Steel corrosion in magnesia–phosphate cement concrete beams

The acoustic emission (AE) technique was employed to investigate the corrosion-induced deterioration of steel-reinforced magnesia–phosphate cement (MPC) concrete beams under the coupling effect of loading and accelerated chloride diffusion. A cement-based piezoelectric sensor was used for AE detection owing to its high sensitivity and good compatibility with the concrete matrix. Power spectral density analysis and continuous wavelet transform were used to process the detected AE signals. It was found that the average frequency shift was closely related to the damage accumulation level in the reinforced MPC concrete beams. Based on the frequency characteristics of the detected AE signals during wet–dry cycles, the corrosion-induced degradation process of MPC beams was divided into three stages, from micro-cracking to localised macro-crack propagation. Wavelet analysis revealed the energy density distribution of the AE waveform, which was used to differentiate signal features between reinforcement corrosion and concrete cracking. In addition, comparisons in terms of the accumulated AE event number and half-cell potentials showed that MPC and OPC concrete had comparable corrosion inhibition capabilities.