Kryton: tried and tested waterproofing
Integral crystalline waterproofing, a revolutionary method developed by Kryton International a decade ago continues to hold good as a genuine waterproofing agent, says vice president (operations) Kevin Yuers.
01 September 2003
The efficacy of chemical water-proofing lies in the fact that it prevents the movement of water through concrete by plugging or blocking natural pores and capillaries.
This is in contrast to conventional means of waterproofing, which usually involves applying some sort of coating or membrane on to the concrete surface.
In the last three decades, advancements made in chemical technology by Canadian manufacturers such as Kryton International have resulted in the use of integral crystalline waterproofing. This technology can be installed in various methods, resulting in the improved performance of structures and savings in time and money.
How it works
Generally, chemical waterproofing products are supplied as a dry, powdered mixture of Portland cement, silica sand, and special chemicals, which is mixed with water to form a thick slurry. On brushing the slurry on to a prepared concrete surface, the chemicals contained in the waterproofing compound combine with water to initiate a chemical reaction. This results in the formation of long, narrow crystals, which grow in and through the pores, capillaries and hairline cracks of the concrete mass thereby sealing the passages and preventing the movement of water.
The chemicals themselves are carried into the concrete by capillary action and diffusion. Capillary action is the natural wicking movement of liquids in a porous structure, while diffusion is the natural movement of chemical molecules. These processes cause the crystals to penetrate deep into the concrete.
The crystals continue to grow as long as there is moisture, and can reach lengths of several feet through the concrete over a period of days, weeks and months. In the absence of moisture, the chemicals become dormant, waiting for the next dose of water to start the growth again.
This ability of the chemicals to stay dormant and then become active again in the presence of water gives the treated concrete a self-healing ability. Sometimes new cracks will form in concrete from settling or some other cause. Water entering through these cracks will come into contact with the dormant chemicals of the chemical waterproofing and cause them to become active again. New crystals form and grow to again shut off the water. The self-healing ability is one of its best and most unique features.
Its benefits
Besides its self-healing properties, chemical waterproofing treated concrete has additional advantages when compared to conventional membranes. The biggest advantage is the ability to make the application to the negative side of the concrete (the side opposite the source of the water against the pressure).
As opposed to chemical treatment, membrane treatment can be successful only if it is applied to the positive side of a leaking concrete structure. But in many cases, it is often impractical or even impossible to access the positive side. Since chemical waterproofing grows into, and becomes part of the concrete, it makes no difference which side of the concrete it is applied to, making it a viable waterproofing option.
Another important advantage of chemical waterproofing is its near immunity to damage. Membrane systems, unlike chemical systems, often fail when they become scraped, punctured, or torn. Also, because the chemical waterproofing acts within the concrete, the coating on the surface is not vital. Since the majority of the active chemical migrates into the concrete in the first 28 days, chemical waterproofing can actually be completely removed from the surface after this time with little effect.
The dry shake method
Chemical waterproofing has been used for many years for repairs and it was recently that the benefits of the use of the mixture in new construction projects was recognised. The dry powder product could be spread onto the setting concrete and trowelled into the surface - usually with a power trowel, when placing concrete slabs. This method of application has become known as the 'dry shake method.'
The dry shake method has several advantages over the brush-on method:
Following the success of the dry shake method, a further innovation was made to chemical waterproofing in new construction. In the late 1970s, Kryton launched a version of integral crystalline waterproofing that can be added into the concrete mixture before it is placed. This method of application shares the self-sealing and immunity-from-damage properties of the slurry application, along with the advantages of the dry shake method.
Most important, the admixture version eliminates the need to make any kind of surface application at all and it also has benefits in shrinkage reduction, placing and improvements in long-term performance. The additional cost added to the concrete gets offset by the savings gained by eliminating time and the labour that would otherwise have been required to apply a product to the surface. These benefits have seen the emergence of integral crystalline waterproofing as an accepted replacement to conventional membranes in new construction.
How to choose brands
Choosing the best product can be problematic, especially as the literature of one reads very much the same as the other. Chemical waterproofing products should not be confused with products that are simply concrete densifiers or pore blockers. Care should be maintained so that the user does not end up buying products that claim to grow crystals but in reality will only crystallise as they dry. Such products do not grow through the concrete, nor do they reactivate in the presence of water to fill cracks. Products, which contain silicates, stearates, or talc, are temporary waterproofing agents at best.
With all systems in construction, good communication and co-ordination between the manufacturer, specifier and contractor are paramount for total success.
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