Hygric properties of porous building materials (V): Comparison of different methods to determine moisture diffusivity

Abstract

Moisture diffusivity is an important material property for performing the hygrothermal analysis of buildings and the built environment. Its experimental determination is still a challenge, albeit various destructive and non-destructive experimental methods are available. This paper compares the X-ray method, the ruler method, the multi-step method and the Kießl-Künzel method to non-destructively determine the moisture diffusivity of calcium silicate, ceramic brick and lime mortar. Results show that the ruler method can provide the closest results to the well-known X-ray attenuation method with a more straightforward process, but it's mainly suitable for materials with a sharp and visible water front. The multi-step method is easy to operate in experiments and suits most porous building materials, but it takes a long time to condition samples and needs complicated data processing, which seems too complex to get the moisture diffusivity as a step function. The Kießl-Künzel method is the simplest but not always accurate.