High Temperature Material Properties of Calcium Aluminate Cement Concrete

Abstract

Fire is one of the most dangerous hazards that can occur in any type of structure which result in the loss of life and property. Currently, the primary material used for construction of most structures is concrete. Material strength is one of the most important factor which define the performance of structure when exposed to fire. In recent years, researchers have been focusing on fire performance of both normal strength concrete (NSC) and high strength concrete (HSC) for structural members used in buildings. When concrete is exposed to elevated temperatures rapidly, it results in additional stresses that are relieved by explosive spalling and cracks extending to the surface. This result in the decrease of strength and ultimately the capacity of the concrete in addition to that, it does not regain its original strength on cooling which makes concrete vulnerable to fire. Calcium aluminate cement concrete (CACC) is a type of high performance concrete (HPC) which is much more durable and resistant to fire and can be used as a replacement of ordinary Portland cement concrete. A test program was designed to undertake high temperature tests on CACC and normal strength concrete (NSC) commonly used in buildings, domestic construction. Material properties include compressive and splitting tensile strength, elastic modulus, stress-strain response, toughness and mass loss of both CACC and NSC. These properties were investigated at various temperatures of 23, 200, 400, 600 and 800°C. Unstressed and residual test procedures were adopted to measure these properties. The results obtained from high temperature tests of CACC revealed that the presence of alumina as a binding agent showed considerable enhancement in the mechanical performance compared to NSC. At elevated temperatures, the loss of compressive strength in NSC is much more prominent as compared to CACC. Reduction in the stress-strain response was observed in both CACC and NSC with the increase in temperature; however, an increase in axial strain was more in of CACC. Compressive toughness was higher in case of CACC as compared to NSC which increases up to 200°C, but decreases beyond this temperature. Scanning electron microscope (SEM) was also performed to differentiate the microstructural changes taking place in both types of concrete at elevated temperatures. Visual investigations after high temperature exposure revealed that CACC exhibits low cracking with less color changes as compared to NSC. Further, data generated from material property tests was utilized to develop simplified relations for expressing material properties of CACC as a function of temperature.