From: Bull-Wasser, Rudi [Bull-Wasser@bast.de] Sent: jeudi 3 août 2006 16:46 To: 'msj@cowi.dk'; 'ao@cowi.dk' Cc: DELCAMPE David (ENV) Subject: Stakeholder workshop on noise classification Dear Mrs. Sand Jespersen, dear Mr. Ohm as a participant of the workshop on Tuesday, I would like to thank you for the opportunity to have an open discussion about such an important matter. I want to add some comments or thoughts not as an expert for acoustics but as an pavement engineer. They are mainly related to the use an assessment of Porous Asphalt (PA) as the current most effective silent road surface. Some speakers asked for a more precise production of PA to achieve a better reliability of the performance of the laid material. I agree that there is some potential in that point (we have now a controversial discussion in Germany in which way the tolerances for the mixture should be fixed, as we are going now to declare it as a regular paving method). Minimising the tolerances will fore sure increase the price for the paving. The reason are the selection of raw materials (transport is expensive and causes noise again), and the productivity of a plant must be reduced. The higher price has to be taken into account in the cost-benefit-calculation. May be it is pave more areas with a not so effective PA than to have a high tech product which is very expensive and the application therefore limited. Lifetime of PA: as I understood on Tuesday, for the lifetime is 7,5 years for the upper layer of a PA. For the calculation the time of the acoustic effectiveness is important. In Germany, where we use PA with a very high void content, for the assumed noise reducing effect there is only guarantee of 6 years. PA with a much lower void content can be ineffective after only some 2 or 3 years. Classification-System: I personally think that the mandate for a classification system of laid material doesn't go under the CPD, as the laid material can't be traded. Nevertheless the need for the harmonisation of the test methods is also seen by us and we see here the most beneficial aspect of a projected mandate. The classification has to take into account the variation of the mixes all over Europe. As an member of TC 227 WG1 (Bituminous Mixtures) I can say that an Asphalt designed in one country can be totally different to the same (by the nomial declaration) coming form an other country. E.g. the void content of a PA with the same maximum aggregate size can be between 14 an 28 %. They will be poles apart regarding to the noise reducing effect. So the classification can't be linked to the asphalt mixtures directly. It has to have some neutral classes and the Initial Type Test has to show to which class the defined mixture belongs. So in contracts a client can ask for a pavement which meets classification A, B or C and it is up to the manufactor or the company to provide a pavement which meets that requirement an e.g. excellent Stone Mastix Asphalt or a less excellent PA. If a further explanation is needed, please don't hesitate to contact me. Kind regards R. Bull-Wasser Federal Highway Research Institute Leader of Section Asphalt Pvements Brüderstraße 53 51 467 Bergisch Gladbach Federal Republic of Germany Telephone Int: +49 (2204) 43 750 Fax. Int.: +49 (2204) 43 673 e-mail bull-wasser@bast.de