An article on page 183 in your June/July 1995 issue described how epoxies can be used as thin overlays on bridge decks. I understand that epoxies are not resistant to ultraviolet (UV) radiation. If this is true, won't they degrade when exposed to sunlight on bridge decks?
We spoke to Michael Sprinkel of the Virginia Transportation Research Council, and he said that very little of the epoxy used in bridge overlays is exposed to sunlight because most of the resin is shielded by the gap-graded aggregate that is broadcasted over it. Oil, dirt, and other debris provide additional protection for the epoxy. Sprinkel concedes that, if applied neat, the epoxy binders degrade quickly when exposed to UV radiation. However, epoxy overlay samples taken from several bridge decks show very few signs of UV degradation.