Technical Notes

Phone: 02 - 49319277 - Licence Number: #298174C

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Bitumen


Driveways are made from a wide range of materials, including rock, polished stone, concrete etc......but often today, bitumen is added to stone for improved quality and performance. Bitumen can be used for roads, footpaths, residential driveways, car parks....airport runways, racing tracks, storage areas and many other facilities for the community.

BITUMEN BINDER AND STONE MIX

 
 
The most commonly used mixture of bitumen binder and stone is called asphalt. Asphalt is a blend of graded aggregate, sand, filler (generally flyash) and liquid bitumen. The materials are heated and mixed with hot bitumen which binds the materials together. The hot mixed asphalt (160 - 180 degrees C) must be laid and compacted before cooling.


Asphalt can be placed as a thin layer to act only as a surfacing on a prepared base, or, it can be placed in one or more thick layers that contribute to the strength of a road. The asphalt surface allows any applied wheel loads to be transferred to the base beneath.

When thick layers are used, the asphalt itself provides support for the wheel loads.

The surface texture is smooth and uniform, (although some asphalt designs are open-graded and course textured to reduce water spray and noise on highways). The compacted layer thickness for drives and residential streets is 25 - 40mm, increasing to 50mm + for main roads and highways.

 

CHOOSING THE TYPE OF ASPHALT SURFACE

Before choosing asphalt there are many factors to consider. It is very important to clearly identify the area location and purpose. Issues that must be considered, include:
• Durability.
• Environment (wet, hilly, alpine, flood prone).
• Appearance.
• Conditions of use, vehicle size and type, vehicle speed, vehicle maneuvers, exposure to chemicals and spills.
• Existing surface (gravel, rock, sand, asphalt).
• Size of job (total area, length, width, depth).
• Future maintenance.
Specialist advice about the effects of these variables on the choice of bitumen road must be sought from ASP Engineers.

ESSENTIAL GUIDELINES


The information about asphalt given below should only be used as an initial guide.

When asphalting you should consider:
• The type of edging, brick, gutters, treated pine, pavers, etc.
• The shape of the area to be asphalted.
• The size of the area to be asphalted.
• If a uniform appearance is required for a visually smooth effect.
• A hard wearing surface with long life durability.

 

Specifications

The specifications outlined here are general in nature. Pavement designs for driveways, carparks and industrial applications will vary according to site specific conditions such as design use of pavement, existing ground type, slope of land, water flow control etc. Advice should be sourt from ASP asphalt engineers.
 
Footpaths
  • Minimum 100mm road base
  • Minimum 25mm asphalt

 

Driveways

  • Minimum 150mm road base
  • Minimum 25mm asphalt

Spoon drains may be required to collect run-off from drive and land
Sub-surface drainage may be required to protect the pavement
Concrete, paver or timber edging may be required on some sites

 

Carparks

  • Minimum 150mm road base
  • Minimum 25mm asphalt
  • Sub-surface drainage may be required to protect the pavement
  • Concrete kerbing or edging may be required on some sites

 

Industrial Pavements

  • Minimum 200mm road base (possibly cement treated)
  • Minimum 40mm asphalt
  • Sub-surface drainage may be required to protect the pavement
  • Concrete kerbing or edging may be required on some sites