A guide to road construction

The process of constructing a road is both complex and time-consuming. Here is a brief explanation of how this type of structure is built.

Planning and design

The planning and design stage of the road-building process can take several months. A wide range of experts, including architects, environmentalists, civil engineers, construction contractors and transportation planners will be consulted during this phase.

The area in which the road is to be built will also be surveyed. The survey will include an inspection of the area's drainage systems, soil properties, terrain characteristics and current traffic volume. It may also make note of the proximity of nearby residents and the presence of rare or endangered plant and animal species, all of which may be affected by the construction of a new road.

Preparation and Excavation

If the road is to be constructed in a hilly or mountainous area, a drilling and blasting contractor will usually be hired to break up this rock to create space for the new road and to make the excavation process easier. Drilling and blasting involves the use of explosives and is a dangerous task which needs to be performed with extreme care.

A very detailed assessment will be carried out before this process begins. This will involve determining the dimensions of the hole that needs to be created and calculating the blast pattern and the level of rock fragment displacement that will occur. The contractor will be tasked with ensuring that the drilling and blasting processes are performed in a controlled and safe manner and that nearby infrastructure and housing are not damaged by these activities.

After this is complete, the excavation work can begin. This is arguably one of the most crucial stages, as the quality of the excavation work determines how stable the road's foundation will be. Heavy construction equipment, such as trenchers, excavators, bulldozers and backhoe loaders, will be used to extract unneeded soil and to create a tightly-compacted, level base for the road's subsequent layers. If there is no existing drainage system, sewers and pipes may also be installed at this point.

Building layers

Roads are made up of several different layers. After the above-mentioned sub-grade has been created, aggregate materials (such as gravel and crushed rock) will be layered on top to further increase the road's stability.

Following this, the top layer of the road will be added. Asphalt, or a composite material like asphalt-concrete, will be used for this section of the road. Asphalt is favoured for road construction largely because it is an exceptionally durable material which can withstand years of constant heavy traffic before it begins to deteriorate. Asphalt also has a very smooth finish, which makes it easier for road users to drive on. A piece of construction equipment known as a 'paver' is used to pour the asphalt.