Performance enhancement and characterization of limestone calcined clay cement (LC3) produced with low-reactivity kaolinitic clay

Abstract

This study investigated the possibility of using a low-reactivity kaolinitic clay (LRKC), calcined to 800 °C, in the formulation of LC3. White ordinary Portland cement (WOPC), LRKC, and limestone powder (LP) of two fineness levels were used to prepare LC3 mixes with and without hemihydrate. The normalized heat evolution was found to increase in the LC3 mixes because of the filler effects provided by LRKC and LP. Without hemihydrate, an intense aluminate peak associated with the formation of AFt, AFm, and C-(A-)S-H occurred early and overlapped the C3S peak. Hemihydrate at 3 wt% delayed the aluminate peak, and more ettringite was formed, yet carboaluminates were reduced due to preferential AFt formation under limited aluminate phases from WOPC and LRKC. The best-performing LC3 mix exhibited a 90-day strength of 12.3% lower than the reference mix, and the strength of all the LC3 mixes converged regardless of the limestone content and fineness.