Mathematical Modeling and Numerical Simulation of Self-healing Concrete Concrete

Sammanfattning

Self-healing is a promising route toward more durable and sustainable infrastructure by enabling microscopic cracks in concrete to seal naturally. In this thesis, we study carbonation-induced self-healing through a two-scale reaction-transport model. We formulate balance equations for nine chemical species across the air-filled, water-filled, and solid subdomains of the material geometry. The chemistry combines the primary carbonation of portlandite with the competing secondary carbonation of calcium silicate hydrate and of the unhydrated clinker phases. Through formal asymptotic homogenization, we obtain the corresponding macroscopic balance equations. We then solve the two-scale model in FreeFEM++ under natural exposure over a sixteen-year horizon. The simulations reveal a narrow carbonation front marked by inward carbon dioxide transport, depletion of calcium hydroxide, and accumulation of calcium carbonate. A power-law fit of the front, with the coefficient and exponent estimated jointly, gives an effective exponent approximately 2/3, exceeding the classical Fickian value 1/2. The contribution to self-healing is strongly dominated by the primary portlandite pathway (approximately 97 %). We also note that the material geometry shifts the healing response quantitatively, with the idealized circular inclusion configuration contributing more to the self-healing. The qualitative features of the reported results are in good agreement with those in the selected carbonation literature.