Management of pavement service life by using new technology. Final report

This study investigated the use of instrumented pavements to enhance the management of highway infrastructure. A novel sensor technology was explored to continuously monitor road structures to gain more insight and understanding of pavement performance and deterioration caused by heavy truck traffic. With the help of monitoring data, it was possible to assess the current analytical pavement analysis method, which is based on multi-layered elastic analysis, and, thus enhance the pavement design practice in use. Three instrumented pilot projects were constructed in 2006, which were located at Vt20 in Taivalkoski, Mt 2983 in Vesilahti, and Pt 11568 in Vantaa. The volume of traffic was 1,500, 400, and 3,250 vehicles per day, respectively. A total of 200 sensors and 600 m of fiber optic cables were installed. In addition, near Tampere, a relatively thick test section was constructed where only air and pavement temperatures were measured. Different sensors, installed at various depths in the pavement, were used to measure stresses, strains, and deflections caused by pavement bending under loading. In addition, vehicle locations in the traveled lane and vehicle speeds were recorded. Also, environmental effects, including the air and pavement temperatures, the moisture content, and the ground water table level, were monitored. The pavement responses were recorded with the help of an automated data acquisition and storage system and vehicles were also photographed to ease the data interpretation and analysis work.Structural deterioration of the pavement layers was also studied indirectly by measuring the pavement surface characteristics; 3D laser scanning was used to obtain 3D pictures of the pavement surface, and Stratotest profile measurements and surveying were used to study changes in the pavement layer thicknesses. The transverse lateral expansion of the road cross section caused by heavy truck traffic and frost heave was measured by surveying and pavement deflections were measured using the Falling Weight Deflectometer (FWD). All of these measurements were obtained to monitor changes in pavement response with time. The most important findings were obtained from the test loading of the pavements, which were conducted by using trucks, with known weights, driven different paths at different speeds in the traveled way. Knowing the exact weight of the truck enabled calculation of the pavement response. Similarly, it was possible to back-calculate the pavement loading by knowing the measured pavement response. It was found that the stiffness of the unbound layers was minimally affected by the wheel load. However, the depth of the monitoring location had more effect on the obtained stiffness values. Based on the vertical strain measurements, it appears that the unbound aggregate structure was moving underneath the wheel load. The material was densifying underneath the wheel and dilating beside the wheel, which caused the material to lose its structure. The FWD measurements indicated that the shape of the deflection bowl was dependent on the thickness of the bound layers or asphalt layers. As all of the test sections had thin bound layers, the shape of the deflection bowl was sharp. Also, the pavement was bending faster than it recovered. This report may be found at http://www.tut.fi/units/rka/mpr/tutkimus/tieika/Loppuraportti/TIEIKA_Loppuraportti.pdf