Understanding the limitations of waterproofing options in concrete structures

by Ofentse Sefolo
Understanding the limitations of waterproofing options in concrete structures

At Totally Concrete 2019, which was held recently, Sandor Dowling from Sanika Waterproofing gave a presentation on crystalline waterproofing admixtures, membrane barriers for waterproofing, and the limitations of the different types of waterproofing options.

“Concrete is used because of its low cost, durability and its unique engineering properties. From sidewalks and skyscrapers to dams, houses and bridges, concrete has been used to create the world we live in. The biggest threat to concrete, however, is water,” said Sandor.

How water harms buildings
She points out that water damages more buildings than natural disasters, which many people struggle to believe.

“People mistakenly believe that concrete is waterproof and that it doesn’t crack, but anyone who says that concrete doesn’t crack is misled. Changes in volume caused by shrinkage or other reasons, as well as water, can quickly cause a beautiful structure to deteriorate and fail,” says Sandor.

There are three essential components necessary for corrosion in reinforced concrete: steel, water and oxygen. Eliminating any of these will prevent the chemical reaction that leads to corrosion and the resulting damage. This is why there is no corrosion in dry concrete and also why concrete fully submerged in water has limited corrosion, except in instances where the water can entrain air.

When water penetrates into concrete, the steel reinforcement corrodes and rusts, which leads to expansion stressing, more cracking and deterioration of the concrete. This cycle will continue unless water is prevented from permeating into the concrete.

Corrosion of reinforced steel in concrete is a global problem, deteriorating structures at an extremely high rate. The issue makes up for more than 80% of all damage to reinforced concrete structures, racking up repair costs for countries. With repair to steel in concrete climbing, sustainability measures cannot be feasibly met.

The problem with moisture
“More moisture will lead to more contaminants getting into your concrete. Ultimately, the more impermeable your concrete is, the more durable your structure will be. By effectively waterproofing the concrete, the structure will be protected from acid, sulphite, frost, efflorescence and the other ailments that can plague concrete,” says Sandor.

She adds that waterproofing is absolutely essential in any building construction. “If your waterproofing fails, your construction will eventually deteriorate and fail. Whether you need to keep water in or out of the structure, you need to stop it from entering the concrete because as soon as it starts passing through the concrete, it will carry harmful contaminents causing corrosion to the reinforced steel and in turn the structure,” says Sandor.

Types of waterproofing
The two main types of waterproofing are internal and external membranes. An internal membrane is created with a waterproofing admixture that is added to the concrete. This can include crystalline, water-repelling admixtures and densifying admixtures. An external membrane is a sheet-applied membrane on the outside of the concrete.

“Surface applied membranes have their limitations because this installation is only as good as the applicator and the surface that it is applied on. They can fail because of delamination, are susceptible to mechanical and chemical damage, and are essentially dependent on the perfect installation. Another common problem is that a membrane can be costly to repair due to civil excavation and downtime. If the membrane is in a reservoir, for example, the reservoir would have to be emptied to start assessing where the delamination or puncture is,” says Sandor.

Kryton’s Krystol concrete waterproofing products are either added directly to the concrete mix or applied to the surface of concrete. Once added, Krystol chemically reacts with water and un-hydrated cement particles to form insoluble needle-shaped crystals. These crystals fill capillary pores and micro-cracks in the concrete to block pathways for water and waterborne contaminates.

If water is re-introduced through a rise in hydrostatic pressure or through hairline cracks, Krystol will initiate further crystallization to ensure permanent waterproof protection. Krystol works for the life of the concrete.

Crystalline waterproofing is a technology that involves the development of crystals to help achieve watertight concrete structures. According to Sandor, crystalline gets better with time. “When crystalline is used for waterproofing, it is there for the structure’s life expectancy. The future of concrete waterproofing is internal because it turns the concrete itself into a membrane and barrier. By adding the crystalline to your concrete, your concrete becomes the barrier,” concludes Sandor.

Sanika Waterproofing
Tel: 011 425 3061
Website: www.sanika.co.za.

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