The Guide to the Code Requirements for Evaluation, Repair, and Rehabilitation of Concrete Buildings uses examples of real projects to illustrate how ACI 562 provisions apply in typical concrete repair situations. One of these projects involves an 11-story office building over a two-story, 100,000-square-foot parking structure supporting an open-air plaza.

The supported garage slab was a reinforced concrete flat plate, and the plaza slab was a reinforced concrete flat slab with drop panels. Shortly after construction was completed, the garage slab began to develop excessive cracking.

Engineers determined the structure’s construction varied from its original design: The drop panels were 6 inches thick compared to the design thickness of 14 inches, and the concrete cover over reinforcing bars of the supported garage slab was 4 inches, as opposed to the ¾-inch design. The engineer determined these deviations from the design, and the cracks in the supported slab, indicated significant safety concerns.

The garage was closed to traffic and a contractor was hired to add additional thickness to the drop panels in certain locations and supplemental concrete column capitals underneath the garage slab where required. CFRP strips were also installed as additional flexural reinforcement. The contractor injected epoxy into the surface cracks and applied an elastomeric coating to prevent future damage from water and deicing salts.

The guide lists specific ACI 562 provisions concerning the contractor’s responsibilities during this process, including monitoring conditions that might affect shoring and bracing requirements and environmental issues, such as water runoff and disposal of construction debris.