Analysis of the phases and functions of the various compounds of calcium sulfoaluminate cement after exposure to high temperature

Abstract

High temperature (HT) in-situ XRD method was adopted to investigate the calcium sulfoaluminate cement (CSA) or C4A3$ crystal architecture as well as its phases when passing through the temperature range of 20° to 70 °C. We examined the particle size analysis of the CSA ground powder when heated to different temperature (e.g., 35, 50, and 70 °C) in correlation with the HT X-ray diffraction (HT XRD) pattern as well with the compressive strength. The particle size of the lattice parameters increased during heating. The architecture transformation phase of the CSA took place at 50 °C. The transformation of the crystal cubic structure phase of the C4A3$ when passing from orthogonal to cubic space group was unstable with more heating (70 °C) and was adjustable. The C4A3$ compound's orthogonal and cubic crystal structures were clearly identified. The crystal structures were found to be responsible for the dehydration that occurred as the temperature rose and also for the decrease in compressive strength. The obtained final products of the C4A3$ were in cubic and orthogonal forms. The exothermic form of the C4A3$ was mostly observed at 20 °C and at 35 °C. The AFt and AFm crystal structure framework was constituted of AlO6 (in octahedral form) and AlO4 (in tetrahedral form).