Gas permeability and meso-structure of fiber reinforced concrete under carbonation based on different pore sizes

In order to investigate the relationship between gas permeability and meso-structure of carbonated concrete, carbonation tests and gas permeability tests of ordinary concrete (OC) and polypropylene basalt fiber concrete (BP) with 0, 7, 14, 28, 56 and 80 days carbonation were performed respectively. The parameters of concrete meso-structure were obtained by RapidAir 457 concrete pore structure analyzer (Denmark). Based on the influence levels of different pore size ranges and calculation methods on the air content and fractal dimension of concrete, the pore size of concrete is divided into 0-160 µm, 160-300 µm, 300-4000 µm. The air content and fractal dimension were calculated respectively. The influences of carbonation age and materials on the macroscopic and microscopic properties were analyzed. The internal relationship among the gas permeability, fractal dimension and meso-structure of concrete was studied. Then, the sensitive pore size range was given. The results show that the gas diffusion coefficient and air content of BP are less than that of OC in general, which shows that hybrid can improve the carbonation resistance of concrete by improving the balance of three-dimensional distribution of fiber from different levels. With carbonization age increasing, for OC, the correlation between pore mass fractal dimension in small pore size range and gas diffusion coefficient is higher than other ranges. For BP, the correlation between solid mass fractal dimension in medium pore size range and gas diffusion coefficient is higher than other ranges. The solid mass fractal dimension is employed to characterize the concrete internal structure more accurately than pore mass fractal dimension. Based on the comprehensive analysis of air permeability, fractal dimension and meso-structure, it is identified that the sensitive pore size range of OC is the small pore size rang, and the sensitive pore size range of BP is the medium pore size range. © 2021 Editorial Board of Journal of Jilin University (Engineering and Technology Edition). All right reserved.