Influence of limestone addition on sodium sulphate activated blast furnace slag cements

The effect of limestone replacement in the reaction and phase assemblage evolution of two sodium sulfate activated slag cements was investigated. The slag composition and its reactivity influenced the reaction kinetics of these materials. Paste with limestone addition exhibited an acceleration in reaction kinetics, particularly for slowly reacting slags. Ettringite and an aluminium substituted calcium silicate hydrate were identified as main reaction products in these cements, independently of the slag type or limestone replacement level. No significant changes in phase assemblages were observed with limestone addition for over 365 days of testing; however, these composite cements exhibited an increased compressive strength, consistent with a refined pore structure. These results indicate that it is possible to partially replace slag by limestone in sulfate activated slag cements without changing the type of reaction products forming in these systems, while also increasing compressive strength and achieving a similar refined pore structure.