New Design of Exposed Aggregate Surface for Northern Entrance of Apeldoorn Constructional and Acoustical Aspects

Traffic noise, which is in fact the sum of tyre/road and engine noise, is one of the major disturbances for inhabitants. This has resulted in strict legislation with respect to maximum allowable noise levels at the facades of houses. Reducing traffic noise at the source by minimizing tyre/road noise can be achieved by advanced pavement engineering. In the past, many exposed concrete surfaces have been realised. Starting from concrete with a higher amount of fine aggregates in the surface to special designs with a uniform fine aggregate size. But all the pavements in The Netherlands show poor till just acceptable noise emissions. In all cases a poorly textured surface caused these disappointing results. Coming from the north, the entrance road to the city of Apeldoorn had only one lane in each direction and needed doubling of the cross-section. Two of the most important issues here are noise reduction as well as durability. The city of Apeldoorn requested a durable low-noise pavement combined with limited maintenance. In the future, residents and the business community are not be disturbed, neither additional costs are to occur. Although the underlying contract required a noise reduction of the surface of 2 dB(A), the city of Apeldoorn has built an additional noise barrier in case the noise reduction would not meet the required value which is needed for the protection of the residents. Unique in this project is the short line between initial choice of the mixture and the actual construction. Due to new fundamental insights and models in tyre/road noise generation mechanisms the usual phase of making test tracks could be skipped. This has led to a significant reduction of time and especially costs. This paper describes first the choice of the concrete mix, the construction, and testing during finishing the exposed aggregate surface and second the acoustic modelling of the design and the results of the noise measurements.