What Are Waterstops?

August 30, 2021

Waterstops are a vital part of any construction project where water is involved.

According to White Cap:

Waterstops are important construction elements that prevent water ingress at construction joints. Contractors place these products in concrete structures to form watertight diaphragms at structural transitions where leakage is most likely to occur. Common waterstop installations are between the horizontal and vertical concrete precast components; long length wall areas, where two or more formwork setups are used to cast the structure; and cold joints that may occur during placement. Waterstops are common details on foundations, tunnels, retaining walls, water treatment facilities, bridge abutments, and slabs. These barrier materials are strategic to the long-term performance of a building envelope

Choosing The Right Waterstop

The key selection criteria for a waterstop is whether the construction joint will move or not. Contraction joints, expansion joints, and isolation joints are designed to accommodate significant movement due to drying shrinkage, temperature changes, settlement, creep, or live load deflections. For these circumstances, manufacturers offer a wide range of waterstop profiles designed to match the joint’s expected lateral, transverse, and joint movements.

Common profiles for movement joints include:

1. Ribbed with Centerbulb

Ribbed with Centerbulb profiles are the most versatile and best sealing type of waterstops available. The centerbulb accommodates lateral, transverse, and shear movement.

2. Base Seal with Tear Web

Base Seal with Tear Web profiles accommodate lateral, transverse, and shear movement.

3. Tear Web

Tear Web profiles accommodate large movements. When joint movement occurs, the tear web ruptures and allows the U-bulb to deform without placing the material in tension.

4. Dumbbell with Centerbulb

Dumbbell with Centerbulb profiles accommodate lateral, transverse, and shear movement.

Two Options For Steel Reinforced Joints

There are two options to stop water ingress at construction joints with continuous steel reinforcement at which there will be no movement.

1. PVC Waterstops

PVC waterstop are one option. Flat Ribbed profiles are preferred for non-moving joints and provide the best sealing characteristics. Labyrinth profiles are used in vertical joints. Labyrinth shapes create a keyed joint and do not require split bulkheads.

2. Hydrophilic Waterstops

Hydrophilic waterstops are adhered directly to the surface of the first concrete pour in preparation for the second concrete pour to form the joint area. The material in the strip reacts with water and swells to form a positive watertight seal in the concrete joint. Hydrophilic waterstops are produced in rolls or strips and simple to install. The American Concrete Institute (ACI) recommends against the use of hydrophilic waterstops for hazardous fluids such as fuels, acids, and process chemicals, as the products may not swell as intended in fluids other than water. Hydrophilic waterstops are also available as moulded plugs and rings to create a seal around formwork spacers, center pens and tie rods.

Special Waterstop Considerations

Retrofit waterstops seal joints where new construction meets an existing structure and can be suitable for moving joints. These systems include stainless steel batten bars and fasteners for anchoring to the existing structure with the aid of a structural epoxy gel.

When joints are in conditions that may have chemical exposures, waterstops made with metal or a non-corrosive material can be utilized.

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