Microstructural Investigation and Strength Properties of Clay Stabilized with Cement, Rice Husk Ash and Promoter

Abstract

A clay soil, classified as Clay of High plasticity (CH) according to Unified Soil Classification System (USCS) was stabilized with cement, Rice Husk Ash (RHA) and promoter. The mineralogy of the clay soil and the morphology of the clay and clay specimens admixed with varied composition of cement, RHA and promoter were evaluated in order to determine effect of the RHA on promoter stabilization of cement based clay soil. The promoter used in this study consists of calcium chloride and sodium hydroxide in the ratio of 1:1. The clay was remolded at standard Proctor compaction energy and the specimens were mixed with 0, 1.0, 2.0 and 3.0% cement, admixed with 1.0, 2.0, 3.0% RHA each, and 0.3, 0.6, 1.0% promoter each. The molded specimens were cured for 1, 7, 14, 28, 60 and 90days before testing for Unconfined Compressive Strength (UCS) and consequently the modulus of elasticity. The UCS of specimens without cement increased from 20 kN/m2 for the natural clay soil to 95 kN/m2 on addition of 3% RHA and 1.0% promoter after 28 days of curing, representing 475% increase in the UCS. This increase was confirmed by morphology of the clay soil mixed with RHA and promoter only, which showed presence of calcium silicate hydrate. Addition of 3.0% cement with 3 and 1.0% RHA and promoter respectively, increased the UCS from 220 to 375kN/m2 after 28 days of curing, which was also confirmed by the morphology of the specimens. The highest elastic modulus of 48.3 MPa was observed at specimens containing 3% cement, 3% RHA and 1.0% promoter.