The Mount Road Bridge Interchange is one of the largest of its kind in the Eastern Cape and is situated on one of the busiest freeways in central Port Elizabeth. Critical safety measures were therefore implemented when renovations began at the request of Nelson Mandela Metropolitan Municipality. Started in August 2009 by Ibhayi Contracting, this large-scale project is scheduled for completion in June 2012. Sika’s reputable range of concrete repair/rehabilitation and protection products were the top choice of the specifier, Africoast Engineers.

The entire bridge structure was initially treated with Sika FerroGard-903 (2550 litres), a migrating corrosion inhibitor based on organic and inorganic compounds, which penetrate the concrete up to a depth of 60mm, thereby forming a protective monomolecular layer on the reinforcing steel. Used in conjunction with other Sika products in the Concrete Repair and Protection System, Sika FerroGard-903 decreases the corrosion rate by such an extent that the service life of aesthetically valuable fair-faced concrete can be increased by up to 15 years. It can be used where other repairs or prevention options are not viable, does not change the appearance of the concrete, and can be applied to the surface of existing repairs to prevent the development of incipient anodes.

As a curing compound to prevent premature water loss, Sika’s Antisol E (1100litres) was sprayed onto areas of mass concrete. Forming a thin film barrier, this ready to use liquid curing compound does not disturb the normal setting action of concrete which is then allowed to cure and achieve maximum properties.

Sika’s high performance SikaGrout-212 (4717 x 25kg) has been used under all new precast concrete barriers. This fluid grout provides adjustable consistency, rapid strength development and high final strengths. It expands by gas generation whilst in the plastic state of curing. To waterproof the barriers, the product of choice was Sika TopSeal-107 ZA (464 x 25kg), a two-part mortar slurry comprising a liquid polymer and a cement-based mix incorporating special admixtures. It is easy to apply and provides excellent adhesion while protecting concrete against carbonation and water penetration.

The old concrete was primed using Sika MonoTop-610 (176 x 25kg), an easy to apply cementitious, polymer-modified, one-component slurry. Another primer used in the project was SikaTop-Armatec 110 EpoCem (50 x 1.75litres), a sprayable cement-based, epoxy-modified, three-component compound providing an effective anti-corrosion coating on reinforcing steel. These structural bond coats were used where large volume repairs were necessary on newly completed areas which had been subsequently damaged by vehicular accidents. Both these high quality primers provide excellent bonding coats for Sika MonoTop-612 (3591 x 25kgs), a high strength repair mortar containing silica fume and synthetic fibre reinforcement. Providing excellent slump resistance, it is particularly suitable for application on overhead and vertical surfaces as the wet spray method may be used.

Previous repairs to the bridge structure, where areas needed to be made uniform and aesthetically pleasing, were coated with Sika MonoTop-620 (5 x 25kg), a pore sealer and levelling mortar with very similar properties to Sika MonoTop-612. Other sections - where additional protection was required and to seal off fine pores - were coated with SikaGard-720 EpoCem (14 x 18.5kg), a three-part, epoxy-modified, thixotropic, micro mortar providing excellent surface sealing and protection of concrete, particularly in aggressive environments.

Reflective metal strips needed to be adhered to all new concrete barriers. After various site trials, it was decided that Sikaflex-11FC was the ideal product as it is a multipurpose polyurethane adhesive suitable for indoor and outdoor applications. It is non-corrosive and impact and vibration absorbing – ideal for this situation. All repair joints have been protected using Sikaflex-11 FC, a high quality, moisture-curing, elastic joint sealer that is weather and ageing resistant.

Prior to bonding, the reflective strips were cleaned with Sika Kwiklean, a highly effective, solvent based degreasing and cleaning compound. Soluble in cold water, this economical, extremely versatile product has also been used for all general cleaning on site. As the Mount Road Interchange is very close to the sea, the structure was first primed with Sikagard-550 W Elastic Primer (207 x 25 litres), and then coated with Sikagard-540 W (Concrete Grey,319 x 20 litres), a one component, acrylic emulsion based, high build, protective coating. Providing a durable covering with excellent resistance to weathering, Sikagard-540 W is easy to apply and enhances the aesthetic appeal of the structure.

Two main challenges faced during this project were controlling of traffic, especially during peak hours, and working alongside or above the railway power lines that the bridges span. Working in close proximity to these power lines posed such serious dangers that Transnet enforced its own safety measures, compelling all contractors to carefully co-ordinate and plan their schedules accordingly.

Once this project is completed, Nelson Mandela Metropolitan Municipality can be assured that a very important section of the city of Port Elizabeth has been renovated with world-class products.