SMEC South Africa was appointed by Trans African Concessions (TRAC) to undertake the detailed inspection, rehabilitation design and construction supervision of the Komati River Bridge refurbishment project. The bridge is situated on the N4 Toll Route, Section 8 and is an important river crossing for freight traveling between South Africa and Mozambique.
During a scheduled inspection, a number of defects were identified. Defects included locked bearings, shear cracks and flexural cracks in the deck beams. The shear and flexural cracks were believed to have been related to thermal loading caused by the locked bearings.
March 2017 saw the start of the project where Sika’s specialised products were specified by DSC Zendon whom the client, TRAC appointed to complete the rehabilitation. Jaun-Roe van Wyk, Sales Consultant for Sika South Africa, recommended Sika’s most renowned products.
Sikadur-52 ZA was used for crack injection. This was completed by drilling 6mm holes into the cracks to a depth of 20mm. The injection was by means of copper piping used to inject the epoxy into the crack which was bonded to the concrete with Sikadur-31 DW epoxy mortar. The crack was thereafter closed with Sikadur-31 DW and allowed to cure for 24 hours.
Sikadur-30 was used in conjunction with the composite carbon fibre plates which were cut to the correct sizes as specified. All areas that had to be strengthened were inspected for damages and repaired during the concrete preparation stage. Any unevenness or protrusions were grinded flush in the concrete preparation stage.
The product Sikadur-330 was used together with the SikaWrap carbon fibre fabric. All the areas that were strengthened were prepared by means of grinding before applying the SikaWrap.
Sikadur-330 was applied as a bedding layer onto the clean concrete surface. The SikaWrap was then applied onto the wet epoxy adhesive and the surface of the cloth was rolled with a ribbed roller. This was to ensure that all trapped air or bubbles were removed from the layered material and that the resin was pushed through the cloth. A second coat of Sikadur-330 was applied to cover the fabric evenly to ensure complete wet out of the SikaWrap.
One of the key challenges during this project was that works had to be completed under live traffic conditions. Therefore, the N4 had to remain open during the rehabilitation process. Over and above the traffic conditions, crocodiles in the river below posed an additional safety risk, especially during the rainy season when flooding was an issue.
Regardless of the challenges faced, the rehabilitation works were successfully completed in six months.