Volume 1, Issue 7 (July 2004)
Artificial Weathering and Cyclic Movement Test Results Based on the RILEM TC139-DBS Durability Test Method for Construction Sealants
The purpose of this study was to assess the effect of artificial weathering and cyclic movement in a laboratory test based on the RILEM Technical Recommendation (RTR) “Durability Test Method for Curtain Wall Joint Sealants.” Eleven sealants being used in Japan were tested, including two silicones, two silicon-modified polyethers, two polysulfides, two polyurethanes — each as one- and two-part products — one two-part silicon-modified polyisobutylene, one two-part urethane cure acrylic, and one one-part water-borne acrylic. The two-part polyurethane, the two-part urethane-cure acrylic, and the one-part water-borne acrylic were also evaluated with and without painting the sealant surface. Test specimens were prepared using anodized aluminum and mortar as substrate materials; primers were used for all sealant/substrate combinations as recommended by the manufacturers. All sealant specimens were conditioned according to Method A. The durability test, consisting of weathering and thermo-mechanical cycling, was carried out both with and without the influence of fatigue cycling. The durability cycles were repeated three times. Weathering was conducted in a fully automatic weathering machine using a xenon arc light source. Sealants without painting were observed to chalk and craze at an earlier stage in the durability cycles than the ones with painted surfaces, confirming the effectiveness of painting the sealant surface in protecting organic sealants from aging. A substantial difference in the behavior of sealants was observed for exposures with and without fatigue cycling, confirming the importance of fatigue cycling in the degradation of sealants. In order to obtain a good correlation between accelerated weathering and actual service performance, a proper balance of degradation factors is essential.