DAMS & RESER VOIRS Watertightness is achieved by a low water-to-cement ratio, the proper placing and curing of concrete, as well as its compaction
Waterproofing and water-retaining structures Mapei, a global supplier of construction chemicals, speaks to Kirsten Kelly about achieving watertight concrete structures – which takes a combination of design, workmanship and selective materials.
Ross Creasey, product manager, Mapei South Africa
Waterproofing systems will not perform adequately without decent surface preparation
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hen building concrete water-retaining structures (dams, reservoirs, irrigation channels, water and wastewater treatment plants), it is important to ensure their watertightness to prevent the flow of water from inside the structure to outside, and the infiltration of water from the surrounding soil into the structure. High-density, good-quality concrete “Not all water-retaining structures or water/wastewater treatment works use waterproofing products. High-density, good-quality concrete is effectively watertight with a high level of abrasion resistance. Watertightness is achieved
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Polyurea waterproofing can be applied rapidly and creates a seamless, high-performing waterproofing barrier that can withstand chemical attack (like chlorine)
by a low water-to-cement ratio, the proper placing and curing of concrete, as well as its compaction,” states Ross Creasey, product manager, Mapei South Africa. Superplasticisers (like the Mapei Dynamon range) aid in creating dense concrete, as they can reduce the water-to-cement ratio (and increase strength) while maintaining workability. Crystalline admixtures (Mapei Idrokrete) also reduce the permeability of concrete and even seal small hairline cracks. Creasey believes that with waterproofing, it is important to consider the service life of the infrastructure. “Once a waterproofing product reaches its service life, it
needs to be removed and reapplied. For instance, the lining of an irrigation channel is not necessarily a costeffective decision as it will need to be waterproofed again every 15 to 20 years. This can be an expensive and technical exercise. Furthermore, some of these irrigation channels are open at the top, so if a rock or sediment falls inside and is carried away with the flowing water, it could destroy any waterproofing coating. Often, it is less expensive to rely on quality concrete and plan for marginal water loss than to keep relining the channel.” Waterproofing systems There are times when a waterproofing coating is needed, particularly when
