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Construction of a new bridge over the Limpopo River at the Platjan border post is well underway. The Botswana government-owned investment company, which is facilitating the project, awarded the construction of the bridge and two approach roads to Estate Construction in 2016. The contractor commenced work on the project in January 2018 and is due to complete the project in June 2019.

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

CoreCivils helps Estate Construction bridge the divide

A total of 210 precast-concrete beams, 21 elements per span, were manufactured by CoreSlab, CoreCivils’ manufacturing arm, for the project. CoreCivils’ construction division, Corestruc, was also tasked with the installation of the elements, each 15,5m in length and 800mm deep.

As a result of limited space on site, the bridge beams were manufactured ahead of their installation and stored at the CoreSlab factory in Polokwane, Limpopo. 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, was positioned on a newly-built coffer dam. The dam was built because 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 120t 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.

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, says the company’s Julius Katzke. “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. We first had to use large pumps to remove the water and then build a coffer dam to isolate the bases. 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,” he says.

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.

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