Phase-field-based chemo-mechanical modelling of corrosion-induced cracking in reinforced concrete

A new model for corrosion-induced cracking in reinforced concrete is presented [3,4]. Corrosion-induced damage leads to the delamination/spalling of concrete cover (responsible for 70-90% of prematurely deteriorated reinforced concrete structures) or even structural failure as infamously documented by recent collapses of RAAC panels in British schools [2]. The state-of-the-art knowledge of the involved chemo-mechanical processes was captured in several coupled parts of the model. Firstly, the diffusion-driven reactive transport of iron ions from the corroding steel rebar and their precipitation into rust (both in concrete pore space and into dense rust layer in the vicinity of rebar) were simulated. The transport of aggressive species such as chlorides to the steel rebar and the enhanced transport of all considered species through cracks were considered. Rust has a significantly lower density than original steel. Thus, the constrained accumulation of rust in dense rust layer and concrete pores exerts pressure on concrete which was predicted and a new precipitation eigenstrain concept was introduced. The mechanical properties of rust were taken into consideration. The quasi-brittle fracture of concrete was then simulated with the phase-field model. The proposed model was implemented in COMSOL Multiphysics software and solved numerically with the finite element method. Both uniform and non-uniform corrosion case studies were investigated and validated with experimental data. Importantly, the model allows to simulate the impact of the magnitude of the current density on the propagation rate of cracks, which has been puzzling researchers for over 25 years