Strength and microstructural of geopolymer mortar from palm oil ash containing alumina powder with palm oil clinker aggregate

Abstract

This paper presents geopolymer mortars from palm oil ash (POA) containing alumina powder (AP) with palm oil clinker (POC) for fine aggregate. Different AP contents in the geopolymers were investigated along with binder (BD) to alkali activator (AK) ratio, BD to ordinary Portland cement (OPC) ratio, curing conditions and heat curing time. The geopolymer samples were studied for compressive strength, bulk density and microstructure. A combination of sodium hydroxide and sodium silicate was used as an activator. The microstructure was analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray fluorescence (XRF) to detect changes in the geopolymerization process. Results showed that addition of AP increased the compressive strength of the geopolymer binders. At 28 days, compressive strength of up to 18.99 MPa was achieved in samples cured at 80 °C for 24 h, with BD to POC ratio of 1.4 and BD to AK ratio of 1.44 with 5% AP. SEM results showed that the 5% AP samples had a dense compact matrix with higher compressive strength. The POA based geopolymer containing AP with POC as fine aggregate had bulk density ranging from 1,004 to 1,911 kg/m³ at 28 days.