Measurement and analysis of inhomogeneity in asphalt pavements

Abstract

This paper describes a new measurement method using laser scanning to determine the homogeneity of asphalt pavements. The term “homogeneity of asphalt” is used to describe the even-ness of texture and surface characteristics (sub-centimeter) of the asphalt surface. In-homogeneity is the opposite; namely an irregular, un-even asphalt surface. The homogeneity of the compacted asphalt pavements is very important in order to secure a satisfactory lifetime of the pavement. This is particularly important where we use coarse asphalt materials. It is also important for the usage characteristics of the road, notably the friction level presented to normal car tires. This is both true for new-laid surfaces and for surfaces well into its life-span. As of today, contractors have no measurement method of determining the required homogeneity of the newly laid surface, but have to rely on expertise and know-how of the paving crew. In addition, the road authorities have no objective means of approving the pavements for homogeneity. The Norwegian Public Roads Administration has recently purchased 15 ViaPPS measurement vehicles, with the purpose to measure road characteristics like rutting, texture, cross-fall and other parameters related to maintenance planning. However, the laser scanner included in these instruments may, with some adjustments, be used to measure homogeneity of the asphalt surface. The main advantage of this method is the possibility to measure a complete 4m width in one single run. In addition to the measurement vehicle itself, advanced analysis software with focus on homogeneity must be used to extract the correct level of the parameters in question from the measurement data. Some areas of the E6 road south of Trondheim have been measured with the standard ViaPPS vehicle, with focus on detecting inhomogeneity. These preliminary measurements show a good correlation between actual inhomogeneity (visual observation) and measured values using the laser scanner.