This report examines the construction and texturing that can be applied to concrete surfaces to achieve lower tyre noise whilst maintaining adequate standards of skidding resistance performance and durability. A literature review indicated that the exposed aggregate concrete surface (EACS) was currently the most likely to satisfy these objectives. A laboratory study is reported where the optimum time to brush the concrete to produce a uniform acceptable EACS finish was determined. A correlation exercise was performed to assess five methods of measuring the surface texture with good correlation being found between the various sensor measured methods. EACS laid on the M18 and A50 were monitored to determine the texture depth, skid resistance and noise, and to determine how these parameters had changed with time and exposure to traffic. In addition, further EACS laid on the A13, A449 and M23 were also monitored for texture depth, skid resistance and noise. The skid resistance was assessed at both low and high speed and the noise measurements undertaken to establish noise levels at specific points alongside the road as well as establishing the variation in noise along the entire length of the road. The texture, skid resistance and noise measurements on the M18 and A50 EACS sites indicated that these were all performing well after over five years trafficking with satisfactory texture and skid resistance and less noise being generated than on the adjacent hot rolled asphalt (HRA) surfacing. Since the inception of this project there is now a tendency to use a thin surfacing and not HRA, consequently some noise measurements have been included from Safepave and stone mastic asphalt (SMA) surfacings. From the limited results on these materials it would appear that the initial noise levels are lower, or similar, to those on EACS, but the noise tends to increase more rapidly with time on the thin surfacings. (Author/publisher)
Abstract