In this research, the effects of natural seawater (SW) on the properties of alkali-activated slag/fly ash (AASF) are studied. AASF prepared with deionized water is set as the reference mixture. The results showed that the use of natural SW resulted in a prolonged setting time and lower heat release, but no obvious impact on the flowability of AASF specimens. The long-term compressive strength became higher when SW was used, whereas the corresponding flexural strength and fractural toughness turned lower. The use of SW induced the formation of new products that were not identified in the reference mixture, such as Cl–hydrocalumite and gypsum. In addition, it is evidenced that the dissolution of fly ash (FA) particles was significantly delayed with the incorporation of SW. All these results were related to the various ions introduced by the natural SW and their interactions with the alkaline activator as well as the precipitation of salts on slag and FA surfaces or in the matrix.

One-part alkali-activated slag (AAS) binders are more promising in large-scale constructions because one-part mixing procedure is safer and easier to handle compared to normal two-part method. Thus, this study aims at investigating different properties of one-part AAS binders and control samples prepared using the two-part method. Experimental results of the former suggested the hardening time was greatly extended, but the workability showed little difference. Besides, compared to the control, one-part AAS binders had similar early compressive strength (within 7 days) and flexural strength in all tested curing stages but lower later compressive strength (from 28 days). The characterisation of the porous structures suggests that there were fewer C-A-S-H gels for one-part binders evidenced by less volume of mesopores but with larger amount of bigger pores. In addition, mineralogical and microstructural analyses imply that there was no hydrotalcite formed in the one-part AAS binders. Moreover, one-part AAS binders are more susceptible to efflorescence, presumably further affecting their surface and long-term durability.