Orania Wastewater Treatment Plant

Orania, a Karoo town in the Northern Cape, named after the Orange River flowing alongside, has experienced rapid population growth in the last few decades. Consequently, the wastewater plant did not have adequate capacity to cope and a new one had to be built. The appointed contractors were Orania Infrastruktuur and they conducted the project from March through to mid-December of 2021.

Sika SA were consulted, asked to consider solutions, and then supplied the relevant specified materials to the project. It was important to ensure that concrete works and joints be totally watertight. The basic methodology initially required the installation and fastening of Sika-Waterbar® DR EG, an expansion joint sealant for watertight concrete construction, prior to casting of the concrete. SikaPlast® 220VX, a water reducing multi-purpose admixture was dosed at the ready-mix supplier, and Sika® WT-200 P, a waterproofing admixture, was then added to the load just prior to discharge, and thoroughly mixed.

The Sika-Waterbar® DR EG rangeare made from thermoplastic PVC and can therefore be easily heat welded – as adhesive jointing is not permitted. Further advantages include high tensile strength & elongation, permanent flexibility, resistance to hydrostatic pressure/stress, and a resistance to natural soil and groundwater mediums. It is also available in a range of different sizes to suit different structures and applications. The selection of a suitable Sika-Waterbar® is governed by the type of joint, the concrete thickness, grade of concrete, reinforcement position, expected movement (expansion/shear) as well as the waterhead to which it is to be exposed to. The correct consistency of the concrete itself is also important, and the aggregates must be well graded. The Sika-Waterbar® solutionperforms only if both sides are well embedded in the concrete, is centrally placed and heat welded. Sika provided all the information and conducted training in the use of its products.

SikaPlast®-220 VXis a multi-purpose water reducer and superplasticiser, which can be used in both ready mix and on-site batching applications; and is ideal for use with lean, harsh

concrete mixes, and concrete containing, slag, fly-ash or microsilica. The superplasticising action of SikaPlast®-220 VX provides high-slump, flowing concrete that maintains excellent workability and may be placed with minimal vibration. It has been formulated to provide controlled and predictable extended slump life, allowing good slump retention without significant loss in early strength development. The combined high range water reduction and superplasticising action of SikaPlast®-220 VX provides the following benefits in hardened concrete:

• Higher early compressive strengths for earlier removal of forms and structural use of concrete.
• Higher ultimate strengths allow for greater engineering design flexibility and structural economies.
• Reduced water cement ratios produce more durable, dense concrete with reduced permeability.
• It does not initiate or promote the corrosion of steel present in the concrete.

Sika® WT-200 P is a combined water resisting and crystalline waterproofing admixture used to reduce the permeability of concrete and to enhance the self-healing abilities of the concrete. The active mixture of cements, amino alcohols and fillers will form non-soluble materials and seal the concrete permanently against penetration of water and other liquids. In addition, the special Sika formula of ingredients in Sika® WT-200 P will provide the following benefits:

• Improve the ability to heal cracks in concrete.
• Reduced water penetration under pressure.
• Reduced water absorption.

Despite the rain delays, the project was successful and the new wastewater plant now has four times the processing power of its predecessor. Sika SA were there to make sure no resources went to waste – except of course, that which was meant to!