Durability—Resistance to Water Absorption
This requirement is closely related to the requirement that waterproofing resist hydrostatic pressure as well as water vapor. Because waterproofing may be immersed in water for the life of the building, the membrane’s important properties must not diminish as a result of water immersion. Customarily, materials are tested for water absorption at elevated temperatures with the intent of accelerating the effects of water immersion. Refer to Table 6 for a review of standards.
Cold liquid-applied materials test methods in Table 6 are appealing because they test the effect of water immersion on an important property, adhesion. However, the authors have observed excessive water absorption in cold liquid-applied waterproofing materials that meet the requirements of ASTM C 836. Because of this field experience, we believe that a water absorption test such as is specified for hot liquid-applied and for single-ply waterproofing would be an appropriate addition to ASTM C 836.
While single-ply materials are tested at 70°C (158°F), testing liquid-applied materials at a lower temperature, 50°C (122°F), may be suitable. It should be noted that plaza membranes in hot climates may reach a temperature in the range of 50°C (122°F). Testing at 50°C (122°F) should not be regarded as excessive, especially for products that may be installed in hot climates.
At the time when bentonite standards are developed, water absorption must be considered in an
TABLE 6—Durability—Requirements related to resistance to water absorption. Values and units are stated in the table as they are expressed in the standards.
entirely different way. Water absorption is essential to the proper functioning of bentonite. Bentonite should hydrate quickly enough to prevent leakage, but it is preferable if the product does not prematurely hydrate due to exposure to rain or ground water during construction. Manufacturers offer special formulations that promote water absorption in certain conditions, such as saltwater.