Relationship between chloride ion permeation resistance of ultra-high performance concrete and lightweight aggregate ratio

This paper investigates the effects of different substitution rates of lightweight aggregate (LWA) on the workability, mechanical properties, and chloride ion permeability of ultra-high performance concrete (UHPC). A two-dimensional model based on the random distribution of irregular LWA particles was established to simulate chloride diffusion. Based on experimental and simulation results, the influencing mechanism of LWA substitution rate on the chloride ion penetration resistance of UHPC was further explored. The results indicate that during the LWA mixing process, its porous structure causes premature release of water involved in internal curing, leading to degradation of the pore structure and interfacial transition zone. Therefore, with the increase of LWA substitution rate, not only does the working and mechanical properties of UHPC decrease, but also the chloride ion transport channels increase, leading to an accelerated migration rate of chloride ions in UHPC.