Determination of Optimum Cement Content for Stabilization of Soft Soil and Durability Analysis of Soil Stabilized with Cement

Abstract

This research was aimed at finding the optimum cement content for achieving maximum compressive strength and stabilization in soft soil found in the periphery of the city of Chittagong. But, gaining strength was not considered enough unless it can be proved that strength was gained without compromising the durability. As such, durability test was performed on the samples stabilized with different percentages of cement. In this research three different soil samples were used. The samples were collected from three different areas within the city where future expansion of the city is expected. Six different percentages of cement by weight of soil: 0%, 2%, 4%, 6%, 8%, and 10% were used. Cement was mixed with soil at optimum moisture content. Cubes were casted and their compressive strengths assessed after a curing period of 7, 14 & 28 days. The durability test was done in two different cycles: 2 days wetting-drying and 7 days wetting-drying within a time frame of 28 days. The volume and weight were monitored after completion of each cycle of wetting and drying. The performance of the soils modified with different percentages of cement were assessed using Standard Proctor Test, Unconfined Compression Test and Durability Test. It was found that compressive strengths in the samples under test increased with the increase of cement content up to 8%. But when cement content is increased above 8%, the compressive strength increased but in a slower rate. At the end of durability test, it was observed that volume, and weight of the soil samples produced with 2, 4 and 6% cement changes with the variation in wetting and drying periods. But when the cement percentage is increased by 6%, preferably increased to 8%, no appreciable change in weight and volume were observed after the wetting and drying cycles. The samples going through the two days wetting and drying cycles under durability test showed greater unconfined compressive strength compared to samples going through seven days durability cycle of wetting and drying. It may be mentioned here that the three soil samples stabilized with cement did not show any major degradation in compressive strength during durability test.