A sleek new road bridge stands proudly on the western edge of Qonce, formerly known as King Williams Town, in South Africa’s Eastern Cape province. The Tshoxa 1 Bridge, commissioned by the South African National Roads Agency Limited (SANRAL) and constructed by WBHO, is a testament to the versatility and elegance of concrete in modern infrastructure projects.

This 140 metre long bridge stands 18 metres above the Tshoxa River and a railway line with a railway bridge, forming a crucial part of a broader road improvement project. SANRAL’s initiative aims to enhance the safety and efficiency of transportation in the region by upgrading key roads’ alignment and infrastructure. These improvements will not only facilitate logistics and trade but also make driving safer, quicker and more cost effective.

The Tshoxa 1 Bridge’s sustainability is highlighted by its innovative concrete mix design. Cement from AfriSam and readymix from Stutt Group’s batch plant near Daleview Quarry were used to create a sustainable W specification concrete mix. This mix reduced the environmental impact by eliminating dune sand from the mixture, saving approximately 13,800 tonnes of sand. Additionally, the inclusion of fly ash as a cementitious supplementary material significantly reduced the carbon footprint.

Construction on the broader road project began in 2021, with the Tshoxa 1 Bridge’s construction commencing in April of that year. While the bridge itself is complete, the entire contract is expected to be finished by April 2024.

Mariswe served as the consulting engineering company overseeing the contract, with Gibb handling the engineering designs. Stutt Group supplied the readymix for the bridge, using approximately 750 tonnes of HSC 52.5N CEM1 cement from AfriSam. This choice aligns with the government’s policy of using locally manufactured cement for publicly funded projects, reducing reliance on imported cement.

The Tshoxa 1 Bridge reflects the successful integration of concrete’s functionality and aesthetics to enhance the quality of life through infrastructure development. It blends seamlessly into its rural surroundings while boasting an elegant concrete finish, further enhancing its visual appeal.

This project’s environmental sustainability extends beyond its visible aspects. The concrete mix design addressed challenges posed by the region’s natural sand quality by replacing it with carefully selected quarry dust. This not only reduced the carbon footprint but also minimised the need for potable water from the local municipality, saving 690,000 litres in total.

The innovative use of admixtures, including plasticisers and superplasticisers, lowered the cement-water ratio, resulting in less cement consumption. Compared to a standard 40 MPa pump mix, the Tshoxa 1 Bridge’s concrete mix reduced carbon emissions by 28.6%, amounting to only 210 kg/m3 of emissions.

The project’s sustainability extends to its supply chain. The proximity of Stutt Group’s Daleview Quarry to the batch plant and the bridge site reduced transportation distances, saving time and diesel in operations. Additionally, strategic planning ensured adequate supplies of aggregate, water, and concrete pump equipment, mitigating risks associated with large pours.

The concrete placement, rate-of-pour, mix composition and formwork resulted in an exceptional off-shutter finish. Quality assurance measures, including accurate batching, concrete testing, strength evaluations and slump testing, were rigorously applied to meet project specifications. The durability panels, exposed to real-time elements on-site, provided valuable data on concrete performance.

Managing variable weather conditions, from extreme temperatures to downpours during the rainy season, required expertise and adaptability. The project team’s careful handling of moisture levels in the concrete stockpiles and meticulous quality control ensured consistent concrete performance.

The Tshoxa 1 Bridge project made a significant impact on the local community by directing 30% of its contract spend to local subcontractors and suppliers. Over 200 project labourers were sourced locally, providing employment opportunities for residents. The project also engaged local subcontractors for specific tasks, promoting economic development.

In addition to its sustainability efforts in concrete mix design, the project demonstrated a commitment to environmental care. Regular water quality testing in the Tshoxa River, temporary concrete walls to channel water during heavy rainfall and responsible cleaning practices ensured minimal environmental impact.

The project’s environmental consciousness extended to landscaping, where topsoil was carefully stockpiled for use in rehabilitation efforts. The batch plant’s water conservation practices including settlement ponds and material recycling, further reduced its environmental footprint.

The Tshoxa 1 Bridge is a testament to the power of sustainable and innovative engineering, showcasing how concrete can be both functional and environmentally friendly. This project not only enhances the region’s transportation infrastructure but also leaves a positive impact on the community and the environment.

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