Modelling the hydration of cement ‐ Does chemical shrinkage influence autogenous self‐healing?

Autogenous self‐healing of cracks in water retaining concrete structures is included in Eurocode 1992‐3 as a possible measure to heal cracks up to a width of 200 μm without additional repair. Water flow through the crack leads to the closure of the fracture, mainly due to CaCO₃ precipitation. However, despite standardization, the healing effect seems to be random in practice. This study uses thermodynamic modelling of cement hydration to examine how the timing of crack formation affects crack widening or closure due to chemical shrinkage or swelling and discusses the implications for autogenous self‐healing. It is found that the exact timing of early‐age crack formation can lead to crack widening or closure in the range of a few micrometres. This effect is most prominent for cracking within the first two days of curing and dependents on the cement type, the fraction of inert material in the mix design and the amount of shrinkage that translates into a macroscopic volume reduction. However, it is concluded that other more dominant factors must be at play leading to the discrepancy between laboratory results and the unpredictable healing efficiency observed in practice.