Compressive Strength of Rapid Sulfoaluminate Cement Concrete Exposed to Elevated Temperatures

Abstract

The compressive strength, modulus and stress-strain behaviour of rapid-hardening sulfoaluminate cement concrete were evaluated as functions of the temperature increase. The compressive strength decreased from 51.3 to 31.1 MPa (around a 39 % reduction) as the temperature increased from 20 °C to 300 °C while the specimens burst at 400 °C before being removed from the furnace. A significant change in the stress-strain behaviour was noticed with an increasing temperature. For the control specimens (20 °C), linear elastic behaviour was followed by plastic deformation before reaching the peak stress prior to failure, but for higher temperatures, the modulus of elasticity was up to 85 % lower and was characterised by a gradually decreasing slope until failure. The micro-structural changes detected by SEM, DTG/TG and XRD were consistent with this pattern. The degree of cracking at the interfacial transition zone and crack-width growth detected by SEM followed a clear trend with the increasing temperature. The transformation of the primary hydration products (e.g., ettringite and Al(OH) 3) as detected by XRD and DTG/TG provides a useful explanation of the strength reduction with the increasing temperature up to 300 °C. The vapour pressure evolvement within the specimens at elevated temperatures correlates well with the reduced strength and modulus of elasticity, with a very intense effect at 400 °C.

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

“…Although the bursting mechanism has yet to be identified, two main explanations have been proposed: the water vapor pressure mechanism and the thermal stress mechanism [35,36]. Research by Thomas et al [37] and Tchekwagep et al [30] pointed out that the increase in porosity after exposure to elevated temperatures is one of the main reasons for strength loss.…”

“…Then the other samples were subjected to varying temperatures from 50° to 120°C. Previous studies by Tchekwagep et al [30] have shown that major physico-chemical changes occur between 20° and 120°C, so we selected picked roughly equal increments to cover the range. The temperatures of 20° and 100°C were chosen to match previous studies as "control points"; 50° and 70°C were chosen as intermediate temperatures within the zone of ettringite persistence.…”

The ability of different types of sand to preserve the integrity of calcium sulfoaluminate cement cement mortar during exposure to elevated temperatures

“…Recent studies of CSA cement and concrete have shown that heat has a negative impact on CSA structures [24,25]. As the exposure temperature rises, several deformations have been recorded, characterized by a decrease in strength [26] when the deformation increases as the target temperature rises [27].…”

The impact of changes in pore structure on the compressive strength of sulphoaluminate cement concrete at high temperature

“…Tchekwagep et al [3] found that at elevated temperatures, due to the decomposition of hydration products, the strength and stress-strain behaviour of SACC are affected, therefore, understanding the micro structure pore system as the temperature increased is necessary to further explain the strength decrease. Kumar et al [4] used the mercury intrusion porosimetry (MIP) method to test the pore structure of Portland cement concrete under drying at 60°C and 105°C.…”