| Résumé : |
Most of the past Cases from the F-Files have focused primarily (although not exclusively) on coating failures on steel. However, coating failures can and do occur on other substrates such as aluminum, wood, and concrete, to name a few. In this case, a warehouse concrete floor coating was exhibiting blistering only a few months after installation.
A large existing warehouse building was being modified to house a light manufacturing facility. The floor was constructed of concrete slabs. It was reported that there was no moisture barrier underneath the slabs.
The floor coating project included removal of an original clear coating by portable centrifugai blast cleaning. The new system consisted of four coats that included an epoxy penetrating primer, an aggregate filled epoxy base coat, an epoxy grout coat, and an epoxy finish coat. It was reported that moisture vapor transmission (MVT) testing was performed by the contractor prior to the new coating installation. The testing indicated a low MVT of less than 2 lbs./1,000 square feet/24 hours. Blisters began to appear in the coating within a few months of the floor coating installation (Fig. 1). In this case, aggregate in a concrete floor, in the presence of moisture, caused blistering of the coating system. It is a relatively uncommon problem that could have easily been blamed on the contractor as mis-application of the coating, void of a thorough scientific analysis of the problem (in the field and laboratory) as well as knowledge of concrete substrates. Lets take a closer look. |
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The case of the contractor who almost got floored in JOURNAL OF PROTECTIVE COATINGS & LININGS (JPCL), Vol. 30, N° 5 (05/2013)
