Effect of POFA as a replacement material on fly ash based geopolymer mortar

Abstract

Ordinary Portland Cement (OPC) is widely used as the material for the construction. The production of OPC has caused an issue on the environment, due to the release of CO2 in the air. The use of by-product or waste material from the industry as an alternative material in the concrete was considered to be a solution to cover this issue. Geopolymer was the advance method that was able to use by-product or waste material to replace OPC as the binder in the construction. However, this material should be rich in content of Si and Al, it was due to the reaction of waste material with the alkaline solution formed the gel of Si-O-Si and Si-O-Al that contributed to the mechanical properties especially compressive strength. Palm oil fuel ash (POFA) is a waste material from the furnace of oil palm that is also rich in the content of Si and Al so that it was considered a new material in geopolymer binder. The method to general geopolymer binder referred to the conventional method. The results showed that the analysis of XRD described the material of POFA in the crystalline with mullite, magnetite, hematite, and rutile. The analysis of FTIR identified that the material POFA has the stretching in the gel of Si-O-Al. The analysis of SEM showed that the particle of POFA has a rough surface that reduced the workability and longer setting time compared to the mixture of FA based geopolymer. Furthermore, the maximum compressive strength is 23 Mpa with the replacement of 5% POFA.