Assessment of the performance of alkali-activated slag/fly ash using liquid and solid activators: early-age properties and efflorescence

AbstractThe use of solid activators to prepare alkali-activated materials (AAM) holds great potential for on-site applications, as it eliminates the need to transport and store large quantities of concentrated alkaline solutions. This study compared the early-age properties and efflorescence between alkali-activated slag/fly ash (AASF) using solid and liquid sodium silicates as activators. The results revealed that AASF with solid sodium silicates exhibited comparable mechanical strength while possessing reduced initial setting time and flowability. All AASF mixtures were susceptible to efflorescence and carbonation, resulting in varying mineralogical compositions of carbonation products: Vaterite was detected in AASF with solid activators, while aragonite and pirssonite were identified in AASF with liquid activators containing 4 and 6 wt.% Na2O, respectively. The efflorescence of AASF exposed to bottom water was more severe than those exposed to natural conditions, as evidenced by the decalcification of reaction products, migration of alkalis, and formation of crystalline carbonates.Keywords: Alkali-activated materialssodium silicatessetting timeefflorescence Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThe authors thank the financial support from the National Natural Science Foundation of China (52078149, 52378227 and 51925802), 111 Project (No. D21021), Key Discipline of Materials Science and Engineering, Bureau of Education of Guangzhou (Grant number: 202255464).