| Several states have sponsored laboratory and field studies looking at the feasibility of using RAS in HMA pavement. States such as Georgia, Ohio, North Carolina, Minnesota and Texas have performed laboratory studies. Many other laboratory studies may be found on the Technical Reports and Articles pages. Field studies also have been conducted in which portions of highways or trailways have been paved with asphalt containing recycled shingles and have been monitored over time. Pennsylvania , North Carolina and Minnesota have conducted such trials.
|Benefits shown from these studies include:
- Increased stiffness of the asphalt
- Decreased cracking
- No effect on moisture sensitivity
- Decreased susceptibility to rutting
- Decreased optimum content of virgin asphalt cement.
Because of the benefits shown by using RAS in HMA pavement, several states allow a certain percentage of RAS to be used in HMA pavements.
- Florida up to 5% manufacturer's scrap
- Georgia up to 5% manufacturer's scrap
- Indiana up to 5% manufacturer's scrap
- Kansas permits 5% shingles in any mix in which RAP is permitted. The shingles may be manufactured waste or tear off.
- Maryland up to 5% manufacturer's scrap
- Michigan up to 5% manufacturer's scrap
- New Jersey up to 5% manufacturer's scrap
- North Carolina up to 5% manufacturer's scrap
- Ohio "certain percentage of recycled material"
- Pennsylvania up to 5% manufacturer's scrap
Several states have established dedicated offices to increasing the use and applications of recycled materials in highway projects.