To date there is not a large body of experience with repair of cracked and spalled vertical surfaces in architectural-quality structures, so repair and restoration work on these surfaces has been adapted from procedures that have proved effective for bridge and parking deck repairs taking into account the added difficulty of working on vertical surfaces to which access is frequently difficult. Where corrosion-related distress has progressed to serious spalling, the following steps are usually taken: Remove unsound concrete exposing reinforcing steel and clean concrete and steel by sandblasting; restore and protect reinforcement and add anchorage for patches as needed; use one of several patching techniques to restore concrete, usually to the original surface level; and apply paint or other appropriate surface coating.
Where no spalling has occurred, pressure injection of epoxy alone may provide suitable repair. This can be done in structural cracks as well as in corrosion areas where distress is in the early stages. If cracks are active moving due to volume changes in the concrete then a flexible material such as an elastomeric joint sealant may be required. Cracks should be widened sufficiently to provide a favorable width-to-depth ratio in the sealant. Elastomeric sealants will not function properly in narrow cracks.
After the reinforcing steel has been fully exposed and cleaned, a check of steel deterioration should be made. If the cross-sectional area of the steel has been reduced by as much as 15 to 25 percent, additional reinforcement is recommended. This applies to deteriorated ties and stirrups as well as to principal reinforcing bars. To be structurally effective, replacement steel must be carefully tied in position and overlapped adequately with the original bars. Here, the advice of a structural engineer is suggested.