Q.: We need to patch some core holes in a freezer room floor. But the freezer temperature is -10° F and the room can't be warmed to allow patching. Is there a product that can be used under these conditions?
A.: We know of one patching product that might work: Set 45, made by Master Builders Inc., Cleveland. However, some special precautions must be taken at this low temperature. It's best to mix the product at room temperature (about 70° F). Immediately before placing the patch, slightly heat the core hole with a propane torch (if this is permitted in the structure). Then cover the patched core hole with an insulating blanket and an electric heating pad.
Reader Bruce Kahn of Great Wall Products, Waunakee, Wis., says that his company also has a product that will work at very cold temperatures. Called Speedset 60, the patching material reportedly has a compressive strength of 2000 psi after one hour, an ultimate strength of 10,000 psi, and meets ASTM C 928-92a, Standard Specification for Packaged, Dry, Rapid-Hardening Cementitious Materials for Concrete Repairs.
Another reader Jerry Loran of CTS Cement Mfg. Co., Cypress, Calif. reports that his company's Rapid Set Nonshrink Grout and Rapid Set Mortar can hydrate at subfreezing temperatures. Both products have been used to make freezer-floor repairs at -10° F. Customers say they have been able to open up the repaired areas within 90 minutes.