Shear Strength Improvement of Soft Clay Mixed with Tanjung Bin Coal Ash

Coal is one of the world's most important sources of energy. The burning of coal produces coal ash that mostly consists of bottom ash (BA) and fly ash (FA). However, the utilization of coal ash in civil engineering construction applications has just received some attention within the last decade. This paper presents the strength improvement of soft clay mixed with coal ash. Kaolin was used to represent soft clay; mixed with 20%, 40% and 60% of BA and FA independently by weight. The optimum moisture content of kaolin was used in the mixing. Strength properties of mixtures had been carried out by conducting direct shear test and unconfined compression test. By adding FA to kaolin, the value of shear strength increased between 12 to 39 times the initial strength at different curing periods due to the pozzolanic reactions. From direct shear test of uncured mixtures, both kaolin – FA and kaolin – BA mixtures had similar strength at 40% - 60% FA or BA. Beyond this value as the percentage of FA increased the shear strength decreased but the increase in BA content increase the strength of mixture further.