Q.: We're bidding on a crack injection job where the requirements for the injection epoxy resin are specified. The specs require a compressive strength of 15,000 psi, tensile strength of 8000 psi, and slant shear strength of 5000 psi. We're having trouble finding an epoxy resin that meets these specifications. Any suggestions? The concrete we're repairing has a 3500-psi compressive strength.
A.: The required strengths are probably unnecessarily high. Ray Schutz, a consultant on adhesives, suggests that you try to get the specification changed so epoxy requirements are in line with those in ASTM C 881, Standard Specification for Epoxy-resin-base Bonding Systems for Concrete. Schutz says it's likely that an epoxy resin with 15,000-psi compressive strength will be too brittle.