In-depth investigation on macro-properties and micro-mechanism of sustainable alkali-activated slag/fly ash paste incorporating seawater

The impacts of seawater on the workability, hydration product features, and mechanical properties of alkali-activated fly ash (FA)/ground blast furnace slag (GBFS) binary system (AAFS) are investigated. The potential suitability of the AAFS for application in marine construction projects is discussed. The findings illustrate that seawater considerably enhances the dissolution of AAFS. The high pH of the seawater AAFS (SAAFS) pore solution accelerates the early hydration process. The presence of seawater leads to a relatively wide half-peak width and an increased average crystallite spacing in calcium (alumina) silicate hydration (C-(A)-S-H) gels. Moreover, seawater facilitates the transformation of silicate ions ([SiO4]4-) into highly polymerized state. The final setting time and fluidity of AAFS are reduced by the addition of seawater. Furthermore, the introduction of seawater contributes to higher contents of C-(A)-S-H gels, which densifies the SAAFS matrix and improves the compressive strength of SAAFS.