Electrochemical impedance spectroscopy: Effects of stray current and sulfate exposure on rubber powder mortar

Stray current induced by the subway power supply system can significantly accelerate the external sulfate attack of cement-based materials, leading to severe degradation. In this work, two rubber powders with different particle sizes were used to improve the performance of cement-based materials against the detrimental effects of stray current and sulfate. The electrochemical impedance spectroscopy (EIS) method was applied to investigate the effect of rubber powder on the electrochemical properties of cement-based materials exposed to stray current and sulfate. The electrochemical parameters of mortar incorporating rubber powder were obtained by fitting a novel equivalent circuit (Rs + Q 1 /(R ct1 +W 1 ) + Q 2 /(R ct2 +W 2 )). The effects of rubber powde dosage and fineness on EIS parameters were analyzed. The results revealed that the compressive strength of mortar incorporating rubber powder decreased, but both the pore solution resistance (Rs) and charge transfer process resistance (R ct1 ) of the specimens significantly increased. Furthermore, the increase in Rs and R ct1 values correlated with the dosage of rubber powder, and the 74 mu m rubber powder demonstrating a more pronounced effect compared to the 180 mu m rubber powder. After exposure for 30 days, it was observed that rubber powder could effectively improve the performance of mortar against the deteriorated effects of stray current and sulfate. Specifically, the 74 mu m of rubber powder exhibited superior performance compared to the 180 mu m rubber powder. Additionally, it was found that Rs and R ct1 values positively correlated with the compressive strength after exposure. Therefore, the EIS parameters Rs and R ct1 could be used to predict the variation trend of the compressive strength of mortar incorporating rubber powder.