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To this end, Wirtgen Group and Julius Berger Nigeria are working together to carry out a sustainable road reconstruction project in the country.

Innovative technology involving the cold recycling method developed by the Wirtgen Group is being used by Julius Berger Nigeria to reconstruct the 375 kilometres A2 dual carriageway highway in Nigeria connecting Abuja in central Nigeria with Kano in the north of the country.

The route being reconstructed is the Abuja-Kaduna-Zaria-Kano Road. This route is part of the Trans-African Highway Network - a network of transcontinental road projects in Africa being developed by the United Nations Economic Commission for Africa (UNECA), the African Development Bank (AfDB) and the African Union, along with some regional/international communities. The Trans-African Highway Network aims to promote trade and reduce poverty in Africa through highway infrastructure development and the management of road-based trade corridors.

The project scope initially only covered the rehabilitation of the road. However, the Nigerian Federal Ministry of Works and Housing extended the project scope, and instead of a limited ad hoc rehabilitation, the project now includes the complete reconstruction of the roadway and hard shoulders and the provision of additional infrastructure such as footbridges, road lighting, toll roads, service stations, and rest facilities along the highway.

The road reconstruction work is scheduled for completion in the second quarter of 2023, and the special structures (additional infrastructure) is set for completion by May 2024.

The cold recycling method being used for reconstruction of the road is expected to considerably save time on the project. From the planning stage of the project, the environmentally friendly cold recycling method was considered a viable alternative to conventional road construction methods. The proposed use of this method is reported to be one of the factors that led to Julius Berger winning the contract.

The cold 'in-plant' recycling method involves mixing foamed bitumen into the milled existing road structure in-plant with a mobile cold recycling mixing plant located close to the construction site. The mix produced is called bitumen-stabilised material (BSM). After paving and subsequent compaction, BSM has better long-term durability and load-bearing properties. A major advantage of BSM is that the foamed bitumen selectively adheres to the cold recycling layer laid and prevents cracking. As part of the pavement structure, the layers prepared in this way form an ideal base for the final asphalt surfacing with reduced layer thickness or fewer layers.

Julius Berger sees this construction method as a real innovation in the Nigerian road construction sector. “Cold recycling enables optimal use of existing construction materials and conserves valuable resources. This is why we are the first construction company in Nigeria committed to exploiting the full potential of this technology for our company and our clients,” explained Julius Berger Project Director Benjamin Bott.

Inspection of Ongoing Reconstruction of Abuja-Kaduna-Zaria-Kano Dual Carriageway, on Thursday 19th, November 2020, by Chief of Staff to the President, Prof. Ibrahim Gambari, Ministers @FMWHNIG @tundefashola and @FinMinNigeria @ZShamsuna, & Governor of Kano State, @GovUmarGanduje pic.twitter.com/zsCNyUpt4b

— Government of Nigeria (@NigeriaGov) November 22, 2020

Two sets of cold recycling and paving fleets were used at the beginning of the project, consisting of 45 machines in total. The machines included large milling machines, soil stabilizers and cold mixing plants from Wirtgen, cold recyclers and spreaders from Streumaster, Kleeman mobile impact crushers, Vögele Asphalt pavers and mobile feeders, and rollers from Hamm. The efficiency and durability of the initial set of machines, combined with what Julius Berger described as outstanding aftersales service, led to the expansion of the fleet with 30 more machines.

Benefits of the Cold Recycling Method

Carbon footprint is kept to a minimum throughout the implementation of the project. According to Wirtgen, the benefits of the cold recycling method lie primarily in the enormous potentials for saving energy in materials processing. As there is no need to dry or heat the base materials, fuel consumption can be reduced by 10-12 litres/tonne when compared to conventional rehabilitation techniques, which leads to reduced carbon dioxide emissions. 

The almost complete recycling of the surface layer corresponds to a reduction of construction material trucking needs by up to 90% - with corresponding savings in the related costs. 90% of the costs for resources and 100% of material disposal costs can be saved. The cold recycling method also enables savings of up to 50% of the binding agents required – which is the largest cost factor in road rehabilitation projects. Due to to the special properties of BSM, cold recycling technology therefore leads to extremely low costs throughout the service life of roads as is expected to be the case with the Abuja-Kaduna-Zaria Road in Nigeria.

Top Photo: The Wirtgen soil stabilisers homogeneously mix the previously distributed cement into the road bed at the required depth. Regulated by the speed of the machine, a spray bar automatically adds the required amount of water to the cement (wirtgen-group.com)