Subbase (pavement)

Subbase (pavement)

In highway engineering, subbase is the layer of aggregate material laid on the subgrade, on which the base course layer is located. It may be omitted when there will be only foot traffic on the pavement, but it is necessary for surfaces used by vehicles.

Subbase is often the main load-bearing layer of the pavement. Its role is to spread the load evenly over the subgrade. The materials used may be either unbound granular, or cement-bound. The quality of subbase is very important for the useful life of the road.

Unbound granular materials are usually crushed stone, crushed slag or concrete, or slate.

Cement-bound materials come in multiple types. Mass concrete is used where exceptional loads are expected, with thickness usually 100-150 mm, and optional reinforcement with steel mesh or polymer fibers. Other cement bound materials (CBM), with less strength but also lower cost, are used. They are rated by strength, from the weakest CBM 1 (also formerly known as soil cement) through CBM 2 to CBM 3, 4, and 5, which are more similar to concrete and are called "lean mix".

The thickness of subbase can range from 75-100 mm for garden paths through 100-150 mm for driveways and public footpaths, to 150-225 mm for heavy used roads, and more for highways.

External links

* [ Sub-bases] .

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Pavement Classification Number — The Pavement Classification Number (PCN) is an International Civil Aviation Organization standard used in combination with the Aircraft Classification Number (ACN) to indicate the strength of a runway, taxiway or airport ramp (or apron). This… …   Wikipedia

  • Asphalt concrete — Asphalt concrete. As shown in this cross section, many older roadways are …   Wikipedia

  • Crocodile cracking — Crocodile cracking, also called fatigue cracking or alligator cracking, is a common type of distress in asphalt pavement. It is usually studied under the transportation section of civil engineering. Crocodile cracking is characterized by… …   Wikipedia

  • Road transport — (British English) or road transportation (American English) is transport on roads of passengers or goods.A hybrid of road transport and ship transport is the historic horse drawn boat.HistoryThe first forms of road transport were horses, oxen or… …   Wikipedia

  • Road surface — A road in the process of being resurfaced Road surface (British English) or pavement (American English) is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway. In the past… …   Wikipedia

  • roads and highways — ▪ transportation Introduction       traveled way on which people, animals, or wheeled vehicles move. In modern usage the term road describes a rural, lesser traveled way, while the word street denotes an urban roadway. Highway refers to a major… …   Universalium

  • airport — airport1 /air pawrt , pohrt /, n. a tract of land or water with facilities for the landing, takeoff, shelter, supply, and repair of aircraft, esp. one used for receiving or discharging passengers and cargo at regularly scheduled times. [1915 20;… …   Universalium

  • Falling weight deflectometer — A falling weight deflectometer, FWD, is a testing device used by civil engineers to evaluate the physical properties of pavement. FWD data is primary used to estimate pavement structural capacity for 1) overlay design and 2) to determine if a… …   Wikipedia

  • Subgrade — In highway engineering, subgrade is the native material underneath a constructed pavement. It is also called formation level. Explanation Subgrades are commonly compacted before the construction of a pavement, and are sometimes stabilized by the… …   Wikipedia

  • Fly ash — Photomicrograph made with a Scanning Electron Microscope (SEM): Fly ash particles at 2,000x magnification Fly ash is one of the residues generated in combustion, and comprises the fine particles that rise with the flue gases. Ash which does not… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”