Methods and compositions to increase performance of asphalt cement concrete comprising recycled asphalt pavement
Embodiments of the invention are amendments to hot-mix asphalt (“HMA”) which open new price/performance areas to asphalt cement concrete (“ACC”) pavement. Equivalent-performing pavement may be made at lower cost, or higher-performing pavement may be made at equivalent-to-prior-art cost. The amendments, recycled asphalt pavement (“RAP”, and including recycled asphalt shingles [“RAS”]), and reinforcing fiber (aramid fiber) may be adjusted as described herein to achieve a desired price/performance target.
1. A method of producing hot-mix asphalt (“HMA”) to form improved asphalt cement concrete (“ACC”) pavement, comprising:
in a continuous-mix manufacturing process,
heating and mixing aggregate to form dried aggregate;
adding recycled asphalt pavement (“RAP”) and reinforcing fiber to the dried aggregate to form combined aggregate;
mixing the combined aggregate;
adding virgin liquid asphalt and liquid binder modifier to the combined aggregate to form a completed mixture; and
mixing the completed mixture to form a homogenous HMA where aggregate, RAP, reinforcing fiber, virgin liquid asphalt and liquid binder modifier are evenly distributed throughout the homogenous HMA.
2. The method of claim 1 , further comprising:
transporting the homogenous HMA to a road site;
spreading the homogenous HMA over a base surface at the road site; and
compacting the homogenous HMA over the base surface to form an ACC-paved surface.
3. The method of claim 1 wherein the RAP comprises recycled asphalt shingles (“RAS”).
4. The method of claim 1 wherein a weight of the RAP is at least 25% of a weight of the combined aggregate.
5. The method of claim 1 wherein a weight of the RAP is at least 38% of a weight of the combined aggregate.
6. The method of claim 1 wherein a weight of the reinforcing fiber is between about 1 oz per ton of the homogenous HMA and about 6 oz per ton of the homogenous HMA.
7. The method of claim 1 wherein the reinforcing fiber is coated with wax before being added to the dried aggregate.
8. The method of claim 1 wherein the reinforcing fiber is wetted with water before being added to the dried aggregate.