The mechanical properties and microstructure of carbon fibers reinforced coral concrete

Abstract In this paper, the effect of carbon fibers (CFs) on the mechanical properties and microstructure of carbon fibers reinforced coral concrete (CFRCC) were experimentally investigated. Eighteen CFRCC mixtures were designed considering concrete strength grade (C20, C30, C40) and CFs content (0.0%, 0.3%, 0.6%, 1.0%, 1.5%, 2.0%) as variables, and a total of 414 specimens were poured. The cube compressive strength, axial compressive strength, splitting tensile strength, elastic modulus, and Poisson's ratio of CFRCC were obtained by test. Moreover, the microstructure of coral aggregates (CAs) and CFRCC was also observed by X-ray diffractometer, digital microscope, and scanning electron microscope (SEM). The experimental results show that the addition of CFs can improve the compressive strength and splitting tensile strength. The optimum content of CFs is about 1.5% by weight of the binder. However, the effect of CFs on the elastic modulus and Poisson's ratio is not significant. Furthermore, the microstructure investigation reveals that the CAs have a porous structure, and the interfacial transition zone (ITZ) does not be the weak zone in CFRCC. It is also observed from SEM that there are two failure patterns of CFs in CFRCC, namely fiber pull-out and fiber breakage.