The following is a listing and brief comment on some of the more important properties for aggregates that are used in asphalt paving mixes: Since aggregates used in bituminous mixtures (hot mix asphalt, cold mix asphalt, surface treatments) comprise approximately 95 percent of the mixture by mass and roughly 80 percent by volume, the aggregate material(s) used in asphalt concrete have a profound influence on the properties and performance of the mixture. MATERIAL PROPERTIES AND TESTING METHODS Asphalt Aggregate 30) sieve, with at least 65 percent of the particles passing the 0.075 mm (No. A typical mineral filler completely passes a 0.060 mm (No. Mineral fillers make up less than 6 percent of the hot mix asphalt concrete by mass, and generally less than about 3 percent. Mineral filler consists of very fine, inert mineral matter that is added to the hot mix asphalt to improve the density and strength of the mixture. Modifiers include oil, filler, powders, fibres, wax, solvents, emulsifiers, wetting agents, as well as other proprietary additives. The properties of binders are often improved or enhanced by using additives or modifiers to improve adhesion (stripping resistance), flow, oxidation characteristics, and elasticity. Liquid asphalt, which is asphalt cement dispersed in water with the aid of an emulsifying agent or solvent, is used as the binder in surface treatments and cold mix asphalt pavements. Asphalt cement is used in hot mix asphalt. The asphalt binder component of an asphalt pavement typically makes up about 5 to 6 percent of the total asphalt mixture, and coats and binds the aggregate particles together. Proper aggregate grading, strength, toughness, and shape are needed for mixture stability. Asphalt AggregateĪggregates used in asphalt mixtures (hot mix asphalt, cold mix asphalt, surface treatments) comprise approximately 95 percent of the mix by mass. Mineral filler is sometimes added to hot mix asphalt concrete.

The components of asphalt concrete include asphalt aggregate and asphalt binder. This type of pavement is common on light- to medium- volume roads that may or may not already have an existing bituminous surface. Following placement of the aggregate, the mixture is rolled and compacted to provide a drivable, dust-free surface. Surface treatments consist of an application (or sometimes multiple applications) of emulsified or liquid asphalt and select aggregate, placed over a prepared granular base or existing surface. The components of cold mix asphalt can be mixed at a central plant or in-situ with a traveling mixer. For higher traffic applications, cold mix asphalt pavement usually requires an overlay of hot mix asphalt or surface treatment to resist traffic action. The use of cold mix asphalt is usually limited to relatively low-volume rural roads. The components are heated and mixed at a central plant and placed on the road using an asphalt spreader.Ĭold mix asphalt is a mixture of emulsified asphalt and aggregate, produced, placed, and compacted at ambient air temperature. Hot mix asphalt is a mixture of fine and coarse aggregate with asphalt cement binder that is mixed, placed, and compacted in a heated condition. Surface treatment acts as a waterproof cover for the existing pavement surface and also provides resistance to abrasion by traffic. Surface treatments are sometimes used during pavement construction. Pavements can be constructed using hot mix or cold mix asphalt. The entire pavement structure, which is constructed over the subgrade, is designed to support the traffic load and distribute the load over the roadbed. Asphalt concrete pavements consist of a combination of layers, which include an asphalt concrete surface constructed over a granular or asphalt concrete base and a subbase.

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