Properties comparison of one-part and two-part alkali-activated slag pastes

In this paper, the fresh and hardened properties of one-part (that is, mixing a solid precursor with a solid alkali activator and adding water) and conventional two-part alkali-activated slag (AAS) pastes with the same mixture proportion were compared with insights obtained from microstructure characterization by using XRD, SEM, and nitrogen absorption techniques. The reaction degree of slag was determined by analyzing the BSE images. Our results showed that one-part AAS exhibited longer setting time but poorer flowability than two-part AAS. Moreover, the acceleration period appeared earlier while the reaction degree of slag at 28 d was lower for one-part AAS. As a result, it showed a less dense microstructure. The compressive strength of one-part AAS was much lower than that of two-part AAS while their flexural strength was similar. The two mixtures experienced comparable mass loss under drying conditions, but one-part AAS showed much lower drying shrinkage and cracking proneness. These results anticipate a bright prospect for one-part AAS in construction scenarios with low strength requirements. • The rheology and microstructure of one-part and two-part AAS pastes were compared. • The slag's reaction degree of two types specimens at 28d was quantified. • The difference of shrinkage between the two AAS binders was emphasized. • One-part AAS is feasible in construction scenarios with low strength requirements.