The 5 most Popular Road Construction Methods and Techniques
Road construction is the installation of soil stabilisers, concrete, asphalt, and other building materials on a path to create a surface that vehicles can travel on from one destination to another.
While common types of road construction methods differ based on the nature of the envisioned road, every highway project require months or years of planning before work can begin on site.
Here are the five most popular methods of road construction, including gravel road construction methods, asphalt road construction methods, and other temporary road construction methods.
1. Earth Road Construction
Earth road is a type of road whose pavement is made of soil.
To build this type of road, a bulldozer or scraper is driven along the demarcated path to clear the site, remove the top soil and to shape the subgrade.
Once the sub-grade is ready, the desirable type of soil is dumped into the channel, after which the material is mixed, spread and rolled in several layers – each with a maximum thickness of 10 cm.
The compacted surface is then allowed to dry for a few days before opening to traffic.
As the easiest form of temporary road construction methods, earth roads are very common in rural areas, mainly because they do not require specialised skills and huge budgets to put it in place.
One of the drawbacks of earth roads is that they are impassable during heavy rains, which make them slippery and unsuitable for two-wheel vehicles. The road is also not capable of supporting heavy traffic.
2. Gravel Road Construction
A gravel road is an improved version of the earth road – common in rural and semi-urban areas.
The procedure of building a gravel road is similar to that of putting up an earth road, only that you add a layer of gravel after the soil is fully compacted.
Gravel road construction methods begin by preparing the subgrade. The soil is then compacted properly to reduce its volume of water and air – creating a harder, denser surface.
A solid base is then created by mixing a binder (cement or lime) into the soil using a stabilising machine. Once the base hardens, gravel is then added in layers until you get to the top.
A one-off application of a bituminous surface treatment can help a gravel road to remain smooth and free of cracks and potholes.
Unlike earth road, gravel road is free of dust and does not get slippery during the rainy season. However, this type of road wears off quite easily and cannot support heavy traffic.
3. Asphalt Road Construction
Asphalt road is made of asphalt – a mixture of fine aggregate particles and bitumen (a sticky dark viscous liquid obtained through unfinished distillation of crude petroleum.
Asphalt road construction methods are very popular due to asphalt roadway’s flexibility and the ability to acquire the shape of the load above it. This helps it to support heavy commercial vehicles.
This road construction technique starts with the preparation of the subgrade, a process that involves removing any existing vegetation and the topsoil.
The subgrade should be graded to allow the water to run off to the sides or bottom. The ideal slope is a quarter of an inch per foot (0.635 cm per 30.48 cm).
The base soil should be properly compacted, preferably with a 1,361-kg twin drum roller to reduce its volume of water and air – thus creating a harder, denser surface.
The base soil is then covered with crushed rock, whose composition should be rough and jagged. This type of crushed rock is usually called ‘3/4″ minus’ or ‘road-base’ mix.
In the case of clay base soil, 8 inches of crushed rock is recommended.
The next step involves laying the crushed rock mixed with bitumen into the subsoil. Once this is done, you should allow the base to settle for a week. This will result in a stronger, more naturally settled base.
Once the road base is firmly in place, hot asphalt is poured onto a bed of heavier aggregate after which it is pressed into it with a steamroller.
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