HALTING DECK DETERIORATION ON EXISTING BRIDGES

Many reinforced-concrete bridge decks across the U.S. may be headed for rapid deterioration. The concentration of chloride ion in the concrete may be steadily increasing as a result of deck salting. If the concentration of the chloride ion exceeds 2.0 lbs/cu yd at the top layer of reinforcing steel, then corrosion of these rebars is highly probable. But if the deck's chloride ion content is below 0.5 lbs/cu yd, corrosion should not occur. These decks should be covered with an impermeable membrane and asphaltic concrete overlay. California and some other states use three tools for determination of condition of a deck: dragging a chain over the deck to indicate presence of subsurface fractures (delamination); halfcell potential measurements, which indicate active corrosion in rebars; and taking concrete core samples from the deck and analyzing them for chloride concentration. A promising solution for these badly deteriorated decks is cathodic protection, the imposition of a voltage on the deck that stops ongoing corrosion. /AUTHOR/