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The Importance of Waterproofing Joints
Construction World - October 2006

While joints play a vital role in fortifying concrete structures, they represent the most vulnerable part of the structure from a waterproofing perspective. Without an effective joint waterproofing system (known as a waterstop system), it's not a matter of if a joint will leak, but when.

A leaking concrete joint is more than simply a costly inconvenience. In the case of residential or commercial structures, incoming water or moisture can lead to the growth of mold or fungus. A leak in a concrete water tank can contaminate potable water or facilitate the escape of waterborne contaminants into the surrounding environment. Incoming water or contaminants can corrode steel reinforcement, jeopardize structural safety and shorten the lifetime of a concrete structure.

Types of Concrete Waterstop Systems

PVC Waterstops
PVC waterstops are flat strips of high-quality PVC that are embedded into both sides of a construction joint to provide a physical barrier. They're time-consuming to install and they can easily become damaged during a concrete pour and it's virtually impossible to know whether damage has occurred until the joint begins leaking.

Bentonite
Bentonite is a swellable clay waterproofing compound that is glued or nailed in strips into construction joints. Known as a hydrophilic waterstop system, bentonite expands up to sixteen times its dry volume when it comes into contact with water, forming a compression seal in concrete joints. Bentonite's ability to swell enables it to fill small cracks and voids in concrete, preventing the
ingress of water around joints. And since clay is a natural material, bentonite is a popular waterstop choice for potable water applications.

Urethane Waterstops
Urethane waterstops are spongy, hydrophilic compounds that, when exposed to water, swell up to 350% of their original volume, forming a compression seal in concrete joints. Urethane waterstops must be allowed to cure for 24 hours before concrete is poured, and keeping the applied urethane dry in the interim is essential. Similar to other swellable waterstop systems, urethane waterstops will eventually dry, crack and deteriorate.

Metallic Waterstops
Made of steel, copper, bronze or lead, metallic waterstops are embedded in concrete across joints to form a continuous, fluid-tight barrier. Metallic barriers must be embedded and maintained in an upright position across the joint while pouring concrete to ensure they do not fall over or become damaged during pours.

Crystalline Waterstops - The Krystol Waterstop System™

Crystalline waterstop systems utilize advanced integral crystalline waterproofing (ICW) technology to block the movement of water through concrete joints. When applied to concrete, ICW chemicals cause microscopic crystals to grow, permanently sealing the spaces between concrete particles and blocking the movement of water. In a crystalline waterstop system, a cementitious mixture containing highly concentrated ICW chemicals is applied to the joint site before a new wall is poured.

Crystalline waterstops are growing dramatically in popularity because they offer several crucial advantages over other systems. They're quick and easy to install and do not require skilled labor. Premium crystalline waterstop systems have the ability to self-seal small cracks. When a micro-cracks forms in crystalline-treated concrete, incoming water causes additional ICW crystals to grow, filling the crack and maintaining a watertight seal.

Crystalline waterstops like “KRYSTOL WATERSTOP SYSTEM™” combine two levels of protection – a virtually indestructible physical barrier and a crystalline chemical barrier. Many crystalline waterstop manufacturers also produce waterproofing systems for walls and slabs, offering one-manufacturer accountability for an entire structure.

Unlike some other waterstop systems, crystalline technology lasts the lifetime of the concrete structure. And unlike the vast majority of waterstops, crystalline technology can be used to retrofit areas where no waterstop system was installed, or where the installed system has become damaged or deteriorated over time.

Crystalline waterstops are highly affordable and can cost up to 50% less than bentonite or PVC waterstops.

Choosing the Right Waterstop System

With so many different types of waterstop systems available, it's important to choose the one that's right for each concrete construction project. Since costs and installation times vary widely between systems, budget and construction timeline should be key considerations. Consider also what's at stake if the waterstop fails – if a leak jeopardizes zero-tolerance areas such as electronics or computer rooms, you may want to choose a waterstop system that's less likely to become damaged during concrete pours.

Download the complete Article in ADOBE ACROBAT (.PDF) format.

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