Epoxy injection is commonly used to restore the pre-cracking condition of the member without increasing its strength. The epoxy tensile bond to the concrete substrate is stronger than the concrete’s tensile strength. Future cracking may occur at the same load as that of the original uncracked member but at different locations. Strengthening is provided by installing additional reinforcement across the failure plane in combination with the resin injection. Frequently, internal or external reinforcement is installed in combination with the epoxy injection for strengthening and restoration.Crack injection can be successfully performed on cracks as narrow as 0.013 mm in width with general epoxy injection resins. Cracks with less width can be injected with epoxy or other polymer systems having a low viscosity of 200 cps.
Epoxies and other resins lose strength when exposed to fire or sustained elevated temperatures and fireproofing protection is required for such structural repairs. Epoxies that are labeled water-insensitive during curing may develop milky white bond lines if injected into wet or damp cracks. Verification that the epoxy is completely water-insensitive should be made by injecting the test epoxy into pre-wetted cracks, then evaluating the cored sample of the cured epoxy injected into the crack. Slabs and walls restrained at their ends may develop full-depth slab cracks due to shrinkage as a result of volume changes during concrete curing or during extreme thermal fluctuations. The cause for the local overstress should be either eliminated or considered in the repair. Injecting the crack at the midrange temperature minimizes thermal stress fluctuations.
Epoxy injection for Concrete Crack Repair in foundations, basements, beams, columns, slabs, walls and other concrete structures