Recycled asphalt mixes

For over ten years in a row, asphalt pavement is the most recycled material in America!

Nearly 100 million tons of recycled asphalt pavement (RAP) is re-used in the U.S. every year. RAP has been used widely for more than 30 years and now makes up about 12 percent of the volume of the asphalt mixtures produced in the U.S. Asphalt pavements are also the most recycled material in the rest of the world.

Recycled asphalt pavement (RAP)

Asphalt pavements are comprised of layers or “lifts” of asphalt concrete, a combination of graded aggregate and sand, typically 94 to 96 percent, bound together by asphalt cement (better known as asphalt binder). Asphalt cement/binder is a most unique material. A solid “glue” or cement at room temperature, it becomes an oil-like lubricant when heated allowing the asphalt paving industry to coat aggregate particles while they are hot, then place and compact into pavement layers before it cools and glues all the particles together.

RAP is the term given to removed and/or processed materials containing asphalt and aggregates. These materials are generated when asphalt pavements are removed for construction, resurfacing, or to obtain access to buried utilities. When properly crushed and screened, RAP consists of high-quality, well-graded aggregates coated by asphalt cement.

Here’s what separates asphalt from all the rest

Unlike Portland cement, which chemically changes when mixed with water (think of two-part epoxy), asphalt cement/binder’s properties change from solid to liquid to solid again as a function of temperature. This is a physical change in properties—no chemical change takes place.  Therefore, asphalt pavements and mixes can be removed at the end of their long service lives, reprocessed, heated again and turned back into new asphalt pavement. 100 percent of the aggregate and asphalt binder is recovered and reused as aggregate and asphalt binder! 

Using RAP

The HMA industry has been recycling on a large scale since the 1970s when the oil embargo resulted in drastic price increases and shortages of gasoline, diesel fuel, asphalt cement/binder and other petroleum products. Research on mix properties and modifications to plant equipment were quickly done in response to the asphalt shortages at that time, and within a few years, recycling became a commonplace practice.

Top 10 benefits of using RAP

  1. Reduces cost and bid prices of hot mix asphalt materials.
  2. Reduce consumption of our natural resource supply.
  3. Less dependence on foreign oil because of energy savings in haul, mining, etc. and less new asphalt cement (binder) is required.
  4. Competitive bidding process to obtain the HMA material alternative at the least cost.
  5. For pavement design, recycled hot-mix can be assigned the same structural equivalency factor as a conventional mixture.
  6. Eliminates decisions of logistics of the salvage material, processing form, use of excess materials, and how to incorporate materials into future contracts.
  7. Acceptability of the recycled material and proportions can be determined through mix design prior to allowing the use provided that the recycled product meets minimum criteria for all layers.
  8. Provides a means where pavement material removal is economically justified, thus, stretching available funds to meet current needs.
  9. If designed correctly it can meet all Superpave design criteria.
  10. Long-term performance is equivalent to or better than virgin mix.
©2013
Asphalt Pavement
Association of Oregon

5240 Gaffin Road SE
Salem, Oregon 97317
P 503.363.3858
F 503.363.5571