Moisture in building materials and components is a key aspect to be considered when assessing buildings performance, as it may influence their durability and mechanical resistance, thermal comfort and indoor air quality and buildings energy efficiency. Therefore, studying the humidification phenomena is of major relevance. The presence of moisture in building materials/components is related to temperature variations. The surface temperature of the object can be measured using infrared thermography (IRT), a non-destructive technology to assess the buildings behaviour. Hence, it is important to understand its applicability to assess moisture related phenomena. In the present study an analysis of the humidification phenomena using IRT was intended. Lightweight concrete specimens were used and tests were carried out under stable hygrothermal conditions. Two different humidification conditions were assessed: (1) partial humidification by the specimens' bottom surface; (2) partial humidification by the specimens' top surface. Thermal images were taken periodically during 24 hours. Both qualitative and quantitative analysis of the results was performed. The results pointed that assessing the humidification phenomena using IRT is possible under stable conditions. The boundary conditions for the humidification process affected the results interpretation as it was easier to detect moisture when the surface under study was in direct contact with liquid water (partial humidification by the specimens' bottom surface). In this case clearer surface temperature differences could be found between the moist and the dry areas, which appear sooner in time. The surface temperature decrease was marked near the bottom during humidification by the bottom and near the top during humidification by the top, highlighting the effect of evaporation at the surface.
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