The effect of carbon nanotube on self-healing properties of engineered cementitious composites subjected to high temperatures

Abstract

This study aims to examine the effect of carbon nanotubes (CNT) on the self-healing performance of engineered cementitious composites (ECC) subjected to high temperatures. In ECC samples, CNT was used at 0%, 0.25%, 0.50%, and 0.75% by weight instead of cementitious materials. The cylindrical specimens containing CNT (o100 x 200 mm) were manufactured. The produced specimens were subjected to temperatures of 23 +/- 2, 100, 200, 300, 400, 500, 600, 700, and 800 degrees C after being cured at 23 +/- 2 degrees C for 28 days, and then, they left to cool at 23 +/- 2 degrees C for 1 day. Then, these specimens were preloaded at 70% of the ultimate splitting tensile strength to produce microcracks. Lastly, wetting-drying cycles were performed on ECCs for self-healing. The ultrasonic pulse velocity (UPV), splitting tensile strength (fst), and rapid chloride permeability (RCPT) tests were applied to evaluate the self-healing performance of specimens. Moreover, microstructural analyses such as scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) were accomplished to identify the healing products formed in self-healed cracks. According to the results of this study, the highest recovery rate of fst with 103.46% was attained from the ECC specimen containing 0.25% CNT exposed to 200 degrees C.