CoreCivils helps Estate Construction bridge the divide

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A new bridge over the Limpopo River at Platjan border post will enable the faster movement of people and goods between South Africa and Botswana.

It supports the establishment of another commercial border at Platjan border post to alleviate vehicle congestion, comprising mainly trucks, at the existing Martin Drift Border Post.

The new structure will replace an existing low and narrow bridge that is often flooded during heavy rains, hindering the movement of people and goods between both countries. Many farmers within the immediate vicinity of the border crossing are among those who have been severely inconvenienced during the wet season.

Importantly, the new commercial border crossing is intended to stimulate the development of many industries and small businesses in Selibe Phikwe, Botswana. Among these are the numerous small farmers in the Bobirwa district and tourism-related industries that have developed around attractions at Letsibogo, Dikgathong and Thune Dams.

These benefits are in line with the Selibi Phikwe Economic Diversification Unit’s (SPEDU) mandate to diversify the predominantly mining economy in Selibi Phikwe.

The Botswana government-owned investment company, which is facilitating the project, awarded the construction of the bridge and two approach roads to Estate Construction, a seasoned local contractor, in 2016.

Estate Construction commenced work on the project in January 2018 and is due to complete the project in June 2019, while the construction works are being supervised by Botswana-based consulting engineer, ACE GIBB.

The bridge is more than 9 m high, 155 m in length and 12,7 m wide. It comprises two 3,7 m-wide traffic lanes in either direction and 2,5 m-wide pedestrian walkways on both sides of the carriageway.

By March 2019, Estate Construction was already forging ahead with the installation of the few remaining precast-concrete T beams and fixing of the reinforcing for the deck of the structure.

A total of 210 precast-concrete beams, 21 elements per span, were manufactured by CoreSlab, CoreCivils’ manufacturing arm, for the project at its factory in Polokwane, Limpopo.

CoreCivils’ construction division, Corestruc, was also tasked with the installation of the elements, each 15,5 m in length and 800 mm deep.

“The project is being built according to the same exacting standards as those typically undertaken across the borders in South Africa. We, therefore, visited a number of manufactures’ factories ahead of the construction of the bridge to witness for ourselves the processes that they deploy in their manufacturing processes. Estate Construction was very impressed with the quality controls in place at CoreSlab’s factory and, therefore, decided to appoint the company as its bridge-beam supplier on this project,” Julius Katzke of Estate Construction says.

Considering the limited space on site, the bridge beams were manufactured ahead of their installation and stored at the factory.

Five elements per load were then dispatched to site where they were lifted directly from the truck trailers and placed on top of the 1m wide and 9m high tapered piers using a 30 ton mobile crane.

The crane, which was supplied by CoreHire, is positioned on a coffer dam that was built during the construction of the bases of the structure as the existing bridge is too narrow to accommodate the machine with its outriggers fully extended.

Corestruc’s team started working from the South African side of the bridge, completing two spans a day, enabling Estate Construction to commence installing the 120 t of reinforcing bar for the deck.

Once the centre portion has been cast, Estate Construction will easily access the bridge with a truck-mounted boom crane to complete the side sections, with the precast-concrete bridge barriers serving as a shutter.

Close attention will also need to be paid to the drilling of the 80 mm diameter core holes that accommodate the drainage pipes and service ducts.

The bridge will then receive a 60 mm thick asphalt layer and the two concrete-pavement approach roads completed as part of the final phases of the project.

Katzke says that one of the challenges on this project has been working in an extremely remote area.

CoreFleet ensured the timely delivery of the many precast-concrete elements to site, located more than 150 km from CoreSlab’s factory in Polokwane.

Meanwhile, all of the 3 200m3 of 35MPa concrete for the main bridge structure is being produced on site by Estate Construction.

Aggregate for the concrete was sourced from a crushing operation that recycles mine waste rock in Selebi Phikwe and stockpiled, together with the sand, on site.

A slump test is undertaken before every pour to ensure that the concrete meets the required specifications.

Working in such a remote location, Estate Construction has also ensured that it is equipped to undertake the basic repairs of its large fleet of equipment on site.

Despite a slow start due to extreme flooding and complex ground conditions on the Botswana side of the structure, Estate Construction has made swift progress on the project

The contractor first had to use large pumps to remove the water and then build a coffer dam to isolate the bases.

Meanwhile, extensive drilling and blasting was also required to remove the bedrock on the Botswana side of the structure and this was an extremely onerous and time-consuming process.

Katzke says that he is proud of the opportunities that this project has provided members of surrounding communities, as well as small- and medium-sized businesses in Botswana. These include the steel-fixing companies that worked alongside Estate Construction’s team on site.

“As a project that is being driven by the Botswana government, it was imperative the construction phases benefited mostly Botswana citizens and companies. Barring the precast-concrete beams, we sourced all products and services from Botswana. Meanwhile, 50 people were employed to work on the project when it peaked,” he says.

Jaco de Bruin, CoreSlab’s managing director, compliments Katzke for Estate Construction’s stellar workmanship on a highly-anticipated project that is set to benefit so many businesses and communities on both sides of the border when it is completed.

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