EVALUATION OF THE ENGINEERING PROPERTIES OF FLY ASH-BASED GEOPOLYMER BRICKS

This paper is aimed to evaluate the engineering properties of fly ash-based geopolymer bricks. Four geopolymer brick mixtures were designed with a constant solution-to-binder ratio of 0.40 and various concentrations of sodium hydroxide solution. The engineering properties of fly ash-based geopolymer bricks consisting of compressive strength, unit weight, water absorption, water permeability, and ultrasonic pulse velocity were investigated. The microstructure of fly ash-based geopolymer bricks was also investigated by using the scanning electron microscope (SEM). Test results indicated that the compressive strength, unit weight, and ultrasonic pulse velocity (UPV) of geopolymer bricks increased, while the water absorption and water permeability of geopolymer bricks reduced with increasing NaOH concentration. Moreover, brick samples with high NaOH concentration showed a higher geopolymeric reaction of fly ash than brick samples with low NaOH concentration. All geopolymer brick samples produced in this study showed a good quality with compressive strength of above 10.1 MPa, water absorption of below 9.4%, water permeability of below 1.84 L/m2 .h, and UPV of above 2500 m/s.