ASTM C1521 – Standard Practice for Evaluating Adhesion of Installed Weatherproofing Sealant Joints
Description:
Significance and Use
4.1 Many parameters contribute to the overall performance of a sealant application. Some of the most significant parameters are sealant bead size and configuration, joint movement, quality of workmanship, the quality of the adhesive bond, and the quality of the sealant material.
4.2 A sealant usually fails to perform as a weatherseal when it experiences cohesive or adhesive failure.
4.3 If a sealant bead fails, an evaluation of the total joint movement may be needed to determine if the joint sealant was strained beyond its intended design, or if the sealant failed within the design parameters.
4.4 If a sealant bead fails adhesively, there is no straightforward procedure for determining the cause. The adhesive failure may be due to workmanship, the specific surface preparation used, the specific sealant used, poor “installed” joint design, poor bond chemistry and other causes.
4.5 Because of the complex nature of the performance of a sealant bead, an understanding of the quality of the adhesive bond is instrumental in any evaluation of sealant performance. It is critical that the evaluation procedures used truly evaluate the quality of the adhesive bond and do not simply take advantage of the tear resistance of the sealant.
4.6 This method does not evaluate the performance of a sealant bead as a weatherseal. It only evaluates the characteristics of the adhesive bond relative to the cohesive strength of the sealant in a particular installation. Since any failures that result from use of these procedures are intentionally induced, they do not necessarily mean that the sealant bead will not perform as a weatherseal.
4.7 The results of these methods are most useful in identifying sealant beads with poor adhesion. The continuous inspection procedure is also useful in the identification of places of poor joint configuration. Obvious cohesive failures are also identified. The results of these methods can be used to assess the likely performance of the sealant bead and to compare the adhesion of different substrate preparations and sealant materials.
4.8 The non-destructive methods are most effective while the sealant is in a state of extension due to mild or low temperatures. They are least effective during high temperature when the sealant is in a compressed condition.
Scope
1.1 This practice describes destructive and non-destructive procedures.
1.2 The destructive procedure stresses the sealant in such 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 objective is to characterize the adhesive/cohesive performance of the sealant on the specific substrate by applying a strain that correlates to the strain that the sealant bead may experience when subjected to its maximum published movement capability, when known; or a reasonable strain when the movement capability is unknown. It is possible that the strain applied to the sealant bead may result in no failure of the sealant or the substrate, failure of a deficient substrate before effecting a failure in the sealant, or a failure of the sealant.
NOTE 1: The destructive procedure requires immediate repair of the sealant bead. Appropriate materials and equipment should be available for this purpose.
NOTE 2: Sealant formulations may fail in cohesion or adhesion when properly installed, and evaluated by this method. The sealant manufacturer should be consulted to determine the appropriate guidelines for using this method.
1.3 The non-destructive procedure places strain on the sealant and a stress on the adhesive bond. Though termed non-destructive, this procedure may result in an adhesive failure of a deficient sealant bead, but should not cause a cohesive failure in the sealant. The results of this procedure should be either adhesive failure or no failure.
NOTE 3: The non-destructive procedure may require immediate repair of the sealant bead, if sealant failure is experienced. Appropriate materials and equipment should be available for this purpose.
1.4 The non-destructive procedure can be used for continuous inspection of 100 % of the sealant bead(s), or for any areas where deficient conditions, which are inconsistent with the practices of Guide C1193, are suspected.
1.5 The committee with jurisdiction over this practice is not aware of any comparable practices published by other organizations or committees.
1.6 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
ASTM C151