Because appearance is important, patching and repair of architectural concrete needs to be done carefully. Attempts to patch minor defects can make flaws more noticeable. In most cases, having the precaster repair on-site is a good idea, since previous experience can be applied. The PCI recommends completing on-site repairs before final cleaning and caulking, but it's not a good idea to wait until all panels are erected to begin repairs.
Effective repairs can be made in the field; however, preventing damage is best. Typical problems include: damage during transportation, handling, and erection; conspicuous lifting anchors; falling debris; difference in tolerances or appearance between adjacent units.
Choose repair materials and methods based on the size of the defect, and requirements of color, texture, and finish. Keep in mind how different materials or methods may affect the in-place items, in terms of evidence of the repair as well as blending in with surrounding pieces.