Numerical Simulation of the Chloride Penetration in Cracked and Healed UHPC via a Discrete Multiphysics Model

Concrete cracks in service conditions, and this accelerates the degradation of both cementitious matrix and steel reinforcement. The inherent capacity of cementitious materials of autonomously sealing the cracks might result in a higher durability in aggressive environments. Recently, at Politecnico di Milano, the effect of both autogenous and crystalline admixture-stimulated healing on chloride penetration has been experimentally investigated for an ultra high performance concrete (UHPC). In this research work, the whole laboratory campaign has been numerically simulated through a multiphysics-lattice discrete particle model (M-LDPM)-based numerical model, in order to validate its capability of simulating the effect of autogenous and stimulated healing on the chloride penetration. The healing process is simulated through an improved version of the hygro-thermo-chemical (HTC) model, in which the effect of cracks (opening and closure) on permeability is implemented. Aiming to capture the results obtained through the afore-mentioned experimental campaign, the healing model is coupled and harmonized with an existing M-LDPM-based chloride diffusion model for saturated and nonsaturated concrete. The numerical results prove the model capability of capturing both the reduction of chloride penetration due to the cracks sealing, and the different degree of closure reachable with and without employing crystalline admixtures as healing agents, and thus pave the way toward incorporation of the benefits of self-healing cement based materials in predictive modeling and design tools. The research activity from which this work stems was framed into the H2020 project ReSHEALience.