Performance of fly ash based geopolymer concrete in seawater exposure

Abstract

Geopolymer is a new development in the world of concrete which cement is replaced by pozzolanic materials such as fly ash and activated by an alkali activator. Alkali activator will act as a binder in concrete mixtures. An exposure condition of seawater to the geopolymer concrete is significant to be studied since the properties of concrete will be affected especially exposure to an aggressive environment. The aim of this study is to evaluate the durability of fly ash-based geopolymer concrete in seawater exposure, then compared to ordinary Portland cement (OPC) concrete. The ratios of fly ash to alkali activator (FA/AA) and sodium silicate to sodium hydroxide (Na2SiO3/NaOH) were fixed as 2.0 and 2.5, respectively. The concentration of NaOH used was 12M. The fly ash will be mixed with alkali activator until homogeneous. After moulding process, the sample of concrete will be immersed in seawater for 7, 14, 21, 28 and 60 days. The results showed that the density of geopolymer concrete was higher than OPC concrete. The water absorption for 60 days of curing showed the geopolymer concrete was 0.9%, meanwhile OPC concrete achieved 8.3%. The different percentage of weight loss test for geopolymer concrete and OPC concrete was 1%. The compressive strength for geopolymer concrete was reported as higher than OPC concrete.