Surface preparation is an essential step in ensuring a successful decorative concrete coating, or any other coating for that matter. It is a time-consuming task that many contractors reluctantly perform or are tempted to overlook it altogether. The preparation can be carried out using scarification, brushing or grinding, abrasive blasting, shot blasting and flame cleaning. Dust and debris produced as a result of surface preparation must be removed before applying the surface treatment.
In addition to testing moisture levels, it is important to test for oil and grease, which will affect the method used to clean the surface. Some methods, such as acid etching, are ineffective in removing these contaminants and should not be used when they are present. In most cases, if water droplets accumulate on the surface of the concrete, there is oil, grease or some sealing agent on the surface and they will need to be removed. These tests must be supported by more rigorous tests that measure condensation on the plastic film if there is any doubt about the moisture content.
Acid etching is another method sometimes used to profile a concrete substrate, but this method has severe limitations. Acid etching is a very low-cost chemical method commonly used to treat concrete floors to eliminate laitance and provide a profile. If shot blasting or scarifying is used to remove the top of the concrete surface to profile the concrete, this opens the pores of the concrete. To make concrete repairs that last, you will need the repair material to adhere to the surface securely.
Contractors and manufacturers are divided between roughening concrete by mechanical profiling or acid etching. The tensile strength of concrete is approximately 10 to 15% of the compressive strength. The specifications should also indicate how uniform, clean, rough and what strength the concrete substrate should be prior to the installation of a coating or coating. Pour some water on the surface, and if it accumulates or settles on concrete, there is something there that will prevent the layer from sticking. If you are a facility owner or manager in charge of evaluating proposals for concrete surface preparation work, know that there are a few things that need to be clearly stated in a contractor's proposal. It should be borne in mind that improperly performed mechanical preparation can seriously damage a concrete floor.
When the bond holds but the concrete fractures at less than 10% of the expected compressive strength of the concrete, it is a good indicator that the concrete is not yet solid. When you make repairs to a properly prepared surface, the repair or finish and concrete will be joined as a single unit. It is often misunderstood as a material or product failure, says Brian Anderson, chief operating officer of Concrete Coatings Inc. As mentioned earlier, it is important to realize that concrete is like a sponge, it is filled with ventilation holes. Preparing concrete surfaces for coatings, coatings, stains, or repair materials requires careful consideration and attention to detail.