Hydro-expansive rubber seal for spacers of the tubular formwork

Code: PRS.0142

Components: 1

Appearance: Gasket

RINGSEAL T­21 is an o-ring made with a specialised hydro-expansive rubber that in contact with the water reacts by increasing its own initial volume. RINGSEAL T­21, used in combination with a tubular spacer for metal formwork, hermetically seals any discontinuities which could easily settle in the concrete due to the presence of the spacer, and which would compromise the watertightness of the masonry itself.

General characteristics


Shelf-life: 24 months






Diameter: 21 mm


Suitable for contact with drinking water


Hydroexpansive product: +200 / +900 %

Available colours

- Blue

Packaging and dimensions

- Small bag 100 unit


In the standard version the seal RINGSEAL T­21 is designed for tubular spacers with 21.5 mm inner diameter (without external ribs), normally used in the construction industry and usually having an outer diameter of about 24 mm. Given the elasticity of the seal, greater diameters up to about 30 mm are tolerated.


No. 1 RINGSEAL T21 gasket for each tubular formwork spacer (average 1 - 2 pieces per square metre for metal formworks).

Use fields

Construction of subterranean structures in concrete by metal formwork, where the wall is in direct contact with the ground and where there is the presence of waterproofing layers outside the masonry itself: basements, garages, underground rooms, etc.

Use method

Manually place the hydro-expansive seal RINGSEAL T­21 around the spacers of the formwork, in a central position. Build the planned formwork using the tubular spacers thus prepared and proceed with the usual operations of casting the concrete.

Application methods

- Apply by hand

Permitted supports

- Concrete

- Tubular spacers for steel formworks

Warnings, precautions and Ecology

Do not use RINGSEAL T­21 with spacers with outer diameter less than 23.5 mm. Further, spacers with protruding external ribbing cannot be used, as their non-circular shape does not allow the protective sealing to adhere to the outer surface of the spacer, making it ineffective.

In cases of expansion with very marked changes in volume (>500%), and in the absence of restrictive conditions, there may be some lacerations of the seal; these phenomena do not compromise the features that protect the protective sealing at all, and they especially do not occur under normal operating conditions, i.e. when the seal is inserted in confined spaces.


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