Constructed in 1951, the Modder River Bridge lies on the Bloemfontein/Brandfort road near Glen in the Free State. Sixty years on the ageing bridge, for the first time in its history, required some cosmetic “surgery”. Engineering company Aurecon was responsible for the 637m² operation and instantly specified Sika products, not only for their outstanding quality, but also for their excellent pricing and accessibility.

The project commenced in January 2011 with contractor Roadcrete Africa repairing the beams and columns of the bridge. SikaTop-Armatec 110 EpoCem (40 kits) was used as a primer and bonding agent prior to application of the repair mortar. This cement-based, epoxy-modified, three-component product provides excellent adhesion to steel and concrete, acts as an effective barrier against penetration of water and chlorides and contains corrosion inhibitors. It also provides a high degree of mechanical strength and may be spray applied.

After the required waiting period, the beams and columns were then coated with Sika MonoTop-615 HB (50 bags). This is a high build, cementitious, polymer-modified, one component repair and reprofiling mortar containing silica fume. It is designed for thick layer concrete repairs and its excellent thixotropic behavior is especially suited for overhead and vertical applications making it an ideal product for this project. Sika MonoTop-615 HB provides excellent workability characteristics, requires mixing with water only, has an adjustable consistency, and is sprayable by the wet spray method. It also provides good mechanical strength, good freeze/thaw resistance as well as good resistance to water and chloride penetration.

Following the repair phase of the project, the entire bridge was coated with Sika TopSeal-107 ZA (15 kits) which is a two-part, polymer-modified, cementitious, mortar slurry comprising a liquid polymer and a cement-based mix, incorporating special admixtures. It is used for exterior and interior waterproofing and damp-proofing of concrete, including basements and cellars. It provides protection of concrete structures against the effects of chloride and Carbonation attack and freeze/thaw attack, and may also be used for pore/blowhole filling, sealing of hairline cracks and as a leveling mortar. Sika TopSeal-107 ZA is easy to mix and provides ease of application, either by hand (using a brush or thin trowel) or by the spray method. Providing very good adhesion, it is also non-corrosive to steel or iron, is overpaintable and possesses approval for potable water contact.

Heavy rains causing delays and interruptions caused the contractor to be behind schedule and the project was completed in September 2011. Now that the Modder River Bridge has been repaired, strengthened and protected with Sika’s high quality products, there is no doubt that it will continue to carry traffic between Bloemfontein, Brandfort, Theunissen and Welkom far into the foreseeable future.