# Development and Application of a New Apparatus for Moisture Measurement in Building Composites
## 1 Introduction  
Moisture in a building structure accelerates its ageing and degradation [1]. Moisture is one of the main decay factors in building envelopes, increasing the repair costs of structures to several billions. Such damage is apparent in historical and traditional buildings, since they are exposed to the moisture influence for longer time periods, as well as in contemporary building envelopes [2]. Composites with ultrafine polymer fibres may perform interesting properties, which could be an advantage in some applications [3, 4]. Functional clothing, for example GORE-TEX membrane, is known throughout the world. The garment was made of a fabric that has the ability to retain moisture and also release water vapour. [5]. The clothes tag thus added another figure, i.e., the height of the water column that the fabric holds. This was the main idea for the project--to use the principle of textile membrane as a protection against dampness of the building. Nanofibers are a very promising type of material with a broad range of possible applications. [6]. Generally speaking, the permeability of membrane must depend not only on the water content, i.e., the degree of hydration, but also on the geometrical structure of the membrane and subsequent conditions [7]. In the building industry, we encounter materials that are water repellent, but they are presented in such a way that creates the feeling of materials being waterproof. These are mostly materials applied by spraying, i.e., they work only temporarily, not permanently. The methodology and results of the first experiment were presented for building materials with a nanofiber membrane [8]. Two types of composites were investigated. The gravimetric method was used for evaluation of water permeability in the material. The amount of water that penetrates the building composite over a defined area over a given time (up to six days) under hydrostatic pressure (P = 14750 Pa) was also determined. The obtained results showed that a newly developed \"breathing\" building composite with nanofibermembrane can be used as a barrier against moisture contamination in masonry with long-lasting effects of water. The durability of concrete depends to a large extent on the difficulty of external aggressive agents in penetrating the porous network of concrete. The ability of this material to withstand the intrusion of these aggressive agents is mainly characterized by water permeability. [9]. In the subsequent study, geopolymer samples were used. This material has the same property as concrete, as it is porous. When the nanofiber membrane was used, the waterproof material obtained was able to withstand the long-term effects of water [10]. There are a number of instruments for measuring the resistance of materials to water column pressure. Such instrument include the KJ -3093 Hydrostatic Head Tester from Kejian, and the Automatic Hydrostatic Head Tester from TEXTEST AG, which can detect penetrated water drops. Another possible device is the Hydrostatic Head Tester M018 from SDIAtlas. [PERSON] et al. [11] described the water permeability measurement method through cracked concrete, and they claim that the higher permeability of concrete is indicative of its poor quality due to the presence of additional pores, voids, and cracks. [PERSON] and [PERSON] [12] tested the water permeability of concrete samples on a similar apparatus. However, they selected a reservoir with a constant level of water for high throughput samples. For samples that showed low permeability, they used the decreasing water column method. [PERSON] et al. [13] presented a rapid test for establishing the water permeability of cracked mortar specimens. The samples were placed in a section of the pipeline and covered with silicone, which was allowed to cure for 24 h. The water flowing through the sample flowed into the collecting containers and its weight was recorded after five minutes. The water level of each column was maintained between 1.05 and 1 m, giving an almost constant water head of 0.1 bar.