Noise characteristics of an exposed aggregate cement concrete surface
Paper in proceedings, 2007
On high-volume roads cement concrete surfaces may be economically favourable in comparison to asphalt concrete. When a bypass for motorway E4 in Uppsala (Sweden) was built, cement concrete was therefore selected as the wearing course. It is well known that noise characteristics of cement concrete surfaces may be poor unless a suitable texture is created. Earlier, the Swedish Road Administration has used the exposed aggregate technique to create a favourable surface texture on newly laid cement concrete on some motorways in Sweden, with both good and poor results. This time a special aggregate grading of the top layer was selected, attempting to combine the desire to have excellent durability against the wear of studded tyres in winter, and the desire to limit tyre/road noise emission from the motorway. Being a bypass, this motorway at some locations run rather near to suburban areas where noise immission might become a serious issue. Noise measurements were made with the CPX method, using four test tyres. The results on the exposed aggregate cement concrete (EACC) were compared with similar measurements on SMA surfaces with the same maximum aggregate size. As a reference for comparison three SMA 0/16 were chosen since this is the surface type that would normally be used on a motorway of this kind. The results indicated approx. 2-3 dB(A) lower tyre/road noise emission on the EACC than on the SMA 0/16 which was better than expected. In the paper the probable causes of the relatively low noise emission are analyzed. The positive results suggest that with a suitable proportioning of the aggregate in the surface layer and high quality exposure technique, the EACC may be used as a standard technique for texturing of cement concrete.