Paper by VAN KEULEN VAN LEEST from ISCR 9th 2004 Instanbul Turkey
About nine years ago, the Dutch Association of the Netherlands Cement industry (VNC) initiated indicative noise measurements on three new types of concrete roads. It was shown that exposed aggregate had a potential for further optimising. The Dutch Information and Technology Centre for Transport and Infrastructure (CROW) initiated in 1996 an extensive research to update the knowledge about acoustical characteristics of concrete roads. M+P Raadgevende ingenieurs bv conducted this research by performing the necessary measurements and analyses. The optimisation of Exposed Aggregate Concrete (EAC) concerned the acoustical properties within specifications regarding skidding resistance. Starting point herein was a fine gap-graded mixture put in a thin layer. In various other countries, good experiences with this kind of surface have been obtained. In the Netherlands, several test tracks have been constructed with fine (4/7) and coarse (10/14) EAC and on eight of them acoustical measurements have been performed. In order to gain the noise emission of EAC objectively, two types of measurements have been performed according the Statistical Pass-by (SPB) method and the Close Proximity (CPX) method. From these measurements it followed that the effect of the supersmoother is about 1 dB(A) for light vehicles. Light vehicles on the fine mixture show a noise emission similar to the reference (dense asphaltic concrete) and 2 dB(A) higher than the reference on the coarse mixture. Heavy vehicles on the fine mixture and coarse mixture show a 2 dB(A) and 1 dB(A) lower noise emission than the reference, respectively. This means for mixed traffic flows at 80 km/h that the noise emission on the fine and coarse mixture is 1 dB(A) lower and 1 dB(A) higher, respectively. This noise emission can be accurately estimated from texture measurements. In cases where heavy traffic is dominant for the overall noise emission, application of EAC will lead to lower immision levels of 1 to 2 dB(A). This particular situation occurs in the night period at the majority of the Dutch motorways.