Experimental Study of Stabilization on Natural Soil Subgrade Using Rice Husk Ash

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Experimental Study of Stabilization on Natural Soil Subgrade using Rice

Husk Ash

Vikash Kumar Singh

1

_{A. K. Saxena}

2

_{T. R. Arora}

3

1

_{M. Tech. Scholar}

2,3

_Professor

1,2,3

_{Department of Civil Engineering}

1,2,3

_{Lakshmi Narain College of Technology, Bhopal, India}

Abstract— The objective of this work is to utilize the effectiveness of Rice Husk Ash (RHA) material to enhance the properties of natural soil used for subgrade material in pavement. The quality of a flexible pavement depends on the strength of its sub-grade soil. In view of the above the present investigation has been carried out with rice husk ash mixed individually and also in combination with locally available natural soil in different proportions stepped concentration of 5%, 10%, 15%, 20%, 25% and 30% by dry weight of the soil individually are used to stabilized of Natural Soil (CL) and to evaluate its properties like Grain Size Distribution, LL, PL, PI, OMC, MDD, CBR and Swelling Pressure. The test results indicate that the addition of RHA enhances the percentage of grain size distribution, but with addition of RHA till 10% the LL, PL, PI and swelling pressure decreases, while these parameters further increases in this limit beyond i.e. 10% to 30% of RHA while enhancement is observed above 20% to 30%, Specific Gravity and Maximum Dry Density (MDD) decrease with addition of RHA, for all percentage values, whereas OMC increases in each material. The CBR value increases with the addition of RHA till 10%, while it decreases beyond the limit 10% to 30% with addition of RHA.

Key words: Subgrade, Rice Husk Ash, LL, PL, PI, MDD, OMC, CBR

I. INTRODUCTION

India has a road network of more than 33 lakhs km which is the second largest road connecting system in a country in the world. About 65% of freight and 80% of passenger traffic are carried by the roads. Roads are one of the strongest measures of economic activity and the development of any nation. The quality of a flexible pavement depends on the strength of its grade. The sub-grade acts as a support for the entire pavement system. In case of the flexible pavement the sub-grade must be uniform in terms of properties like index, compaction and strength etc. Materials selected for use in the construction of sub-grade must have to be of adequate strength and at the same time it must be economical for use. If the natural soil is very soft and weak it needs some improvement for use as sub-grade. It is, therefore, needed to stabilize the existing weak soil to achieve increased strength and reduced compressibility.

II. RELATED WORK

A number of researchers have studies on soil stabilization for the last few years. Some salient works are as follows; In 1995, Raza and Chandra used were performed used alluvial soil, Rice husk ash and geo-fabric to stabilize expansive soil. For this study, they were performed various test such has Compaction, Swelling, CBR & UCS tests. The result indicates that soil treated with Rice husk ash gave

considerable improvement in CBR value of soil. With incorporation of geofabric CBR value further increased. In 2004, Phanikumar and Sharma used expansive soil, Rice husk ash to stabilize expansive soil properties. For This study ,the following experimental programme was carried out such as Free Swell Index, Swelling potential, Atterberg’s limit, Compaction, UCS, Hydraulic conductivity. The hydraulic conductivity of expansive soils decreases when mixed with Rice husk ash .When the Rice husk ash content increases, there is a decrease in the optimum moisture content and thus maximum dry unit weight increases. The undrained shear strength of the expansive soil blended with Rice husk ash increases with the increase in the ash content. In 2006, Edil et al. used soft fine grain soil, Rice husk ash for improvement of soil properties. For This study, atterberg’s limits and CBR test were conducted. The results indicated that, addition of Rice husk ash appreciably increased CBR and resilient modulus of soils. In 2006, J.N. Jha used soft clay soil and Sugarcane bagasse ash and RHA for the improvement soil properties. For This study, compaction, USC and CBR test were conducted. The result shows that addition of RHA enhances only strength developments but also durability of Sugarcane bagasse ash stabilized soils. In 2002, Pandian et.al. Rice husk ash is used for the improvement of soil properties of black cotton soil. For This study, CBR test was conducted. The results indicated that, addition of Rice husk ash appreciably increases CBR values of expansive soil.

III. MATERIAL USED

The materials used in the present investigation were Rice husk ash and locally available natural soil. The physical properties of these materials are summarized in the following sections.

A. Soil

The Natural soil sample is used in this study were taken from Lakshmi Narain College of Technology (LNCT) Campus Bhopal (M.P) from depth of 2.5 m from ground level. It contains deleterious substances and of various sizes. The soil was air dried and pulverized manually. This natural soil is grey and black in colour.

B. Rice Husk Ash (Rha)

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IV. METHODOLOGY & TEST PROGRAMME

All the tests of soil before and after stabilization with different mixtures of NR Sample were carried out as per the Indian standard. For laboratory tests specimens of soil with and without admixtures were prepared by thorough mixing the required quantity of soil and stabilizers in pre-selected proportions in dry state and then required quantity of water was added and mixed thoroughly to get a homogeneous and uniform mixture of soil and RHA. There are various test performed in laboratory as per IS code standards like test Grain size distribution, LL,PL,PI, specific gravity, compaction, OMC, MDD, swelling and California CBR and their result are discusses by graph and tables which are given below.

The samples used in the research work are Natural Soil, Rice Husk Ash (RHA) and Natural Soil stabilized with varying percentages i.e. (5, 10, 15, 20, 25 & 30%) of RHA individually for the construction of sub grade soil. These parents samples i.e. Natural soil, Rice husk ash are named as N and R notation respectively in further research work. The artificial Mix Samples i.e. NR which are mix of Natural Soil plus Rice Husk Ash, The details of the prepared samples and their notation are discussed below in Table No.1:

S. No

Details of Prepared Samples

Notation used for samples

1 Natural Soil (NS) N

2 Rice Husk Ash (RHA) R

3 Natural Soil + 5% RHA NR-1

[image:2.595.299.555.53.344.2]

Table 1: Details and Notation used for Prepared Samples.

Fig. 1: Natural Soil with RHA Mixture.

V. LABORATORY TEST RESULTS

The laboratory test results for different parameters of NR Sample are presented in Table No.2 below:

S.N. Properties Natural Soil N NR-1 NR-2 NR-3 NR-4 NR-5 NR-6 R

1

Grain Size Distribution

Gravel (%) 18.4 14.89 15.45 12.35 15.36 12.42 12.48 0.27

Coarse Sand (%) 7.2 7.08 15.43 16.3 15.3 17.3 17.1 4.53

Medium Sand (%) 52.6 50.37 46.84 47.4 46.3 31.6 46.1 40.40

Fine Sand (%) 20.3 22.38 20.08 21.12 19.94 19.82 20.6 46.60

Silt and Clay (%) 1.5 1.74 2.2 2.83 3.1 3.36 3.72 8.20

2 IS Classification CL CL CL CL CL CL CL --

3 AASHTO Classification A-6 A-6 A-6 A-6 A-6 A-6 A-6 --

4 Liquid Limit (%) 26.00 21.00 19.00 22.00 24.00 27.00 31.00 NP

5 Plastic Limit (%) 17.40 14.80 13.20 15.90 17.80 18.60 21.20 NP

6 Plasticity Index (%) 8.60 6.20 5.80 6.10 6.20 8.40 9.80 --

7 Specific Gravity 2.63 2.59 2.54 2.48 2.42 2.36 2.28 1.64

8 OMC (%) 12.18 13.88 16.55 19.90 21.70 22.90 25.78 66.57

9 MDD (gm/cm3) 1.88 1.78 1.68 1.64 1.56 1.47 1.43 0.76

10 CBR (%) Unsoaked 7.04 11.73 13.36 11.19 9.93 8.12 6.68 11.19

Soaked 4.21 6.86 7.58 6.50 5.78 4.69 3.79 6.68

11 Swelling Pressure 2.15 1.65 1.40 1.72 1.88 2.06 2.18 1.49

Table 2: Laboratory Test Results for Index, Compaction and Strength Properties of NR Artificial Sample.

VI. RESULTS AND DISCUSSION

The different properties of soil like Liquid Limit and Plastic Limit, Maximum Dry Density and Optimum Moisture Content and California Bearing Ratio are obtained after carrying out tests and different change of these soil properties with addition of RHA Mix are studied as follows. The different properties of NR Sample like Liquid Limit and Plastic Limit, Maximum Dry Density and Optimum Moisture Content and California Bearing Ratio are obtained after carrying out tests and different change of these Natural

soil (N) properties with addition of RHA (R) are studied as follow.

A. Index Properties (Grain Size Distribution, LL, PL, PI and Specific Gravity)

[image:2.595.43.542.265.609.2]

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Fig. 1: Variation of Liquid Limit with Natural Soil and RHA Combinations.

[image:3.595.309.558.55.211.2]

Fig. 2: Variation of Plastic Limit with Natural Soil and RHA Combinations.

Fig. 3: Variation of Plasticity Index with Natural Soil and RHA Combinations.

Fig. 4: Variation of Specific Gravity with Natural Soil and RHA Combinations.

B. Compaction Properties (OMC And MDD)

The variation of OMC and MDD with the different percentages of RHA combinations as shown in Figure No: 5 and 6 respectively shown by below and their details are given in Table No.1.

Fig. 5. Variation of Optimum Moisture Content with Natural Soil and RHA Combinations.

[image:3.595.46.542.217.698.2]

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C. Strength Properties (CBR and Swelling Pressure) The results of California Bearing Ratio tests on the Natural Soil with the various mix proportions of RHA in Unsoaked and soaked conditions as shown in Table No: 2.The different changes of CBR values with different mix proportions in Unsoaked and soaked conditions are also presented in fig.7 and fig.8. The comparative Effect in CBR value of NR Sample towards Natural Soil are also presented in fig. 9.

Fig. 7: Variation of CBR Value with Natural Soil and RHA Combinations.

Fig. 8. Variation of Swelling Pressure with Natural Soil RHA Combinations.

Fig. 9: Variation of Percentage Increase in CBR with

VII. CONCLUSION

The following conclusions may be drawn from the present investigation on the basis of the laboratory test results of RHA stabilized with the Natural Soil:

– In Grain Size Distribution, major part of the soil belong to sand, it has been observed that increasing percentage of RHA decreases the gravel content and increases the silt and clay content in soil mixture. Investigation also shows that all soil mixture belongs to CL Class according to IS classification and A-6 Class under AASHTO classification.

– The results of Liquid Limit tests on CL soil goes on decreasing from 26 to 19%, when RHA Sample is increased from 0 to 10%, increase in from 19% to 31% when RHA Sample is increased from 10 to 30% and further increase of value for 100% RHA is sample shows non plastic behavior.

– The results of Plastic Limit tests on CL soil goes on decreasing from 17.4 to 13.20%, when RHA Sample is increased from 0 to 10% and increase from 13.20 to 21.20% when RHA Sample is increased from 10% to 30%.

– The results of Plasticity Index tests on CL soil goes on decreasing from 8.60 to 5.80 %, when RHA Sample is increased from 0 to 10% and is increases from 5.80 to 9.80% when RHA Sample is increased from 10% to 30%.

– The results of Specific Gravity tests on CL soil goes on decreasing from 2.63 to 2.28 with increase in percentage of RHA from 0 to 30% and 1.64 for 100% RHA.

– The results of OMC of CL Soil continuously increases from 12.18 to 25.78% from 0 to 30% of RHA and for 100% RHA its value is 66.57% and MDD decreases from 1.88 g/cc to 1.43 g/cc from 0 to 30% of RHA and 0.76 for 100% RHA.

– The results of Unsoaked CBR of CL Soil goes on increasing from 7.04 to 13.36% when RHA is increased from 0 to 10% and is decreases from 13.36 to 6.68% when RHA waste is increased from 10% to 30% and for 100% RHA is 11.19% and in Soaked CBR of soil goes on increasing from 4.21 to 7.58% when RHA is increased from 0 to 10% is and is decreases from 7.58 to 3.79% when RHA Sample is increased from 10% to 30% and for 100% RHA is 6.68%. In Soaked and Unsoaked CBR test on soil sample it has been observed that Natural Soil with 10% RHA mix gives maximum value of CBR in both Soaked and Unsoaked condition.

– The results of Swelling Pressure on CL Soil goes on decreasing from 2.15 to 1.40 when RHA is increased from 0 to 10% and is increases from 1.40 to 2.18 when RHA Sample is increased from 10% to 30% and for 100% RHA is 1.49.

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RHA Sample is increased from 10% to 30% and for 100% RHA is 58.67%.

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