Our March 2013 article, “Using Pre-cured Sealants in Construction Applications,” written by Jason Bakus, resulted in a letter to the editor from Gerald “Jerry” Zakim, CSI Emeritus.
Zakim, who has written for The Construction Specifier’s Failures column, e-mailed his comments:
With interest, I read Jason Bakus’ March article and its advocacy for the material’s use adhered to residual sealant. Since it is a given, in all circumstances, that surfaces must be clean, dry, free of foreign matter, and sound to receive any materials applied, I was disappointed there was no mention of the importance of inspecting the surface. This needs to be done to determine whether further preparation has to be made to ensure the ability of the old sealant/adhesive to hold/adhere the pre-cured sealant under the stress and strain of the movement that must take place.
In my opinion, the article could cause the specifier to overlook the important steps of inspection, preparation, and the like.
The condition of the substrate is certainly a very important aspect of the integrity of a pre-cured sealant system. It is recommended the surface of the substrate be clean, dry, and frost-free prior to the application of the adhesive for a pre-cured sealant. Pre-cured sealants are typically applied over (i.e. spanning) existing sealants, with the adhesive bonded to the substrate on either side of the existing sealant and not bonded directly to the existing sealant, if possible. The adhesive manufacturer should be consulted in determining the appropriate surface preparation method as well as the use of a primer, if required.