Performance of geopolymer mortar cured under ambient temperature

Abstract

Recently, the application of green concrete as an alternative for conventional concrete has become popular worldwide. The innovative green concrete can be produced using waste materials as one of its components. Therefore, recent years witnessed a huge increase in the studies that investigate geopolymer’s fresh and hardened properties. The previous studies show that workability loss, rapid setting time and the need for heat curing are the main constraints that restrict the production of cast in place geopolymer concrete. This study aims to reach the optimum activator modulus which achieves the maximum compressive strength with acceptable workability. Nine different mixtures were blended using industrial by-products, such as Ground Granulated Blast Furnace Slag (GGBS) and Metakaolin (MK). Two main materials mixtures were used; either slag or 50/50 slag/MK. Sodium hydroxide and sodium silicate were used as an activator. The main variables were the base material (GGBS and MK), water/binder ratio (0.0, and 15.0%), and modulus of silicate (1.1, 1.3, 1.5, and 1.7). Fresh and hardened properties were examined using the flow table test, and compressive strength test, respectively. It has been observed that by increasing the modulus of silicate, the workability increased and the compressive strength decreased. Adding water decreased compressive strength significantly, as well. Based on the statistical analysis, it was concluded that the mixture of 1.7 modulus of silicate is the optimum mixture. It worth mentioning that the compressive strength of the optimum mixture after 7, 28 and 90 days of water curing were 19.6, 33.4 and 35.6 MPa, respectively, and its flowability was about 150%.