Review of Some of the Questions Examined during Development of ASTM C 1736

Answers to the following three questions provide additional insight into the sci­ence behind ASTM C 1736.

Question 1: Where Exactly Do the Stresses Produced by This Method Affect the Sealant-to-Substrate Bond-Line?

Because the joint sealant material is elastic, bond-line stress is created when the sealant is stretched inward from the surface perpendicular to the joint as the roller pushes on the bead. ASTM C 1736 refers to the resulting geometry as a bead “depression." Bond-line stress induced during a roller pass-through-bead “depression moment" is tension concentrated at the uppermost corner of the sealant, where it intersects the substrate. One way to think of this, in compari­son, is as a non-destructive in-field peel test (Fig. 2).[34]

As a peel test, the roller width affects the amount of measurable bead depression (and the angle of “peel") per specific amount of force but does not affect the total force at the bond-line stress focus point, provided there is adequate clearance between the wheel and the substrate joint wall.[35]

Rolling Device

Depression

Total Bond Line

FIG. 2—Depiction of how the method of ASTM C 1736 can be thought of as a field “peel test."