As temperatures fluctuate, concrete expands and contracts. This doesn’t make it unique from other materials, but it does present a challenge for contractors who are building concrete structures. Expansion joints are needed to prevent walls from cracking when expansion and contraction occurs, and these joints can allow water into the structure. For this problem, contractors turn to waterstops. which can be manufactured from a variety of materials, but always fall into one of two categories.
- Non-moving joints
If there is no movement of the adjoined concrete sections, as you would find in a cold joint between a footing and foundation, it’s considered a non-moving joint and calls for a specific type of waterstop. Typically, these will use expanding Bentonite clay as the active component. In most cases, whatever the material being used, this application calls for a hydrophillic waterstop. In basic terms, when the material used to make the waterstop is exposed to water, it will expand to form a compression seal. This is an effective way to seal joints with no movement, but is easily broken if this type of waterstop is used in a joint with movement.
- Joints with movement
If there is movement between the adjoined concrete sections, as you would find in a dilation joint, a simple rubber or clay hydrophillic joint won’t hold up. Instead, a mechanical waterstop is needed that’s able to create a diaphragm by spanning from one side of the joint to the other. It’s typically understood that a mechanical waterstop is what’s needed when designers use the term waterstop. Again, a variety of materials can be used to create a mechanical waterstop. PVC and rubber are the most common materials used, but you’ll also often see copper and stainless steel used in some applications. Unlike for non-moving joints, waterstops for joints with movement must be installed before concrete is placed. Once construction is finished, the waterstop should be encased in concrete with the center of the waterstop aligned with the center of the joint.
At Maxwell Supply in Tulsa, we carry the products you need to complete your concrete projects, including waterstops. Give us a call, stop by and see us or browse through our inventory right here on our website.