Influence of iron ore tailings by-product on the mechanical and electrical properties of carbon fiber reinforced cement-based composites

This research evaluated the feasibility of using iron ore tailings (IOTs) to produce functional conductive composite materials as cement-based sensors based on carbon fiber (CF) reinforced cement composite. In this study, recycled IOTs are used as an alternative material to natural fine aggregate (0%, 30%, and 60%). Nine mixtures were produced. The effects of CF and IOTs content on mechanical properties and electrical conductivity were investigated; Based on the digital image correlation (DIC) system, the stress sensing ability of the specimen was evaluated and the strain field distribution was extracted; According to the results of compressive stress sensing, a predictive compressive stress model was proposed, and the ratio of fractional changes of resistivity (FCR) with unit stress and CF content were fitted; The pore size distribution was studied using nuclear magnetic resonance (NMR) technology; Besides, scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to analyze the microscopic morphology and crystal phase composition. The experimental results revealed that the appropriate IOTs content could improve the pore size distribution and the mechanical properties, which is a maximum increase of 28.12% compared with the plain cement (PC). The DIC strain field distribution shows that the excessive IOTs could increase the brittleness of the matrix, and XRD crystal phase analysis showed that the calcium silicate hydrate (CSH) gel is reduced and the bond with CF is weakened. The addition of CF significantly reduces the resistivity of the composites by an order of magnitude, and the self-sensing capability can be increased by 3 times. The compression stress sensitivity has a linear relationship with the amount of CF, which can be used to predict the compression stress sensing efficiency. It is expected to develop industrial waste IOTs as an effective conductive filler to promote the wider use of CF conductive composite materials.