The effect of Rehydration Conditions on the Mechanical Properties of CNT reinforced cementitious composites at Elevated Temperature

Abstract

Abstract This study aims to investigate the effects of rehydration conditions (under 25℃/65% RH and in water for different rehydration durations) on the mechanical recovery of heated cement paste with different contents of CNT (0wt%, 0.1wt%, 0.25wt%, and 0.4wt%) to elevated temperatures (200, 500, and 800℃). The variations in mass, density, compressive strength, tensile strength and surface morphology of the paste due to heating and rehydration were characterized. Mechanical deterioration and surface crack formation was found in the OPC and CNT samples immediately after heating at 500℃ and 800℃ whereas heating the sample up to 200℃ possessed no crack formation and enhanced heated samples’ compressive strength. CNT samples showed a dramatic recovery by water-rehydration after 500℃. The strength of the OPC and CNT sample increase after rehydration at 200℃ and 500℃. When the temperature reached at 800℃, the decomposition of C-S-H resulted in a dramatic mechanical degradation of the paste. But the mechanical strength of CNT samples will recovery after water-rehydration due to the generation of the 〖Ca(OH)〗_2.