Effect of coffee husk ash on geotechnical properties of expansive soil

Road constructed on an expansive soil needs special attention during the design and construction stages. This study investigates the possibility of using coffee husk ash as an expansive soil stabilizer. Coffee husk is a by-product of coffee beans: when coffee husk is burnt the resulting ash is coffee husk ash (CHA). To investigate the effect of adding CHA to an expansive soil, laboratory experiments such as Proctor density, swelling index, consistency limits and unconfined compressive strength (UCS) tests were performed for different percentages of CHA. Standard Procter tests were conducted to evaluate the compaction behavior and unconfined compressive tests were performed on samples of 5 cm diameter and 10 cm height, after curing for 1, 7 and 14 days. The laboratory test results show that the addition of CHA increases compressive strength and decreases swelling ratio and shrinkage. From Atterberg limit and Proctor tests a decrease in the plasticity index and optimum moisture content while an increase in dry density as the CHA percentage increases were observed. The study reveals that the addition of CHA improves the geotechnical properties of expansive soil.