Measurement of moisture profiles in porous materials based on optical perception

Moisture profile measurement is a key material characterisation procedure in building science and drying technology. The current standard method followed for this is X-ray attenuation, which is expensive in terms of acquisition and can lead to complex data processing and high occupational-safety standards. We present a method based on the changes in optical perception at different moisture saturations. The experimental setup is inexpensive, and the data are easy to process. We test autoclaved aerated concrete, ceramic brick, calcium silicate, and gypsum using this method. Calibration samples with a known moisture content yield correlation functions that are used to calculate moisture profiles from the changes in optical perception. The results are compared to X-ray results obtained from literature. Calcium silicate exhibits good compliance with the reference data, with a deviation of 2–5 % to our control measurement. Results for autoclaved aerated concrete and gypsum differ by 5–6 %. Brick shows a broad moisture range with no change in colour and is therefore challenging for correlation. It differs 8–11 %. The results demonstrate the potential of the proposed method. The approach is restricted to materials with a one-to-one relationship between colour and moisture content, but it has the potential to serve as a complementary method to the current moisture profile measurement techniques.