Manufacture and performance of cold bonded lightweight aggregate using alkaline activators for high performance concrete

Cold bonded lightweight aggregate (LWA) was produced by adding 12–50% ground granulated blast furnace slag (GGBS) and/or rice husk ash (RHA) to fly ash (FA) by the pelletization process without cement additives. Alkaline activator solution (as a combination of sodium silicate and sodium hydroxide) was the wetting agent acting as coagulant. The selected LWA was used as coarse aggregate for producing high performance concrete. The addition of GGBS and RHA in both binary and ternary blends improved crushing strength of LWA. The crushing strength of the binary and ternary blends was in the range of 6.0–15.7 MPa, while that of the only use of FA was 5.7 MPa. The unit weight of LWA ranged from 769 to 1060 kg/m3. Fresh high performance lightweight concrete (HPLWC) with unit weight in the range of 1836–2056 kg/m3 showed excellent flow-ability without bleeding or segregation. The 28-day compressive strength of HPLWC in the 14.8–38.1 MPa range was obtained. The electrical resistivity and ultrasonic pulse velocity results showed that the physical conditions of HPLWC with the binary use of FA and GGBS and the only use of FA was better than that of the others.