Waterstops or waterbars are premanufactured joint filler used to prevent the transmission of water through the construction joint. Waterstops are mainly used for the waterproofing of below-grade concrete structures like tunnels, water treatment facilities, parking structures, water reservoirs, sewage treatment facilities, and marine structures.
The basic features and types of waterstops used in construction are explained briefly in the article.
Waterstops for Construction Joint
Waterstops are highly demanded in locations where the construction joints are common:
- The transition area between the horizontal and vertical concrete components.
- Long length wall areas, where two or more formwork is required for casting
- Situations when concrete placement is paused or stopped for some reason
- Where a change in design form is required for the design elements.
The construction joint is also referred to as cold joints which occur when the before placed concrete cures earlier than the adjacent one. These are the most likely areas which can result in water ingress. In most of the cases, the construction joint is not actually formed. But, a construction joint, like the control joint is introduced in order to facilitate the shrinkage caused due to large displacements.
Also Read: Construction Joints
Most of the below-grade concrete structures have conditions that result in the infiltration of the water into the construction joints. To prevent such leakage, waterstops are introduced into the construction joint. Waterstops have proven best for such infiltration issues observed in the construction joint.
Material for Waterstops
Waterstops are premanufactured joint fillers that come in numerous size, shapes, and types. The most widely used waterstops from 1950s are made from PVC. PVC waterstops are flexible and strong. New materials like asphalt, myriad metal, hydrophilic materials with different compositions are now commonly used for the manufacture of waterstops that suits the varied application in construction.
The waterstops are available in the following compositions:
- Neoprene Rubber
- Polyvinyl Chloride (PVC)
- Thermoplastic Rubber
- Hydrophilic
- Bentonite Clay
- Asphalt Plastic
Types of Waterstops
The 4 major types of waterstops are:
- PVC Waterstops
- Bentonite Waterstops
- Urethane Waterstops
- Metalic Waterstops
1. PVC Waterstops
A PVC waterstops is installed on either side of the construction joints, hence creates a tough physical barrier. Based on the type of construction joint, the width, size and thickness of the waterstop varies. A PVC waterstop due to its material property can be installed in any climatic conditions. These tend to be highly durable.
The installation of PVC watertsop is carried out during the concrete process, which if not performed carefully results in the damage of the PVC joint.
2. Bentonite Waterstop
Bentonite waterstop is a type coming under the hydrophilic waterstop category. Bentonite, as we know is a swellable clay compound. It has the property to expand sixteen times when it comes in contact with the water.
This filling property is used to seal the concrete joints. This waterstop actually compression seal the system thus filling the cracks and the voids in the concrete.
One of the challenges in installing this system is that the bentonite must be maintained dry until it is poured into the joint which has to be sealed. Premature exposure of the bentonite to moisture results in the damage of the joints and weakening of the concrete around the joint.
In the long run, the number of expansion and contraction of the bentonite waterstops reduces. Hence it is necessary to replace it. Hence, bentonite is best suited for areas when moisture and extreme weather conditions are not so frequent.
3. Urethane Waterstops
Urethane waterstops also comes under the hydrophilic category. This material also swells and forms a compression seal in the construction joints in the concrete structure. An increase of 350% is expected by this type.
Urethane waterstops can be either applied in the form of strips or by means of a caulking gun, which makes the installation process easy. This material requires 24 hours for curing, only after which concrete pouring is expected to perform. So, throughout the curing process of the concrete, the urethane material must remain dry. Long exposure of waterstops to water results in its wear out.
4. Metallic Waterstops
Metallic waterstops are mostly made from bronze, steel, lead or copper. These waterstops are embedded similar to PVC waterstops. These are very strong and can be exposed to extreme temperature conditions and chemical atmosphere. This is hence highly applied in the construction of dams and heavy construction projects.
Also Read: How to Cut Control Joints in Concrete?