Assessment of sustainable eco-processed pozzolan (EPP) from palm oil industry as a fly ash replacement in geopolymer concrete

This research focusses on the feasibility of using eco-processed pozzolan (EPP), a palm oil industrial by-product, as partial replacement for fly ash (FA) in the geopolymer concrete (GPC); in addition, the effect of another palm oil industrial by-product, palm oil clinker (POC) as the lightweight coarse aggregate in the EPP-based GPC was also investigated. The ratios of alkaline activator to binder and sodium silicate to sodium hydroxide were kept constant, and the specimens were cured at 60 degrees C for 24 h. The mechanical properties, namely compressive, splitting tensile and flexural strengths, and modulus of elasticity (MOE) were investigated; further, microstructural analyses such as SEM, XRD and EDX were conducted. The test results show that the utilisation of 10-30% of EPP as FA replacement produced the compressive strengths in the range of 28-39 MPa. The splitting tensile strength of both the lightweight (LW) and normal weight (NW) GPC, except for M6 containing 30% of EPP substitution, fulfilled the minimum requirement of 2.0 MPa. In addition, the flexural strength of GPC produced about 12% of the respective compressive strength. The lower MOE of LW GPC compared to the NW GPC is attributed to the lower stiffness and specific gravity of POC aggregates. The XRD analysis shows the evidence of geopolymerization products of quartz, sillimanite, magnetite, and almandine.