Composition of a Pavement (Pavement Structure)

Road Prism

A road is generally made up of a road bed, earth works, pavement layers and surfacing. The road bed would be the compacted in-situ material, while the earthworks are the cuts and fills which establish the vertical and horizontal alignment of a road. The pavement layers are there to handle the mass of the heavy vehicles while the surfacing, which is the top part of the road supplies certain ride ability and permeability.

Pavement Structure

A typical pavement is made up of layers i.e. selected layers, sub-base layers and a base layer.

Sub-grade pavement layers are part of the earthworks. the lower selected layer being part of the first pavement layer on top of the earthworks. This layer is mainly there to neutralise any inconsistencies in the thickness of the pavement/earthworks interface. The upper selected layer is the second layer and is part of the pavement. The following layer to be installed is the sub-base layer/s. Depending on the type of pavement that has been designed, there can be two sub-base layers as well. In a lot of instances, the sub-bases are stabilised using cement. the sub-base is the layer that assists in neutralise any tensile forces in the pavement. the base layer is the upper layer of the pavement, this layer has to neutralise the mass of the heavy vehicles as well as the wheel action of the vehicle on the road.