Currently spain has 3 million sq m of porous asphalt roads. Porous asphalt is being used for all types of traffic conditions and forany type roads and highways. The most common practice today is to use 4 cm layers with 0/12 gradings, with a very low amount of sand (about 15%) and 4.5% Of pure or modified bitumens which results in a voids content in the mix of more than 20%. In the first application of porous asphalt, a conservative approach was taken, primarily usingmixes with a moderate content of voids (15% to 18%). The good durability of mixes with voids contents of more than 20% in the experimental road sections and the closing up observed in the mixes with a low voids content has meant that since 1986 the more open mixes have been preferred. Porous asphalts with voids content of less than 20% have varied widely in their behavior. With heavy traffic, they have closed up after 2 years' use. With medium traffic, however, they havemaintained their drainage capacity after 9 years. None of the pavements using this material have shown any serious deterioration. Despite reduced drainage capacities, all the pavements, including those that have closed up, show a dry appearance during light rains or immediately after a heavy rainfall. Until now, the skid resistance has been very good. Porous asphalts with voids contents higher than 20% held up very well even under heavy traffic, although in this case theexperience has covered only three years. As in the case of the other mixtures, these have not shown any serious deteriorations, and after several years, they maintain excellent skid resistance. This paper appears in transportation research record no. 1265, Porous asphaltpavements: an international perspective 1990.
Abstract