Skid Resistance Properties of Concrete Pavement Surfaces in Tunnels

Skid resistance properties of concrete pavement surfaces in tunnels are measured with the dynamic measuring device TRT on a regular basis in the Czech Republic. Measurements are usually carried out before and after putting the tunnel into operation and then approximately once a year; the skid resistance is also measured after each maintenance of the pavement surface. With the regular measurement of the friction coefficient Fp it was found out that depending on the traffic intensity, the quality of skid resistance deteriorates quickly. As a part of research and development projects, causes of this rapid decrease of skid resistance of concrete pavement surfaces in tunnels were investigated. It was found out that apart from rapid abrasion of concrete pavement which is textured with burlap drag during placement, the dangerous slipperiness is caused by pollution of the surface by greasy dirt coming from exhaust fumes of the passing vehicles. While outside tunnels, the greasy residues are dusted off during rain and carried away from the road with the water spray, in tunnels they cling to the walls and pavement surface and on the polished surface, they cause slipperiness dangerous for road traffic. The article introduces examples of skid resistance measurements where the decrease of the friction coefficient Fp depending on traffic intensity in time is shown. Furthermore, results of research of concrete pavement pollution by greasy residues are stated, which affect the skid resistance to the highest degree, and also influence of the protective steam-tight coating on wax basis which is applied to fresh concrete is described. In conclusion, maintenance technologies that re-establish skid resistance are introduced which were tested in tunnels.