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:

o        crusher fines

o        lime

o        portland cement

o        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 below)

·         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

Rubber-Plastic Combinations

·         Blends of rubber and plastic

Fiber

·         Improving tensile strength of HMA mixtures

·         Improving cohesion of HMA mixtures

·         Permit higher asphalt content without significant increase in draindown

·         Natural:

o        Asbestos

o        Rock wool

·         Manufactured:

o        Polypropylene

o        Polyester

o        Fiberglass

o        Mineral

o        Cellulose

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