AASHTO Journal, 24 July 2015
The Maryland Department of Transportation’s State Highway Administration is using a “foamed asphalt” road base to recycle old pavement and reduce its use of new materials.
The agency said that on a $32.7 million roadway widening project on US 29 in Columbia, this technique will let crews use 2,600 tons of recycled material.
The process requires injecting water into reclaimed asphalt pavement in a special chamber, causing the road “millings” from other projects to foam and bind together. The SHA said, “This produces a usable material that is 10 to 15 times the original volume of the millings. Crews then mix the material with Portland cement to create foamed asphalt. The recycled material will be used as a base course and will be the proper load-bearing strength after compaction.”
SHA Acting Administrator Douglas Simmons said that “using recycled materials in road building and maintenance supports practical design principles … Using less new asphalt and wasting less from other projects is an environmental benefit.”
A Federal Highway Administration website says foamed asphalt has been widely used in Europe but “is relatively new here in the United States.” A scanning team, however, found that “significant advances” in the equipment used to apply foamed asphalt “allow for deep road base stabilization at low cost compared to other stabilization techniques.”
