Limestone calcined clay (LC3) cement: Ice content profile and calcium carbonate reaction vs pore structure and mechanical properties development

Correlating the evolution of the pore structure, phase composition and mechanical properties of the LC3-based (limestone calcined clay cement) materials is essential for the future guidelines of this eco-friendly binder. Accordingly, the present study focused on the ice content profile and calcium carbonate reaction and their correlation with the pore structure and mechanical properties of the LC3-based materials during the first 56 days of hydration. The ice content profile of the LC3 paste was investigated for the first time via differential scanning calorimetry which requires no pre-drying of the samples. Mercury intrusion porosimetry, X-ray diffraction pattern and thermogravimetric analysis were the techniques utilized for reading the pore structure and phase composition evolution of the LC3 paste. Compressive and flexural strength, and ultrasonic pulse velocity of the LC3 mortars were also studied. Both ice content profile and calcium carbonate reaction were shown to be reliable predictors of the pore structure evolution (i.e. decrease of the capillary pores and emergence of the ink-bottle pores) and mechanical properties built-up in the LC3-based materials. The rate of calcium carbonate reaction in LC3 was the fastest between the 2nd and 7th days of hydration, that reached 1.6 % per day.