Recycled Asphalt Materials are Black Gold to Local Highway Agencies

۱۳۸۶ تیر ۱۶, شنبه

Recycled Asphalt Materials are Black Gold to Local Highway Agencies

Through the partnership of the Utah Department of Transportation (UDOT) several Utah counties and towns are recipients of some excellent road building materials. Over the past few years UDOT has had a number of major rehabilitation and reconstruction projects involving the roto-milling of deteriorated asphalt pavements. The roto-milled asphalt materials make excellent base and surfacing materials for local roads and streets.

Box Elder County is the latest recipient of UDOT's team spirit. Major reconstruction projects on Interstate 15 in Box Elder County (11 +/-miles) have yielded approximately 300,000 cubic yards of recycled asphalt materials. Arrangements were made to provide this material to Box Elder County at no charge. In fact, there were savings to UDOT and their contractors by eliminating the cost of double handling and stockpiling the material. Box Elder County was able to coordinate operations with the contractor so they could load and haul the recycled asphalt material as the milling operations were being performed.

Box Elder County used belly-dump trucks to haul and spread the recycled material on the gravel roads selected for upgrading. The following photograph (figure 1) shows the existing condition of one of the gravel roads on which the recycled asphalt material was placed.

Using the belly-dump trucks enabled Box Elder to place the material in a windrow, making it easy for the motor grader operator to spread the material to the planned 6 inch thickness prior to compaction. This operation is shown in the second photograph (figure 2).

Once the recycled asphalt material was spread to proper depth, the material was compacted with a steel wheel vibratory roller. The resulting product after compaction is shown in the following photographs (figures 3-4).

Box Elder County Road Superintendent John Collom reported that the best results were achieved in spreading and compacting the recycled material when temperatures were the warmest. Water was also used to facilitate the spreading and compaction process. The material is more workable and can be compacted to its maximum density under these conditions. This process yields a road with a stabilized asphalt base that can carry heavy agricultural truck loads year round. From a pavement design perspective it is estimated that a structural number on the order of 1.50 is achieved which is equivalent to about three and one half inches of asphalt concrete surfacing.

Box Elder has taken a second step in their road upgrading process and that is to place a chip seal over the recycled asphalt material. This seals the surface and keeps surface moisture from soaking into the recycled asphalt base and roadbed. The chip seal consists of an asphalt emulsion (CRS-2) placed at a rate of 0.5 gallons per square yard and a one half inch maximum size aggregate chip placed at 25 +/- pounds per square yard. An example of the completed road is shown in the photograph below (figure 5).

The estimated cost of Box Elder County's road improvement program using the recycled asphalt material including chip seal is about $36,000 per two lane (26 feet wide) road mile. This includes all equipment, labor and materials costs. In addition, they have become heroes in the eyes of Box Elder County residents. Ms. Ida Cannon, secretary for the county road department, reports residents are standing in line to have the road to their house upgraded accordingly.

Similar road improvements using recycled asphalt material have been done in Summit County, Sevier County, and a number of towns in Utah. We commend UDOT, their contractors, and the county road department personnel who have taken the initiative to use this renewable road building resource, "black gold," to provide excellent road and street facilities to the user at minimal cost.

As the old saying goes, "One man's junk is another man's treasure." Recycled asphalt pavement materials can truly be a treasure to local highway agencies. A special thanks goes to the Utah Department of Transportation for working so closely with local highway agencies and making this valuable resource available

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