Asbestos Fibers?
Old concrete shingles were sometimes manufactured with asbestos fibers that served to increase their strength and durability. As you know, a person struggling with asbestosis cannot pass the fibers out of their body. The fibers are extremely resilient... holding on to the body and refusing to let go. Due to the serious health concerns caused by asbestos, manufacturers were eventually forced to find an alternate way to simulate these resilient benefits. They needed a material that would hold the concrete together without the health risks. That alternative for many manufacturers was wood "cellulose" fibers. While wood fibers initially did a good job of adding strength and durability to concrete shingles, many soon revealed their alleged fatal flaw... When it rains, unprotected wood fibers attract and hold water. As the temperature changes, the fibers expand and contract separating the shingle back into brittle layers. The Hardishake roofs did not originally reveal these problems because they had a glossy finish that ...