Tensile strength of a calcium-aluminate cementitious composite reinforced with basalt textile in a high-temperature environment

The effect of elevated temperatures on basalt textile reinforced calcium aluminate cementitious composite is reported. After being exposed for 1 h at various constant temperature levels, samples were tested in hot as well as after cooling down at room temperature conditions (termed as residual tests). Targeted constant temperatures considered varied from 25 up to 400 °C, representing the range that affects the main dehydration of hydration products present in the matrix. The residual mechanical response of basalt fabric at similar temperature ranges was also measured. Thermogravimetry and X-ray diffraction analysis were used to study phase changes as a function of temperature. Scanning electron microscopy (SEM) was used to study damage processes in the fiber–matrix interfaces. Results indicate that the tensile strength of composites in residual conditions is higher than that in hot conditions. This traced back the mechanism that the fabric-coating visco-elastic/plastic interface changes with temperature, which affects the textile-cementitious adhesion properties. When the composite was tested in hot conditions, a much more aggressive loss of the load-carrying capacity was observed. With increasing temperature, the hot tests, showed a significant reduction in tensile strength, elastic modulus and strain capacity. Ultimate direct tensile strength values obtained under hot condition were, on average, 50% lower than the residual ones.