Distribution of initial transport parameters for the interfacial zone of new–old HPC impregnated by silane

A wet joint in silane‐impregnated high‐performance concrete (HPC) is either a typical connection form or a durability control component in precast concrete structures exposed to harsh environments. However, knowledge of their special durability features, especially at the quantitative level, is still very limited. This paper focuses on the initial transport properties of the interfacial zone of new–old concrete in this type of joint. This study investigates the distribution characteristics of coarse aggregate volume fraction and porosity, and establishes corresponding models for these two basic physical state parameters. On this basis, a distribution model for the chloride diffusion coefficient is derived, providing a basis for predicting chloride‐erosion durability in this part. Specifically, using digital image processing (DIP), the deep valley distribution characteristic of the coarse aggregate volume fraction in the interfacial zone is revealed, and a distribution model based on a Gaussian function is established. Through scanning electron microscopy (SEM) tests, the sharp peak distribution characteristic of porosity in the interfacial zone is revealed, and a distribution model based on the Gaussian function is established. The nominal porosity at the unchiseled interface decreased from 15.6% to 10.5% after silane impregnation. The model also includes the correction for the pore‐filling effect of silane impregnation. Based on the above porosity and coarse aggregate volume fraction distributions and considering the change in pore wall wettability induced by silane impregnation, a chloride diffusion coefficient model is established. This model can jointly reflect the pore distribution, the hydrophobic effect induced by silane, the tortuosity effect induced by coarse aggregate, and the interface shift and pore structure improvement induced by chiseling.