Concrete Repair and Restoration
The keys to concrete repair include removing all deteriorated concrete, exposing corroded reinforcing steel, surface prep of exposed steel and concrete, proper treatment of the bond lines, and application of an appropriate patching material with similar properties to the original concrete. Experience has shown that there are certain portions of exposed concrete structures more vulnerable than others to deterioration from weathering in freezing climates. These are exposed surfaces of the top 2 feet of walls, piers, posts, handrails, and parapets; all of curbs, sills, ledges, copings, cornices, and corners; and surfaces in contact with spray or water at frequently changing levels during freezing weather. The durability of these surfaces can be considerably improved and serviceability greatly prolonged by preventive maintenance such as weatherproofing treatment with concrete sealing compound. Selecting the most satisfactory protective treatment depends to a considerable extent upon correctly assessing the exposure environment.
Concrete sealing compounds and coatings that provide good protection from weathering in an essentially dry environment may perform poorly in the presence of an abundance of water such as on some bridge curbs and railings, stilling basin walls, and piers. Freezing and thawing tests of concrete specimens protected by a variety of concrete sealing compounds and coatings,including epoxy, urethanes, and water-proofing and penetrating sealers, have been performed in Reclamation laboratories. These tests indicate that proprietary epoxy formulations, siloxane and silane formulations, and the high molecular weight methacrylate formulations clearly excel in resisting deterioration caused by repeated freezing and thawing in the presence of water. None of these formulations, however, will totally "waterproof" concrete. That is, they will not prevent treated concrete from absorbing water and becoming saturated under conditions of complete and long-term submergence. The performance of new concrete sealing compounds is continually being evaluated by the Materials Engineering and Research . If use of these materials is being considered, the project should contact Armaco Construction for the latest recommendations on materials, methods of mixing, application, curing, and precautions to be exercised during placement. Except for hand-placed mortar restorations of deteriorated concrete, concrete sealing compounds are ordinarily not applied on new concrete construction. The treatments are most commonly used on older surfaces when the earliest visible evidence of weather-ing appears. That is, the treatment is best used before deterioration advances to a stage where it cannot be arrested. Such early evidence consists primarily of fine surface cracking, close and parallel to edges and corners. The need for protection also may be indicated by pattern cracking, surface scaling or spalling, and shrinkage cracking. By treatment of these vulnerable surfaces in the early stages of deterioration, later repairs may be avoided or at least postponed for a long time.