Effect of alkali activator concentration and curing condition on strength and microstructure of waste clay brick powder-based geopolymer

The effect of alkali activator concentration and curing conditions on consistency and strength of waste clay brick powder-based geopolymer composites was investigated. For this purpose, geopolymer mortars with twenty different activator concentrations were produced and those mixtures having optimum alkali activator concentration were subjected to different curing conditions. Test results indicated that the optimum alkali activator concentration corresponded to Ms (SiO2/Na2O) ratio of 1.6 and Na2O content of 10% by weight of the binder. A maximum compressive strength of 36.2 MPa was achieved by curing at 90 °C, 40% RH for 5 days. In order to characterise the morphology and the structure of the resultant composites, x-ray powder diffraction analysis, thermogravimetric analysis, fourier transform infrared spectroscopy analysis, scanning electron microscopy analysis and micro computed tomography analysis were performed. It was determined that the microstructure analysis results were consistent with the compressive strength results. Denser structure was observed by microstructure analysis in the mixtures having high compressive strength.