Hydro-expansive rubber plug for tubular PVC formwork spacers

Code: PRS.0028

Components: 1

Appearance: Plastic plug

CORKSEAL T­21 is a special sealing closure device for tubular formwork spacers, consisting of a rigid core made of polyamide plastic material and a corrugated cap in hydro-expansive rubber. The core of CORKSEAL T­21 is provided with special circular lamellas that surround it and that, if properly inserted into the spacer, provide a high pressure mechanical seal, so that the sealing element is not removed from the seat where it is placed even in the presence of negative thrust. CORKSEAL T­21's hydro-expansive cap is designed to ensure the hermetic sealing of the internal part of the tubular spacer.

Linee di appartenenza

General characteristics


Diameter: 21 mm


Hydroexpansive product: +200 / +900 %




Shelf-life: 24 months


Suitable for contact with drinking water

Technical specifications

Alkali-resistant material

Non-toxic material


Available colours

- Blue

Packaging and dimensions

- Small bag 100 unit


No. 1 cap of CORKSEAL T21 for each formwork spacer provided, preferably on the side where the water exerts positive thrust.

Use fields

Concrete subterranean construction by metal formwork, where the wall is in direct contact with the ground and where there is the presence of waterproofing layers external to the masonry itself: basements, tavernas, underground garages, underground rooms and basements, etc. CORKSEAL T­21 is designed for tubular spacers of 21 mm inner diameter, normally used in the construction industry.

Use method

The sealing protection CORKSEAL T­21 should be used after the removal of metal formworks, thus only on spacers already "in work" and immersed in the concrete. The installation of the sealing protection to be executed by simply inserting the plug by hand, inside each empty spacer, as far as possible, to then complete the insertion using a light hammer until "full insertion".

Even though CORKSEAL T­21 has been designed and tested to withstand pressures up to about 5 bar in negative thrust (i.e. from inside the masonry), it is advisable to apply the product in positive thrust, therefore, by inserting it from the external side of the masonry, after stripping and before backfilling.

It is advisable to use the product in combination with non-"preformed" spacers (which often have changes in diameter depending on the model and which therefore might affect the hermetic sealing at high pressures of the protective sealing. It is recommended to use the spacers sold in rods to be cut to size directly on site .

The insertion of CORKSEAL T­21 in spacers not assembled in the works (in the absence of external contrast) could cause the spacer itself to break.

In cases of expansion with very marked changes in volume (>500%), and in the absence of restrictive conditions, there may be some superficial lacerations; these phenomena do not compromise the features that protect the protective sealing and especially they do not occur under normal operating conditions, i.e. when the expansive phenomenon is in constrained conditions with reference to the usable volume (inside the spacer).

Application methods

- Hammer

Permitted supports

- Concrete

- Tubular spacers for steel formworks

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