Electrical resistivity and capillary absorption in mortar with styrene-acrylic emulsion and air-entrained agent: improvement and correlation with pore structure

Abstract In realistic situation, the uptake of water through capillary absorption process substantially decrease the bulk electrical resistivity. Pore structure is vital to both the bulk electrical resistivity and the capillary absorption process. In this study, to improve the bulk electrical resistivity and mitigate the capillary absorption, styrene-acrylic emulsion (SAE) and air-entrained agent (AE) were incorporated into the mortar sample to modify the pore structure. The evolution of bulk electrical resistivity during the capillary absorption process was investigated. Results showed that the evolution of bulk electrical resistivity exhibits a periodic change along with the water absorption process. The addition of 6% SAE executes a significant improvement on both bulk electrical resistivity and sorptivity coefficient. To reveal the underlying mechanism, the evolution of electrical resistivity of pore solution and porosity was estimated and measured by a theoretical method and mercury intrusion porosimetry (MIP). Characteristic values of pore structure including tortuosity and connectivity were deduced from models. These obtained values indicated that the tortuosity or connectivity exerts a greater influence on the bulk electrical resistivity compared to porosity. No evident relationship between pore structure and sorptivity coefficient was observed via the conventional Lucas-Washburn model. To integrate the effect of the characteristic parameters of pore structure on the capillary absorption, a fractal model was established. The alternations of SAE and AE on the pore structure were manifested into the change of tortuosity fractal dimension and pore fractal dimension. The sorptivity coefficient calculated from this proposed model is in good agreement with the experimental value.