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

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.