Grouted Macadam: Material Characterisation for Pavement Design

2 REVIEW OF “TRADITIONAL” ROAD PAVEMENT
TYPES AND DESIGN
2.1 Introduction
In this chapter, a review of the pavement types traditionally used in road construction
is presented. Additionally, a description of the materials used in each of the
construction types is discussed. The main pavement design methods are also
described in order to support the work carried out during the present project.
A road pavement can be defined as a structure that provides support to the vehicles
using the road. Since the route selection process for the road does not usually take
into account the bearing capacity of the foundation (soil, in most cases), also known
as the subgrade, a structure is necessary to withstand the vehicle loads and to
guarantee a surface with adequate evenness and skid resistance to be used by
vehicles, with sufficient comfort and safety for the users. In the absence of this
protective structure, the repetitive loads applied by the vehicles, together with
adverse climatic conditions, would cause permanent deformation or even failure of
the subgrade. To minimize the damage, a set of layers is normally built on top of the
subgrade to spread the loads and dissipate the stresses, at the subgrade level, to an
acceptable value.
The surface layer, also known as the surface course, has to provide good riding
quality for the users (skid resistance, noise, spray, etc.) and also prevent the ingress
of water through the pavement structure and ultimately into the subgrade. Thus, the
surface course should ideally be impermeable, otherwise the water that penetrates
through the voids or cracks can alter the structural properties of the layers
underneath, thus decreasing the bearing capacity of the pavement.
Depending upon the constitution of materials used in the top layers of the pavement
and their behaviour, pavements are normally classified into three main types, i.e.
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