Test sections to study the acoustical quality and durability of thin noise reducing asphalt layers

Within the context of the European Noise Directive, action plans have been established. Noise reducing road surfaces are seen as a cost-efficient measure for t raffic noise abatement. Therefore ten test sections were installed in May 2012 in Belgium, with the objectiv e of integrating noise friendly bituminous wearing courses in the Flemish road surface policy in a lat er stage. Eight test sections are paved with hot la id, bituminous wearing courses with a thickness of maxi mum 30 mm and a maximum content of accessible voids of 18 %. The other two sections consist of a double layer porous asphalt (PA) and a stone mastic asphalt (SMA) (reference section). The acoustical quality a ssessed during measurement campaigns in the first t wo years after construction is discussed in this paper . Statistical Pass-By (SPB) and Close-ProXimity (CP X) measurements are performed according to ISO 11819 within certain time intervals to follow up the evolu tion. Also other important factors, like durability, are studied. Resistance to raveling and adhesion to the base course are critical parameters for the lifetime of a thin noise reducing asphalt layer because of the high void content and limited thickness. BRRC measured the raveling resistance on test plates made with the asph alt mixtures sampled at the construction site. Tensile adhesion and shear bond tests were performed on dri lled cores to measure the adhesion of the wearing course to the base course. Results of these laboratory ra veling and adhesion tests are linked to the evolution on s ite and to the evolution of the noise measurement r esults.