Highway & Airport (Airfield) Pavements: Definition, Types & Components
A highway or airfield pavement is a structure consisting of superimposed layers of selected and processed materials which have the primary aim or function of distributing the applied loads to the sub-grade.
The main aim is to ensure that the applied loads are sufficiently reduced such that they will not pose adverse effect or exceed the load bearing capacity of the sub-grade.
Majorly, there are two types of pavements viz. flexible pavement and rigid pavement.
While in flexible pavements, the load is transmitted to the sub-grade through its lateral distribution with depth, in rigid pavement, the load is transferred through slab and beam action.
The main components of a highway/airport pavement include the following:
Surfacing: The main function of the surfacing is to provide a running surface capable of carrying wheel loads without causing undue discomfort to motorists.
Surfacing can be in the form of:
(i) Surface dressing
(ii) Reinforced concrete slab as in the form of rigid pavements.
(iii) Premixed asphalt bituminous materials as in the case of flexible pavements.
Road Base: The road base is the main structural load carrying component of the pavement. It receives the stresses and distributes them to the underlying layers. The road base can be in the form of:
(i) Crushed stones or gravel (lateritic materials)
(ii) Decomposed rock
(iii) Sand or sandy clay stabilized with lime, cement or bitumen.
Subbase: This is the main load spreading component of the pavement. The subbase lies underneath the road base and above the subgrade and help to distribute the stresses from the road base across the subgrade. The provision of a subbase depends on the bearing capacity of the subgrade. Aside the load distribution function of the subbase, it also helps to protect the base from adverse soil conditions that may prevail in the subgrade.
Subgrade: The subgrade is the natural or improved soil or ground on which the pavement is constructed. The pavement structure should be designed in such a way that excess deformation on the subgrade is minimized.
