Paving porous asphalt under sub-zero conditions

<p align="LEFT">The average service life of Porous Asphalt (PA) in the Netherlands is about 12 years. Due to the sea climate the winters are normally quite mild, but the last 2 winters the temperatures were significant lower than usual. As a consequence of this more frost damage occurred in predominantly old PA road sections. Frost damage caused premature raveling and potholes. The potholes were repaired with cold or mastic asphalt, but road sections with severe raveling in PA couldn’t be repaired immediately because of the long frost period. The Dutch regulations don’t allow laying PA under 5&ordm;C. Because of safety reasons on some locations the total raveled PA layer was milled and traffic had to drive temporarily with a speed limitation on milled asphalt until the temperatures were suitable enough to lay new PA again. In other urgent cases the PA was temporary replaced under sub-zero temperatures, but had to be replaced again after some months because of premature raveling. Those two solutions have a negative effect on the mobility and give extra costs. To avoid these problems Rijkswaterstaat gave two contractors the opportunity to replace PA on two test sites on motorway A58 near Breda under sub-zero temperatures. The goal of these test sections, laid in the night from 19 to 20 Ferbuary 2010, was to realise the same PA quality as PA laid under normal weather conditions. In this paper the production and laying process as well as the results of the field and laboratory tests are discussed.</p>