Chairman, Nigerian Institution of Highway & Transportation Engineers (NIHTE), Dr. Isa Usman Emoabino has advocated the use of concrete and asphalt overlay in road construction in the country.
According to the chairman, concrete roads are highly durable, less fuel use and environmentally friendly, compared to asphaltroads, but concrete construction cost far exceeds that of asphalt for same road type.
Emoabino stated this in his presentation, ‘Concrete Road in Nigeria: Durability, Acceptability and the Economic Benefitto a Developing Nation’, as guest speaker at the 20th annual Construction and Engineering Digest (CED) forum/award at Ikeja, Lagos, recently.
Asphalt road, he said provides better safety of thevehicle against heavy rains, snow and skidding, but that “composite pavement that combines theadvantages of concrete for high load carryingcapacity and asphalt for safety would be moresustainable for a developing nation, especiallyfor Nigeria where maintenance budget is always low or sometimes zero.”
He said, “The alarming rate of deterioration of our road network/infrastructure, despite the enormous amount of budgetary allocations suggests strongly that the road sector is in dear need of attention, reforms, and alternatives.”
Composite Pavement, he said is asphalt overlay on concrete. “Typically, composite pavements are asphalt overlays on top of concrete pavements; The asphalt overlay may have been placed as the final stage of initial construction, or as part of a rehabilitation or safety treatment; Composite pavement behaviour under traffic loading is essentially the same as rigid pavement.”
Selecting a pavement type is an important decision, the chairman said, stating that “The 1993 American Association of StateHighway and Transportation Officials(AASHTO) Guidestates, “The selection of pavement type is not an exact science but one in which the highway engineer must make a judgment on many varying factors. . .”There areprincipal and secondary factors to consider in the selection process.
Rigid Pavement Types…
Different pavement types use different types of joints and reinforcement to control the forces acting on the concrete pavement.
He said, “These forces include curing shrinkage of the concrete, environment changes and traffic loads; Forces in the concrete pavement will cause cracksto form without traffic; The designer can select the location where thejoints will be placed and, consequently, where thecracks will form.
Joints may be thought of as “controlled cracks” that will reduce the stresses the concrete will experience during its life and greatly increase the life of the concrete pavement. Through the use of reinforcement, the location and spacing of cracks can also be controlled. Two types of concrete pavements commonly used are continuously reinforced concreted pavement (Deck on Piles, Bridges, Ports, Airports Runways) and jointed concrete pavement (Petrol Stations).
Durability of Concrete Roads…
He said “Concrete roads are durable and safe; less prone to wear and tear; low maintenance requirements; long-term performance (40years) of rigidpavement (depends on proper pavement design,materials selection, good construction practices).
Poor construction practices have resulted inpremature failures of rigid pavement (Expert supervision is essential); safety depends on the finishing, shoulders among others.
He gave the advantages of concrete roads as durability and maintenance-free life. “Concrete roads have a long service life 40years, whereas asphalt roads last for ten years. Moreover, during this service lifeconcrete road do not require frequent repairor patching work like asphalt roads.
Vehicles consume less fuel: A vehicle, whenrun over a concrete road, consumes 15-20%less fuel than that on asphalt roads. This isbecause of the fact that a concrete roaddoes not get deflected under the wheels ofloaded trucks.
Resistant to automobile fuel spillage andextreme weather: unlike asphalt roads,concrete roads do not get damaged by the leaking oils from the vehicles or by theextreme weather conditions like excessrain or extreme heat.
Greener process: Asphalt (bitumen)produces lots of highly polluting gases atthe time of melting it for paving. Also, less
fuel consumption by the vehicle runningon a concrete road means less pollution.
Affordability for a developing Nation where numerous infrastructure needs seek the attention of inadequate funds.
Paving cost: The initial construction cost of the concrete road is generally higher compared to asphalt paving.
Maintenance Problem: In case the concrete road breaks, the whole concrete slab needs to be replaced leading to higher costs
Safety features: In rainy season vehicles tend to slip or slide on concrete road due to rain. So could be prone to more road accidents.
Emoabinosaid, “For economic benefit on Nigeria roads, CompositePavement structure should be considered.”