Consisting of forty-six concrete towers, the Gouda Wind Farm, situated in the Cape Winelands District, is one of the largest wind farms in Southern Africa, and the first of these to use locally produced concrete instead of the usual imported steel towers. For construction of these 100 metre tall towers, vast quantities of Sika products were supplied, including one that received the prestigious Fulton Award from The Concrete Society of Southern Africa. Jacques Reinecke, Head of Renewable Energy for Sika SA, spearheaded the specification and installation of the Sika product as well as on-site training.
In September 2015, the Gouda Wind Farm, owned in partnership by the South African company, Aveng, and the Spanish renewable energy company, Acciona Energia, commenced operations with a generating capability of 423 gigawatt hours of electricity through which 200 000 homes will be powered per annum. It is estimated that the clean energy generated by this wind farm will prevent the emission of 406 million metric tons of carbon dioxide per year. One of the client’s primary requirements was a high local content on products. 100% of all Sika South Africa’s products used in the Gouda Wind Farm project were locally produced.
Sika products, tried and tested for their reliability and endurance adding to the sustainability value of Gouda Wind Farm, included Sikadur®-31 CF (one ton per tower), Sealing Backing Cord (22km) and SikaGrout®-295 ZA (30 tons per tower). Each column is comprised of four precast segments that were sealed and grouted together onsite. Due to the extreme height of the towers, each tower is comprised of four precast concrete columns of 20m in height, joined on site, one on top of the other. A final segment carrying the nacelle brings the 46 towers to a height of 100m each.
Horizontal joints on the tower segments were sealed with Sika EVA Backing Strip. This semi-rigid, closed cell cross-linked construction foam is designed as a tough, flexible and resilient back-up support material for surface seals in load bearing joints. It can also be used as a bedding seal under precast concrete panels and to prevent loss of grout when joining precast concrete components.
Once joined together, the vertical and horizontal joints of the precast segments were sealed with Sikadur®-31 CF and Sikadur®-31 DW. Both products are moisture tolerant, thixotropic, structural two-part adhesives and repair mortars based on a combination of epoxy resins and special fillers. Easy to mix and apply, they are suitable for both dry and damp concrete surfaces and harden without shrinkage. They provide high initial and ultimate mechanical strength and are impermeable to liquids and water vapour. Sealing Backing Cord was placed into the expansion joints to regulate the depth of seal and to provide a solid backing onto which the sealants were placed.
Mould imperfections of the newly produced towers were repaired with Sika MonoTop®-620, a cementitious, polymer modified, one-component pore sealer and leveling mortar containing silica fume. With an adjustable consistency, it can be applied by the wet spray method and provides excellent adhesion with good resistance to water and chloride penetration.
DD Materials, who used a local labour team of 24 skilled and semi-skilled applicators, trained by Sika’s Head of Renewable Energy, Jacques Reinecke and Sika Technical Sales Consultant, Anthony Webster, completed the grouting of all vertical cavities using SikaGrout®-295 ZA. SikaGrout®-295 ZA is a one-component, ultra-high strength, cement-based grout, specifically designed for use in the renewable energy field, under metal bases, between concrete segments and to fill cracks, gaps and large voids. Due to its good flow properties this is a pumpable grout that provides rapid strengt development.
During the project SikaGrout®-295 ZA was sent for fatigue testing and Sika is proud to announce the product is now certified for durability.
As a final accolade for Sika South Africa, this project at Gouda Wind Farm won the coveted Fulton Award for Innovation in Concrete. Since the emphasis on this huge project was to use local content and local labour, it surpassed all expectations, proving local really is better!