Construction World June 2019

Left: Catastrophic pavement failure due to unacceptable moisture conditions combined with overloading ( Looking for good in Lagos , 2011) Right: Trucks blocking a section of the Oshodi-Apapa Expressway at Second Rainbow inward Mile 2, and commercial buses driving against traffic. (Bakare, T. 2018)

a very weak pavement structure, while very poor materials were also used in the construction of the existing road, especially for the foundation layers. Testing undertaken on asphaltic concrete samples showed that all of the properties met the specification requirements and that the grading of the aggregates was within the specification envelope for wearing course. However, unsuitable material was identified in the samples of sub-base and sub-grade layers that were collected from various locations along the road. Meanwhile, a visual condition assessment undertaken by the team of engineers showed significant distresses and failures on most sections of the existing road infrastructure. According to the study, it will be possible to source sufficient filling material from all of the borrow pit areas that were investigated, while suitable crushed rock aggregate for the base course can be obtained from the rock outcrops that were observed along Logos-Ibadan road. The engineers also found the available aggregate, water and

river sand to be of a suitable quality for the construction works. Should there be insufficient river sand, they have recommended supplementing supply with quarry dust. JG Afrika also noted that adequate provision be made in the Detailed Design Report for drainage and sub-drainage improvement, especially in the swampy areas, in addition to the need to reinstate the shoulder of the entire road. Dr. Horak says the concrete pavement design expertise of Ane’ Cromhout, pavement engineer with the JG Afrika team, formed the basis of the recommendations to use CRCP. These recommendations made by JG Afrika were well received by the contractor and he anticipates work to commence imminently on the rehabilitation of this critical road infrastructure. “Dangote Construction deserves to be lauded for the innovative approach that it has taken to rehabilitating the many roads in the country that have fallen into a serious state of disrepair. This has added impetus to the Nigerian government’s already-heightened focus on repairing these strategic assets and building new roads to expand the national network,” he concludes. 

HP : MUCH ASPH

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CONSTRUCTION WORLD JUNE 2019