Modified Free Swell Index for Clays

Free swell tests are commonly used for identifying expansive clays and to predict the swelling potential. The method as proposed by Holtz and Gibbs suffers from inaccuracies in volume measurement of dry powder in air. In this paper, a nondimensional modified free swell index is proposed, which removes the uncertainties present in the Holtz and Gibbs method. The modified free swell index is shown to bear unique correlations with liquid limit (volume basis) and percent swell of oedometer specimens compacted to proctor optimum conditions.