Construction World December 2018

Specialist Contractors or Suppliers

PROJECT INFORMATION

• Company entering: Sika South Africa • Client: Department of Water and Sanitation • Start date: October 2016 • End date: July 2018 • Main Contractor: Raubex Construction • Project Manager: RudNat Projects • Specialist Supplier: Sika South Africa

CORNELIS RIVER DAM: REFURBISHMENTS The Phumelela Local Municipality has recently been experiencing severe water shortages and has considered options to ensure the provision of a sufficient and sustainable potable water system for the future for both the short and longer term. Water usage has been restricted throughout the past years, but water quality deteriorates on a daily basis. The high rural to urban migration and changing water use pattern, mainly as a result of the introduction of water borne sewerage systems under the bucket eradication programme, place additional stress on existing infrastructure and resources. The final objective of this project was to implement a sustainable regional bulk water supply scheme in the Phumelela Local Municipal area, prioritising the Warden region.

T he Cornelis River Dam, situated in the Free State between Johannesburg and Durban, 56 km north of Harrismith, has undergone major refurbishment. The project commenced in October 2016 by contractors Raubex Construction, and was completed in the allotted timeline by July 2018. Sika’s reputable range of concrete repair and protection products were the top choice of specified products by project managers, Rudnat Projects. The dam, which was completed in July, spans 23 metres in length with the wall measures 205 metres in height. It has a storage capacity at spillway level of 4 500 000 m 3 . BHM readymix, situated in Harrismith, supplied all the concrete using SikaPlast V220 and Stallion-2 admixtures supplied by Sika. This was to enable the grouting of the the anchor rods into the rock, before pouring the concrete to create the steps. Intraplast-Z was used, a grouting admixture that is designed to introduce micro bubbles into the grout mix, thereby creating wet volume expansion and to increase fluidity without segregation. As a curing agent to prevent premature water loss, Sika’s Antisol-E 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. Separol-GU, an oil based release agent used to provide easy release properties to the formwork, permitting a high quality surface finish of the dam wall. Sika micro fibres were specified to be used in the spill way concrete as well as in the concrete mix of the dam wall to reduce any crack tendencies in early-age concrete. The structure was primed with Sikagard-550 W Primer, prior to

the application of Sikagard-550 W Elastic, an acrylic based emulsion, high-build, and protective coating providing a durable covering with excellent resistance to weathering. As a surface hardener for concrete, Sikafloor CureHard-24 was used in the spillway concrete. This easy to apply compound reduces dusting of concrete as well as improves chemical and abrasion resistance compared to untreated concrete. The concrete wall was repaired using Sika MonoTop-610 an easy to apply cementitious, polymer-modified, one-component slurry. This high quality, anti-corrosion primer provides excellent bond for Sika MonoTop-612 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. Sika Waterbar Type O-20 was centrally placed in all the expansion joints. Manufactured from virgin thermoplastic PVC for strength and flexibility and easy, on-site welding. Internationally tested Sika- Waterbars are used to seal construction and expansion joints in all water retaining structures. They are designed to withstand high water pressure and are supplied in rolls of various widths and types Two main challenges faced during this project was the drilling of 21 m into the ground and create a grout wall before starting with the actual wall as water kept rising when drilling into the ground. Drilling into the rock for the anchor rods was also another challenge due to the rock being so hard, which in turned caused the drill bit to break off or go blunt. Regardless of these challenges, the project was completed in the timeframe of 18 months. 

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