Bituminous Mixtures and Applications in Road Construction

Irrigation of Primers

Irrigation of primers: The application of a binder with bitumen on a bituminous layer, *not* followed by a sand coverage, to receive further bituminous material. The natural sand used has a uniform granulometry. Before the application of bitumen, it should be watered with surface water to moisten it, but not to the point of saturation. Then, a layer of asphalt agglomerate, called a *watering adherence*, is spread.

Irrigation of Adhesion

Irrigation of adhesion: The application of a layer of bituminous binder before the extension of another underlayment. Historically, hot bitumen was used. Currently, fluidized bitumen emulsions are preferred.

Surface Treatments

Surface treatments: The application of a bituminous binder on a surface, followed by the extension and compaction of a layer of aggregate. This is performed on a firm base formed by a compacted granular layer. They can be:

• “Single-layer treatments”: A thin layer of asphalt with pebbles adhered to it.
• “Multi-layer treatments”: Formed by overlapping several single-layer treatments.

Their purpose is to provide waterproofing and resistance to erosion.

Bituminous Macadam by Penetration

With Viscous Binders

Bituminous Macadam by penetration with viscous binders: The application of a bituminous binder on a thick layer of compacted aggregate with uniform granulometry. The binder penetrates the aggregate by gravity. Then, a layer of fine aggregate is spread, and compaction forces it into the remaining gaps between the larger aggregate.

With Fluid Binders

Bituminous Macadam by penetration with fluid binders: The application of a bituminous fluid on a thick layer of compacted aggregate of uniform granulometry. The surface voids are then filled with fine aggregate, followed by another application of the binder.

Slurry Bituminous

Slurry Bituminous mixtures are fine-grained, dense, or fluid-consistency bituminous mortars made with aggregates and asphalt emulsion. Their purpose is to waterproof and standardize aging and porous surfaces.

Bituminous Mixtures

Bituminous mixtures are similar to concrete, where the conglomerate is bitumen. They can be mixed hot or cold.

• Cold bituminous mixtures are composed of aggregate and a bituminous binder. The extension is performed at room temperature.
• Hot mixtures are formed by aggregate and bituminous binder that have been heated before mixing. Their extension and compaction are performed at a temperature above ambient. Temperature should be monitored because if it is too high, the mixture can burn.

Several types exist: open, thick, semi-dense, and dense.

Drainage Mixtures

Drainage mixtures: These are bituminous mixtures dosed with the primary objective of achieving a large number of interconnected voids. These voids allow rainwater penetration and evacuation to areas outside the pavement’s side.

Fluidized Bitumen (Cutbacks)

Fluidized bitumen (cutbacks): These are a mixture of penetration bitumen with compatible volatile hydrocarbon solvents, such as gasoline or kerosene. These solvents promote entry into force, as during the curing process, they are removed by evaporation with heat, leaving the bitumen adhered to the aggregates.

Bituminous Emulsion

Bituminous Emulsion: These are intimate mixtures of two immiscible liquids, where one is dispersed into very small drops within the other. The dispersed phase is fluidized penetration bitumen or water, and the other is continuous. The viscosity depends on the bitumen and the proportion of water. When the bitumen and water are mixed, the emulsion is hot, but when it cools, the dispersed particles coagulate, and the emulsion breaks. To prevent this, emulsifiers are used, which prevent the bitumen particles from joining (cationic emulsion).