Investigating the retarding effect of CAC in alkali-activated cements

This paper discusses the design of hybrid alkali-activated binders at ambient temperature, specifically development mixes based on ground granulated blast-furnace slag (GGBFS) with calcium aluminate cement (CAC) as an additive, aiming to obtain high early strength optimised Al incorporation, increased crosslinking and degree polymerisation. The effects 10 wt% CAC replacement GGBFS, activated sodium silicate varying modulus (SiO 2 /Na O molar ratio) or hydroxide, fresh hardened properties are investigated. inclusion in GGBFS mixtures using results unexpected retardation polycondensation reactions required form main aluminosilicate hydrate gel phase. is due incomplete dissolution precursor, inhibited by rapid formation additional reaction products (especially cubic hydrates, C 3 AH 6 ) resulting lowered kinetics, thus delayed setting hardening times. For activators, this retarding effect appears be only slightly dependent activator solution modulus. When activating 4 M NaOH, reduced, along incorporation C-A-S-H gel, increasing amount reactive aluminium present binder a more compact product. Increasing molarity NaOH solutions similar delay kinetics. suggest existence limited pH range which addition can promote binding enhanced mechanical properties, whilst other factors including systems still unclear. typical hydration were not detected study.