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The destructive procedure stresses the sealant in a way as to cause either cohesive or adhesive failure of the sealant or cohesive failure of the substrate where deficient substrate conditions exist. The nondestructive procedure places strain on the sealant and a stress on the adhesive bond. The Flap Procedure is utilized to evaluate the bond at each substrate, particularly if the substrates on each side of the joint vary. Applicable Products: Weatherproofing sealant joints.
Technique 1: Using the probing tool, the center of the sealant bead is depressed to create an elongation strain on the sealant joint. The depth of the depression is recorded as a percentage of the width of the bead. The sealant bead should be depressed in such a way that the probing tool does not contact of scrape against the substrate, nor slide toward the center of the joint.
Method A: Mark the cut portion of the sealant 1 inch from the adhesive bond. Pull the tail at an angle of 90 degrees to the substrate to effectively elongate the 1 inch mark to two times the stated movement capability of the sealant.
Record the type of failure that occurs and the distance of the mark from the adhesive bond when failure occurred, or the distance recommended by the manufacturer without causing failure. Method B: Mark the cut portion of the sealant 1 inch from the adhesive bond.
Grasp the sealant tail at the mark 1 inch from the adhesive bond. Various tests can be performed pulling the tail slowly at an angle of 30, 90 or degrees to the substrate, keeping the tail in line with the sealant bead as precisely as possible.
Monitor the extension to determine the elongation resulting in failure. If sealant begins to experience cohesive failure, stop pulling and readjust the grasp on the tail and begin pulling again. The tail is pulled in whatever direction or manner that best avoids cohesive tearing and encourages adhesive failure to occur.
Repeat the procedure as necessary to evaluate adhesion to both substrates forming the joint. Flap Procedure — Sealant is cut 3 inches along the bond-line on the substrate opposite to the substrate to be evaluated.
Make two cuts across the sealant bead horizontally at each end of the 3 inch cut. Pry up the flap that is formed by the three cuts through the sealant bead. Grasp the flap near the edge opposite the bond line to be evaluated. Pull the flap in the tensile mode until the onset of adhesive or cohesive failure occurs. Stop pulling and grasp the flap near the other end. Pull the flap in a shear mode until the onset of adhesive or cohesive failure.
Trim away the portions of the flap that have failed. The Nondestructive Procedure may result in the failure of a deficient substrate before effecting a failure in the sealant. The weatherproofing may require additional remediation in order meet the performance criteria.
ASTM C1521-13: Evaluating Adhesion of Installed Weatherproofing Sealant Joints
Ductile Iron Pipe Standards