Concrete Coating Problems
Floor Coating: Understanding and Preventing Problems
Even with the best products in the world and the most highly trained installers problems can happen. Preventing problems from arising prior to, during and after an installation is dependent upon proper pre-job evaluation, system recommendations and application expertise.
The first step in any coating installation is the pre-job evaluation. This consists of understanding the needs of the application, any restrictions on the installation such as timing, or the need for odorless resins. What the system will be used for including chemical resistance needs, abuse it will be subjected to, area size and layout, as well as surface condition.
The next step in a pre-job evaluation is testing. Minimum testing should include moisture testing, alkalinity/pH Level testing, concrete hardness testing, and adhesion testing if an existing coating is present.
Selecting the Right System
Recommending the right flooring system will depend upon the traffic conditions during use, the physical and chemical exposure, and finally the time frame allotted for installation. After satisfying the performance demands of the installation, aesthetic options can be reviewed.
Professional flooring installation contractors take their responsibility of preventing installation related problems seriously. There are a number of factors that can lead to unacceptable installations and all can be prevented. In construction, the finishes receive the most attention and critique because they are the last to be installed and are highly visible. Some problems can occur during the installation, including out-gassing from the slab, and bubbles or fisheyes in the coating. Out-gassing is caused by a difference in the temperature and humidity of the air versus the concrete. When the air temperature is warmer than the slab, especially in a low humidity, vapor will leave the slab. This problem can be avoided by checking the conditions and installing during stable or falling temperatures. Double priming or using a higher build primer can help alleviate the problem.
Fisheyes are most frequently caused by a contaminant on the concrete surface. This is a surface preparation issue and the contaminant must be removed before continuing.
Amine blush is a normal chemical reaction of between the amines present in epoxy with Carbon Dioxide and moisture in the air forming carbamate which appears as a greasy surface film. This is especially true at low temperature and high humidity.
A coating which appears white or cloudy immediately after installation has most likely been exposed to water prior to complete cure. This exposure may be due to moisture from the concrete, moisture from the environmental conditions (Dew Point), or from placing the coating into wet service prior to complete cure.
Surface stickiness, difficulty cleaning and poor hardness are symptoms of improper mixing or incomplete cure. Proper mixing is the single most important job during the installation process.
Pealing from the concrete substrate is frequently associated with surface preparation. Mechanical preparation is far superior to acid etching. Pealing in the form of blisters is most likely due to moisture vapor emissions. If this is experienced within several months of the installation it is due to a surface saturation affect from the dew point during installation. Aged floors which develop blisters are due to moisture vapor transmission or alkali aggregate reaction.
The Negative Effects Of Visible Light
Almost all epoxies and most urethanes, especially urethanes made using aromatic isocyanates, contain chromophores which interact with light. This is of particular interest where light stability is a critical factor and is the main reason that aliphatic isocyanates are used in making polyurethane coatings. When a single component polyurethane coating is exposed to visible light it discolors, turning from off-white to yellow to reddish brown after extreme long term exposure to UV light. It has been generally accepted that apart from yellowing, visible light has little effect on wear properties.
In summary, seamless flooring requires surface evaluation, accurate system selection, and professional installation to prevent expensive problems. Taking the time and effort to understand the potential problems and implementing the correct measures to prevent them is the hallmark of a successful professional flooring installer.