Major Asphalt Applications

Major Asphalt Applications

Road Paving

Hot-Mixes
Bitumen is added to hot aggregate, either in a batch operations, or continuous process. Normally penetration grades are used, although hard grades, cutbacks, emulsions and modified bitumens are used to provide specialist products.

Surface Dressing
One or more bitumen layers are sprayed onto a road surface, and immediately covered by aggregate. Cutback bitumen or emulsion would normally be used but in special circumstances modified bitumens or penetration grades may also be used.

Note: Recycling
In its broader concept pavement recycling covers the re-utilisation of road-making materials, by recovery from the existing road pavement. It maybe subdivided into various methods as defined below:

Hot in-situ:
The removal or partial removal of the existing asphalt layer either by milling or hot scarifying, and the insitu re-application of these materials. This process may include heating of the reclaimed asphalt pavement (RAP) and the addition of virgin materials.

Hot in-plant:
The asphalt layer removed either by cold milling or in partial block form, is then transferred to an asphalt plant where the material is crushed and graded (if required) and then added to virgin material in an asphalt mixing plant. The ratio of RAP to virgin materials depends largely on the design of the asphalt plant, and the heat transfer mechanism used to heat the RAP.

Cold in-plant: As above but using bitumen emulsions, and no heating stage.

Cold In-situ:
The total or partial removal of an asphalt layer, and/or base material either by milling or scarifying followed by a further material classification stage if appropriate, after which, the resulting material is mixed with bitumen emulsion and recompacted.

Roofing

In Europe, the major outlets for bitumens in roofing are the manufacturing of rolled bituminous membranes and as a mopping adhesive for the former. Some bitumen is being used in liquid roofing formulations. The manufacturing of bitumen shingles is a limited application. Roofing membranes manufacture involves either a plain blown bitumen or a penetration grade bitumen modified with polymeric materials.

The use of the latter requires a blending step, where the bitumen is heated up to 160200°C and modified with polymers. The membrane coating medium may contain a mineral charge at the same temperature range as above; the coating mixture is then applied to a reinforcing matting and formed as a surfaced roll. Rolls are installed on the roof either by welding with a flame, taking advantage of a controlled melting of the bottom of the membrane, or by use of a hot "mopping" bitumen adhesive; fumes evolution may be observed during those operations.

Mopping bitumen is a blown grade with a high Ring and Ball Softening Point; it is heated to a high temperature in kettles (up to 200-250°C) and spread onto the roof with brushes.

"Liquid roofing" materials are fluid pastes containing bitumen, various additives and inorganic materials and solvents. They are cold-applied and therefore do not generate bitumen fumes in normal use.

Other applications

The following is a list of applications and is not exhaustive:

- lining of canals, water reservoirs, dams and dikes;
- flooring;
- mastic application;
- protective coating for walls, pipes, water mains, motor cars;
- paper or cardboard impregnation;
- components of products such as adhesives, joint fillers, paints, lubricants, rubbers, etc.
- coal briquetting;
- electrical insulation;
- manufacture of electric batteries;
- encapsulation of radioactive materials;

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