Expansion Joints and Watertightness in Concrete: SikaSwell and Waterbar
Quick answer: expansion and construction joints in concrete need specific sealing that can withstand water pressure and structural movement. SikaSwell® A is used inside the concrete, in cold construction joints; Sika Waterbar® O ES is also embedded in the concrete, but in expansion joints with continuous movement, such as water tanks and civil engineering works.
PVC strip with a central bulb embedded in the concrete on both sides of the joint
Expansion joints with continuous movement, water tanks, civil engineering works
Key Difference: Cold Joint vs. Expansion Joint
Construction joint (cold): occurs when concrete pouring is interrupted and resumed later (for example, between the foundation slab and the wall). No movement is expected, but it's a weak point against water. This is where SikaSwell® A fits.
Expansion joint: deliberately designed to absorb the thermal or structural movement of the construction throughout its service life. It needs a flexible embedded strip like Sika Waterbar® O ES.
How They Are Installed
SikaSwell® A is fixed with adhesive or nails onto the already hardened concrete, just before pouring the next phase, so it becomes embedded in the new pour.
Sika Waterbar® O ES is positioned centered in the formwork before pouring, so that half of the strip sits on each side of the expansion joint.
Frequently Asked Questions
Can I use SikaSwell A in an expansion joint with movement?
That's not its primary use: it's designed for cold construction joints with no expected movement. For expansion joints with continuous movement, the solution is a waterstop strip like Sika Waterbar® O ES.
What happens if SikaSwell A gets wet before pouring concrete over it?
If it swells prematurely due to contact with water or rain before pouring, it loses some of its sealing capacity; it must be protected until the moment of pouring.
Can both systems be combined on the same job?
Yes, it's common practice: SikaSwell A in cold construction joints and Sika Waterbar in the expansion joints designed into the project, such as in a tank or basement.
