Understanding Concrete Floor Coating Adhesion

Concrete Coating Failure

Concrete Coating Failure

A critical component to the longevity of any floor coating is how well it adheres to concrete. Proper substrate adhesion allows for coatings to last longer and retain the superior protective capabilities they were designed for. As is the case with all resinous flooring systems, proper concrete surface preparation is the key to good adhesion.

Concrete Surface Preparation:

Concrete floors should be mechanically profiled with a floor grinder or in some cases a shot blaster. Mechanically profiling the floor is superior to acid washing or chemically etching the floor.

Surface Preparation

Surface Preparation

Often times, these chemicals do nothing but weaken the bond point at which the coating adheres to the substrate. Typically, floors are not properly neutralized, which inevitably leads to floor coating failures. Floor grinders will remove the weak latent material on the top of the concrete substrate along with any surface contaminants.

This process will help to ensure that the pores of the concrete are open and ready to accept a coating.

Concrete Contaminants and High Moisture:

Oil contaminated concrete

Oil contaminated concrete

As part of the surface preparation process, contractors must be aware of significant contaminants that may be present within the concrete. Often times floors may contain oil, grease or other chemicals. These materials will almost certainly lead to future bonding issues and should be appropriately dealt with. Biodegradable degreasing agents as well as organic oil emulsifiers work well to help clean contaminated areas.

Floors should also be tested for high moisture vapor emission rates (MVER). All concrete slabs contain some level of moisture.

Floor coating moisture failure

Floor Coating Moisture Failure

Slabs with higher moisture readings spell trouble for not only floor coatings but all sorts of commercial flooring, including wood, tile and laminate. Industry accepted methods to test for moisture include calcium chloride testing and relative humidity testing.

Both methods are acceptable and HP Spartacote recommends that installers carefully follow all processes mandated by testing equipment manufacturers to ensure accurate readings. For floors exhibiting elevated moisture levels, contractors may elect to install a prime coat of Hydro-Shield SL™ moisture mitigation primer. This unique primer is designed to be used over damp concrete floors and even new concrete that is only 5 days old.

Testing Concrete Floor Coating Adhesion:

Adhesion Test Dolly

Adhesion Test Dolly

Once a floor coating is installed, architects, owners and contractors may look to test the coating for proper adhesion. Testing for adhesion is completed using a pull test under the guidelines of test standard ASTMD 4541.
This test consists of a steel dolly being adhered to the coating on the concrete substrate. Once adhered properly, a cylinder is placed over the dolly and slowly pressurized, essentially sucking the dolly up from the concrete. As the pressure increases, one of two things will happen:
The coating delaminates from the concrete or it doesn’t.

Pull Test Results

Pull Test Results

Concrete will typically fracture at a pressure in excess of 400-500 PSI. Concrete fracture in the context of this test represents superior coating substrate adhesion. Coatings that simply delaminate from the concrete represent poor adhesion. The concrete itself fractures and the dolly breaks free with the coating and concrete attached.

All HP Spartacote coating systems are rigorously tested for not only acceptable but superior adhesion to concrete, helping to ensure a durable and long-lasting floor coating.

Have questions regarding floor coating adhesion ? Please contact one of our technical representatives today at (303) 534-9244.