CRACKS IN A REPAIR (ACI 364.9T-03)

Description

Concrete repairs can be broadly classified into structural and nonstructural. Structural repairs are designed to participate in carrying load and to protect the underlying concrete and embedded reinforcing steel from deterio-ration and corrosion. Nonstructural repairs are repairs designed for protection and/or aesthetic purposes only. The presence of cracks may adversely affect the load-carrying behavior of the repaired structure. Thus, cracks in repaired portions of the structure may not be acceptable. In such cases, the effect of cracking on structural performance of the repaired structure should be evaluated by the licensed design professional.

Both types of repairs are intended to mitigate the ingress of potentially deleterious elements, such as water, chlorides, carbon dioxide, and sulfates, into the repair as well as into the existing concrete (Fig. 1). Cracking is probably the biggest single factor in the overall durability of the repair, especially in harsh environments. From a durability point of view, an ideal repair would have no cracks; however; in practice, the goal should be to minimize the amount and width of the cracks.

Guidance on tolerable crack widths in concrete structures is presented in reports from ACI Committee 224, Cracking.1-3 While these documents were developed for cracking in new concrete structures, the recommendations can be applied to concrete repairs. Guidance on achieving crack-resistant repairs can be found in documents prepared by the American Concrete Institute,4 International Concrete Repair Institute5,6 and U.S. Army Corps of Engineers.