THE EFFECT OF BOTTOM ASH AND KAOLIN ON THE STRENGTH OF POOR SUBBASE

Abstract

The lateritic soil in this study represented weak subbase for road construction. This induced
low compressive strength and poor durability of subbase. This research investigated the use of bottom ash
and kaolin to improve the strength and durability of lateritic soil. The unconfined compressive test conducted
on the soil samples mixed with cement at 1-1.5%, kaolin at 0.5-1% and bottom ash at 2-8% by weight of soil.
The samples were cured in a plastic bag at 3, 7 and 14 days then soaked in the water at 2 hours before the
test. The results shown the unconfined compressive strength of the soil improvement tends to increase with
an increase in the amount of bottom ash. The soil mixed with cement at 1.5%, kaolin at 0.5%, and bottom ash
at 6-8% can be developed the strength near the soil mixed with cement at 3% in 7 days. Moreover, the soil
samples mixed with bottom ash at 6%, kaolin at 0.5% and cement at 1.5% can be increased the compressive
strength 87% of the samples without bottom ash and kaolin. The strength requirement of subbase
improvement is 689 kPa at the curing time 7 days. The results demonstrated the strength of soil mixed with
cement at 1.5%, kaolin at 0.5% and bottom ash at 4-8% was higher than the requirement. In conclusion, bottom
ash and kaolin can develop the strength of poor subbase and reduced the utilized amount of cement to
improve the strength of soil.