Media

Protecting concrete joints

Mena Infrastructure – Q3 2010

Kryton International Inc.’s ALIREZA BIPARVA explains how to find the best waterproofing solution for the most vulnerable part of your concrete structure.

Joints play a vital role in fortifying concrete structures. But when it comes to waterproofing, joints represent the most vulnerable part of the structure. Without an effective joint waterproofing system, it’s not a matter of if joints will leak, but when.

A construction joint, also referred to as a cold or nonworking joint, marks the spot where two sections of concrete meet. It is a pre-planned separation in the concrete that allows for limited movement caused by natural factors such as seismic activity or freeze-thaw cycles. The waterproofing challenge posed by these joints for contractors and engineers lies in their design itself – the physical separation between concrete slabs creates vulnerability where water ingress is likely to happen.

Leaking joints can not only result in costly repairs but, incoming water can bring contaminants into the concrete, corrode steel reinforcements, jeopardise structural safety and shorten the overall lifetime of the concrete structure. So, protection is a must.

In the past, waterstop systems have been used to act as a physical barrier to block water penetration at joints. The most common, PVC, is a plastic strip that is put in place before the concrete is poured. Half of the PVC sheet is submerged into the joint area while the other half is secured into the formwork. The strip must be spliced correctly and rebar installed without puncturing or cutting the PVC. In addition, extreme care needs to be taken during the concrete pouring and compacting to ensure that the PVC is not displaced or folded. Installation is difficult and often done incorrectly, leaving joints at risk of leaking. To make matters worse, once the damage has been done, it’s virtually impossible to recognise a problem until the joint starts to leak.

Over the last 25 years, more advanced and economical waterproofing systems and materials for joints have been developed. These new systems are easier and more efficient to use and most importantly, give your structure longer lasting protection.

One of these systems is Kryton International Inc.’s Krystol Waterstop System. This revolutionary system provides both a physical and chemical barrier to water ingress. It relies on two products for guaranteed protection: Krystol Waterstop Grout, the physical barrier, and Krystol Waterstop Treatment, the chemical barrier. When mixed with water, Krystol Waterstop Grout forms a stiff putty like consistency that is molded into a triangular strip along the centre of the joint. Krystol Waterstop Treatment is then brushed on top of the grout and around the joint area. The Treatment comes in a powdered form that is mixed with water to form a slurry consistency. Once applied, active crystalline chemicals in the slurry cause microscopic crystals to grow, permanently blocking the movement of water (Fig 1). When the Treatment has hardened, you are ready to pour the remaining concrete and can do so with confidence that your joint is waterproof.

Kryton’s innovative system has been growing in popularity because it offers several fundamental advantages to traditional joint waterproofing methods. The Krystol Waterstop System is quick and easy to install. It does not require skilled labour and adheres extremely well to concrete surfaces. Unlike PVC waterstop treatments, Kryton’s system is not at risk of being displaced or folding during concrete pouring. Additionally, because the system uses Kryton’s proprietary integral crystalline waterproofing formula, it has the ability to self-seal small cracks that may develop over time. It is durable, long-lasting and will give you the peace of mind you need when tackling a concrete joint waterproofing project.

Every concrete jointing system will have its advantages and limitations. What is critical is that you take the time to consider what is appropriate for your construction project. Look at your project timeline and budget. Think about how much risk of failure you are willing to take and the level of protection you need. Then make the best decision that will guarantee watertight joints for the lifetime of your concrete structure.

Alireza Biparva is Technical Services Rep/Concrete Specialist, Research & Development at Kryton International Inc. Ali received his M.A.Sc. in civil engineering from University of British Columbia specialising in cement-based materials, and Bachelor Degree in Engineering from Shiraz University of Iran.