Coating a concrete substrate to protect an industrial floor is complicated and presents challenges not found when coating steel. Potential sources of concrete coating failure can be attributed to variability of concrete chemistry, presence of moisture in or under the concrete substrate, osmotic or hydrostatic pressures causing blisters or delamination, high alkalinity of concrete substrate, insufficient surface preparation, and selecting the incorrect coating for the service environment.
To achieve success, the following six processes must be done carefully:
- Selecting a competent contractor
- Specifying an appropriate coating type and reputable supplier
- Assessing the concrete condition before starting work
- Surface preparation
- Coating application
- Quality control
Here is a closer look at each of these important steps:
Selecting a Competent Contractor
To assure the contractor has the expertise to do the job right, conduct an interview with its management team to find out the skill level and knowledge the company has. Determine what training the contractor's personnel have and any certifications they hold. Ask the contractor what projects it has completed, and also determine if they were similar to the project being planned.
Specifying an Appropriate Coating Type and Reputable Supplier
Conduct a complete profile of the protective coating requirements. Ask the owner for his expectations of the coating to be applied. Ask about the anticipated life of the coating, project schedule, budget, and required aesthetic properties. Determine the chemical and physical conditions the floor will be exposed to. These include chemical exposures and processes and mechanical stresses. Once the profile is complete, the correct generic coating type can be specified.
Assessing the Concrete Condition Before Starting Work
At the pre-bid and pre-job meetings, verify the substrate conditions to determine the following: if a vapor barrier exists; if curing compounds were used and types; if there are admixtures in the concrete; and if environmental controls were used before, during, and after concrete work. Simple ASTM tests to determine the presence of contaminants and moisture on the existing substrate must be conducted.
The three main methods of surface preparation are steel shot blasting, scarifying, and diamond grinding. The specified coating thickness determines the chosen method. Thin film coatings, less than 15 mils, require diamond grinding. Coatings of moderate thickness require shot blasting. Thick coatings, 1/8-¼ inch, require scarifiying.
To help ensure the success of your floor coating project, it is best to use applicators who have been trained and certified by a recognized authority.
The Society for Protective Coatings (SSPC) is one organization that has developed programs designed to educate and certify even the most learned professionals.
Education and training are the keys that open the doors to success in every profession. For many years, the concrete industry has relied on outsiders to provide the critical technical knowledge that is demanded by today's high-tech coating projects. Now, SSPC certifications enable you to quickly and easily identify applicators and quality control personnel that are experienced enough to meet the strict criteria necessary to achieve certification.
The following courses are representative of what personnel working on concrete coating projects should know:
C2-Specifying and Managing Protective Coatings Projects is designed to sharpen your skills in managing the specific requirements of protective coatings projects.
C10-Coating & Surfacing Concrete for Contractor Supervisory Personal provides an overview of concrete components, coating and surfacing types, and surface preparation and substrate repair techniques.
CCI-SSPC Concrete Coating Inspector Program and Certification program will certify concrete coating inspectors in correctly observing, assessing, documenting, and reporting all relevant job data as determined by the specification and referenced documents.
The owner's representative should invest in stringent record keeping of tests conducted on adhesion; ambient conditions prior; during; and after application; batch numbers of product used; and quality acceptance testing of coating such as a certificate of analysis. Superior quality control records are an excellent investment when considering the costly consequences of failures.
Through proper training and good communication there should be no surprises.