The Class 25 sealant stretched well—until it didn’t. At roughly 35% elongation, a tiny hairline crack appeared at the bond line. The Class 50, meanwhile, stretched like warm taffy to nearly double its width, then snapped back without a mark.
But for the tower that had to survive Seattle’s wind and sun? Only Class 50 would do. astm c920 class 25 vs class 50
Marcus closed his eyes. This was the ancient conflict: The Class 25 sealant stretched well—until it didn’t
“What’s the spec?” Marcus asked, pulling his collar against a sudden gust. astm c920 class 25 vs class 50