Soft clay improvement using kaolin-Rice husk ash geopolymer activated by sodium hydroxide

Abstract

This research studied the improvement of Bangkok clay using kaolin - rice husk ash activated by sodium hydroxide. Kaolin (KA) was thoroughly mixed with rice husk ash (RA) in the proportion of KA: RA 90:10, 80:20, 70:30, 60:40 and 50:50.  The mixture was then activated by sodium hydroxide solution of 8 molar concentrations at the optimum moisture content. The maximum unconfined compressive strength (q_u) was obtained from sample with KA: RA 70:30 which was used as soil stabilizing agent. The clay samples were treated by KA-RA geopolymer replacement of 10, 20, 30, 40, and 50% by weight of dry soil. The samples were cured at 25, 70, and 100°c for 7, 14, 28, 60 and 120 days. Engineering properties were tested including unconfined compressive strength, durability in term of wetting and drying condition, and permeability. Clay sample replaced by 30% KA-RA geopolymer at curing period 60 days and curing temperature  70°c exhibited q_u  115.38 ksc, which is close to qu at curing temperature  100°c but the advantage is more energy saving. Moreover, unconfined compressive strength after 12 rounds of wet and dry conditions was 93.55 ksc which comply with the ASTM D559 A permeability coefficient (k) is 7.25 x 10^-7 cm/s which can be used as impervious material and extends service life as well.