The durability of building joint sealants is generally assessed using a descriptive methodology involving visual inspection for defects. It is widely known that this methodology has many inherent limitations and is only qualitative in nature. A new test method is proposed that would provide more fundamental and quantitative information about the changes that occur in the sealant during durability testing. This test method utilizes a stress relaxation experiment to evaluate the non-linear viscoelastic behavior of sealants. In particular, changes in the time dependence of the apparent modulus can be observed and related to molecular changes in the sealant. Such changes often precede the formation of cracks and the ultimate failure of the sealant. This paper compares the new test method and the currently used descriptive methodology and demonstrates that changes in a sealant can be detected well before any visual alterations are observed.
Citation: Journal of ASTM International
Pub Type: Journals
Construction, sealants, test method, ASTM, Durability, Building Envelope, elastomers, stress relaxation, modulus