How a bentonite swell bar works
The swell bar is fixed to the cured face of the first concrete pour, along the centre of the construction joint, before the next pour is cast over it. When water reaches the joint, the sodium bentonite hydrates and expands within the confined space, filling voids and forming a dense, low-permeability seal that resists hydrostatic pressure from groundwater.
Installation good practice
Keep the bar dry and protected from rain or standing water until it is covered by concrete, because premature hydration reduces its sealing capacity. Fix it firmly so it cannot move during the pour, and maintain adequate concrete cover on both sides as advised by the designer. For joints that may cycle between wet and dry, or where early water contact is likely, compare it with our hydrophilic swell bar.
