Active Iron-Rich Belite Sulfoaluminate Cements: Clinkering and Hydration

摘要

Ordinary Portland cement (OPC) is an environmentally contentious material, as for every ton of OPC produced, on average, 0.97 tons of CO_2 are released. Conversely, belite sulfoaluminate (BSA) cements are promising eco-friendry building materials, as their production may deplete CO_2 emissions up to 35% (compared to OPC). However, the hydration rate of belite is slow. Here, we report the clinkering of iron-rich BSA materials, their activation with B_2O_3, and establishing a methodology to measure their improved reactivities. Nonactivated BSA clinker contained only β belite phase, 52 wt %. Meanwhile, BSA clinkers activated with 1 and 2 wt % of B_2O_3 contained 28 wt % of β and 25 wt % of α'_H; and 54 wt % of α'_H phase, respectively. Therefore, activation of BSA has been proved as α'_H belite is stabilized. The hydration of the cements has been studied by laboratory and synchrotron X-ray powder diffraction (using Rietveld method and chemical constraints), calorimetry, and environmental scanning electron microscopy. Cement pastes have different hydration rates. For nonactivated BSA cement 20 and 48% of the belite reacted after one and three months, respectively. Conversely, 37-49% after one month and 52-62% after three months of overall belite reactivities have been measured for BSA cements activated with B_2O_3.