Work on the longest uninterrupted stretch of concrete roadway in Nigeria has been completed.
For the construction of the roadway, which is over 24km long and which connects the towns of Itori und Ibese in the Nigerian state of Ogun, AG-Dangote Construction Company used the sophisticated technology offered by Wirtgen’s SP500 slipform paver. For the project, the contractor, a joint venture between the Brazilian company Andrade Gutierrez and the Dangote Group from Nigeria, relied heavily on the the Wirtgen slipform paver in inset application, where the concrete is either deposited right in front of the slipform paver or is fed in front of the machine from the side via a belt conveyor or side feeder.
In the next step, the concrete is distributed evenly across the full paving width by a spreading auger or spreading plough, and integrated electrical or hydraulic vibrators ensure homogeneous compaction of the concrete. The inset mould forms the concrete slab to the specified thickness and width while the slipform paver advances.
In addition, a dowel bar inserter can be integrated which inserts the dowel bars into the concrete, as specified, parallel to the paver’s direction of travel. Central tie bars or side tie bars can be inserted transversely to the concrete pavement. The surface is levelled off transversely to the paver’s direction of travel by the finishing beam.
The grinding movement produces a small concrete roll in front of the beam which enhances the high quality of the concrete surface. A super smoother, oscillating in a combination of lateral and longitudinal movements, ensures the final surface accuracy.
Wirtgen texture curing machines such as the TCM 95 or TCM 180 then create the desired surface structure, applying a dispersion to the concrete surface which prevents the surface and edges from drying too quickly.
Before the slipform paver could begin work in Itori, the substrate first had to be prepared using compacted laterite and a 20cm layer of crushed rock.
“The SP 500 then paved the concrete quickly and cost-efficiently. At the same time, it also helps us ensure that our production quality meets the specifications for surface evenness,” says Ashif Juma, managing director of AG-Dangote Construction Company.
The SP 500 laid down the new 7.5m-wide and 20cm-thick roadway in two separate passes.
To continuously provide the concrete paver with sufficient material, a steady convoy of up to 15 concrete-mixing trucks drove to the job site, depositing their loads directly in front of the machine.
The concrete production chain begins with limestone, one of the raw materials used in cement, which in turn forms the basis of concrete. The Dangote Group extracts limestone from its open-cast mine in Ibese, where the Dangote Cement Company operates 14 Wirtgen surface miners of the type 2500 SM, which cut, crush and load the rock in one single operation.
“The SP 500 not only ensured that construction project processing went off without a hitch, but also produced a paving result that impressed both us and the client. We processed more than 35,000m³ of concrete using the Wirtgen slipform paver, and produced a very even surface,” says Juma.
A new generation of slipform pavers lined up in Wirtgen’s new SP 60 Series, which comprises the SP 61/SP 61i, SP 62/SP 62i and SP 64/SP 64i models, is set to replace the SP 500 model, and it is said to offer a range of options to meet the diverse demands of inset and offset paving.
For example, the side tie bar inserter, which, for this project, inserted 12mm diameter tie bars into the sides of the pre-compacted concrete to securely connect the two adjacent roadways, can be selected as an equipment option with the SP 64/SP 64i.
After completion of the paving work on the new roadway, a concrete cutting machine cut slits at right-angles into the road surface at intervals of 3.65m so that the resulting joints could be filled with expandable material. These pre-determined breaking points prevent potential tension cracks.
“With professional maintenance, this will ensure that the roadway lasts for at least 40 years,” says Juma.
