Chloride Transport Modeling of Binary Mineral Admixture High-Performance Concrete Under Sustained Compressive Stress

The objective of this study was to experimentally quantify and analytically model chloride ion transport in high-performance concrete incorporating single and binary mineral admixtures under sustained compressive loading, thereby improving durability prediction for load-bearing concrete exposed to chloride environments. A series of accelerated chloride transport experiments was conducted on high-performance concrete subjected to sustained compressive loading. The surface strain evolution of concrete was investigated under different compressive stress ratios and admixture dosages. The effects of the admixture dosage and sustained compressive stress ratio on chloride distribution were analyzed. A chloride diffusion coefficient model that incorporated sustained compressive loading and composite mineral admixtures was established, and its validity was verified. The influences of key parameters on chloride transport in binary-blended high-performance concrete were further discussed. The results showed that the strain of ordinary concrete specimens was the largest, followed by that of high-performance concrete with a single admixture of fly ash or silica fume, and the strain of high-performance concrete with double admixtures of fly ash and silica fume was the smallest. The chloride concentration in concrete first decreased and then increased with the increase in compressive stress level. The largest change amplitude was observed in ordinary concrete, and the smallest was in high-performance concrete with double admixtures of fly ash and silica fume. An increase in the time decay coefficient caused the chloride concentration in binary-blended high-performance concrete to decrease first and then increase. When the fly ash content was kept constant, the chloride concentration gradually decreased with increasing silica fume content. When the silica fume content reached 17%, the chloride concentration at a diffusion depth of 11 mm approached zero.