Papers by Author: Qing Hua Huang

Abstract: Concrete was considered as a three-component composite material consisting of mortar matrix, coarse aggregates and interfacial transition zones (ITZ) at the mesoscale level. Based on the random accumulation model of spherical aggregates, a mesoscale geometric model was developed after discretizing the mortar matrix and ITZ into mesh elements using Voronoi diagram method. Combined with the third boundary condition, a mesoscale three-dimensional model to simulate the moisture transport process in concrete exposed to atmosphere environment was then developed using finite difference numerical method, where the transport of liquid water and water vapor were considered as permeation and diffusion respectively. Moreover, the model was verified and then applied to investigate the influence of ITZ on the distribution of relative humidity in concrete. The results indicated that the moisture transport process was overall accelerated since blocking effect of coarse aggregates was partially counteracted by the existence of ITZ.

Abstract: Acceleration penetration tests of chloride ion were conducted for typical diurnal and semidiurnal tidal types in China with consideration of various values of soaking time. It was found that the content of chloride ion from shallow area near the surface of concrete to the pure diffusion area of concrete reduced more significantly with the depth than that in the pure diffusion area of concrete. Based on Fick’s second law, the variation laws of chloride ion content at the edge of the pure diffusion area and chloride ion diffusion coefficient in the pure diffusion area under different soaking time ratios were identified by using the chloride ion content distributions that were established based on the test results of concrete in the pure diffusion area. It was found that the chloride ion content and the apparent chloride ion diffusion coefficient in pure diffusion area may be very high when the ratio of soaking time ratio is between 0.3 and 0.42 or 0.6 and 0.7 for diurnal tidal type and 0.83 for semidiurnal tidal type, which will cause severe erosion in concrete structures in tidal zone.