Volume 6, Issue 2 (February 2009)
Quantification of Effect of Enforced Cyclic Movement and Regional Exposure Factors on Weatherability of Construction Sealants
This paper presents information on the weatherability of construction sealants based on a newly developed test specimen design that allows simultaneous exposure of the sealant to forced compression and extension movement in a single specimen. In this study, exposure to cyclic movement and weathering is carried out simultaneously. Furthermore, an evaluation method for surface cracks induced by weathering is presented that allows an assessment of the overall “degree of degradation,” a single number characterizing the state of degradation of the sealant surface. In order to study the effects of the extent of extension and compression as well as the regional exposure factors on the degree of degradation, twelve sealants were exposed to outdoor weathering for four years at three exposure sites, located in the northern, central, and southern areas of Japan. The evaluation of surface cracks was carried out according to the rating provided in ISO 4628-4, with the modification that new rating criteria were introduced to evaluate minute cracks. A mathematical equation determining the “degree of degradation” was obtained for each sealant, which is based on a component reflecting aging under static condition and another component reflecting the dynamic conditions induced by mechanical movement and regional exposure factors. This equation provides a reasonable relationship between the experimental observation and calculated degradation over the exposure period.