Permeability evolution and pore characteristics of reactive powder concrete of drilling shaft with initial salt erosion damage

The aim of this study was to investigate the relationship between permeability properties and pore characteristics of reactive powder concrete (RPC) of drilling shaft under the coupling effect of high-salinity underground water pressure and surrounding rock pressure. Stress-seepage coupling tests were performed on the RPC specimens with standard curing and autoclave curing (prepared using the same mix ratio) after composite salt damage erosion. The characteristics of initial absolute permeability and permeability evolution of RPC in the entire process of volume deformation were analyzed accordingly. Then, computed tomography and AVIZO software were used to construct a three-dimensional meso-equivalent pore network model of RPC. The model was used to analyze the spatial pore structure characteristics of both RPC specimen groups. The results showed that during volume deformation and failure, the permeability of RPC exhibited three stages along with the volume strain: obviously decreasing, sharply rising, and tending to be stable. The larger porosity and more seepage channels in the RPC matrix increased its permeability. Additionally, the pore structure obtained by three-dimensional reconstruction simulation showed that the pore throat area of the RPC specimens with standard curing and autoclave curing ranged from 0 to 11.40 mm2 and 0 to 1.35 mm2, respectively. The size distribution range of their pore throat was 1-8 mm and 1-4 mm, respectively. The research results can accelerate the application of RPC in building drilling shaft structures.