Pulverised coal bottom ash (PCBA) obtained as residue from the firing of coal was tested on cement stabilised tropical black clay classified as A-7-6 or CL in the AASHTO and Unified Soil Classification Systems, respectively. PCBA at stepped concentrations (5,10,15, 20,25 and 30%) were admixed with soil — cement mixtures containing 2,4,6 and 8% cement by weight of dry soil, respectively, in order to establish the soil improving potentials of the pulverized coal bottom ash. Unconfined compressive strength (UCS) and California bearing ratio (CBR) tests on the admixture stabilised tropical black clay specimens (i.e. soil — cement — PCBA) yielded peak values at 5% PCBA concentration, in all cases considered, which were markedly higher than values obtained for the natural soil and soil — PCBA combination.