MODELING OF CONCRETE CRACKING INDUCED BY STEEL EXPANSION

When steel reinforcement cui-rudes 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 he 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 critical expansion that is strongly dependent on initial flaw size: and (3) the steel expansion to generate a given crack size is strongly affected by interfacial bonding. When the theoretical findings are compared to available experimental results, good agreement is obtained. Based on the theoretical results, several guidelines for controlling expansion-induced cracking can be proposed. These include proper control of initial flaw size, addition of fibers to produce an /?curve behavior, and the enhancement of bond and/or friction at the steel/concrete interface.