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A two-component asphalt-extended urethane membrane was developed which satisfies the requirements demanded of a waterproofing membrane for protecting reinforcing steel in concrete bridge decks from corrosion. A technique for application of the membrane is described which essentially eliminates blister formation. Blisters caused by thermal expansion of gases in the concrete have been a constant problem with liquid-applied membranes. The technique consists of: applying a black prime coat to the deck, allowing the black-primed deck to heat up by absorbing radiation from the sun, and applying the membrane after the maximum average deck temperature has been reached. The black prime increases the absorptivity of the deck, causing it to heat up more than an unprimed deck. It thus avoids the sudden increase in temperature caused when a dark membrane is applied over a white deck on a sunny day. Then, by applying the membrane after the sun has passed its zenith and the deck temperature has started to fall, blister formation caused by the outgassing of the concrete deck is avoided. This technique works equally well on damp or dry decks. The system is completed by applying a tack coat of hot asphalt and a 2-in. overlay of asphalt concrete.
corrosion, concretes, reinforcing steels, membranes, waterproofing, bridge decks, corrosion prevention, urethanes, blistering
Senior research associate, Chevron Research Company, Richmond, Calif.
Technical coordinator, Chevron USA, Inc., Baltimore, Md.
Specialist, New Products Introduction, Asphalt Division, Chevron USA, Inc., San Francisco, Calif.