International Journal of Civil Engineering and Technology (IJCIET) Volume 7, Issue 6, November-December 2016, pp. 67 72, Article ID: IJCIET_07_06_008 Available online at http://www.iaeme.com/ijciet/issues.asp?jtype=ijciet&vtype=7&itype=6 ISSN Print: 0976-6308 and ISSN Online: 0976-6316 IAEME Publication INFLUENCE OF FLY ASH IN STRENGTH CHARACTERISTICS OF COHESIVE SOILS Jeevanantham V. Assistant Professor, Department of Civil Engineering, Sri Ramakrishna Institute of Technology, Coimbatore, India Jayashree J. Assistant Professor, Department of Civil Engineering, Sri Ramakrishna Institute of Technology, Coimbatore, India ABSTRACT In this work, the influence of fly ash on the behaviour of Expansive soil were studied with varying percentage as 10%,20%,30%,40%,50% and compared with the control sample. For the study, soil sample is collected from the southern coimbatore and the admixture is fly ash categorized under class F. The clay fraction and consistency limit test results show that the sample is Highly Compressible Clay. The free swell value for control sample is 52% and reduced to 45% for 30% fly ash admixture. The standard proctor test result shows that addition of flyash to the soil improves the maximum dry density from 1.45 g/cc to 1.64g/cc and optimum moisture content decreases from 23% to 19.5%. The unconfined compressive strength results of various percentages of fly ash increases from 4.32 kg/cm 2 to 6.115 kg/cm 2 when compared with the control sample. Key words: cohesive soil, Atterberg limits, Standard proctor, Unconfined Compressive Strength Cite this Article: Jeevanantham V. and Jayashree J., Influence of Fly Ash in Strength Characteristics of Cohesive Soils. International Journal of Civil Engineering and Technology, 7(6), 2016, pp.67 72. http://www.iaeme.com/ijciet/issues.asp?jtype=ijciet&vtype=7&itype=6 1. INTRODUCTION Problems like swelling, shrinkage and unequal settlement of structure and Pavements are occurred, when it is get wet. An attempt to study such unpredictable behaviour and through research on how to bring these problems under control. Pre-stabilization is very effective method in tackling expansive soil. Therefore number of laboratory experiments is conducted to ascertain host of soil engineering properties of a naturally available expansive soil before and after stabilization. Pre and post stabilized results are compared to arrive the conclusion. In this study fly ash is the admixture selected. Fly ash is useful in many construction applications because it is a siliceous or alumino-siliceous material which possess cementitious value, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties. So the main objective of flyash addition is to study the performance of soil after adding various percentage of fly ash as admixture and the Effective utilization of fly ash for replacement purposes. http://www.iaeme.com/ijciet/index.asp 67 editor@iaeme.com
Influence of Fly Ash in Strength Characteristics of Cohesive Soils 2. EXPERIMENTAL INVESTIGATION Tests were conducted in laboratory premises by mixing natural clay soil obtained from Southern region of Coimbatore Flyash categorised under class F was collected from Mettur Thermal Power station, Mettur. Random proportions were tried to find out the optimum percentage of admixture in improving the strength characteristics clayey soil. The properties of the materials and tests conducted are furnished below. 2.1. Materials and Properties The properties of the clayey soil and Fly ash in Table 1, 2. Table 1 Properties of clay Properties Values Specific Gravity 2.46 Differential free swell % 40 LL% 44.8 PL % 16.67 PI 28.13 BIS classification CH Table 2 Properties of Fly ash Properties Values Specific Gravity 2.05 Bulk density g/cm3 1.51 PI NP Absorption (%) 1.9 2.2. Laboratory Test on Soil Stabilised with Flyash 2.2.1. Standard Proctor s Compaction Test Standard proctor test were conducted with and without flyash to determine the maximum dry density at minimum optimum moisture content. The additives are added to the soil sample in percentages of 10%, 20%, 30%, 40% and 50% to the dry soil mass. The observed results of Standard proctor test for the corresponding fly ash addition is shown in table 3 and the plot between dry density and moisture content for control sample is indicated in figure 1. Figure 2 indicates the dry density and moisture content values of various proportions of fly ash addition with the control sample. http://www.iaeme.com/ijciet/index.asp 68 editor@iaeme.com
Jeevanantham V. and Jayashree J. Table 3 Standard Proctor test results for various proportions of Fly ash S.No Soil composition OMC % MDD g/cc 1 Soil 23.1 1.44 2 Soil + 10% Fly ash 23.7 1.5 3 Soil + 20% Fly ash 21.4 1.58 4 Soil + 30% Fly ash 20.8 1.64 5 Soil + 40% Fly ash 19 1.6 6 Soil + 50% Fly ash 18.8 1.56 1.46 1.44 Max. dry density in g/cc 1.42 1.4 1.38 1.36 1.34 1.32 13 15 17 19 21 23 25 27 29 Moisture Content in % Figure 1 Standard proctor test for Control sample 1.7 Max. dry density (g/cc) 1.65 1.6 1.55 1.5 1.45 1.4 1.35 1.3 15 17 19 21 23 25 Moisture Content (%) Contr ol samp le 10 % Flyas h 20% Flyas h Figure 2 Standard proctor test for Fly ash proportions http://www.iaeme.com/ijciet/index.asp 69 editor@iaeme.com
Influence of Fly Ash in Strength Characteristics of Cohesive Soils 2.2.2. Unconfined Compressive Strength Test A cylindrical specimens were prepared at the desired water content obtained from standard proctor test. The specimen is then subjected to major principal stress until the failure due to shearing along a critical plane of failure. The tests were repeated with various percentages of flyash. The percentage of additives that carries maximum load can be determined from this test. The plot between compressive strength and strain for the soil sample is shown in figure 3, while the figure 4 indicates the compressive strength and strain values of various proportions of fly ash addition with the control sample. Stress Kg/cm 2 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 0 0.02 0.04 0.06 0.08 0.1 Strain Figure 3 UCS test for Control sample stress kg/cm 2 7 6 5 4 3 2 1 0 0% 10% 20% 30% 40% 50% strain Figure 4 UCS test for Fly ash proportions 3. RESULTS AND DISCUSSION From standard proctor test the optimum moisture content and dry density of swelling soil with various percentage of flyash (0%, 10%, 20%, 30%, 40%, 50%) were determined. The change in maximum dry density and optimum moisture content with addition of fly ash at varying proportions is shown in Figure 5. it is observed that the increase in flyash content increases the maximum dry density and optimum moisture content up to 30% and decreases the both after the 30 % gradually. In flyash treated soil the OMC value decreases from 23% to 19% and increase in maximum dry density is about 1.5 g/cc to 1.6 g/cc.this indicated that the addition of fly ash to black cotton soil will affects the compaction characteristics. http://www.iaeme.com/ijciet/index.asp 70 editor@iaeme.com
Jeevanantham V. and Jayashree J. Max. dry density in g/cc 1.65 1.6 1.55 1.5 1.45 1.4 Max. dry density vs Fly ash % 0 5 10 15 20 25 30 35 40 45 Fly ash addition in % Figure 5 Comparison of dry density values with flyash proportions The results obtained from Unconfined Compression test with varying proportions of fly ash is shown in Figure 6. it indicates that the addition of flyash to clay soil induce pozzolanic reaction in the soil mass and contributing to shear strength improvement. Figure 6 Comparison of compressive strength values with fly ash proportions It is observed that the strength properties of clay soil can be changed favourable using the fly ash addition and the best possible results can yield between 20-30% of fly ash addition REFERENCE Ucs Value in kg/cm2 6.5 6 5.5 5 4.5 4 3.5 3 2.5 2 Compressive Strength vs Fly ash % 0 10 20 30 40 50 60 Fly Ash Addition in % [1] B.Bose, Geo Engineering properties of expansive soil stabilized with fly ash, Electronic Journal of Geotechnical Engineering, Vol. 17, Bund. J, 2012, pp. 1339-1353. [2] Cokca, E, Use of Class C fly ashes for the stabilization of an expansive soil. Journal of Geotechnical and Geo environmental Engineering, 127(7), 568-573, (2001). [3] Lin, B., Cerato, A.B., Madden, A.S., & Elwood Madden, M.E. Effect of Fly Ash on the Behavior of Expansive Soils: Microscopic Analysis. Environmental & Engineering Geoscience, 19(1), 85 94 (2013). http://www.iaeme.com/ijciet/index.asp 71 editor@iaeme.com
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