The application of X-ray absorption to building moisture transport studies

It is well accepted within the international research community that there is a requirement for a high resolution facility for carrying out multi-dimensional moisture content measurements under transient conditions. This investigative tool should be capable of accommodating material samples large enough to incorporate the various macroscopic features, including mortar joints and material interfaces, which are known to exert a significant influence on moisture transport within building envelopes. Such a tool, based on the principle of X-ray absorption, is being developed at Glasgow Caledonian University. A brief description of the facility is given here, together with modifications which allow the imaging of samples to be generated using computer-aided tomography. Also reported are the results of liquid water diffusivity experiments carried out on four masonry materials. These formed part of the calibration and validation procedure. The test data, describing the evolution of moisture content with time at various locations from a wetting plane, were collapsed to single curves using the Boltzmann transformation. These curves were then fitted to yield liquid diffusivity for application within moisture simulation models. The relationships derived are based on a novel simplified approach, which is easier to apply than the complicated procedures generally adopted hitherto.