Swelling cords: bentonite or acrylic - which one to choose

To seal technological joints in concrete (cold, working, concreting break joints), embedded materials are very often used, which tend to expand upon contact with water, and thus seal the seam itself. Such materials include swelling cords: bentonite or acrylic. They are very similar to each other, have the same principle of operation, and, in fact, the result. What, then, is the difference between bentonite and acrylic cord? Which swelling cord to choose?

Bentonite cord – 75% consists of bentonite clay, as a result of hydration it increases in volume, forming a gel-like mass that fills all cracks and voids and reliably seals the seams of the concrete structure.

Advantages:

• Withstands hydrostatic effects up to 7 atmospheres
• Chemical resistance
• Environmental safety
• Easy installation (does not require highly qualified installers and special tools)
• Installation on a wet base is possible
• Low price

Disadvantages:

• Designed for a limited number of cycles (expansion/compression).
• As a result of a large number of expansion/compression cycles, there is a possibility of delamination and cracking in the cord.
• With prolonged contact with moisture, it may swell prematurely.
• An uncontrolled expansion process can lead to the extrusion of the concrete screed and the formation of cracks and destruction of waterproofing.
• Possible leaching from the seam cavity.

Acrylic cord – consists of an acrylic-based polymer with the addition of rubber and synthetic resins, which increase in volume upon contact with water, in proportion to the amount of water absorbed.

Advantages:

• Unlimited number of expansion/compression cycles.
• Impossibility of leaching from the seam cavity.
• A controlled expansion process that depends on the build-up of pressure. Thus, this process eliminates the formation of cracks and extrusion of the concrete layer.
• Resistant to salt water and various chemicals.
• Withstands hydrostatic effects up to 5 atmospheres.
   

Disadvantages:

• High cost.
• Installation on a wet base is prohibited.

Thus, depending on the technical tasks and many nuances of the design, bentonite or acrylic swelling cords are chosen, correctly assessing the characteristics of both materials.

Both materials are presented in the assortment of Sanpol and you can buy them by contacting our specialists.