REHABILITATION OF THE M1 DOUBLE DECKER

When the M1 ‘double decker’ highway bridge in Johannesburg between Newtown and Fordsburg was found to be posing a safety threat to motorists, the Johannesburg Roads Agency decided to rehabilitate this major bridge. This R15m project, with a bridge-span of 1.02km, required the expertise of many specialists. Khato Civils (Pty) Ltd was appointed as the main contractor, assisted by 17 small-, medium- and micro-enterprises, employing a total of 164 people.

The bridge consists of two reinforced concrete deck superstructures, one directly above the other, that are supported on trestle-like piers. A variety of Sika products were specified for structural repairs, structural strengthening and coatings. SikaTop Armatec-110 EpoCem was used as a rebar protective coating in the structural repairs, as it is highly effective for corrosion prevention in concrete reinforcing. Also used in the repair process were the user-friendly Sika Monotop-615 HB, which is designed for thick-layer concrete repairs, especially for overhead and vertical applications; as well as SikaGrout-212. For structural strengthening of reinforced concrete structures, and to increase sheer load capacity, SikaWrap-300 C was used. The concrete surface area was treated with Sikaguard-705 L silane water repellent and SikaTop Seal-107, a polymer modified cement waterproof and chloride- and carbonation -resistant liquid applied membrane coating for concrete. To ensure that all product applications were executed correctly at every stage, all those involved in the project were provided with training and onsite support by the Sika team. This included training in processes such as surface preparation, product mixing and product application.

The motorway was under daily use, which posed a major challenge to all involved because disruption to traffic had to remain limited. It was expected that it would be difficult to complete the task within the allotted 22-month time frame. However, with the use of superior tailor-made products and the appointment of a committed contractor, the project was completed three months ahead of time.

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