Topographical characterization and permeability correlation of steel fiber reinforced concrete surface under freeze-thaw cycles and NaCl solution immersion

Abstract

This study investigates the relationship between the surface topography of steel fiber reinforced concrete (SFRC) and both the freeze-thaw damage and permeability of the concrete matrix subjected to freeze-thaw cycles and immersion in a sodium chloride solution. Rapid freeze-thaw tests were conducted on concrete immersed in NaCl solution to introduce freeze-thaw damage. A custom-developed 3D laser-scanning device was employed to capture the surface topography information of concrete subjected to freeze-thaw cycles. Multivariate analysis was utilized to determine the suitable parameter for evaluating the roughness of the concrete surface. A correlation analysis was carried out between the surface topography of concrete and the freeze-thaw damage parameters, including mass loss (ΔWn), relative dynamic modulus of elasticity (RDME), and ultrasonic pulse velocity (Uv). A custom-designed vacuum permeability device was used to measure the permeability of concrete matrix. The relationship between the surface topography and permeability of concrete subjected to freeze-thaw damage is studied. The results show that the steel fibers significantly reduce the freeze-thaw damage and surface roughness of concrete subjected to freeze-thaw damage in the sodium chloride solution. Roughness number (RN) is the most representative parameter for evaluating the topographical characterization of concrete surface and can be used to quantify the surface topography of concrete exposed to freeze-thaw cycles. The absolute values of correlation coefficient between RN and its ΔWn, RDME, and Uv reach up to 0.89, which suggests that RN can indirectly evaluate the freeze-thaw damage of concrete. Furthermore, there exists a logarithmic relationship between RN and the permeability of the concrete matrix, with the correlation coefficient R2 exceeding 0.86. This relationship can be utilized to quickly estimate its permeability based on the surface roughness of SFRC exposed in cold coastal regions.