Modeling of concrete cracking induced by steel expansion

When steel reinforcement corrodes in a concrete structure, the expansion of corrosion products often leads to cracking in the concrete. In this paper, a simple physical model is developed to relate the size of cracks to steel expansion. By assuming the steel/concrete interface to be perfectly smooth or perfectly bonded, upper- and lower-bound solutions can be obtained; The results indicate (1) the presence of an expansion threshold below which no crack propagation can occur; (2) a "pop-in" behavior occurring at a critic al expansion that is strongly dependent on initial flaw size; and (3) the s teel expansion to generate a given crack size is strongly affected by inter facial bonding. When the theoretical findings are compared to available exp erimental results, good agreement is obtained. Based on the theoretical res ults, several guidelines for controlling expansion-induced cracking can be proposed. These include proper control of initial flaw size, addition of fi bers to produce an R-curve behavior, and the enhancement of bond and/or fri ction at the steel/concrete interface.