SUBGRADE STABILIZATION USING RICE HUSK ASH AND CEMENT

Abstract

Subgrade acts as foundation for a pavement structure. Subgrade soil plays an important role in performance of the road pavement as it provides bearing support to the overlying pavement layers. Subgrade stabilization has become a major issue for areas having weak soil conditions. Soil strength can be increased through addition of chemical additives like cement, lime, Rice Husk Ash, Fly Ash etc. depending on the availability of additives. Stabilization of soil using cement or lime only is not cost effective. The use of Rice Husk Ash may minimize cost as it can act as a stabilizing agent. It will also minimize the environmental hazards as its disposal causes environmental pollution. The present study is carried out on the soil of Islamabad-Murree-Muzaffarabad Expressway near Shawala to investigate its stabilization potential. A small amount of cement is mixed with different percentages of Rice Husk Ash (RHA). Soil properties like, Optimum moisture content (OMC), Maximum dry density (MDD), California bearing Ratio (CBR) and unconfined compressive stress (UCS) are observed. The results obtained show that the increase in RHA content increases the Optimum moisture content but decreases the Maximum dry density. There is a considerable increase in the CBR value and UCS of soil with RHA content. After increase in a certain percentage of RHA content the strength of soil starts decreasing. Addition of 6% cement and 15% RHA content is recommended as an optimum amount to gain maximum improvement in strength.