Capillary Uptake Monitoring in Lime-Hemp-Perlite Composite Using the Time Domain Reflectometry Sensing Technique for Moisture Detection in Building Composites

The use of waste plants in the production of building materials is consistent with the principles of sustainable development. One of the ideas involves using hemp shives as an aggregate for the production of a composite used as a filling of the timber frame construction of the walls. The most important disadvantage of using the building materials based on organic components is their susceptibility to the water influence. The wall material is exposed to rising groundwater. The research part of the paper presented the preparation method and the investigation of the hemp-perlite-lime composites. Flexural and compressive strength, apparent density, total porosity, thermal conductivity, and mass absorptivity were examined. The main research part pertained to the analysis of capillary uptake occurrence in the composites, being the important phenomenon present in the external walls. The study on this phenomenon was carried out using the technique of indirect moisture evaluation—Time Domain Reflectometry (TDR). The indirect readouts were additionally verified with the traditional evaluation using the gravimetric method based on the PN-EN 1925 standard. The study proved that the tested composites were characterized by low apparent density, thermal conductivity, strength parameters, high total porosity, and mass absorptivity. The partial replacement of hemp shives by expanded perlite had a beneficial effect on the tested properties of composites.

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Time Domain Reflectometry (TDR) technique – A solution to monitor moisture content in construction materials

E3S Web of Conferences ◽

10.1051/e3sconf/202017217001 ◽

2020 ◽

Vol 172 ◽

pp. 17001

Author(s):

Teresa Stingl Freitas ◽

Ana Sofia Guimarães ◽

Staf Roels ◽

Vasco Peixoto de Freitas ◽

Andrea Cataldo

Keyword(s):

Moisture Content ◽

Time Domain ◽

Building Materials ◽

Correct Diagnosis ◽

Construction Materials ◽

Gravimetric Method ◽

Reference Method ◽

Time Domain Reflectometry ◽

Relative Dielectric Permittivity ◽

Porous Building Materials

Measuring moisture content in building materials is crucial for the correct diagnosis of buildings’ pathologies and for the efficiency evaluation of the treatment solution applied. There are several different techniques available to measure the moisture content in construction materials. However, perform long-term minor-destructive measurements is still a great challenge. The TDR – Time Domain Reflectometry – technique is commonly used for moisture content measurements in soils, but is considered a relatively new method with regard to its application in construction materials. In the present state of research, the current use of the TDR technique for monitoring moisture content in all types of consolidated porous building materials is not possible yet. Indeed, the empirical conversion functions proposed for soils are mostly not suitable for building materials. Furthermore, to successfully use the TDR technique, a good contact between the TDR probe and the material under study is required, which may be difficult to achieve in hard materials. In this paper, the TDR technique was implemented in two limestone walls constructed in the lab to test experimentally the efficiency of a wall-base ventilation channel to speed up drying after a flood. Each wall was equipped with four two-rod TDR probes for continuous monitoring the moisture content in both situations: with and without the ventilation channel. All the equipment used, procedures followed during the drilling until the probes’ final installation, as well as the individual calibration required for each probe are explained in detail. Instead of using unsuitable functions proposed for soils, the evaluation of the moisture content from the apparent relative dielectric permittivity measured was established using as reference method the gravimetric method. The results obtained suggest that the TDR technique is suitable for moisture content monitoring in consolidated porous building materials.

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Is the Time-Domain Reflectometry (TDR) Technique Suitable for Moisture Content Measurement in Low-Porosity Building Materials?

Sustainability ◽

10.3390/su12197855 ◽

2020 ◽

Vol 12 (19) ◽

pp. 7855 ◽

Cited By ~ 1

Author(s):

Teresa Stingl Freitas ◽

Ana Sofia Guimarães ◽

Staf Roels ◽

Vasco Peixoto de Freitas ◽

Andrea Cataldo

Keyword(s):

Soil Moisture ◽

Moisture Content ◽

Time Domain ◽

Building Materials ◽

Construction Materials ◽

Gravimetric Method ◽

Time Domain Reflectometry ◽

Advantages And Disadvantages ◽

The Time Domain ◽

Low Porosity

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.

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A new generalized soil thermal conductivity model for sand–kaolin clay mixtures using thermo-time domain reflectometry probe test

Acta Geotechnica ◽

10.1007/s11440-016-0506-0 ◽

2016 ◽

Vol 12 (4) ◽

pp. 739-752 ◽

Cited By ~ 16

Author(s):

Nan Zhang ◽

Xinbao Yu ◽

Asheesh Pradhan ◽

Anand J. Puppala

Keyword(s):

Thermal Conductivity ◽

Time Domain ◽

Time Domain Reflectometry ◽

Kaolin Clay ◽

Soil Thermal Conductivity ◽

Conductivity Model ◽

Thermal Conductivity Model ◽

Probe Test

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Quantitative, zerstörungsfreie Feuchtemessung in Baustoffen vor Ort mit der Time Domain Reflectometry / Quantitative, non-destructive moisture measurement in building materials on site by time-domain re ectometry

Restoration of Buildings and Monuments ◽

10.1515/rbm-1999-5423 ◽

1999 ◽

Vol 5 (6) ◽

pp. 609-618

Author(s):

M. Stacheder ◽

G. Grassegger ◽

F. Grüner

Keyword(s):

Time Domain ◽

Building Materials ◽

Salt Content ◽

Time Domain Reflectometry ◽

New Method ◽

Measuring Methods ◽

Surface Moisture ◽

Non Destructive ◽

Floor Cover

Abstract A new commercially available dielectric technique for the non-destructive determination of moisture in building materials based on the principle of 'time-domain reflectometry' (TDR) is presented. TDR measurements on samples of sandstone, brick, concrete and floor cover matched very well with results of conventional moisture measuring methods such as oven-drying or calciumcarbide-technique. The new method showed only a low influence of salt content or surface moisture of the material on the results.

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Comparison of Standing Wave Ratio, Time Domain Reflectometry and Gravimetric Method for Soil Moisture Measurements

Sensor Letters ◽

10.1166/sl.2011.1405 ◽

2011 ◽

Vol 9 (3) ◽

pp. 1140-1143 ◽

Cited By ~ 1

Author(s):

Lei Feng ◽

Yiming Wang ◽

Weizhong Yang ◽

Qinglan Shi

Keyword(s):

Soil Moisture ◽

Standing Wave ◽

Time Domain ◽

Gravimetric Method ◽

Time Domain Reflectometry

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A Noninvasive TDR Sensor to Measure the Moisture Content of Rigid Porous Materials

Sensors ◽

10.3390/s18113935 ◽

2018 ◽

Vol 18 (11) ◽

pp. 3935 ◽

Cited By ~ 12

Author(s):

Zbigniew Suchorab ◽

Marcin Widomski ◽

Grzegorz Łagód ◽

Danuta Barnat-Hunek ◽

Dariusz Majerek

Keyword(s):

Moisture Content ◽

Porous Materials ◽

Building Materials ◽

Capillary Rise ◽

Capacitive Sensor ◽

Time Domain Reflectometry ◽

Capillary Uptake ◽

Individual Calibration ◽

Sample Application ◽

The Time Domain

The article presents the potential application of the time domain reflectometry (TDR) technique to measure moisture transport in unsaturated porous materials. The research of the capillary uptake phenomenon in a sample of autoclaved aerated concrete (AAC) was conducted using a TDR sensor with the modified construction for non-invasive testing. In the paper the basic principles of the TDR method as a technique applied in metrology, and its potential for measurement of moisture in porous materials, including soils and porous building materials are presented. The second part of the article presents the experiment of capillary rise process in the AAC sample. Application of the custom sensor required its individual calibration, thus a unique model of regression between the readouts of apparent permittivity of the tested material and its moisture was developed. During the experiment moisture content was monitored in the sample exposed to water influence. Monitoring was conducted using the modified TDR sensor. The process was additionally measured using the standard frequency domain (FD) capacitive sensor in order to compare the readouts with traditional techniques of moisture detection. The uncertainty for testing AAC moisture, was expressed as RMSE (0.013 cm3/cm3) and expanded uncertainty (0.01–0.02 cm3/cm3 depending on moisture) was established along with calibration of the applied sensor. The obtained values are comparable to, or even better than, the features of the traditional invasive sensors utilizing universal calibration models. Both, the TDR and capacitive (FD) sensor enabled monitoring of capillary uptake phenomenon progress. It was noticed that at the end of the experiment the TDR readouts were 4.4% underestimated and the FD readouts were overestimated for 12.6% comparing to the reference gravimetric evaluation.

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