ABSTRACT
The use of expansive soils in civil constructions can damage the structure due to volumetric fluctuations. The coffee husk ash was mixed with expansive soil in different proportions, and the laboratory tests including compaction, free swell, Atterberg limits, sieve analysis, and California bearing ratio (CBR) were used in this study to examine their properties. The neat soil presented high to very high degrees of expansion, reaching a swell of around 1.66% and plasticity index of 32.16%. To evaluate the effect of coffee husk ash (CHA) in soil-ash mixtures using CHA contents of 5%, 10% and 20%, the results confirmed that as CHA content increased to 20% the properties of neat expansive soil were modified due to reduced clay fraction, increased silt fraction and CBR to 19.70%, and decreased plasticity index and CBR swell to 20.61% and 0.47% respectively.
