What is Stone Mastic Asphalt (SMA)?
A. Stone Mastic Asphalt (SMA) is a relatively new (to Virginia and the U.S.) asphalt mix that is proving to be a superior paving material for high traffic roadways such as interstates and primaries. The mix contains a high percentage of coarser aggregate that is more cubical in shape and has a higher percentage of liquid asphalt binder. It provides a strong stone skeleton with good stone on stone contact to increase stability. Mineral filler and fibers are added to create a stiff mortar that when combined with the liquid asphalt helps lock the aggregates together. The mix was first developed in Europe and has been proven to provide a very tough and stable pavement that is virtually rut-proof and lasts much longer than conventional asphalt mixes. The first SMA placed in Virginia was on I-95 between Washington, D.C. and Richmond in 1993. Since then, the use of SMA on interstates and primary roads has steadily increased with about 360,000 tons scheduled to be put down this year. The mix i
