Suitability of Rice Husk Ash to Improve Geotechnical Properties of Soil for Embankments

This study investigates the applicability of Rice Husk Ash (RHA) as an alternative material for soil improvement. The soil was obtained from a borrow pit located in Kuduvil, Sri Lanka (7°16'36.0"N 81°45'32.8"E) and RHA was collected from a power plant belonging to the Bio energy Solution (Pvt) Ltd, located in Oluvil, Sri Lanka (7°19'28.1"N 81°50'54.0"E ). The soil was blended with RHA in weight percentages ranging from 0% to 18% at an increment of 3% to study the improvement of particle size distribution analysis, liquid limit, plastic limit, specific gravity, California Bearing Ratio (CBR), Maximum Dry Density (MDD), Optimum Moisture Contend (OMC) and Unconfined Compressive Strength (UCS) of the samples. Results showed a good improvement in particle size distribution with increasing percentage of RHA. As the RHA percentage increased from 0% to 18%, the liquid limit and plastic limit increased from 36% to 62.5% and 19.7% to 42.4%, respectively. Further, the MDD decreased from 1,980 kg/m3 to 1,610 kg/m3 whereas the optimum moisture content increased from 8% to 16.25%. In addition, CBR increased by up to 30% from 7.6% to 15% of RHA, and decreased subsequently. Similarly, UCS increased at 6% of RHA, followed by a decrease thereafter. It was revealed that 9% of RHA amendment provided an optimum mix proportion yielding overall the best results. Furthermore, a series of correlations between CBR and geotechnical properties were derived using multiple linear regression analysis.