TECHNICAL PERFORMANCE AND LONG-TERM NOISE REDUCTION OF POROUS ASPHALT PAVEMENTS

As part of a joint Nordic research project concerning noise reduction of asphalt pavements, several test sections were established in Denmark in 1990. The test sections consisted of 3 sections with porous asphalt, 1 section with open grade asphalt and 1 reference section consisting of an ordinary dense asphalt concrete. The test sections were established on the island Zealand on a main road leading to a ferry harbour, which meant that the test sections were heavily trafficked. The main objective for establishing the test sections was to examine how the noise reduction behaviour of the test sections performs on long term. But also issues, such as general performance and winter maintenance of these types of pavements were studied. These parameters are of vital performance for the road users as friction and evenness can have significant influence on both safety and economic aspects for the road users. In Denmark, use of porous asphalt has previously caused severe problems for the road users in the winter period due to icy conditions. The paper will concentrate on the evaluation of the functional performance of the test sections of the project. These functional parameters have been measured since the construction of the test sections in 1990 and cover measurements every year until 1998.The measurements include friction measurements carried out by the Danish Road Institute's Stradograph which measured the friction in each wheelpath using a 20% slip. Evenness and rut depth measurements are carried out by using DRI's Profilograph. The Profilograph is a laser based high speed profiling device, which records the longitudinal and transverse profile of the pavements. From the profiles measured, evenness is calculated as the International Roughness Index (IRI) and rut depth is calculated from the transverse profile. Also texture depth is measured every year on the test sections by the sand patch method. In 1998, trial measurements using laser technology were performed to measure the macrotexture of the test sections in accordance with ISO Standard 13473-1 and 2. Finally, also noise was measured by using the statistical pass-by method. The paper will report the development of the parameters described above during the eight year period were the test sections have existed and combine the result of the functional performance of the test sections with their noise reduction performance.