Volume change behaviour of an expansive clay blended with lime and pond ash – controlling swell

Abstract

This paper presents the influence of lime content on free swell index (FSI) of an expansive clay powder passing through a 425 µm sieve and on some significant swell-compressibility characteristics of oven-dry, expansive clay with grains of a size <4.75 mm. One-dimensional swell-consolidation tests were conducted on the expansive clay passing through a 4.75 mm sieve to which lime powder (CaOH2) was added at 0, 1, 2 and 4% by dry weight of the clay. Swell potential, swelling pressure, coefficient of compressibility (av), compression index (Cc) and linear shrinkage (LS) were evaluated. While av, Cc and LS decreased significantly with increasing lime content, swelling pressure increased. Heave and swell potential also decreased with increasing lime content but only up to 2% and were found to have increased at 4% lime content. The paper also compares the swell-compressibility behaviour of 2% lime-blended expansive clay lumps and powders. Heave and swell potential were higher for clay powder than for clay lumps at 2% lime. However, swelling pressure (ps) was found to be more for clay lumps than clay powder. Furthermore, the paper also presents the variation of FSI and swell-compressibility characteristics of another expansive clay powder (of different properties) blended with pond ash contents of 0, 5, 10, 15 and 20%. One-dimensional swell-consolidation tests were conducted on clay–pond ash blends in an oedometer. Swell potential and swelling pressure decreased up to 15% of pond ash content and increased thereafter, when pond ash content was increased to 20%. FSI of the ash-blended clay specimens was also determined. FSI continuously decreased with increase in pond ash content.