The Impact of Extended Heat Exposure on Rapid Sulphoaluminate Cement Concrete Up To 120°C

This study examined the stability of rapid sulphoaluminate cement concrete (R-SACC) when exposed to heat for extended periods of time. The physicochemical processes present in R-SACC as a function of temperature were determined through various tests. The general behavior of rapid sulphoaluminate cement (R-SAC) at a range of temperatures is summarized. The results show that observing color change could be a simple way to identify deterioration of R-SACC, along with the rebound hammer. The matrix formation of ettringite was broken and the mass of the hydrated product decreased with heat exposure; the major mineral composition of the paste consisted of CaSO4, CaCO3 and β-C2S; and the interface between aggregate and paste in the R-SACC become loosely structured with cracks. Between 50°C and 120°C, the rapid sulphoaluminate cement (R-SAC) paste first expanded and then shrank, and the shrinkage rate of R-SAC was much greater than that of R-SACC

The influence of different fine aggregate and cooling regimes on the engineering properties of sulphoaluminate cement mortar after heating

Previous experimental studies of sulphoaluminate cement after exposure to high temperatures have mainly concentrated on the resulting reduction of strength. Its behavior when heated continues to attract our attention because a systematic understanding of its heat-induced damage is needed to determine its reusability. The post-heating mechanical properties of sulphoaluminate cement mortar (SACM) made with three different types of fine aggregates after natural air cooling (NAC), water immersion cooling (WIC), and fire extinguisher cooling (FEC) are presented in this paper. Basalt and artificial sand have strong angularity, as indicated by their convexity and Wadell roundness values, which has an impact on improving their strength properties when heated. Convexity and Wadell roundness turn out to be independent, with convexity and circularity in good agreement. In addition, the loss of mechanical properties in river sand mortar was greater when either NAC or FEC was adopted than with WIC. The tests showed that independent of the type of sand, the SACM recovers its strength better when WIC or FEC is used in cooling rather than NAC

The effect of extensive heat exposure on the mechanical properties of polymer-modified sulfoaluminate cement repair mortar

In this study polymer-modified mortar (PMM) was prepared by using EVA powder and CSA as main raw materials, and its elevated temperature (ET) resistance was examined. This study investigated the changes in the mechanical properties, chemical decomposition, and pore structure of the polymer-modified sufloaluminate cement mortar (PMSCM) after exposure to elevated temperature. After 28 days of standard curing, PMSCM was exposed to temperatures of 20℃, 200℃, 400℃, and 600℃. With the increase of temperature, the dry density (rho_d) of the PMSCM increase by about 5%, and the crack average size increased visibly; from 200℃ to 600℃ from an average of 0.02 mm to an average of 0.08 mm. Samples were characterized by the presence of some microcracks and holes; this internal state of the samples has led to the lowest ultrasonic pulse velocity (UPV) recorded at 600℃. The sample has received a great deal of damage at simulated elevated temperature; but the strength of the PMSCM sample with EVA is higher than that of the control group and meets the strength requirements of lightweight mortar. The derivative thermogravimetry (DTG-TG) and XRD patterns demonstrated that the addition of EVA polymer to CSA cement improved the thermal stability of the CSA cement and reduced the degradation of the polymer at ETs. This suggests that EVA polymer could be used as a modifier to improve the performance of CSA cement in elevated temperature applications

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

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)