Influence of high moisture content on road pavement structure: A Polish case study

Communication infrastructure is one of the most important criteria determining the comfort and quality of life in a given country, as well as an important indicator helping to determine the pace of its economical growth. The main objective accompanying the development of the road network is to ensure the required durability of the pavement structure. Undoubtedly, one of the factors that shorten the life of the road pavement and cause its premature damage is the increased moisture content in the pavement structure, in particular in unbound granular layers. The article presents a case study on the accelerated degradation of a section of state-importance road located in the southern part of Poland, where a problem of increased moisture content in the road pavement structure occured. The research part shows the results of measurements of the transverse evenness of the pavement, monitoring of the groundwater table level and measurements of pavement deflection using Falling Weight Deflectometer. The conducted research and observations showed that the pavement on the selected road section worked permanently in high moisture conditions, where the groundwater table stabilized at an average level of 30–60 cm below the pavement surface. During the observation period, an increase in the rut depth in the right wheel track was noticed, reaching a value of 3.2 mm. In addition a significant development of damage visible on the wearing course was observed. Based on the results of defelection measurements, a back-calculation analysis was performed, which allowed to obtain estimated resilient moduli values of subsequent pavement layers and the subsoil. Resilient moduli values of the unbound subbase and the bituminous layers were significantly lower than the expected values, which was related to the high moisture content in the road pavement structure.