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Waterproofing of Periodically Moving Cracks and Joints Using Xypex Products


Xypex Crystalline Technology is excellent for reducing the water permeability of concrete and for the healing of leaking, non-moving cracks and joints in concrete structures. The Xypex crystalline formation will bridge most non-moving cracks up to 0.4 m (1/64”). In situations where the cracks are larger, i.e. more than 0.4 mm but less than 3 mm (1/8”), the Xypex chip-and-pack method is used to form a ‘plug’ at the top portion of the concrete cross section, and the Xypex crystallization process heals any crack that may telegraph up through the repair. (Note: while not promoted, Xypex is aware of field reports showing the crystalline healing of cracks that are significantly larger than 0.4 mm and that have not been routed or packed.)

For cracks subject to ongoing or periodic movement and where short-term weeping or leakage is unacceptable, Xypex FCM 80 can be used to stop water leakage. Tests have confirmed that Xypex FCM 80 will give 20% - 40% “elongation to break”. This means that the material will stretch between 20% and 40% of its un-bonded length prior to breaking. Therefore, if FCM 80 is applied over a 0.4 mm (1/64”) crack, it will accept up to 0.16 mm (0.006”) of ongoing movement without rupturing.

In situations where there is greater than 20% to 40% movement or an unsupported width of more than 0.4 mm (1/64”), we recommend using a thin, flexible rubber tape such as “Scotch Linerless Rubber Splicing Tape” as a bond-breaker. This tape is placed over the crack before the FCM 80 is applied. The diagram below illustrates a typical 19 mm (3/4”) bond-break tape assembly using FCM 80 over a 3 mm (1/8”) crack that has 1.5 mm (1/16”) of movement over its width.

Note: a crack with +/-0.75 mm (1/32”) of movement over its neutral position is deemed as having 1.5 mm (1/16”) total movement since the crack’s actual position is unpredictable at the time when the assembly is installed.

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