Effects of natural seawater mixing on the properties of alkali-activated slag binders

A series of experiments were conducted to investigate the effect of seawater on the properties of alkali-activated slag (AAS) binders to seek further potentiality of these binders in marine environments. The experimental results show that on the one hand, seawater may lead to increased setting time, reduced compressive strength after 3 days and a less compact microstructure. On the other hand, however, it could also slightly improve the early age strength, flexural bending strength (after 28 and 56 days) and fractural toughness, and shows almost no impact on the fluidity of AAS binders. Moreover, with the formation of some new hydration products due to seawater mixing, the water absorption and volume of permeable voids had small decreases while the capillary sorptivity obtained a small increase. The concomitant of the acceleration effect due to the presence of salts and hindrance caused by the interaction between the seawater-based alkaline activator and slag make the AAS binding system more complex compared to the distilled water mixed counterparts. The findings of this study reveal the possibility of seawater used as the mixing water for AAS binders in marine or coastal areas.