Acid Dissolution-Induced Damage Mechanisms in Concrete–Rock Composites: Experimental and Particle Flow Simulation

Concrete–rock composites (CRC) in karst regions
face severe
durability challenges from acid dissolution. This study investigates
the damage mechanisms of CRC under sulfuric acid solutions (pH 3,
5, and 7) through integrated laboratory experiments and interface-enhanced
discrete element modeling. The results reveal that chemical degradation
occurs via H+-mineral reactions (e.g., CaCO3 + H2SO4 → CaSO4 + CO2), increasing porosity by 14% at pH = 3 and reducing compressive
strength by 28.5% compared to neutral conditions. Meanwhile, mechanical
deterioration exhibits pH dependency: elastic modulus declines by
24.2% (pH 5) and 41.6% (pH 3), while failure transitions from concrete-dominated
cracking (pH 7) to synergistic concrete-rock failure (pH ≤
5). Moreover, PFC2D simulations demonstrate that crack
initiation consistently originates at the concrete-rock interface,
with tensile cracks comprising >90% of total cracks. Stronger acidity
increases total crack density by 10.7% (pH = 5) and 20.8% (pH = 3)
and homogenizes crack angular distribution. These results establish
a quantitative corrosion-degradation relationship, providing critical
guidance for enhancing the durability of tunnels and bridges in acidic
environments.