Nigeria’s newly appointed works minister, David Umahi, is advocating for the implementation of rigid pavement in road construction, diverging from the prevalent use of flexible pavement. This move comes in light of the deteriorating condition of flexible pavements across the country.
The two primary types of road surfaces under consideration are rigid pavements, which are layered with reinforced concrete, and flexible pavements, which are topped with bituminous (tar) overlay.
Historically, asphalt roads have been the dominant choice for paving in Nigeria, evident in the Lagos-Ibadan, Port Harcourt-Enugu, Lokoja-Abuja, and Abuja-Kaduna expressways. On the other hand, concrete roads, such as the Kaba-Obajana road in Kogi State and Apapa-Oshodi road in Lagos State, are gaining attention as well.
The importance of road infrastructure cannot be overstated in modern economies, as economic growth and development hinge upon mobility and accessibility.
As a seasoned engineering professor with a focus on Nigerian road construction, I bring insights into the minister’s stance and the associated challenges.
The decision to opt for either concrete or asphalt brings forth a design conundrum – a choice between added service and higher costs, or reduced service and lower costs. This predicament is not solely technical but also political.
Despite this, there is insufficient data to decisively affirm whether concrete pavement supersedes flexible pavement for Nigeria’s unique circumstances.
Comparing the features of both flexible and rigid pavements, it becomes evident that the latter is generally more costly and demanding to install and maintain. Rigid pavements, comprising cement concrete with base, sub-base, and subgrade underlay, boast high flexural strength, rendering each layer practically resistant to pressure-induced bending. Conversely, flexible pavements are designed to bend and deflect under external forces, requiring regular maintenance and a lower initial construction cost.
While the initial construction cost of flexible pavements is lower, the maintenance cost is higher. In contrast, rigid pavements entail a higher initial cost but lower maintenance expenditure. Additionally, the lifespan of flexible pavements ranges from 10 to 15 years, whereas concrete pavements can last for 25 to 30 years.
The choice of pavement type must factor in the life cycle and material costs, encompassing initial construction, maintenance, repair, and environmental implications such as emissions and energy consumption. Consequently, a comprehensive life cycle cost analysis should precede the selection of a pavement type.
Ultimately, a well-constructed road should provide the intended level of service and safety while reflecting local values and policies. These considerations should guide Nigeria’s decision on this matter.
Asphalt roads present advantages in terms of lower initial construction costs, reduced repair periods, noise absorption, and recyclability. However, they exhibit a shorter lifespan, necessitate frequent maintenance, and are less suitable for heavy traffic. Furthermore, they have a greater environmental impact due to bitumen production.
On the other hand, concrete roads entail higher construction costs and longer curing and repair periods, yet they offer longer lifespans, lower maintenance, greater durability, and are apt for heavy traffic areas. They also have a lower carbon footprint and are less prone to developing potholes, thereby reducing fuel consumption and carbon emissions.
Hussein Mohammed, Professor of Engineering, Obafemi Awolowo University
