RAAC panels can suddenly collapse before any warning of corrosion-induced surface cracking

2025-05-07

npj Materials Degradation

AI Summary

Reinforced autoclaved aerated concrete (RAAC) panels frequently undergo sudden, catastrophic collapse without visible surface cracking, owing to poorly understood concealed corrosion mechanisms—particularly how high porosity influences rust product transport and expansive constraint. Method: To overcome the limitation of existing corrosion-cracking models—designed primarily for low-porosity concrete—we develop, for the first time, a multiphysics computational model that couples an analytical solution of the corrosion reaction with porosity-adaptive diffusion. Contribution/Results: The model quantitatively captures the full “covert propagation–critical failure” corrosion process in RAAC, revealing that under specific combinations of humidity, chloride concentration, and porosity, rebar corrosion can proceed undetected for extended periods before abrupt loss of load-bearing capacity. Based on these findings, we construct a high-risk collapse condition map, providing both theoretical foundations and quantitative tools for structural safety assessment and early-warning systems for RAAC infrastructure.

Technology Category

Cognitive Modeling & Cognitive Systems: (Computational) Cognitive ArchitecturesReasoning under Uncertainty: ApplicationsKnowledge Representation and Reasoning: Geometric, Spatial, and Temporal Reasoning

Application Category

Web Mining and Content Analysis: Models for Web evolutionUser Modeling, Personalization and Recommendation: Attacks and countermeasures in recommendation systemsGraph Algorithms and Modeling for the Web: Foundation models and LLMs for Web-related graphs

Abstract

Abstractś The collapse of reinforced autoclaved aerated concrete (RAAC) panels has attracted considerable public and academic interest. As detailed experimental data are not yet available and replicating the natural corrosion process requires years or decades, computational modelling is essential to understand under which conditions corrosion remains concealed. The very high porosity of RAAC is widely suspected to be a major contributing factor. However, current corrosion-induced cracking models are known to struggle with capturing the role of concrete porosity. To remedy this critical deficiency, we propose to enrich corrosion-induced cracking modelling with the analytical solution of reactive transport equations governing the precipitation of rust and a porosity-dependent description of diffusivity. With this, the corrosion concealment in RAAC panels is studied computationally for the first time, revealing that RAAC panels can suddenly collapse before any warning of corrosion-induced surface cracking and allowing to map the conditions most likely to result in sudden collapse.

Problem

• RAAC panels collapse without corrosion warning signs
• Current models fail to account for concrete porosity
• Proposing enriched corrosion modeling for RAAC analysis

Innovation

• Enrich corrosion modeling with reactive transport equations
• Use porosity-dependent diffusivity description
• Computationally study RAAC corrosion concealment