Properties of lightweight fly ash geopolymer concrete containing bottom ash as aggregates

In order to evaluate the utilization of waste from coal combustion thermal power plant, the properties of lightweight geopolymer concrete (LWGC) containing fly ash as geopolymer binder and bottom ash as aggregates were studied. Sodium silicate solution (NS) and 10 M sodium hydroxide (NH) were used as alkali activators. The NS/NH ratios of 0.5, 1.0, and 1.5 with liquid/ash (L/A) ratios of 0.70, 0.75, and 0.80 were used. The compressive strength, splitting tensile strength, surface abrasion resistance, density, thermal conductivity, and ultrasonic pulse velocity (UPV) of concrete were tested. The results indicated that fly ash and bottom ash could be used to produce LWGCs with compressive strengths of 14.3-18.1 MPa, splitting tensile strengths of 1.2-2.0 MPa, and densities of 1661-1688 kg/m3. Theirs thermal conductivity coefficients of 0.43-0.47 W/m K were lower than those of the geopolymer concrete containing natural aggregate. LWGCs in this study could thus be used for moderate strength concrete and thermal insulation concrete.