The latest waterproofing admixture innovation to adapt to the ever-changing cement industry is Sika® WT-200 P. This Sika Watertight Concrete system has already been established on significant projects around the world and is providing a much-needed solution for porous, permeable concrete.

Sika® WT-200 P is a combined water-resisting and crystalline waterproofing admixture used to reduce the permeability of concrete and to enhance its self-healing abilities. 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; and it will continue to reactivate whenever water is present.

Additional benefits of Sika® WT-200 P:

• Improved ability to heal cracks in concrete
• Reduced water penetration under pressure
• Reduced water absorption

According to the EN 12390-8, water penetration depth tests have to be conducted over 72 hours (about three days) with a water pressure of five bars. To gain knowledge after these three days, the same tests have been performed with an extended testing time of up to 28 days. The above graph shows the results of these extended tests.

Uses for Sika® WT-200 P

Keeping water out

• Basements
• Habitable basements
• Parking garages
• Utility/plant rooms
• Tunnels

Keeping water in

• Swimming pools
• Water retaining structures
• Dams
• Water structures
• Wastewater treatment structures

Case study 1: SANCCOB exercise pool

Sika WT-200 P helped protect the newly constructed exercise pools for the Southern African Foundation for the Conservation of Coastal Birds (SANCCOB). After operating in Table View in Cape Town for 33 years and having treated nearly 100 000 seabirds, SANCCOB needed new modern facilities. Over the years, SANCCOB has become synonymous with the conservation of the endangered African penguin and is a leader in seabird rehabilitation, chick-rearing and veterinary care, as well as contributing to ground-breaking research. This meant the organisation’s capacity needed to increase to save more birds, improve the standard of care and educate more people about seabird conservation.

Even excellent quality concrete will allow water to permeate the surface; thus, the need for a good waterproof concrete mix that safeguards the exercise pools from damp and water leakage. The application of concrete supplied contained Sika’s watertight solution, Sika® WT-200 P, to provide a durable, watertight finish. The volume of capillary pores provides a pathway for water on one side of the structure and air on the other. The volume of capillary pores in the concrete matrix is proportional to the water/cement ratio. Understanding and controlling water/cement ratio is the basis of concrete technology and, as well as permeability, how it affects the strength and durability of concrete. In addition, the special formula and ingredients of Sika® WT-200 P enhances the self-healing properties of concrete and will improve the ability to heal concrete cracks.

The newly constructed exercise pools were completed to the client’s full satisfaction and meant Sika’s watertight concrete solution played a major part in providing SANCCOB the reassurance of watertight protection, ensuring its stability and performance for many years to come.

Case study 2: Orania wastewater treatment plant

Orania, a Karoo town in the Northern Cape named after the Orange River, has experienced rapid population growth in the last few decades. Consequently, the existing wastewater plant did not have adequate capacity to cope and a new one had to be built. Sika SA was 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 watertight and Sika® WT-200 P, a waterproofing admixture, was added to the load just prior to discharge, and thoroughly mixed. Despite the rain delays, the project was successful, and the new wastewater plant now has four times the processing power of its predecessor.

FAQs

• What minimum cement content or water/cement ratio should we use?

350kg CEM or 0.45 water/cement ratio.

• When should we add the product to the concrete?

Preferably prior to loading concrete.

• Does it affect my slump?

Yes, Sika® WT-200 P, does increase the slump. We suggest holding back on approximately 10 litres of batching water.

• Is the product accredited by independent body?

Yes ‒ the BBA (British Board of Agrément).

• Can it be used in concrete with fly ash or slag?

Yes, although the total supplementary cementitious material (SCM) ‒ i.e., fly ash or slag ‒ should not exceed 40% of total cementitious content.

• Will Sika® WT-200 P improve my concrete?

Yes, it improves the durability index. (Oxygen permeability index, water absorptivity and the Chloride conductivity can be improved, too.)