Epoxy injection is a common method used for repairing cracks in various concrete structures such as foundations, basements, beams, columns, slabs, and walls. It involves injecting epoxy resin under pressure into cracks that have an opening of 0.05mm or larger. However, this method is not suitable for cracks that are still active, when there are numerous cracks, or when water leakage cannot be controlled. It is important to note that if the underlying cause of the cracking has not been addressed, the cracks may reoccur near the original repair. Additionally, when injecting cracks that are not visible on all surfaces, extreme caution must be exercised to ensure proper and effective repair.
Epoxy injection is a commonly used method to restore concrete members to their pre-cracked condition without increasing their strength. The tensile bond strength of epoxy to concrete is greater than the tensile strength of concrete itself. While future cracks may occur at the same load as the original member, they may be in different locations. Strengthening can be achieved by installing additional reinforcement along the failure plane in combination with epoxy injection. Internal or external reinforcement may also be used along with epoxy injection for restoration and strengthening.
Cracks in concrete foundations can be repaired using low-pressure injection of epoxy or polyurethane foam. Similarly, certain epoxies and polyurea materials are suitable for repairing cracks in concrete floors and slabs.
It’s important to note that epoxy and other resins may lose strength when exposed to fire or sustained elevated temperatures, so fireproofing protection is necessary for structural repairs in such conditions. Additionally, epoxy resins labeled as water-insensitive during curing may develop milky white bond lines if injected into wet or damp cracks. It’s important to verify the complete water-insensitivity of the epoxy by injecting it into pre-wetted cracks and evaluating the cured epoxy in a cored sample.
Slabs and walls that are restrained at their ends may develop full-depth cracks due to shrinkage during concrete curing or extreme thermal fluctuations. The cause of local overstress should be eliminated or considered in the repair, and injecting the crack at the midrange temperature can help minimize thermal stress fluctuations.