The Replacing Efficiency Factor of Biomass Ash for Cement Stabilized Low Swelling Clay

Abstract

This research studied the soil improvement with the concepts of chemical ground improvementtechnique on soft clay. The main objective of this study was to present the possibility of utilizing biomassash to partially replace Type I Portland cement for stabilization of a low swelling clay. The kaolinitic soiland soft Bangkok clay in this study are represented the low swelling clay. Type I Portland cement was usedas a main stabilizer and biomass ash was partially replaced with 10-40 % by weight of cement. Thecompressive strengths were investigated through unconfined compression test. For this experimentalresult, strength of the stabilized clay, the 20% biomass ash replacement produces the highest strengthbetween 14 – 60 days of curing. It is found that the prime parameter controlling the strength of cementbiomassash stabilized clay is the clay-water/blended cement ratio, wc/C*. The binder content of the blendedcement, C*is the summation of the input of cement, Ci and the equivalent cement, Ce. The Ce is determinedbased on the concept of an efficiency factor (k), which is adopted as a measure of the relative performanceof supplementary cementing material compared with Type I Portland cement. The Ce is equivalent to k.Fwhere F is biomass ash content and k is efficiency factor. From the analysis, the value of k is dependentupon the replacement ratio and curing time, and irrespective of binder content and water content. Aphenomenological model for assessing the strength development is introduced and verified. It can possiblybe applied as a simple and rational tool for predicting the other blended cement stabilized low swellingclays.