IJIRST –International Journal for Innovative Research in Science & Technology| Volume 3 | Issue 10 | March 2017 ISSN (online): 2349-6010
Durability Studies on Concrete by using Groundnut Shell Ash as Mineral Admixture Dharani D Assistant Professor Department of Civil Engineering SVS college of Engineering, Coimbatore, India
Arivu Thiravida Selvan V Assistant Professor Department of Civil Engineering SVS college of Engineering, Coimbatore, India
Abstract This paper illustrates about the use of groundnut shell ash as a mineral admixture for partial replacement of cement. Chemical analysis for groundnut shell ash was carried out, it shows that it have better pozzolanic properties. Effect of groundnut shell ash for M25 grade of concrete was investigated. Cement is partially replaced with 10%, 15%, 20%, 25% and 30% of groundnut shell ash. Compressive strength test should be carried at 7 and 28 days of curing. The results shows that compressive strength of concrete increases at 10% replacement, after that it get decreases due to presence of potassium oxide in ash content which disrupts the concrete. The durability test shows that the GSA concrete is better resistance to acid, chloride and water absorption. Keywords: groundnut shell ash, compressive strength test, water absorption test, chloride attack test, Acid attack test _______________________________________________________________________________________________________ I.
INTRODUCTION
Concrete is one of the most popular materials in construction. When it is reinforced with steel, it has a higher load carrying capacity. Concrete is a heterogeneous material which is composed of aggregates bonded together with fluid cement. Cement is the binding material which contains lime, silica, alumina and iron oxide. But the production of cement does not meets our requirement and causes global warming due to releases of large amount of CO 2 in the environment. To overcome such difficulties some natural agricultural wastes are used. The agricultural waste such as groundnut shell ash, sugarcane bagasse ash and rice husk ash etc are used. The use of groundnut shell ash will contribute to the production of higher quality concrete at lower cost and also reduces the environmental pollution. GSA has better pozzolanic property. It contains silica, lime, magnesium oxide, iron oxide and aluminium oxide. GSA when react with calcium hydroxide during hydration which forms additional calcium silicate hydrate gel. The pozzolanic activity of ash increases with increases of time. The addition of GSA in cement concrete may reduce drying shrinkage, water absorption, but increases the setting time. Increases of setting time are due to slow reactivity of GSA. The presence of GSA may block the existing pore structure of concrete and thereby increasing its strength and impermeability. GSA shows improved workability at lower replacement level, reduced permeability, and low heat of hydration and higher resistance to chemical attack and also smaller diffusion rate of chloride ions resulting in a higher resistance of steel from corrosion. The main object is to find a solution to reduce the environmental pollution due to cement manufacturing by using GSA. The chemical composition for groundnut shell is given below. Table – 1 Chemical Composition of Groundnut shell Ash Ingredient Loss of Ignition Sand and Silica Calcium Oxide Magnesium Oxide Iron Oxide Aluminium Oxide Alkalis
Percentage 7.85 53.50 4.68 2.25 4.80 2.75 18.30
II. MATERIALS Cement Ordinary Portland Cement of 53 grade locally available is used in this investigation. The cement is tested for various properties as per the code IS: 4031-1988 and it is found to be conforming to various specification of IS: 12269-1987 having specific gravity of 3.15.
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Durability Studies on Concrete by using Groundnut Shell Ash as Mineral Admixture (IJIRST/ Volume 3 / Issue 10/ 029)
Fine Aggregate The sand used for this experimental program was locally available and conformed to grading Zone II as per IS: 383-1970. The sand was first sieved through 4.75mm sieve and having specific gravity of 2.67. Coarse Aggregate Coarse aggregates which were locally available having the size of 20mm were used in the experimental work. Testing of coarse aggregate was done as per IS: 383-1970. The specific gravity of coarse aggregate is 2.87. Groundnut Shell Ash The ash was obtained by burning the groundnut shell in the open air under normal temperature. The burnt ash must pass through a BS sieve of 75 micron. It contains lime, silica, alumina and iron oxide. Water Water is a main ingredient of concrete, as it actively participates in the chemical reactions with cement to form the hydration product such as C-S-H gel. A higher water cement ratio will results in decreases of strength, durability etc. Addition of excess water ends in formation of undesirable voids in hardened cement paste of concrete. The pH value of water lies between 6 & 8 and it should be free from organic matter, acids and other suspended solids. Locally available water conforming to standard specified in IS: 456-2000 is used. Mix design The Mix proportion for the ordinary grade concrete and standard concrete is designed using IS: 10262-2009. The ratio of materials required for 1 cubic meter of concrete in ordinary grade concrete M 25 is 1:1.69:2.93 with water cement ratio of 0.47. III. EXPERIMENTAL INVESTIGATION The compressive strength, Split tensile strength and flexural strength for M 25 grade of concrete were investigated. The cube of 150x150x150mm was used. The test should be carried out as per codal provision IS: 516-1959. Compressive Strength Test Compressive strength test was carried out on the specimens after 7 and 28 days of curing by compression testing machine. The test should be carried out as per codal provision IS: 516-1959. Totally 30 cubes were casted. The compressive strength is calculated as, Fck=P/A Where, Fck= Compressive strength (N/mm2) P = Ultimate load (N) A = Loaded area(mm2) Water Absorption Test For water absorption 100mm X 100mm X 100mm cube was casted and tested after 28 days continuous curing period. Then after cube specimen were dried for 24 hours at normal temperature. This weight should be measured in Kg (W1). Then after specimens were kept in water for 24 hours, this wet weight noted is (W2). % of water absorption should be calculated is [(W2-W1) / (W1)]*100. Where W1= oven dry weight of cube. W2=Wet weight of cube after 24 hours. Chloride attack Test The effect of chloride on concrete was studied through this test. Marine structures are subjected to chloride attack and due to the penetration of chloride the reinforcement is subjected to corrosion. Sodium chloride solution with 3% concentration was used as the standard exposure. The specimens were immersed in the sodium chloride solution in a tank. To prepare the solution of 3% concentration for each 100gm solution 97gm of water and 3gm of sodium chloride powder is added. After preparation of the solution the mould is immersed in solution for 28days, 56 days and 90 days. The compressive strength was calculated by using the following formula: Compressive strength = (P/A) N/mm2 Where, P = ultimate load (load of failure) in Newton A = area of cube in mm2 Loss of weight = [(W1 – W2)/W1] x 100 % Where,
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Durability Studies on Concrete by using Groundnut Shell Ash as Mineral Admixture (IJIRST/ Volume 3 / Issue 10/ 029)
W1 = initial weight of concrete specimen W2 = final weight of concrete specimen Acid Attack Test The effect of 10% concentration of sulphuric acid on GSA concrete is given in table. The test result shows that GSA offered better resistance to deterioration by H2SO4 than portland cement concrete.The enhanced resistance of GSA concrete to sulphuric acid could be due to depletion in the Ca(OH)2 content released from the hydration process and consumed in the GSA pozzolanic reaction, with less Ca(OH)2 left to react with sulphuric acid or due to less C3A available to form the more disruptive ettringnite in the GSA concrete.Acid attack test is shown in figure 4.6. The compressive strength was calculated by using the following formula: Compressive strength = (P/A) N/mm2 Where, P = ultimate load (load of failure) in Newton A = area of cube in mm2 Loss of weight = [(W1 – W2)/W1] x 100 % Where, W1 = initial weight of concrete specimen W2 = final weight of concrete specimen IV. RESULTS AND DISCUSSION Compressive strength test result Compressive strength test results after 7 and 28 days are given in table. The result shows that the strength gets increases at 10% replacement of cement by GSA. Table – 2 Compressive Strength Test Results S.No
%Replacement
1. 2. 3. 4. 5. 6.
CC 10 15 20 25 30
Average Compressive Strength N/mm2 7 days 28 days 20.40 28.67 21.02 29.02 19.60 25.22 16.90 20.58 14.43 16.84 11.10 15.02
There is an increase in strength of concrete up to 10% replacement of cement by GSA because after the replacement of 10% the potassium oxide content in GSA gets increases which disrupt the concrete, thereby decreases its strength. This is illustrated in fig.1
Fig. 1: Average Compressive Strength for all replacement
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Durability Studies on Concrete by using Groundnut Shell Ash as Mineral Admixture (IJIRST/ Volume 3 / Issue 10/ 029)
Durability Test Water Absorption Test Table – 3 Water absorption test result for M25 grade concrete after 90 days curing Type of Concrete CC
GSA
Notation CC 1 CC 2 CC 3 GSA 1 GSA 2 GSA 3
Wet Weight (Kg) 2.52 2.49 2.47 2.45 2.54 2.50
Dry Weight 2.47 2.43 2.42 2.41 2.49 2.46
% Water Absorption 2.024 2.469 2.066 1.633 2.008 1.626
% Avg.Water Absorption 2.186
1.756
The figure 2 shows that water absorption for conventional concrete is more than optimum mix because the GSA is a fineness material, it may block the pores in the concrete there by decreases its water absorption capacity.
Fig. 2: Average water absorption Test
Chloride attack test Table – 4 Chloride attack test result for M25 grade concrete after 28, 56 and 90 days curing Type of concrete CC
GSA
Notation CC 28 CC 56 CC 90 GSA 28 GSA 56 GSA 90
Wt. before exposure 2.46 2.48 2.51 2.53 2.50 2.52
Wt. after exposure 2.49 2.52 2.56 2.55 2.54 2.57
%Weight gain 1.205 1.587 1.953 0.780 1.575 1.946
Average compressive strength (N/mm2) 28.520 27.923 27.431 28.824 28.246 27.832
Days 28 56 90 28 56 90
The figure 3 shows that, the chloride effect is more for conventional concrete compare to optimum concrete. The figure 3 shows that, the chloride effect is more for conventional concrete compare to optimum concrete.
Fig. 3: Average compressive strength for chloride attack test
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Durability Studies on Concrete by using Groundnut Shell Ash as Mineral Admixture (IJIRST/ Volume 3 / Issue 10/ 029)
Acid attack test Table – 5 Acid attack test result for M25 grade concrete after 28,56and 90 days curing Type of concrete CC
GSA
Notation CC 28 CC 56 CC 90 GSA 28 GSA 56 GSA 90
Wt. before exposure 2.52 2.55 2.49 2.45 2.43 2.48
Wt. after exposure 2.47 2.49 2.42 2.41 2.38 2.43
%loss 1.984 2.353 2.811 1.637 2.058 2.016
Average compressive strength (N/mm2) 28.52 28.34 27.95 28.93 28.67 28.12
The figure 4 shows that there is weight reduction of concrete due acid attack. The acid attack is more severe in Conventional concrete than optimum mix. V. CONCLUSION During this experimental study of groundnut shell ash concrete, it is indicated that a combination of OPC and GSA can be effectively used to optimize the behavior of concrete. A description is given for an optimum combination of cement and GSA in concrete. On the basis of the investigations it shows that there is a decrease of strength due to increases of potassium content in concrete. Addition of GSA in concrete proves to give the desired strength in concrete. The compressive strength of 10% replacement of GSA shows an increase of 2.95% and 1.21% for 7 and 28 days respectively when compared to the conventional concrete. Acid attack and chloride attack test shows that the optimum mix has better resistance to acid and chloride attack when compare to conventional concrete Test conducted on water absorption showed that the optimum mix with GSA absorbs only less amount of water when compared to Conventional mix. This may be attributed to the fineness of GSA that blocks the pores thereby reducing its water absorption tendency REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20]
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