Evaluation of hydration behavior of cement-stabilized macadam via electrochemical impedance spectroscopy

Electrochemical Impedance Spectroscopy (EIS) was an important method for continuous and non-destructive monitoring of cement hydration process. The EIS, porosity and compressive strength of cement-stabilized macadam with different structures and cement content at different hydration ages were tested. By fitting the quasi-Randles equivalent circuit model, the electrochemical parameters were obtained to analyze the hydration degree and microstructure changes of materials during the hydration process. The mathematical models of electrochemical parameters and hydration parameters in skeleton dense structure, suspension dense structure and skeleton pore structure were established. The results show that the electrochemical parameters of the quist-Randles equivalent circuits model had a fine correlation with the hydration parameters of cement-stabilized macadam materials. The impedance curves of different cement-stabilized macadam structures had the same variation laws under different cement contents. As the hydration age increased, more hydration products formed and filled the internal pores of the structure, leading to the gradual formation of a dense structure in the material, further reducing the porosity and increasing the pore solution resistance RS. Meanwhile, the increase in cement content also led to a gradual increase in the compressive strength of the sample. The research results show that Rs was inversely proportional to porosity and had a good logarithmic relationship with compressive strength.