Swelling tape

Technologien und Beratung für den Betonbau - B.T. innovation

Sealing tapes for joints

A swelling tape is a joint sealing material that increases its volume by absorbing moisture. Swelling tapes are divided into different types depending on the material and are used, for example, for sealing construction joints and joints exposed to water. With the corresponding building authority approval, the sealing tapes are permissible for WU constructions and are installed in accordance with the WU guideline of the German Committee for Reinforced Concrete Construction (DAfStB).

B.T. innovation has developed a perfect equivalent to this high-performance sealing tape. The building materials InnoElast® and SynkoElast® made of modified bitumen sealant achieve the sealing effect by chemically bonding with the cement, especially with SynkoElast® there is a “caking” of the structures. Also to be mentioned in this context is the product RubberElast®, which gets its high tightness in the installed state from its compressibility.

In the construction sector, especially in concrete construction, different types of joints are distinguished. Sealing with swelling tape is generally suitable for joints that need to be permanently protected against water penetration. A distinction is made between the following types of joints:

  • Movement joints used to compensate for different settlements and temperature differences.
  • Construction joints, also known as concreting joints, occur when an area to be concreted or a concrete component is too large for one work step. In this case, work is done in sections and the aforementioned joints are created. Swelling tapes can be ideally used as a seal for this type of joint in particular.
  • Mock joints are incorporated into the fresh concrete as controlled predetermined breaking points in the form of notches. The depth of a dummy joint must be at least one third of the component cross-section and is not sealed.

DIN 18195 “Building waterproofing” with Parts 1 to 10 describes all types and possibilities of joint waterproofing. In part 1, the different types of waterproofing are used. The choice of waterproofing depends, among other things, on the type of water attack, building ground, stress and use.

The WU guideline “Water Impermeable Concrete Structures”, which was prepared by the German Committee for Reinforced Concrete (DAStB), also provides information on sealing and the use of waterstop tapes.

In some cases, swelling joint tapes are equated with the so-called Kompriband, which is also used to seal joints. This is not correct, because there are crucial differences: On the one hand, the Kompriband consists of a polyurethane-based foam mixture. Its ability to expand does not depend on the addition of water, but on a pre-compressed material slowly unfolding to fill the joint. The reset is purely mechanical, neither chemical reactions nor special physical processes take place.

While swelling joint tapes reliably seal the joints against water, the Kompriband is suitable for creating driving rain and wind tightness. The sealing tape is also used, for example, to seal windows and doors.

The inorganic bentonite is a rock consisting of various clays and 60 to 80% montmorillonite. The frequently encountered layered silicate has a great ability to absorb water and a large swelling capacity. These properties make the material ideal for use in swelling tapes. In addition to bentonite, other substances are added to the sealing tapes to ensure flexibility, durability and ease of application. Bentonite swelling tape can be used, for example, to seal structural joints that are permanently contaminated by groundwater, slope water or surface water. With the corresponding building authority approval (AbP), use in watertight constructions is also possible.

The so-called water-reactive swelling tapes are not made with bentonite, but with an extruded rubber mixture. As a swelling joint tape, these materials are usually used in the area of prefabricated reinforced concrete construction, as it can only absorb water pressures of up to 5 bar. Rubber (for example butyl rubber), water-swelling resins, silicones and other additives are processed into a material that swells strongly in contact with water and thus seals joints reliably and flexibly. Due to the large swelling capacity of up to 400%, even joints and gaps with variable widths can be sealed reliably; even unevenness or rough surfaces do not affect the functioning of the swelling tape.

Sealing is achieved by the contact pressure created during swelling. Once a water-reactive swelling band is activated, this process cannot be reversed. The flexible sealing tapes are used, for example, in segment or element construction as well as in tunnel construction. The swelling tapes are available in various standard sizes and can thus be used as required.

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