Use of crushed clay brick and pumice aggregates in lightweight geopolymer concrete

The study aimed to examine the properties of lightweight high-calcium fly ash geopolymer concrete (LWGC) containing crushed clay brick and pumice aggregates. A high-calcium fly ash activated by sodium silicate and sodium hydroxide solutions was used as the geopolymer binder. The properties of LWGCs including workability, compressive strength, splitting tensile strength, surface abrasion resistance, density, thermal conductivity, ultrasonic pulse velocity, and fire resistance were investigated and compared with those of the normal density control geopolymer concrete. Temperatures corresponding to 400 °C, 600 °C, and 800 °C were used to test the fire resistance of the concretes. The results indicated that both crushed clay brick and pumice LWGCs exhibited better thermal insulation and fire resistance characteristics when compared to that of the geopolymer containing natural aggregates (CGCs). The results suggested that the LWGCs produced with crushed clay brick aggregate are suitable for structural lightweight concrete. With respect to LWGCs produced with pumice aggregate, the compressive strength was significantly lower, and is sutiable for the manufacture of concrete blocks.