Warehouse and retail floors frequently are wet cured for the first seven days. With the knowledge that wet cured concrete develops the best performance characteristics, it's believed that wet curing floors have better surface hardness and resistance to abrasion. However, tests on floors in service haven't been conducted to date, so there isn't empirical evidence to verify the premise. Owners know that their floors with wet curing specifications perform well so they are satisfied with the results.
Without the information from testing to verify the abrasion resistance of floor surfaces, there are other reasons to continue using specifications that require the wet curing of floors. Rick Smith, vice president and general manager of Structural Services Inc., Richardson, Texas, says that other methods for curing floors present different problems. “The three methods most commonly used involve covering a slab with plastic sheeting immediately after finishing is complete, applying a dissipating resin curing membrane, or using a cure-and-seal product to facilitate the curing process,” says Smith.
Plastic sheeting can leave efflorescent markings on floor surfaces which can be difficult, if not impossible, to remove. Resin and cure-and-seal products must be removed before final polishing and the installation of densifier products that increase the gloss numbers increasingly being specified by owners. Smith thinks that the cost of wet curing and cleanup afterward is comparable to or better than costs associated with other curing methods.
Completing floors that are wet cured
After finishing steps are complete, workers flood the surface of a slab with water and roll down cover-curing plastic, being careful to eliminate air voids between the cover and the concrete. During the next seven days, covers are removed when needed to add water if surfaces start to dry out.
After curing is completed, the blankets are removed followed immediately by floor maintenance scrubbing and pickup equipment. Sometimes contractors apply precleaning solutions that hold laitance compounds in solution until they can be removed by the scrubbing machines. Floors are then allowed to dry out for a minimum 48-hour period before the application of a penetrating densifier, which is worked into the surface with strip pads with embedded diamond grits mounted on buffing machines.
Two weeks prior to the ownership taking possession, a test lab measures the reflectivity of the floor using a gloss meter. If corrective measures are required to achieve the right gloss number, contractors burnish the floor with diamond grit stripping pads at high speeds. This process adds heat to the burnishing process, helping to achieve the needed gloss numbers. After specified gloss numbers are achieved, the owner takes possession of the floor.
Floor specifications usually provide for several “or equal” penetrating densifier products. Specifications do, however, almost require that applicators be approved and certified by the manufacturer of the product selected. This often means that a different contractor than the one placing and finishing the concrete floor does the work.
The owners of commercial retail floors have two fundamental requirements for their floors now; low maintenance, long-wear surfaces, and good reflectivity that ensures savings on energy for lighting.