The effect of moisture and reinforcement on the self-sensing properties of hybrid-fiber-reinforced concrete

This study presents the piezoresistive properties of a hybrid fiber-reinforced concrete (HyFRC) for structural health monitoring. This HyFRC mixture incorporates micro PVA and macro steel fibers to control the crack propagation. Investigations on self-sensing concrete (SSC) focus mainly on mixtures containing highly conductive fillers such as carbon nanotubes, graphite or nickel powder which results in a highly engineered cost-intensive mix composition for structural applications. This paper investigates the sensing ability of a cost-effective structural concrete mixture by considering the environmental conditions of engineering structures e.g. the moisture content as well as the influence of reinforcement on the electrical resistance measurement. The sensing parameters were evaluated by performing simultaneously bending tests and Electrochemical Impedance Spectroscopy (EIS) on beams with and without steel reinforcement. Furthermore, the influence of the pore solution on the EIS was investigated on specimens with varying moisture contents. The sensing behavior was compared to a control mixture without steel and PVA fibers. Results showed a significant lower initial resistivity for the HyFRC mixture compared to the ordinary concrete as well as the activation of the self-sensing properties due to the incorporated steel fibers. Finally, the influence of the pore solution on the EIS measurement is addressed and emphasizes the imperative need to consider the moisture content of self-sensing materials.