When rehabilitation of deteriorated structures at the Nelson Mandela Metro University in Port Elizabeth (PE) called for the use of high quality repairs, Africoast Engineers confidently specified Sika’s Concrete Repair and Protection System.

(NMMU) opened in 2005, resulting from the merging of PE Technikon, University of Port Elizabeth (UPE) and the Port Elizabeth campus of Vista University (Vista PE). This union of three very different institutions came about due to the government’s countrywide restructuring of higher education, intended to deliver a more equitable system to meet the needs of South Africa in the 21st century. NMMU caters to approximately 25 000 students and 2 500 staff members, based on seven campuses in the Nelson Mandela Metropole and George. Several buildings on these campuses needed repair work, and Ibhayi Contracting were contracted to carry out on-going maintenance work on the main campus in PE. 

Sika FerroGard-903+ (7 x 200 litres), a migrating corrosion inhibitor, was applied to the old steel reinforced concrete. Based on organic and inorganic compounds which penetrate the concrete (up to a depth of 60mm), it forms a protective monomolecular layer on the reinforcing steel. Used in conjunction with the other Sika products in the Concrete Repair and Protection System, 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 primer for bonding the repair mortar to the old concrete, SikaTop-Armatec 110 EpoCem (120 x 1.75 litre kits) was used.  A cement-based, epoxy-modified, three-component bonding agent, it can also be used as an effective anti-corrosion coating agent where there is corrosion of the reinforcing steel. This sprayable coating has excellent adhesive qualities, acts as an effective barrier against penetration of water and chlorides, and provides a strong bonding coat for Sika’s repair mortar, the next product used. Sika MonoTop-612 (700 x 25kg bags), a cementitious, polymer modified, high strength mortar contains silica fume and synthetic fibre reinforcement, is particularly suitable for application on overhead and vertical surfaces as the wet spray method may be used (up to 30mm thickness). It provides good mechanical strength and has excellent slump resistance.

Once the concrete repairs were completed, the protection element of the Sika system could begin. Sikagard-720 EpoCem (50 x 18.5kg), a three-part, epoxy modified cementitious, micro mortar was applied for the re-profiling, smoothing and levelling of the concrete. It offers easy and fast application (a spray pump machine may be used) and, besides providing excellent protection of concrete in aggressive environments and good chemical resistance, it is impervious to liquids but permeable to water vapour. As there is minimum waiting time prior to the application of Sika finishing products, SikaGard 20 EpoCem is the ideal preparation for smooth surface finishes.

SikaGard-550W Elastic is the high quality coating product used to complete the Repair and Protection System. This one-part, plasto-elastic coating, based on UV-curing acrylic dispersion with excellent crack-bridging properties, offers first-rate resistance against weathering and ageing.

Several challenges were encountered during this project; the most tricky of which was working at night to break the old concrete so as not to disrupt daytime classes. Stringent safety measures had to be adhered to during the day because of the continual movement of students and staff on campus. Following completion of this repair work, the directors of Nelson Mandela Metropolitan University can be assured that their university has been upgraded with Sika products that have the international stamp of approval.