Wearing Surfaces

The wearing surface on an orthotropic steel deck plays an important role in improving skid resistance, distributing wheel loads, and protecting the deck against corrosion. The wearing surface should have sufficient ductility and strength to accommodate expansion, contraction, and deformations without cracking or debonding. The wearing surface should also have sufficient fatigue strength to withstand flexural stresses due to composite action of the wearing surface with the deck plate, resulting from local flexure. Furthermore, the wearing surface should be durable enough to resist rutting and wearing from traffic, impervious to water and vehicular fluids, and resistant to deicing salts and deterioration due to solar radiation.

Problems related to the performance of the wearing surface have been experienced in past applications, and have generally been attributed to inadequate construction control, degradation of the materials, or flexible design of the steel decking. Recent research and design improvements, such as the minimum deck plate thickness currently required by the AASHTO LRFD (7th Edition, 2014), have addressed many of these previous failures. Many current design concepts utilized in modern orthotropic steel deck bridges have shown to be successful.

There are two main categories for surfacing materials that are typically used on orthotropic steel decks. One is a bituminous surfacing system that can consist of mastic asphalts, latex-modified asphalts, or reinforced asphalt systems. Bituminous systems are generally 2.0 inches or greater in thickness. The other surfacing system is a polymer system, which includes epoxy resins, methacrylates, or polyurethanes, all usually having a thickness of 0.75 in. or less. In most cases climate dictates the chosen surfacing system, as bituminous surfaces are more sensitive to thermal changes. However, when specified and installed correctly, and with regular maintenance, both wearing surfaces have demonstrated service lives in excess of 30 years.