Waterstop with sodium bentonite and expanding rubber base

Code: PRS.0014

Components: 1

Appearance: Stripe

Preformed hydro-expansive sealing waterstop joint, for hermetic sealed construction joints in structures, walls and foundations, made with a mixture of sodium bentonite, expanding rubber and special aggregating polymers ("hydrocarbon" ). CLAYSEAL 25.20 has a rectangular cross-section of 25x20 mm, packaged in rolls of 5 m each.

General characteristics


Hydroexpansive product: +350 %


Shelf-life: 12 months


Density: 1.4-1.5 kg/dm³


Temperature of use: -15 / +50 °C

Technical specifications

Unit weight

0.67 kg/m

Expansion after 7 days at pH 7

350 %

Fire resistance

B 2 _

Expansion after 7 days at pH 12.33

128 %

Longitudinal elongation at break

60 %

Sodium bentonite content

> 60 %


Available colours

- Black


CLAYSEAL 25.20 is a simple and easy to apply sodium bentonite waterstop; it does not require any special preparations of the media, pre-shaped seats etc. It is easily fixed by nailing and does not require any special protection. In contact with water, it increases its volume through the formation of a stable colloidal system that guarantees the permanent hermetic sealing of the connection; the initial expansion is delayed through a retardant coating with respect to the first contact with water, to avoid deformations in the initial hardening phase of the fresh concrete.

Use fields

Rigid construction joints (non-expanding) and connections with safe and permanent hydraulic seal.

Preparation of supports

Prepare the smoothest and most planar laying surface, using REPAR TIX to compensate for any inhomogeneity, and accurately remove crumbling, non-adhering, powdery parts.

Use method

Hand spread the CLAYSEAL 25.20 sodium bentonite waterstop in the designated position. Fixing is performed by nailing: one steel nail every 20-25 cm approximately. The sealing of joints between the waterstop kerbs is ensured by simple flanking by at least 10 cm and not by overlapping the ends.

For particularly complex applications, the specific BENTONET steel wire cage, with square mesh 13x13 mm, in profiles of 1 metre each, is available.

Application methods

- Hammer

- Apply by hand

Permitted supports

- Concrete

- Cement-based or lime-based mortars

- Prefabricated concrete

- Rock walls

Warnings, precautions and Ecology

The positioning must ensure a concrete covering of 10-12 cm in order to contain the expansive action caused by hydration. Similarly, the formwork spacers should be placed in such a way as to maintain a minimum distance of 8 cm from the bentonite kerb itself.

Although the product has a delayed expansion of 48h, it is not recommended for use in cases of earlier time-frames or with excessive humidity (for example in the presence of puddles).

In case of groundwater with a high saline content or for leachate and waste water stops, carry out preliminary expansion tests or request the specific waterstop CLAYSEAL 25.20 SW.


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