Abstract
This paper investigates the hydrated phase assemblage, microstructure, and gel composition of sodium hydroxide (NaOH)-activated fly ash–slag blends with either low-calcium or high-calcium fly ash. The results show that the nature of precipitated calcium–aluminosilicate–hydrate (C-A-S-H) and alkali aluminosilicate-hydrate (N-A-S-H) depends on the fly ash composition and slag-to-fly ash ratio. However, regardless of fly ash composition and slag-to-fly ash ratio, a universal linear compositional relationship exists between Al/Ca ratio and Si/Ca ratio in precipitated gels. This indicates that there exists a structural limitation on the incorporation of Al3+ for Si4+ in the tetrahedral silicate of C-A-S-H, N-A-S-H, or metastable N-C-A-S-H gels. In a hybrid slag–fly ash system, the framework structure of precipitated gels is an assemblage of aluminosilicate units with heterogeneous Ca2+ and Na+ distribution. The amount and reactivity of calcium and alkalis seem to play a critical role in determining the structure and properties of precipitated gels in hybrid systems. The low cementitious capability in alkali-activated high-calcium fly ash may be attributed to the unstable N-C-A-S-H gel structure with concurrent high Na and Ca contents.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
