An advanced understanding for synergistic effect of limestone and ethanol di-isopropanolamine on slag-limestone ternary cement

Abstract

The use of limestone can mitigate the limited availability of supplementary cementitious materials while reducing the clinker factor, but it often decreases strength. This study demonstrates that ethanoldiisopropanolamine (EDIPA) enables an increase in strength of slag-limestone cement. EDIPA facilitated the aluminate reaction, enhancing the formation of monocarbonate and ettringite in limestone-containing binder. Meanwhile, additional aluminates were preferentially incorporated into C–A–S–H rather than AFm phases in limestone-free binder. EDIPA improved the slag reactivity, increasing C–A–S–H precipitation with a lower Ca/Si ratio and a higher Al/Si ratio. Although neither EDIPA nor limestone influenced early sulfate adsorption on C–A–S–H, they seem to cause its desorption, resulting in additional ettringite formation at later ages. Consequently, EDIPA did not improve the strength of the limestone-free binder, but the combined increase in hydration products by EDIPA and limestone refined the pore structure and enhanced the strength, exceeding that of limestone-free binder despite a 20% limestone replacement.