Road Construction Materials: Types and Uses
Imagine yourself driving down a well-built road with the wind in your hair and no worries in the world. The journey is seamless, and your vehicle glides effortlessly. Driving on a smooth road in the countryside is a treat; every motorist will agree. Such roads are not just a product of chance; they are the result of careful planning, engineering, and the use of the right road construction materials.
Currently, there is a surge in the construction of highways and expressways all across India, making road construction activities a common sight during a trip. If you wonder what materials are used to build roads that carry massive traffic loads and yet remain strong and stable, here is an introduction to different types of road construction materials.
Materials Used in Road Construction
Road materials can be versatile to cater to a variety of road types and categories. Commonly used road materials range from natural soils, aggregates, binders such as lime, asphalt, concrete, and assorted products used as admixtures for improved road quality.
1. Soil
Soil is the principal material for the foundation, subgrade, or even the pavement (for low-cost village roads with light traffic). On the other hand, when highways are built on an embankment at the desired level, soil is used as the principal embankment material. Moreover, because all constructions must eventually rest on and transmit loads to ‘mother earth,’ soil and rock serve as foundation materials.
Most of the time, the soil is used after some sort of stabilization treatment, such as compaction and strengthening by adding appropriate admixtures, to improve the performance of the road. Mineral aggregates derived from rocks are the primary component of practically all highway pavement sub-bases and bases.
Soils, as a natural material, have many properties that must be carefully considered before constructing a road. For example, soils with more clay and silt particles are more prone to erosion and contraction when exposed to water. To avoid performance degradation, such soils require particular care.
2. Aggregate
Aggregates are used in the construction of granular bases, sub-bases, bituminous mixes, and cement concrete. They are also the fundamental component of a relatively inexpensive road known as a water-bound macadam.
Stone aggregate, often known as mineral aggregate, is by far the most important component of road construction materials. It is created by fracturing naturally occurring rocks into coarse aggregate (like gravel) or fine aggregate (like sand).
Similar to soil, aggregates also need to be evaluated by a road engineer to ensure that they are sturdy and durable enough for a specific project. These properties are influenced by their origin, mineral components, and the nature of the bonds between the components.
To ensure sturdy and durable roads, aggregates like dirt must be evaluated by a road engineer. Their origin, mineral components, and adhesion forces between the components all have an impact on these qualities.
3. Asphalt and Bitumen
Asphalt and bitumen are frequently confused as the same item, but they are not. While asphalt is a mixture of aggregates, binder, and filler and is used to build roads and associated furniture, bitumen is the semi-solid glue that works as the binding agent in asphalt.
Bitumen, commonly known as mineral tar, is produced from the incomplete distillation of crude petroleum. It is composed of 87% carbon, 11% hydrogen, and 2% oxygen.
Asphalt, on the other hand, is produced in a plant that heats, dries, and mixes aggregate, bitumen, and sand into a composite mix. Depending on the type of project, the material is subsequently applied on-site with a paving machine at a specified or required thickness.
When asphalt is employed in road construction, it takes the form of a composite material known as asphalt concrete. This road construction material is made up of 70% asphalt and 30% aggregate. Asphalt is 100% recyclable, making it one of the most preferred materials for road construction.
4. Cement Concrete
Cement concrete is by far the best road material in terms of durability and toughness, and it is also known for its flexibility and ease of construction. It is made by combining cement, coarse aggregate, fine aggregate, water, and chemical admixtures (which account for 25–40% of the total weight of the concrete). A major drawback of cement-based concrete is its contribution to carbon emissions.
Although its initial cost is high, considering its long span of life and low maintenance, the life-cycle cost of cement concrete roads becomes rather low. Concrete can also be utilised to increase the tensile strength of existing pavement layers.
Because of the excellent binding property of cement, well-mixed concrete contains very few voids and quickly sets and hardens. The concrete, when cured with water, provides a durable, stable, and long-lasting road surface that can withstand repeated impacts from heavy commercial vehicles.
5. Composite Pavement
This type of pavement combines cement, concrete, and asphalt to create a “super” pavement.
Because composite pavements can offer higher levels of performance and durability, both physically and functionally, they may eventually become less expensive than regular pavements.
Concrete has the drawback of being prone to issues like reflective cracking and rutting in the surface layer. However, these potential problems can be avoided by using a high-quality asphalt surface or other (expensive) mitigation measures.
6. Eco-Friendly Road Materials
There is growing pressure on road builders to reduce their carbon footprint. This is significant in light of the fact that cement, a crucial component in the construction of roads, emits one tonne of carbon for every tonne that is produced.
The use of alternative road construction materials, such as recycled crushed concrete, which can result in significant energy and manufacturing cost reductions, can reduce carbon emissions.
Utilising environment-friendly concrete, which reduces the need for Portland cement in road construction, is another way to achieve sustainability.
Additionally, by using recycled materials and components made from industrial waste, greenhouse gas emissions can be reduced, along with the cost of construction.
Recycled concrete aggregate, recovered asphalt pavement, and coal combustion products from coal-fired power plants are the ingredients of more sustainable road construction.
Conclusion:
The creativity of human engineers is evident in our highways. Each road-building component, from the sturdy foundations set by aggregates to the supple, long-lasting surfaces offered by asphalt and concrete, is essential to ensuring that our roadways remain safe and reliable.
Despite being concealed below the surface, geotextiles and bitumen emulsions provide crucial contributions to the durability and performance of roads. Additionally, recycling is crucial since products like RAP and RCA not only conserve resources but also encourage sustainability in the construction sector.
Next time you drive down a well-constructed road, take a moment to appreciate the technology and efforts behind it.
Road construction materials will continue to advance as we look to the future, guaranteeing that our roads will stand the test of time. Visit our website to read more blogs like this one and gain more knowledge about road construction.