Type | General Purpose or Use | Generic Examples |
---|---|---|
Filler | Fill voids and therefore reduce optimum asphalt content Meet aggregate gradation specifications Increase stability Improve the asphalt cement-aggregate bond |
Mineral filler crusher fines lime portland cement fly ash Carbon black |
Extender | Substituted for a portion of asphalt cement (typically between 20 – 35 % by weight of total asphalt binder) to decrease the amount of asphalt cement required | Sulfur Lignin |
Rubber | Increase HMA stiffness at high service temperatures Increase HMA elasticity at medium service temperatures to resist fatigue cracking Decrease HMA stiffness at low temperatures to resist thermal cracking (see Figure 2) |
Natural latex Synthetic latex (e.g., Polychloroprene latex) Block copolymer (e.g., Styrene-butadiene-styrene (SBS)) Reclaimed rubber (e.g., crumb rubber from old tires) |
Plastic | Polyethylene/polypropylene Ethylene acrylate copolymer Ethyl-vinyl-acetate (EVA) Polyvinyl chloride (PVC) Ethylene propylene or EPDM Polyolefins |
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Rubber-Plastic Combinations | Blends of rubber and plastic | |
Fiber | Natural: Asbestos Rock wool Manufactured: Polypropylene Polyester Fiberglass Mineral Cellulose |
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Oxidant | Increase HMA stiffness after the HMA is placed. | Manganese salts |
Antioxidant | Increase the durability of HMA mixtures by retarding their oxidation | Lead compounds Carbon Calcium salts |
Hydrocarbon | Restore aged asphalt cements to current specifications Increase HMA stiffness in general |
Recycling and rejuvenating oils Hard and natural asphalts |
Antistripping Agents | Minimize stripping of asphalt cement from aggregates | Amines Lime |
Waste Materials | Replace aggregate or asphalt volume with a cheaper waste product | Roofing shingles Recycled tires Glass |