 42.99 to 45.72 for 90 days, 77.39 to 84.84 for 180 days respectively.

CONCLUSIONS:

The Following Conclusions are drawn from the Experimental Investigation in present Thesis:

1. From the visual observation of test specimens immersed in 5% H2SO4 solution for 28 days, 90 days and 180 days, the specimens has undergone deterioration. Which are viewed in photograph enclosed.

2. The investigation shows that percentage of weight loss of specimens increased as days of immersion in 5% H2SO4 is increased for Ordinary concrete and Ternary concrete for all W/C ratios. In case of Ordinary concrete for 0.55 Water/ Cement ratio the percentage of weight loss is 4.87 at 28 days immersion and it is 17.16 for 180 days immersion. In case of Ternary Blended concrete for 0.55 Water/ Binder ratio the percentage of weight loss is 3.43 at 28 days immersion and it is 15.21 for 180 days immersion.

3. From the visual observation of test specimens immersed in 5% HCl solution for 28 days, 90 days and 180 days, the specimens has undergone deterioration.

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4. The investigation shows that percentage of weight loss of specimens increased as days of immersion in 5% HCl is increased for Ordinary concrete and Ternary Blended concrete for all W/B ratios. In case of Ordinary concrete for 0.55 Water/ Cement ratio the percentage of weight loss is 3.52 at 28 days immersion and it is 12.41 for 180 days immersion. In case of Ternary concrete for 0.55 Water/ Binder ratio the percentage of weight loss is 2.82 at 28 days immersion and it is 10.21 for 180 days immersion.

5. The percentage weight loss of Ordinary concrete and Ternary Blended concrete after immersing in 5 % H2SO4 solution increases corresponding to the time.

6. The percentage weight loss of Ordinary concrete and Ternary Blended concrete after immersing in 5 % HCl solution increases corresponding to the time.

7. The percentage loss compressive strength of Ordinary concrete and Ternary Blended concrete after immersing in 5 % H2SO4 solution and 5% HCl solution increases corresponding to the time.

8. The Durability Factors of Ternary Blended concrete mixes are more than those of Ordinary concrete mixes.

9. Higher the Durability Factor higher will be the resistance to the Acids and Sulphates attacks.

10. A reduction in pores in concrete improves the surface integrity of concrete, improves its homogeneity good bonding and reduces the probability of cracks.

PHOTOGRAPHS:

Ordinary Concrete Specimen of W/C Ratio 0.55 after Immersion in 5% H2SO4 Solution at 28 days

Ternary Blended concrete Specimen of W/B Ratio 0.55 after Immersion in 5% H2SO4 Solution at 28 days

Ordinary Concrete Specimen of W/C Ratio 0.55 after Immersion in 5% H2SO4 Solution at 90 days.

Ternary Blended Concrete Specimen of W/B Ratio 0.55 after Immersion in 5% H2SO4 Solution at 90 days

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Ordinary Concrete Specimen of W/C Ratio 0.45after Immersion in 5% H2SO4 Solution at 28 days


Ordinary Concrete Specimen of W/C Ratio 0.45after Immersion in 5% H2SO4 Solution at 90 days


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Ordinary Concrete Specimen W/C Ratio 0.35 after Immersion in 5% H2SO4 Solution at 28 days




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Ordinary Concrete Specimen of W/C Ratio 0.55 after Immersion in 5% HCl Solution

Ternary Blended Concrete Specimen of W/B Ratio 0.55 after Immersion in 5% HCl Solution



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Author

Ramanujapuram.NandiniAurora's Scientific Technological & Research Academy,Hyderabad,India

K. Mythili,AssociateProfessor,Department of Civil Engineering, Aurora's Scientific Technological & Research Acad-emy, Hyderabad, India

study on durability of concrete when blended with micro silica and flyash

Education