Chemical stability of fly ash geopolymers

Abstract

Effects of different types of chemical effects on fly ash geopolymers properties have been studied. The fly ash geopolymers would be subjected to chemical immersion of alkali and acid. The properties are studied based on the compressive strength, bulk density, pH test and also FTIR and SEM of fly ash geopolymers. However, compressive strength has increased by the immersion in KOH solution. The immersion of samples in HCL shows decrease of compressive strength. It has proven geopolymer is one of the best materials type that could resist chemical attack. The increase in compressive strength depended on the nature of complex geopolymerisation process.The presence of KOH enchances geopolymerisation but takes quite some time for it to be reactive. HCL immersion decrease the compressive strength and also bulk density as well. Deterioration observed could be linked to depolymerisation of the aluminosilicate, which in some cases lead to significant loses of strength after some time. The compressive strength of geopolymers decreases even more if the duration being exposed to acidic environment increases. During immersion in HCL, the bulk density of fly ash samples decreases due to deterioration of polymer matrix and also formation of fragile grainy structures. For pH of KOH, factors which contribute to increase in pH to more alkaline is due to migration of alkalis from specimen into the solution. However after some point, the migration process stops or diminishes after that. As for FTIR, it can be seen the functional group which each peak represents. The most important factor in the geopolymerization process is the amount of reactive silica because with the presence of KOH activated untreated fly ash which makes it reactive. Geopolymer plays an important part in engineering field especially for chemical resistance. From the environmental perspective, this study aims to preserve or uphold the usage of this beneficial geopolymer and to utilize the industrial waste of fly ash.