Processing and hydration activation of limestone calcined clay belite rich cements.

Abstract

Belite-rich limestone calcined clay cements, BR-LC3, could be an alternative for low carbon binders with potentially very good durability properties, given the high amount of C-S-H gel from the cement hydration with additional C-(A)-S-H from the pozzolanic reaction. Nevertheless, BR-LC3 phase hydration rates at early ages are slow and they must be enhanced, for instance by using C-S-H nucleation seeding admixtures. In this work, a BR-LC3 binder was prepared using a clinker-activated Belite-rich cement, BC (58 wt%), kaolinitic calcined clay (26 wt%), limestone (13 wt%) and gypsum (3 wt%). Pastes were prepared with a water-to-binder (w/b) ratio of 0.40 and superplasticizer. Mortars were prepared with the w/b=0.40 and having a target slump self-flow of 210±20 mm. Paste hydration characterization was carried out by thermal analysis, Rietveld quantitative phase analysis and mercury intrusion porosimetry. The compressive strengths of the mortars were also determined. Remarkable compressive strength improvements at 7 and 28 days are shown by using a C-S-H seeding admixture. The improvement of mechanical strengths is not related to belite phase hydration acceleration but mainly to lower porosity.