Q: How can epoxy injection be used to rebond delaminated topping slabs?
A: Here's a step-by-step procedure to effectively rebond delaminated areas:
  1. Map out the delaminated area. Use a chain or hammer sounding technique to locate the delamination. The delamination will sound "hollow" or dull when a chain is dragged across the surface or when a hammer is struck against the surface. Sweep off the surface and use a marker to outline the delamination. It's usually not necessary to to mark delaminations of less than 1 square foot.
  2. Locate injection ports. Mark an X to locate a minimum of 4 ports at the outer periphery of the delamination, about 2 inches in from the outer periphery. For delaminations larger than 16 square feet, use an extra port for each additional 4 square feet.
  3. Drill and set injection ports. Drill 1/2-inch-minimum-diameter port holes with a vacuum-attached swivel drill bit. Drill the holes deep enough to intersect the delaminated area. Use a fast-set epoxy to fix ports in place.
  4. Clean delaminated area. Blow compressed air into drilled holes to force dust out of nearby holes. Limit air pressure to 50 psi to avoid causing further delamination. Some contractors prefer to use water to flush out dust. Either air or water can be used to make sure the drilled holes intersect the hollow separation. If air or water doesn't exit a nearby hole, redrill the holes.
  5. Inject epoxy. Start injection, working from each port and moving across the delamination. Use and injection pressure of 25 to 35 psi. Increase the pressure to 45 psi for delaminations smaller than 2 square feet and to finish filling large areas. Hollow planes occuring along reinforcing bars may require additional resin, since cracks along the bars will fill with resin.

For additional information, see "How to Rebond Delaminations," Concrete Repair Digest, April/May 1994, p. 115.