Wearing Surfaces

In accordance with Article 9.9.8 of the AASHTO LRFD (7th Edition, 2014), wearing surfaces on wood decks are to be of a continuous nature, and bituminous wearing surfaces are recommended.

The surface of the wood deck should be free of surface oils to encourage adhesion, and there should be no bleeding of the preservative wood treatment. Excessive bleeding of the preservative treatment can seriously reduce adhesion with the wearing surface. The contract plans and specifications should clearly state that the deck material be treated using the empty cell process, followed by an expansion bath or steaming.

Due to the smooth surface of individual lamination and glued laminated decks, it is beneficial to provide a positive connection with the wearing surface, in order to ensure proper performance. A tack coat should be applied to wood decks prior to the application of an asphalt wearing surface, which typically improves the adhesion of the asphalt wearing surface to the deck. In lieu of a tack coat, a geotextile fabric may be used, depending on manufacturer recommendations. In any case, the asphalt surface should have a minimum compacted thickness of 2.0 inches.

In practice, cracking of the wearing surfaces on glue laminated wood decks has been observed. The cracks in the wearing surface often develop at joints between panels, and are typically caused by insufficient load distribution between panels. Designers may be able to reduce the potential for cracking by means of a steel channel bolted to the underside of the wood deck panels.