Experimental determination on the capillary water absorption coefficient of porous building materials: A comparison between the intermittent and continuous absorption tests

The liquid water transfer in porous building materials has a great influence on the hygrothremal properties of the materials. The capillary water absorption coefficient a key parameter characterizing the water absorption capability of porous building materials, which is essential to the simulations of moisture transfer. However, the traditional standard measurement (partial impregnation method) which has been widely used today has some disadvantages, such as human error and discontinuous testing. In this paper, an improved continuous measurement method, which is still based on the partial impregnation strategy, was proposed, featuring continuous and automatic data acquisition during the adsorption tests without interruption by an operator. As a typical porous building material, autoclave aerated concrete (AAC) featuring lightweight and high porosity was taken as an example to study the effects of the method on the measured results of capillary water absorption coefficient. Comparisons were made between the results of traditional standard and continuous measurement methods. It was shown that this improved continuous method avoids the process of intermittent sample extraction and weighing, making it more convenient than the standard method. The continuous method was deemed to have the advantages of high precision, simple operation, and high repeatability.