The Uniaxial Compressive Constitutive Behavior and Mesoscopic Numerical Simulation of HPC Incorporating ASR Mitigation Measures After Ten Years of Alkali Solution Immersion

The salt lake and saline–alkali soil regions of high plateaus are characterized by widespread Alkali–silica reactive (ASR) aggregates, which severely threaten the durability of constructed infrastructure, including railways, highways, and buildings. The research systematically investigates the uniaxial compressive mechanical behavior and stress–strain constitutive relationship of high-performance concrete (HPC) with ASR mitigation measures (performance grades C40, C45, C50, and C60) after ten years of immersion in a standard alkali solution. A corresponding three-dimensional random aggregate mesoscopic concrete model was developed, and mesomechanical numerical simulations were performed to explore the failure process, failure patterns, and underlying mesoscopic damage mechanisms of the specimens. Results show that While the uniaxial compressive strength and elastic modulus of HPC show an expected increase with the concrete strength grade following long-term alkali exposure, both properties demonstrate a clear decline as the equivalent alkali content rises. Comparing and analyzing the C50 specimens of different admixtures, it was found that the air-entraining agent provided the most effective ASR suppression and obtained the highest uniaxial compressive strength compared with the rust inhibitor. By normalizing the stress–strain curves, the long-term constitutive behavior of HPC under alkali corrosion was summarized. Furthermore, mesoscopic model visualizations indicate that cracks initially appear in the mortar and gradually propagate inward during loading, leading to compressive failure characterized by diagonal cracks. Tracking the mesoscopic damage patterns within the specimens demonstrates that microcracks originate in the mortar and progressively extend through aggregates, revealing the underlying micro-damage mechanism. By studying the SEM-EDS images, it is found that HPC with a specific mix ratio designed in this paper can effectively inhibit the ASR effect, and it still has good corrosion resistance in long-term alkali immersion.