Influence of elevated temperature on the microstructure and mechanical performance of cement composites reinforced with recycled carbon fibers

This study comprises the investigation on the effects of elevated temperatures (up to 900 degrees C) on the reinforcement mechanism of recycled carbon fiber (rCF) based cement composites. A detail investigation was conducted to study the interaction of rCF with hydration products at different temperatures (25 degrees C, 200 degrees C, 400 degrees C, 600 degrees C, 800 degrees C and 900 degrees C) by using x-ray diffraction (XRD), differential thermogravimetric (DTG) analysis and scanning electron microscopic techniques. Furthermore, mechanical properties, including compressive strength (f'c), splitting tensile strength (f's), and flexural strength (f'F), were experimentally studied as a function of rCF dosage and elevated temperature. Results revealed that the reinforcing effect of rCFs was promising up to 600 degrees C due to the release of high-pressure steam through channels on the surface of rCFs. At 900 degrees C, rCFs were fully decomposed and resulted in empty tunnels which subsequently effected the performance of cement composites. A sharp decrease in the compressive and splitting tensile strength was observed at 800 degrees C while the flexural strength was significantly reduced at 600 degrees C. In the end, the relation of rCF dosage and elevated temperature with residual mechanical properties of cement composites was discussed through multivariate statistical models.