The objectives of applying a bonding aid are to reduce the suction from the substrate and to provide an adhesive that sticks the repair matrial to the parent concrete in the hardened state. Bonding aids can help to hold the first layers of fresh repair material in place in vertical and overhead repairs. In many cases it is not possible to break out all chloride-contaminated concrete; epoxy bonding aids can act as a barrier against any soluble salts remaining in the substrate penetrating back into the repair.
Bonding aids are applied to the clean concrete substrate using a stiff brush, roller or spray. The material should be worked well into the exposed concrete so that the whole surface, including all irregularities, is covered. Repair mortar or concrete should be applied while the bonding aid is still wet.