When the Francois Road Bridge, which links Maydon Wharf to Durban’s CBD, required repairs and waterproofing, Sika was called on to supply significant repair and waterproofing products for this critical project. Ethekweni Municipality awarded the contract to consulting engineers PD Naidoo and Associates, whose specifications were to remove the asphalt, achieve a milled surface, prime, waterproof and produce a stippled finish, ready for new asphalting.

In January 2012 when contractors, Mdeni Freyssinet removed the asphalt from the bridge, an immediate challenge was encountered; the levels of the concrete deck had been left incomplete and the concrete was undulating, presenting high and low areas. The variation in levels meant that it was impossible to scarify and level out the concrete deck for the waterproofing layer to be applied. Two of Sika’s grouting products were used to level off the worst areas, along with a low level of breakout to the surface-crete. SikaGrout-212 is a cementitious, fluid, expanding grout that offers rapid strength development and high final strengths. Sikadur-42 ZA is a solvent-free, fluid grout based on a combination of epoxy resins and special fillers. It is self-leveling, provides excellent mechanical strength and is ideally suited for grouting under bridge bearing plates.

Bridge bearings were replaced using Sikadur-43 ZA, an epoxy resin, solvent-free repair mortar used as a bedding mortar for the bearings. Providing rapid, shrinkage-free hardening and high mechanical strength, its curing is not affected by high humidity, a vital factor for a project situated in Durban. Sikadur-52 ZA, a solvent-free, low viscosity injection resin was used to fill and seal voids and cracks.

Only once the complete deck had been repaired, was the contractor able to commence the main project of waterproofing. Sikafloor-156 ZA, a two-part, epoxy resin primer was the product of choice for the double priming stage; a first coat was thinned by 10% to penetrate the substrate and eliminate blow holes, and was followed by a second un-diluted coat. This easy to apply primer provides good penetration, high bond strength and short waiting times and is suitable for interior and exterior use.

Waterproofing was also performed in two stages using Sikalastic-841 ST, a pure polyurea liquid applied, spray membrane designed for spray application only. An initial layer, applied at 1mm thick, was inspected for blowholes. These were subsequently closed with Sikaflex Fix, a multipurpose polyurethane joint sealer, which cures on exposure to atmospheric moisture to form a durable elastomer. This was followed with a second layer of Sikalastic-841 ST sprayed 1mm thick and stipple finished, as specified. Sikalastic-841 ST provides a fast reactivity and curing time, is 100% solids with zero VOC, has excellent crack-bridging and anticorrosion properties and is UV resistant. This versatile product can be used in a wide variety of applications on many substrates.

After initial problems were solved, this 2000m2 project was completed in July 2012 and once again Sika’s high performance, durable products will stand the test of time.