Effect of curing temperature on the soil physical and mechanical properties on clay shale geopolymer fly ash stabilization

Abstract

Clay shale will have a low strength and durability when exposed to weathering. The properties can be improved by geopolymer stabilization. Geopolymer is the latest method in recent years, and it shows its economic benefits and lower carbon footprint. This study utilizes fly ash-based geopolymer to examine the effect of curing temperatures on the physical modification and strength behavior. The clay shale was taken from the road-side slope of the Bawen-Semarang toll road. The geopolymer was made of fly ash and an activator. The activator ratio was 1:2 for sodium hydroxide (NaOH) and sodium silicate (Na2SiO3), diluted with water to create a 12 M solution. All specimens underwent a seven-day curing period. Prior to conducting the unconfined compressive strength test, the specimens were subjected to various curing temperatures from 26oC to 60oC. The test result shows that, in general, the soil density increased with the temperature but the soil moisture and volume decerased. The dry density exhibited an increase from 1.66 g/cm3 to 1.84 g/cm3, while the unconfined compressive strength multiplied about 3.5 times. Meanwhile, the moisture content decreases from 19% to 2.5% after curing. The results led to the specimen volume experiencing decrement due to the shrinkage during the curing period. The volume reduces from 67.7 cm3 to 63.5 cm3. In general, temperature play a significant role in enhancing the strength of clay shale stabilized with fly ash-based geopolymer.