Studies on compressive strength of sand stabilized by alkali-activated ground bottom ash and cured at the ambient conditions

Abstract

Background: Bottom ash is a by-product generated during the coal combustion of thermal power plant. Bottom ash-based geopolymer has been reported as a promising substitute of cement in concrete. Methods: In this study, bottom ash collected from Honam Coal Power Plant was ground to be used as a soil stabilizer. Sodium hydroxide solution (NaOH) with different molarity concentration and sodium silicate solution (Na 2 SiO 3 ) were added to enhance the polymerization reaction of ground bottom ash. The effects of water/ground bottom ash, Na 2 SiO 3 /NaOH ratio and concentration of NaOH solution on the unconfined compressive strength of sand mixture at the ambient curing conditions were investigated. Results: The results indicated that ground bottom ash can be utilized to stabilize sand as a main binder at the ambient curing conditions. In particular, with the 4 M concentration of sodium hydroxide solution, the Na 2 SiO 3 /NaOH ratio of 1.5 and the water/binder ratio of 0.35, the highest compressive strength obtained at 28 days was around 9 MPa. Conclusions: The compressive strength of sand mixture increased with an increase of NaOH solution concentration and the ratio of Na 2 SiO 3 /NaOH, however, it dramatically decreased with the addition of water to the mixture.