Stabilization of black cotton soil subgrade using sawdust ash and lime

This research dwells on how black cotton soil (BCS) could be stabilized and made a suitable subgrade material using sawdust, a readily and cheaply available material. Sawdust was burnt to ashes in a furnace at a temperature of 800 degrees C and then mixed with BCS in varying proportions of 4%, 8%, 12%, 16% and 20%. Since the trial mixes showed that the use of 16% sawdust ash gave better results, the BCS treated with optimum sawdust ash content of 16% was further stabilized with 2%, 4%, 6%, 8%, and 10% lime. Optimum reduction in liquid limit, differential free swell, plasticity index as well as optimum increase in CBR and specific gravity was achieved when BCS treated with 16% sawdust ash was stabilized with 4% lime. Scanning electron microscope images of the freshly prepared stabilized soil showed the occurrence of flocculation and agglomeration while X-ray diffraction tests on the cured stabilized soils showed the occurrence of pozzolanic reactions. It was thus concluded that treating BCS with sawdust burnt in an appropriate environment and combined with lime enhances its strength. It also offers another way to dispose of sawdust. (C) 2019 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.