Fire-induced damage behaviour in corrosion-damaged concrete: Thermal-mechanical coupling phase field meso-scale modeling

Abstract

The mechanical performance degradation of concrete in marine environments is often caused by multi-hazard, such as long-term environmental loads and short-term extreme loads, which also lead to more complex damage pattern. This study presents a thermal-mechanical coupling phase field meso‑scale model to simulate the damage evolution process of concrete subjected to rebar corrosion and fire hazards. This model employed a fracture phase-field model to characterize damage progression in concrete and utilized thermal expansion strain, temperature-dependent material property phase field-dependent thermal conductivity to realize the coupling of temperature field, mechanical field, and phase field. We validated the proposed model with examples of concrete fracture, fire-induced damage and fire-induced mechanical property degradation. Subsequently, we simulated the fire-induced damage in corrosion-damaged concrete with varying corrosion-induced damage extents and aggregate volume fractions, which involves two steps: (1) simulation of damage induced by corrosion; (2) utilizing results as initial conditions for subsequent simulation of fire-induced damage. Simulation results indicate that fire-induced damage originates in the interfacial transition zone and propagates radially, ultimately resulting in a failure pattern of mesh cracks and local spalling. The corrosion-induced damage extent influences the fire-induced damage evolution process, spalling location and fire-induced damage extent, while the aggregate volume fraction primarily affects damage extent. Finally, we further researched and compared the fire-induced damage of corrosion-damaged concrete with one middle rebar, one corner rebar and multiple rebars.