GEOTECHNICAL CHARACTERIZATION OF LATERITES STABILISED WITH SAWDUST ASH-LIME AS SUBGRADE MATERIAL IN ROAD CONSTRUCTION

ABSTRACT 

Samples  of  laterites  classified  by  American  Association  of  State  Highway  and  Transportation Officials (AASHTO) as A-7-6 and A-7-5, collected from two different borrow pits in Ado-Ekiti were tested for the assessment of their geotechnical properties in natural and stabilized states. The research is aimed at assessing effects of sawdust ash (SDA), lime and the combination of sawdust ash and lime (SDAL) on the properties of the soil samples. The samples were subjected to laboratory tests such as particle size distribution, consistency limits, compaction and California bearing ratio (CBR). SDA and lime were added separately to the soil samples in steps of 2% until it reached 10%. The effects of sawdust ash was uneven on the plasticity of the soil samples, while increase in lime contents up to 8% reduces the plasticity of the samples. The properties both soil samples improved with 8% (4:4) SDAL, as the plasticity index reduced from 21.75% at 0% to 19.13% and 36.31% at 0% to 28.87%, the maximum dry density (MDD) of both samples also increases from 1565 kg/m3 at 0% to 1740 kg/m3 and 1500 kg/m3 at 0% to 1710 kg/m3, the CBR values increases from 1.12% at 0% to 6.71% and 1.83% at 0% to 4.89% for soil samples 1 and 2 respectively. From the results gathered from the study, it was concluded that SDAL is suitable for poor rated laterites.  Keywords: Sawdust ash, Liquid limit, Lime, Laterite, Stabilization