Measuring moisture content in building materials is essential both for professional practice and for research. However, this is a very complex task, especially when long-term minor destructive measurements are desired. The time-domain reflectometry (TDR) technique is commonly used for soil moisture measurements, but its application in construction materials is considered a relatively new method, particularly for low-porosity building materials. The major obstacles to its current use in construction materials are (1) the difficulty of ensuring good contact between the TDR probe and the material, and (2) the lack of appropriate conversion functions between the measured relative permittivity and the moisture content of building materials. This paper intends to contribute to overcoming these difficulties by explaining in detail all the required steps to monitor moisture content in real-scale limestone walls. For that, a device is presented to guarantee the correct installation of the TDR probes on the walls, and a calibration procedure through the gravimetric method is proposed to avoid the use of an unsuitable calibration function developed for soil moisture measurements. In addition, the importance of the individual probe calibration is discussed, as well as TDR advantages and disadvantages for construction materials. The results obtained so far reveal that the TDR technique is suitable to detect moisture content variations in limestone, which is a low-porosity building material.

The study of moisture transfer in porous building materials after a long contact with liquid water is crucial to prevent damages, in particular, when it comes to extreme rain events or floodings. Several experimental techniques are available to measure the moisture content evolution during water absorption tests, although the great majority of them are time-consuming and require expensive equipment. For this reason, the use of validated hygrothermal simulation tools is essential for a faster analysis without losing accuracy. The main goal of this paper is to compare the simulated moisture content profiles provided by the program TRHUMIDADE with those obtained by the gamma-ray attenuation method and by WUFI program. In TRHUMIDADE the heat and moisture phenomenon is described by the moisture content gradient, which may be more appropriate in predicting scenarios involving liquid water transport. The obtained results showed a good agreement for the red-brick and the autoclaved cellular concrete, which contributes to validate the future use of the program in the development of advanced hygrothermic studies in multi-layered building walls.

Floods are a worldwide problem, causing several types of damage to historic buildings that deserve special preservation. In this work, a ventilated underground channel is proposed as a solution to protect historical buildings from the harmful effects of flooding. To evaluate the efficiency of this system, an experimental setup was prepared in the laboratory to compare the drying time after flooding of two limestone walls, one with the ventilation channel and the other without. The drying process was monitored with Time-Domain Reflectometry (TDR) probes. The obtained results show a substantial reduction in the drying time of the wall with the ventilation channel. Still, more studies are required to evaluate the conditions where the system application is most impactful.

Measuring moisture content in building materials is crucial for the correct diagnosis of buildings pathologies, for the adoption of appropriate intervention measures and for the efficiency evaluation of the treatment solutions applied. There are several different techniques available to measure and monitoring the moisture content in building materials. However, it still remains a great challenge to perform those studies in historical buildings, since minor-destructive techniques are required. Furthermore, if continuous moisture content readings in space are desired, in order to study the moisture transfer phenomenon along the wall thickness, the challenge is even greater. The TDR technique is a relatively new method for measurement of moisture content in building materials with a set of unexplored potentialities capable of satisfying the two mentioned requirements. In this paper, the suitability of the TDR technique to obtain continuous cross-section moisture content profiles has started to be tested on two limestone prototype walls. Each wall was equipped with four TDR probes, designed practically with the same length of the wall thickness and placed at different heights. All the necessary equipment, installation steps, and difficulties are here presented. The preliminary results suggest that the TDR technique is suitable for moisture content monitoring in consolidated porous building materials.