Setting and mechanical properties of alkali-activated fly ash/slag concrete manufactured at room temperature

This study aims to investigate the setting and mechanical properties of alkali-activated fly ash/slag concrete manufactured at room temperature. It also examines to what extent the slag in the alkali-activated fly ash/slag mixture improves the mechanical properties of the mixture under room-temperature curing conditions. A series of tests of the compressive strength, elastic modulus, splitting tensile strength, flow, setting time, and porosity of the alkali-activated fly ash/slag concrete were carried out. The test results showed that the setting time decreased as the amount of slag and the concentration of the NaOH solution increased. The proper slag content in an alkali-activated fly ash/slag mixture was determined to be 15–20% of total binder by weight considering the setting time and compressive strength of the alkali-activated fly ash/slag concrete cured at room temperature. In addition, the modulus of elasticity and splitting tensile strength of the alkali-activated fly ash/slag concrete were slightly lower than those of ordinary concrete as predicted by the ACI code and Eurocode 2. The total porosity of the alkali-activated fly ash/slag mortar was similar to that of ordinary cement mortar, whereas the mean pore size tended to be smaller than that of ordinary cement mortar.