Evolution of Pavement Winter Roughness (05-1880)**
Nicolas Fradette, No Organization
Pascale Pierre, Laval University, Canada
Guy Doré, Universite Laval, Canada
Serge Hébert, Laval University, Canada

The functional service level of roads is quantified in terms of roughness. This parameter considers every road surface defect causing passenger vehicle discomfort. Roughness is measured using a quality index, the IRI (International Roughness Index). Roughness gives an overall appreciation of road profile quality without, however, permitting a deeper analysis. In fact, the overall value of the IRI does not discriminate between the two main factors responsible for winter deterioration of roughness, the first being the subgrade differential heave and the second being heave cracks. Differential heave is obtained from the variability in frost susceptibility of subgrade. This phenomenon, which occurs deep in the subgrade, is detectable by isolating the long wave lengths produced at the road surface from the longitudinal profile. Heave cracks are a superficial phenomenon greatly influenced by the application of de-icing salts. By isolating the short wave lengths from the profile, it is possible to highlight the influence of this phenomenon on deterioration. The goal of this research is therefore to establish, using a filtering technique of road profile, the contribution of these two main factors to winter deterioration of roughness on five road sections in the Québec City area. This study will then allow the development of a tool to determine the dominant factor for deterioration and therefore the use of the best technique to rehabilitate roads.