Q.: We need to place an overlay on existing concrete to correct a grade problem. The existing concrete was placed last week and still has a pigmented curing compound on the surface. An acid etch didn't remove it. Does it have to come off before we place an epoxy bonding agent? The area is about 3 feet wide by 400 feet long.

A.: Remove the curing compound. Otherwise the overlay may not bond properly. Try using mechanical methods such as shotblasting or scarifying.