Three Factors Affect the Quality of Bentonite Swellable Waterstops

All our waterstops are manufactured in accordance with national standards and have undergone strict tests before leaving the factory to ensure high quality. However, the quality of waterstops on the market varies widely. You may use the following method to check whether bentonite swellable waterstops are qualified.

  • Volume expansion rate

    Bentonite swellable waterstops are further divided into C type (expansion type) and S type (slow expansion type).

    1. Use a sharp knife to cut three samples with a dimension of 30 mm × 10 mm × 10 mm. Each sample weighs about 4 g. Put a bridge-shaped bracket on the balance pan for testing.
    2. First weigh the mass of samples in air M1 and the mass of samples immersed in water m1 (before immersion).
    3. And then immerse samples in water. Weight the mass of samples in air M2 and the mass of sample immersed in water m2 every 2 hours.
    4. Weigh the mass of samples in air M2 and the mass of sample immersed in water m2 every 12 hours.
    5. Keep measuring until the volume expansion rate is basically fixed. C type products shall be measured by 24 h while S type products shall be measured by 240 h.

    The average value of three samples is taken as the volume expansion rate, and is calculated as follows:


    • △V represents volume expansion rate, expressed in %;
    • M1 represents mass of samples in air before immersion, expressed in expressed in g;
    • M2 represents mass of sample in distilled water before immersion, expressed in g;
    • m1 represents mass of samples in the air after immersion, expressed in g;
    • m2 represents mass of samples in distilled water after immersion, expressed in g;

    According to the equation aforesaid, calculate the volume expansion rate at corresponding period. The results that meet the following technical data are considered as qualified.

  • Heat resistance

    Prepare three samples with a length of 100 mm. These samples were passed through a wire and suspended in an oven at 80 °C for 2 h. Observe whether the heated samples have flow trace. If three samples have no flow trace, it is considered as qualified.

  • Low temperature resistance

    Prepare three samples with a length of 150 mm. Lay these samples flat and a metal rod with a diameter of 20 mm in a refrigerator at -20 °C for 2 hours. Open the refrigerator door, place the frozen samples on the metal rod surface within 3 seconds. Wind these samples around the metal rod at 180° and take them out. Observe these samples with a 5x magnifying glass. The three samples are considered as qualified if there is no crack on the surface.

    Bentonite Swellable Waterstop Technical Data
    Material Test Item Technical Index
    C Type S Type
    Bentonite Swellable Waterstop Volume expansion rate within specified period 4 h 200% – 250%
    24 h 200% – 250%
    48 h
    72 h
    96 h
    120 h
    144 h
    Maximum volume expansion rate (%) ≥ 4 00 ≥ 300
    Heat resistance 80 °C, 2 h, no flow
    Low temperature resistance -20 °C, 2 h around φ 20 mm round rod, no crack

    Only when all technical indicators are met, it can be deemed as qualified. If an indicator fails to meet the technical requirements, double samples shall be prepared for retest. If the test result is unqualified, this batch of products is considered as unqualified.

All our products are produced in strict accordance with national standards, and each batch of products will be tested before leaving the factory. Corresponding test report will be provided, you can buy these waterstops without worry.

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Hengshui Jingtong Rubber Co., Ltd.

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