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

Abstract

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.

Keywords

• Sulphoaluminate cement
• EVA polymer
• Mechanical property
• Elevated temperature exposure