Synergistic effect of alkanolamines and nano-SiO2 on hydration and mechanical properties of Portland limestone cement

Abstract

This study examined the synergistic effect of alkanolamines (i.e., Triethanolamine (TEA), Triisopropanolamine (TIPA)) and nano-SiO2 on the hydration kinetics and mechanical properties of Portland limestone cement (PLC). Due to distinct hydroxyl groups linked to TEA and TIPA, their combined use with nano-SiO2 resulted in different hydration kinetics and physicochemical properties of the PLC pastes. The combined use of nano-SiO₂ and TEA selectively accelerated the aluminate reaction before the onset of the silicate reaction in PLC, whereas incorporation of nano-SiO₂ and TIPA highly promoted both the silicate and aluminate reactions. Although TEA alone contributed to strength reduction, the co-incorporation of nano-SiO₂ successfully mitigated this effect. The highest compressive strength was attained via combined use of nano-SiO₂ and TIPA, which also induced a greater formation of carboaluminate phases and led a significant pore size refinement effect. While use of TEA and nano-SiO₂ both refined pores, the effect was less pronounced compared to that with nano-SiO₂ and TIPA. These findings demonstrate that the combined use of nano-SiO₂ and TIPA offers a superior route for enhancing the early-age mechanical performance of PLC.