For newly formed concrete structures, the responsibility for ensuring that coatings are applied properly typically rests on the shoulders of the concrete or general contractor. It's necessary to develop detailed coating procedures, monitor the coating contractor's work, and understand what tests should be performed to determine the quality of the finish. Addressing these issues before the job begins can help prevent premature coating failures, costly reworks and delays, and damage to a contractor's reputation.
Laying the Ground Rules
To achieve the desired results, the coating contractor should be provided with detailed specifications on how to prepare and coat the concrete surface. The specifications should be flexible enough to accommodate differences in the environment or the situation but specific enough to prevent error. Instructions concerning the inspection, testing, and documentation of the coating application should also be included. Tests are generally related either to surface preparation or coating application.
Surace Preparation and Coating Application
Coatings must be applied to concrete that is structurally sound, clean, and well-cured. Contaminants such as dirt, grease, efflorescence, and laitance interfere with the coating's bond. The surface also should be rough enough for the creation of a good mechanical bond and should not be powdery. Equally as important as surface preparation is proper coating application. Supervision of the applicator's work is necessary during all phases of this process.
Inspecting the Work
Inspections should be carried out at various stages of the project, typically after surface preparation and before coating application, between each coating application, and soon after the final coat has properly cured. A number of recognized standards for performing various inspections can be referenced from ASTM.