ASTM Standard Practice ASTM C 1521 and Its Limitations
The most commonly used industry protocol for checking joint sealant adhesion has been the destructive “pull test." The procedures for properly conducting pull tests are codified in ASTM C 1521-09e . In this method, a 6 in. (150 mm) section of sealant is cut away from the joint, creating a handle that is pulled to two times movement capability or to cohesive failure from both joint substrates in combination (tail procedure) or singly (flap procedure). The average recommended frequency is once every 1000 linear feet (305 m). This practice has been used for decades by sealant manufacturers to verify the adhesive performance of their product(s) in the field.
However, a 6 in. (150 mm) sealant handle pulled every 1000 ft (305 m) is a statistical sampling with a 1:2000 sampling rate if used to evaluate the continuity of the seal. Clearly, a new test method has been needed in order to meet the demand for continuous joint seals.