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Asphalt Paving of Treated Timber Bridge Decks


Long-term asphalt pavement performance on treated timber bridge decks depends on a number of factors. The structural design of the deck must restrict differential deck deflection between deck panels to 0.05 inches, either through deck stiffness or through mechanical interconnection of deck panels. The asphalt paving system must be properly designed. Contact between preservative-treatment residue and free asphalt must be minimized.

Contact between the asphalt and timber decks treated with preservative cannot be avoided. The most important factor is to prevent treatment chemicals and solvents from leaching to the wood surface. Compliance with new BMPs for timber treatment and proper curing of the bridge deck before placing paving membranes or asphalt pavement will greatly reduce treatment residues.

Free asphalts at the surface of treated timber decks should also be avoided. Proper surface drainage of decks may eliminate the need for waterproof paving membranes. If a paving membrane must be used, the deck should be treated and cured to minimize future interaction between the treatment and the asphalt. Another alternative is to sandwich the paving membrane between two layers of asphalt pavement.

Use the thinnest possible tack coat. Follow the mix and application specifications and all BMPs.

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