Determination of moisture distributions in porous building bricks by neutron radiography

Abstract Water transport into construction building materials is an important subject since it may deteriorate them because it can carry harmful biological and chemical substances. Some of the reported results in literature for moisture transport in construction building materials follow Fick's law of diffusion while others show anomalous diffusion. There is not enough reliable and accurate data in the literature to discuss this issue. Therefore, in the present work moisture transport into four different kinds of brick samples was studied using the real time neutron radiography method. Neutron radiography images were registered continuously during the moisture absorption process. Simple procedures based on the Cd-umbrella method were used for the first time to correct for the neutron scattering during the water absorption process. The images showed clearly that the absorption process is different from one sample to another. The water content distribution along the flow direction, x (profiles) and positions of water front as the time of moisture absorption elapses were determined from the images obtained. The results obtained showed that the water front positions do not scale with the square root of the absorption time. It was shown that moisture diffusion processes in the samples investigated could be described by an anomalous diffusion approach of the sub-diffusive type. The moisture diffusivities were determined for every sample. The neutron radiography method and the neutron scattering correction procedures used are proven to be a powerful and effective for studying transport process in porous media.