By Moses Braimah
In Nigeria, roads are constructed using multiple layers, each designed for a specific purpose.
These layers include the subgrade, sub-base, base course, and surface layer, typically made of bitumen or asphalt. The subgrade forms the foundation and must be compacted to support the above layers.
The sub-base provides additional support, while the base course distributes traffic loads to prevent excessive stress on the subgrade. The topmost layer, usually bitumen, offers a smooth, durable surface for vehicles.
As a key component in in road construction in Nigeria, it is important to delve in more into the role of bitumen. It is a viscous, petroleum-based material, primarily used for binding the road layers and providing a weatherproof surface. Its flexibility allows roads to expand and contract with temperature changes, reducing cracks and wear.
However, bitumen is highly susceptible to damage caused by water infiltration, which explains why potholes quickly reappear after patching. When water seeps through cracks in the surface, it weakens the lower layers, causing the road to collapse under pressure from vehicles.
Drainage and its Importance
Proper drainage systems are critical in road construction. Effective drainage systems are essential for maintaining road longevity. When present and functional, they divert water away from the road, preventing waterlogging, erosion, and weakening of the subgrade.
In contrast, blocked or absent drainage systems cause water to seep into the road layers, weakening the structure and accelerating pothole formation. This is particularly problematic during Nigeria’s rainy season, where the heavy downpour overwhelms poorly designed drainage systems, leading to rapid deterioration of roads.
So, what are the alternatives to bitumen? Given the limitations of bitumen in handling water damage, suggested alternative materials can be explored. These include materials such as geopolymer binders, recycled plastics, and composite materials. They offer greater resistance to environmental factors. However, the most promising alternative to bitumen is concrete pavement.
Why is concrete pavement a superior alternative? Concrete pavement is known also as rigid pavement. It is made from cement and aggregates. It is stronger and more durable than bitumen, particularly in areas with heavy rainfall or high traffic volumes. Concrete’s rigid structure resists deformation, making it less prone to potholes and other surface failures. It also has a longer lifespan, reducing maintenance costs over time.
Advantages of Concrete Pavement over Bitumen
Durability: Concrete lasts 30-50 years compared to bitumen’s 15-20 years, making it a more cost-effective option in the long run.
Water Resistance: Concrete is less permeable than bitumen, offering better protection against water damage and reducing the risk of potholes.
Load-Bearing Capacity: Concrete can handle heavier loads without warping, making it ideal for highways and high-traffic routes.
Reduced Maintenance: While concrete is more expensive to install initially, its low maintenance requirements translate into significant savings over time.
Thermal Resistance: Unlike bitumen, concrete is not sensitive to extreme temperature changes, making it more stable in Nigeria’s varied climate.
Bitumen vs. Concrete: A Comparison
Cost: Bitumen is cheaper to install but requires frequent maintenance, while concrete has a higher upfront cost but lower long-term expenses.
Environmental Impact: Bitumen is derived from petroleum, contributing to environmental degradation. Concrete, though energy-intensive, can be more eco-friendly, especially with newer technologies like carbon capture during production.
Application: Bitumen is more flexible and easier to work with for smaller roads and projects. In contrast, concrete is better suited for highways, bridges, and areas with high traffic.
| Aspect | Bitumen (Asphalt) | Concrete |
| Cost | Cheaper upfront | Higher initial cost |
| Lifespan | 10-15 years | 20-40 years |
| Maintenance | Frequent repairs | Low maintenance |
| Water Resistance | Prone to water damage | Highly water-resistant |
| Thermal Performance | Softens and cracks in heat | Stable under temperature changes |
| Sustainability | Less eco-friendly (derived from oil) | Can be made from recyclable materials |
In summary, while bitumen has been the traditional choice for road construction in Nigeria, it may no longer be the best option in the face of recurrent potholes and rising maintenance costs.
With its superior durability, load-bearing capacity, and water resistance, concrete pavement presents a compelling alternative, particularly for high-traffic and coastal roads like the Lagos-Calabar Coastal Highway.
Implementing better drainage systems alongside this shift in materials could significantly improve Nigeria’s road infrastructure for future generations.
– Braimah is an Executive Project Director at PacificMessages.
