GUIDELINES FOR DESIGN, INSTALLATION, AND MAINTENANCE OF A WATERPROOF WEARING SURFACE FOR TIMBER BRIDGE DECKS

To enhance long-term timber bridge performance, timber material must be protected from moisture. Wearing surfaces made of asphalt pavement with and without a waterproof membrane have been used to provide protection from moisture on timber decks. This type of wearing surface also protects the deck from other damage while providing a smooth, skid-resistant surface. However, the long-term performance of timber bridges has often not been satisfactory as a result of cracking of the wearing surface or separation of the asphalt or membrane from the deck. Cracking or separation allows moisture migration to the timber deck and decreases ride quality. To improve the performance of a wearing surface, it must be designed, installed, and maintained properly. This document provides guidelines for the proper design, installation, and maintenance of a waterproof wearing surface for timber bridge decks. The design section includes material descriptions and asphalt mixture recommendations. The installation section presents material testing, field inspection, detailed drawings, and errors to avoid. The maintenance section explains the typical signs of distress and corrective procedures.