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Creating a Leak-Free Water Containment Tank

Construction World – February/ March 2007

When it comes to preventing water damage and preserving the Integrity of concrete structures, waterproofing is essential. In the case of concrete tanks, however, effective, reliable waterproofing is doubly critical.

Concrete tanks play a vital role in many communities. They function as drinking water containers, wastewater treatment plants and water storage reservoirs. Not only is a leak in a facility like this expensive and time-consuming to repair, it can be inconvenient and even dangerous to the community.

Water-borne chemicals migrating into drinking water can compromise a community’s water supply. In drought-affected areas, water lost through leakage from a reservoir can be costly. And wastewater leaking from treatment plans can contaminate the ground or environment.

Effective waterproofing is especially important in underground or partially buried concrete tanks, since belowground cracks and leaks may be more difficult to detect and more expensive and time-consuming to repair.

Recognising that the vast majority of concrete will eventually crack (and leak) due to shrinkage, settling, seismic activity and other factors, how do you protect your concrete tanked structure and keep water in and contaminants out? The best solution is to plan ahead and invest in a high quality, long-lasting concrete waterproofing system.

Even years later, Integral Crystalline Waterproofing’s crystals remain, continuing to block water and self-seal cracks.

Selecting the right waterproofing solution

A wide range of waterproofing systems are available, including:

• Self-adhering, rubberised asphalt sheet membranes or barriers.
• Liquid membranes that are applied by spray, roller or trowel.
• Cementitious products that are mixed with water and brush applied.
• Built-up systems, where layers of hot asphalt are alternated with perforated felt layers to form a physical barrier.
• Sodium bentonite, a clay material that is applied In panels to the outside of a structure and works by absorbing water and swelling to fill the cracks and voids in concrete.
• Integral crystalline waterproofing (ICW) systems, which create a chemical reaction within concrete that causes crystals to form and grow, filling the spaces between concrete particles and permanently blocking water.

• Each system offers different strengths and challenges. To determine which one is best for your specific tanked structure, consider the following ten questions:

1. How much does the system cost? Labour-intensive waterproofing systems or those that are complex or time-consuming to install are generally more expensive.
2. How long does installation take and does the required installation time fit within your construction timeframe? Installation times vary widely between waterproofing systems, so this is a vital question if your timeline is short. To avoid surprises or construction delays. find out how long installation can reasonably be expected to take.
3. How much design flexibility does the system offer? Some waterproofing systems must be applied to the positive side of a structure, which can present challenges in below ground or blind wall applications. Others can be applied to either the positive or negative side.
4. How difficult is the installation process? Some waterproofing systems are painstakingly difficult to apply, which can lead to inconsistent (and therefore. less reliable) application. Be sure to understand the human error factor of the waterproofing system you choose and how this could potentially impact the effectiveness of the end result.
5. How durable is the system and how long will it last? Some waterproofing systems can be inadvertently punctured or damaged by formwork crews. Others are more resistant or impervious to physical damage. Some systems have a finite useful life and will eventually crack, dry out or otherwise deteriorate, leaving structures vulnerable to water leakage and contamination while others are designed to last the lifetime of the structure.
6. How much maintenance does the system require? Some systems require periodic maintenance to repair damage or cracking and maintain their effectiveness. Others, like crystalline waterproofing systems, have the ability to self-seal cracks over time. which can help reduce downtime and save maintenance costs over the life of the structure.
7. How well does the system protect against corrosion? The corrosion of steel reinforcements by water and waterborne contaminants can significantly shorten the life of a concrete tanked structure. Look for a waterproofing system that offers proven corrosion protection.
8. Is the system certified non-toxic and safe for the environment? This is especially important if your tank will hold potable water that could become contaminated by the inward migration of waterborne chemicals, chlorides, sulphates and silt.
9. What kind of guarantee does the manufacturer/distributor offer? Always choose a manufacturer or distributor that stands behind the products they sell. Follow the manufacturer’s instructions closely, as this can impact the warranty. For example, some manufacturers only guarantee their products when installed by certified applicators or used in certain types of applications. Before you choose a waterproofing system, be sure you understand the warranty and any limitations or restrictions associated with each one.
10. What other attributes or benefits does the system offer? Some crystalline waterproofing admixtures, for example, can help to improve the performance and durability of the concrete while protecting it against shrinkage and cracking.

The Krystol system provides two levels of protection for all cold joint: an integral crystalline waterproofing barrier, plus a physical grout barrier with a compressive strength greater then most structural concretes.

Crystalline systems improve with time and exposure to moisture. A key advantage of the best systems is the ability to reactivate to seal fresh cracks in weeks, months, even years after the application. In addition, crystalline is highly resistant to hydrostatic pressure and will not break down over time – providing long-term protection against water damage, reduced maintenance cost and peace of mind.

How does Integral Crystalline Waterproofing work?
When applied to existing concrete, crystalline chemicals are absorbed into the concrete by capillary action (the natural wicking movement of liquids through a porous structure) and diffusion (the natural movement of chemical molecules). Once inside the concrete, crystalline chemicals begin growing crystals and filling the spaces between concrete particles. As long as moisture remains present, crystals continue to grow throughout the concrete, reaching lengths of many centimetres over time. Once the concrete has cured, the crystalline chemicals sit dormant until another dose of water (such as through a new crack, or rising water table) causes the chemical reaction to begin again.

The ability to reactivate in the presence of water gives crystalline-treated concrete the ability to “self-seal” When cracks form due to curing shrinkage, settling, seismic activity, etc, water entering through them causes new crystals to form and grow, blocking and filling the cracks. Its ability to selfseal cracks is one of crystalline technology’s most unique and useful features, and can help to dramatically reduce the long-term maintenance and repair costs of a concrete structure.

In a hot climate, external membrane systems can become brittle and deteriorate when exposed to prolonged heat, resulting in leaks and increased repair and maintenance costs. Crystalline is unaffected by climate and remains effective for the life of the structure.

Also, the soil in hot or tropical climates may contain high levels of sulphates, chlorides and other chemicals that decrease concrete’s integrity and corrode steel reinforcements. By blocking the penetration of water that can carry these contaminants and safeguarding concrete and reinforcements against corrosion, crystalline systems will prolong a structure’s useful life.

Waterproofing Joints with Integral Crystalline Waterproofing
In building a below-grade concrete tanked structure, extra care must be taken when waterproofing construction joints, since these areas are the most vulnerable to water intrusion. Until recently, the best option for waterproofing joints was to place a plastic barrier or Bentonite strip into the joint before adjoining wall was poured. However, this method can be unreliable since physical barriers easily become dislodged or damaged during subsequent concrete pours, rendering them ineffective and leaving joints susceptible to leakage.

Integral crystalline waterproofing products such as Kryton International’s Krystol Internal Membrane™ (KIM®), which is certified non-toxic, is ideal for use in a wide variety of pre-cast, shotcrete and cast-in-place applications such as bridges, dams, tunnels, swimming pools, water storage and wastewater treatment facilities, reservoirs, pipelines, parking garages, basements and foundations. The Krystol® concrete waterproofing system provides two levels of protection for all cold joints: an integral crystalline waterproofing barrier, plus a physical grout barrier with a compressive strength greater than most structural concretes.

Conclusion
Take the time to assess each system, bearing in mind the specific requirements and challenges of your project. Before you select a waterproofing system, ask lots of questions, carefully review brochures and literature and speak with manufacturers’ technical service reps if you need additional information. It may even be worthwhile to have a manufacturer’s field rep visit the site.
Investing the time to research, compare and select the best waterproofing system for your tank will save you a lot of time and expense in years to come.