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17 September 2013

Road-surface grinding benefits environment and health

Uneven road surfaces create noise, boost particle concentration in the area and raise vehicles’ fuel consumption. Mistra Innovation is now investing SEK 4 million on a project to find out whether grinding away a few millimetres of the asphalt can mitigate these problems.

It is well known that road traffic generates noise and results in elevated particle concentrations in the air. Remedying these problems, however, is not always easy. In recent years, rising particle concentrations have attracted most attention because they represent a substantial health risk. One explanation for these problems is that the asphalt laid on Swedish roads contains a large quantity of coarse pebbles that make for uneven surfaces.

 Attempts to reduce noise have involved laying asphalt containing smaller stones, but this has been shown to cause considerably faster road wear. This method has therefore not come into common use.

Promising tests on noise reduction
HTC Sweden, a company that specialises in concrete grinding, has now launched an alternative method. By grinding off a few millimetres of the asphalt surface, HTC believes that it can tackle the problems of both noise and particles without making road wear worse. In cooperation with the Swedish National Road and Transport Research Institute (Statens väg- och transport­forskningsinstitut, VTI) and Linköping University, the company has carried out tests on the E4 highway near Huskvarna. Although the stretch of road used for the testing was already surfaced with noise-reducing asphalt, the researchers managed to reduce the noise level by some 3 decibels. This represented an actual halving of the volume, although the human ear perceives the difference as smaller.

‘If you grind off a newly laid asphalt coating you also get a roadway of a lighter colour, which enhances safety when it’s dark and wet outside. What’s more, the film of oil that settles on the road when asphalt is laid can be removed. This contains substances harmful to the environment and health — substances that in the normal course of events are slowly worn away by the traffic and, as a result, spread to the natural environment,’ says Per Sandström, Business Area Manager (Infrastructure) at HTC.

Road service life improved as well
Besides the advantages for health and the environment, the company estimates that a road surface that has undergone grinding also lasts 20–50% longer than one that has not. If the forthcoming experiments show that these calculations are correct, a substantial decrease in society’s costs of road maintenance will be possible.

The method is also interesting for airports. Every time an aircraft lands, rubber from the landing wheels burns and sticks to the asphalt, making the surface extremely slippery when it rains. This is presumably less of a problem when the runway has been retextured by grinding.

Mistra Innovation has awarded SEK 4 million to the research project known as Via Futura. The aim in this project is to investigate whether the promising results from the prestudy are repeated in more rigorous testing and whether the method can be developed further. Apart from HTC, VTI and Linköping University, participants in the project include the Swedish Transport Administration, Svevia and Projektengagemang, a consulting group in Stockholm.

Text: Per Westergård, Vetenskapsjournalisterna

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