1.1 This standard defines a procedure to determine the water absorption coefficient of a material by partial submersion. The scope is to evaluate the rate of absorption of water due to capillary forces for building materials in contact with normal or driving rain above grade. The procedure is typically suitable mainly for masonry material, plaster, or a coating in combination with a substrate; but it can also be used for insulation materials. It is not within the scope of this standard to determine liquid uptake phenomena in below-grade applications. The water absorption coefficient is mainly used as an input datum for numerical simulation of the combined heat and moisture transport in building envelopes for design and forensic investigation purposes 1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. However, derived results can be converted from one system to the other using appropriate conversion factors
Talking about numerical simulation of the combined heat and moisture transport and storage, most important material properties as well as their determination are covered by ASTM standards. The only important material property which is missing is the liquid water absorption coefficient. This material property is an integral property summarizing the capillary activity of all different pores sizes of a material. The determination of this material property is already covered by ISO 15148. I used this ISO standard as basis for the ASTM proposal, extended the units to be SI as well as IP. Furthermore I made one major change regarding the content as follow. In case the measurement does not result a constant slope (which is defined to be the absorption coefficient) the average slope within the 24 hours time span should be used for the absorption coefficient. I think there is no justification to use 24 hours. Furthermore, if this material property is used for hygrothermal simulation, a time span which represents an average rain incident is supposed to be much more appropriate. Therefore I replaced the 24 hour time span with a 4 hour time span. I should mention that this approach is state of the art at Fraunhofer IBP for many years when measurement results are used to create material properties for hygrothermal simulation.
Keywordsliquid water absorption, test method for, hygrothermal simulation.
The title and scope are in draft form and are under development within this ASTM Committee.Back to Top