A new concrete roadway connects the towns of Itori und Ibese in Nigeria’s Ogun State. The construction work has been carried out by AG-
For this project, the contractor, a joint venture between the Brazilian company
For the inset application, 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. Integrated electrical or hydraulic vibrators ensure homogeneous compaction of the concrete. The inset mold 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 transverse to the concrete pavement. The surface is levelled off transverse 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 boosts the quality of the concrete surface. In the next step, a super smoother, oscillating in
a combination of lateral and longitudinal movements, ensures the final surface accuracy. Wirtgen texture curing machines such as the
This is the longest concrete roadway in Nigeria. But before the slipform paver was able to begin work in Itori, the substrate first had to be prepared. The construction company used compacted laterite and a 200mm 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," explained Ashif Juma, managing director of AG-Dangote Construction Company Limited. The SP 500 laid down the new 7.5m-wide and 200mm-thick roadway in two separate passes. Extending over 24km, the new road is the longest uninterrupted stretch of concrete roadway in Nigeria.
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. However, before concrete can be paved, it must first be produced. The production chain begins with limestone mining. This mineral is one of the raw materials used in cement, which in turn forms the basis of concrete. The Dangote Group extracts limestone from its quarry in Ibese, where the Dangote Cement Company operates 14 Wirtgen 2500 SM surface miners.
The Wirtgen surface miners cut, crush and load the rock in one single operation. The rock is broken down directly during the extraction process into grain sizes that are suitable for belt conveyors, making the use of a crusher superfluous. This saves time and reduces the costs of the entire mining process. Wirtgen had already supported the Dangote Group before operations at the Ibese facility began, not only with the machinery, but also with production process planning and training for the specialists on site. This partnership has now endured for more than 15 years. It therefore stood to reason that AG-Dangote Construction Company Limited would opt to use Wirtgen technology and applications know-how for the road construction project between Itori and Ibese.
“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 an even surface,” said Juma.
For example, the side tie bar inserter, which in Nigeria 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. The new generation of slipform pavers combines the application diversity of the SP 500 Series with the sophisticated technology of the larger SP 90 Series.
Work on the 24km concrete roadway was completed after six months of construction. After completion of the paving work, 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 predetermined breaking points prevent potential tension cracks. “With professional maintenance, this will ensure that the roadway lasts for at least 40 years," said Juma, explaining the last step of the construction procedure. The managing director also decided to acquire additional concrete equipment from Wirtgen. AG-Dangote Construction Company Limited has expanded its fleet of road construction machines, purchasing two of the last SP 500 pavers produced, along with a TCM 95 texture curing machine.