Overlays on Deck
by Paul Tarricone, Assoc. Editor;Serial Information: Civil Engineering—ASCE, 1992, Vol. 62, Issue 9, Pg. 42-45
Document Type: Feature article
Abstract:
By the summer of 1993, a standard specification may be on the books for polymer concrete bridge-deck overlays�a high-tech rehab technique requiring a combination of plastic binder�such as epoxy, polyester or methacrylate�and aggregate�including silica or basalt. No cement or water is used in the overlays, which typically reach strengths of 1,000-2,000 psi in 3 hours and 4,000-6,000 psi in 24 hours. The oldest polymer overlay still in service was placed on Route 44 in Grand Rapids, Mi., in 1976. Yet questions remain about long-term effectiveness and cost. Proponents in California and Virginia say service life can reach 20 years, but some DOTs (Washington and Ohio, for instance) have experienced deck failures anywhere after three to eight years. Also, costs vary from as low as $20 per sq yd in Virginia to $162 per sq yd in New York. Still, the overlays have a number of advantages. They're extremely thin (only � in. in some applications) and add very little load to a bridge's substructure. They're highly impermeable, protecting steel reinforcing bar from corrosive deicing salts, and they offer impressive skid resistance. Also a minimum cure time of 2 hours is possible at 90F, and more than 100 sq ft of deck can be covered per minute, putting lanes quickly back in service. Most experts agree that quality control during surface preparation, mixing and placement is the key to a successful overlay, and two groups are currently working toward a standard specification and user's manual that the Federal Highway Administration will recognize and states can turn to for guidance.
Subject Headings: Pavement overlays | Synthetic materials | Bars (structure) | Standards and codes | Polymer | Decks | Bridge decks
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