Asphalt

Asphalt pavement refers to any paved road surfaced with asphalt. Hot Mix Asphalt (HMA) is a combination of approximately 95% stone, sand, or gravel bound together by asphalt cement, a product of crude oil. Asphalt cement is heated aggregate, combined, and mixed with the aggregate at an HMA facility.  The resulting Hot Mix Asphalt is loaded into trucks for transport to the paving site.  The trucks dump the Hot Mix Asphalt into hoppers located at the front of paving machines.  The asphalt is placed, and then compacted using a heavy roller, which is driven over the asphalt. Traffic is generally permitted on the pavement as soon as the pavement has cooled.

Some Useful Definitions:

Unbound Flexible Pavement

A pavement consisting of an unbound granular base and subbase with a thin asphalt or sprayed bituminous seal surfacing.

Deep Strength Asphalt Pavement

A pavement comprising asphalt wearing, intermediate and base courses placed on a cementitiously treated subbase. Full Depth Asphalt Pavement

A pavement comprising asphalt wearing, intermediate and base courses placed directly on a layer of unbound subbase material.

Mechanistic Pavement Design Procedure A pavement design procedure used for pavements consisting of one or more bound layers based on determination of strain and use of material performance relationships to calculate the number of allowable load repetitions.

Heavy Vehicle Axle Groups (HVAG)

A set of closely spaced axles acting as a unit, including a single axle on a heavy vehicle, whereby a heavy vehicle is:

  • A two-axle vehicle with the minimum axle spacing greater than 3.2 m, or a three or more axle vehicle configured at least with two axle groups (excluding short towing vehicles, e.g. trailer, caravan, boats, etc.); or
  • A vehicle having a gross vehicle mass exceeding 4.5 tonne; or
  • A Class 3 or higher classification vehicle.

Standard Axle

Single axle with dual wheels applying a load of 80 kN.

Equivalent Standard Axles (ESA)

The number of standard axle loads that are equivalent in damaging effect on a pavement for a given vehicle or axle loading calculated with a load damage exponent of 4.

Design Traffic Loading (DTL)

Design Traffic Loading is equivalent to Design Traffic when expressed in terms of ESA. Also referred to as DESA.

Design Traffic

The design number of Equivalent Standard Axles of traffic loading (DESA) for flexible pavements and the cumulative number of HVAG for rigid pavements.

Design CBR

The Design CBR is the CBR value given to an imported earthworks layer in fills or to prepared insitu material in cuts, at or below subgrade level, which is used to determine the structural thickness of a pavement.

Design Thickness The required structural thickness of pavement including a design allowance for construction thickness tolerances.