Strength Development of Soft Marine Clay Stabilized with Cement and Fly Ash

Abstract

                This study combined the concepts of chemical ground improvement technique with environmental geotechnics for improvement of a soft marine clay. The objectives were to study strength development of the cement stabilized soils and to illustrate potential use of the fly ash obtained from a vegetable oil factory as a cement replacement material. Attempt was also made in order to elucidate contributions of fly ash as well as reaction products to the development of strengths. Hardening effects were investigated through unconfined compressive strength. In order to elucidate strength development and its correlations to reaction products, X-ray diffraction analysis (XRD) were also performed after strength tests.

                Based on the experimental results, strengths were markedly increased when mixed with OPC and OPC with 10% fly ash replacement. Soil mixtures with fly ash content higher than 20% exhibited relatively lower strengths at short term, however, steady gains in strength could be observed at long term. In addition, correlations between reduction on strength and fly ash content were proposed and prediction on strengths for the predetermined fly ash content could be made. It could be concluded that strength development was attributed to the hydration and pozzolanic reactions. It was also found that increase in compressive strength was directly proportional to amounts of the major reaction product such as calcium silicate hydrate (CSH).