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2018 | Buch

Introduction Kapitel lesen Erstes Kapitel lesen

Methods of Measuring Moisture in Building Materials and Structures

State-of-the-Art Report of the RILEM Technical Committee 248-MMB

herausgegeben von: Prof. Lars-Olof Nilsson

Verlag: Springer International Publishing

Buchreihe : RILEM State-of-the-Art Reports

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

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SUCHEN

Über dieses Buch

RILEM TC 248-MMB was established in 2012 with the main aim to improve and distribute knowledge related to moisture measurement in construction materials in various scientific and industrial applications.

Properties and performance of building materials and structures are influenced to a large extent by the moisture conditions in the materials. Obvious examples are heat conductivity, shrinkage and creep, transport properties, most types of deterioration, discoloration etc. For research and applications the moisture conditions must be quantified, by measurements in the laboratory or under field conditions. There is much variation in methods being used, even within the same topic, in different countries, both with regard to materials and to applications. No consensus whatsoever does exist. For the construction industry it is important to be able to quantify the moisture conditions in an accurate way in various applications.

This state-of-the-art report is divided into two parts, Principles and Applications, with altogether 28 chapters on various moisture measuring principles and a number of applications.

Inhaltsverzeichnis

Frontmatter
Chapter 1. Introduction
Abstract
The amount of moisture and the state of water in porous materials are decisive for the properties and the behaviour of the materials and structures. Thermal and mechanical properties of a material are directly affected by the moisture content. Moisture content variations in a material cause dimensional changes; swelling, shrinkage and other deformations.
Lars-Olof Nilsson, Elisa Franzoni, Hemming Paroll
Chapter 2. Definitions
Abstract
For the various sections of the report a number of common expressions and symbols are used. Most of them are defined here. Most of the definitions and symbols are the same as in CIB-W40(2012), with some minor revisions.
Lars-Olof Nilsson, Elisa Franzoni, Olivier Weichold

Moisture Measuring Principles

Frontmatter
Chapter 3. Drying Methods
Abstract
When measuring the moisture content of a material by gravimetry, or when another method for measuring moisture content is to be calibrated, it is of course essential to be able to determine the exact amount of water in a sample. This may be done for instance by radioactive methods or by some technique in which the water is removed from a representative sample of the material. The latter technique is simply known as drying.
Kurt Kielsgaard Hansen, Sture Lindmark, Lars-Olof Nilsson, Oliver Weichold
Chapter 4. Calibration Techniques
Abstract
Many moisture-measuring principles have to be calibrated against a sample with known moisture content. The preparation of samples with a well-defined, and evenly distributed, moisture content requires a thorough procedure. This is dealt with in Sect. 4.1. The measuring principles where the state of water is measured in a material need calibration against well-known and well-defined humidity conditions. This is described in Sect. 4.2.
Miguel-Ángel Climent, Sture Lindmark, Lars-Olof Nilsson
Chapter 5. Gravimetry
Abstract
The principle of using gravimetry to measure the moisture content of a sample or a specimen is to determine the weight by a balance before and after drying.
Lars-Olof Nilsson
Chapter 6. Chemical Reaction
Abstract
The principle of using chemical reactions to measure the moisture content of a sample is to determine the consumption of a reactant A that reacts chemically with water or to determine the amount of a reaction product B from such a reaction
Lars-Olof Nilsson, Miguel-Ángel Climent, Oliver Weichold
Chapter 7. Infrared Thermography
Abstract
The infrared thermography is a non-destructive technique (NDT) allowing the evaluation of the material surface temperature. It is a non-contact technique, particularly adapted for high yield investigation. The method records the electromagnetic ray in the infrared spectrum, emitted from the external surface. The surface temperature of a material is influenced by the moisture conditions in some cases; this could be detected by IR-thermography.
Jean-François Lataste, Lars-Olof Nilsson
Chapter 8. Electrical Resistance
Abstract
Electrical resistance is the ability for a material to impede the flow of electrical current. The resistance (R) is expressed in ohm (Ohm), its inverse is the conductance (C) is expressed in siemens (S). The resistance is function of geometry of tested body and measurement device. So one generally prefers the resistivity (ρΩ) expressed in ohm-meter (Ohm·m), or its inverse the conductivity (σ) in siemens per meter (S/m), representing the intrinsic material’s property.
Jean-François Lataste, Charlotte Thiel, Elisa Franzoni
Chapter 9. Gas Permeability
Abstract
The effective, or relative, gas permeability of a partially saturated porous media depends on the amount of available porosity for gas percolation, its connectivity, tortuosity and pore throat diameter. It is well known that gas permeability varies significantly with the distribution and the amount of moisture present in the porous network. For each concrete, the relationship between gas permeability and water saturation has to be determined through laboratory study. In situ measurement of effective gas permeability can then be used to determine water saturation in concrete structures.  
Franck Agostini
Chapter 10. Hygrometry
Abstract
The humidity of air can be measured with a number of various methods, i.e. psychrometers, dew-point sensors, mechanical hygrometers and electronic RH-probes (RH = Relative Humidity).
Lars-Olof Nilsson, Kurt Kielsgaard Hansen, Miguel Azenha
Chapter 11. Pore Water Pressure
Abstract
The pressure of the pore water in a porous material is a measure of the state of the water.
Lars-Olof Nilsson
Chapter 12. Introduction to Electromagnetic Radiation
Abstract
The following chapter focuses on the use of electromagnetic radiation to detect and determine the moisture content in civil engineering materials. This introduction intends to recapitulate the most important aspects of electromagnetic radiation and how it interacts with water.
Oliver Weichold
Chapter 13. Nuclear Magnetic Resonance and Magnetic Resonance Imaging
Abstract
Nuclear Magnetic Resonance (NMR) enables to quantify the hydrogen nuclei in a sample and thus indirectly the water content. Here, hydrogen nuclei are put in oscillation (resonance) by applying a magnetic field and additional irradiation with pulsed electromagnetic waves of certain frequencies. In case all hydrogen nuclei of a sample are exclusively bound in water molecules, the resulting initial amplitude of the detected NMR signal is directly proportional to the water content. The subsequent attenuation of the oscillation is caused by relaxation mechanisms and provides information on the mobility and thus the binding states of the hydrogen nuclei. Therefore even the pore size distribution can be determined in completely water-saturated samples. If the magnetic field is graded, images can be created based on spatially resolved nuclei density distributions (MRI). Depending on the research objective, tailored choice of equipment and settings can be used to qualitatively and mostly quantitatively analyze almost every moisture-related problem. The article gives an overview of the existing NMR methods, equipment, influencing parameters, calibration techniques, applications and limitations.
Charlotte Thiel, Christoph Gehlen
Chapter 14. Capacimetry
Abstract
Capacimetry consists of the assessment of a material’s electrical permittivity (or dielectric constant, noted ε). The relative permittivity is defined as normalized: ε’r = ε/εo, where ε is the materials permittivity and εo is the absolute permittivity of vacuum (8.854… × 10−12 F.m−1). This value (ε’r) is then always higher than 1.
Jean-François Lataste, Walter Denzel, Hemming Paroll
Chapter 15. Time Domain Reflectometry
Abstract
Originally, the TDR measurement technique was developed to detect defects in telecommunication cables and electrical wires, Moffitt (1964). Within recent decades, TDR was also applied to determine and monitor volumetric moisture contents in particulate and porous media, in particular soil but lately also building materials such as building bricks, concrete, sandstone, etc., see e.g. Dobson et al. (1985), Topp et al. (1980), and Phillipson et al. (2008). TDR is in general based on the measurement of the propagation time of an electromagnetic signal along a wave guide also referred to as probe, usually there and back. In the low frequency range, i.e. <10 GHz, water possesses a considerably higher relative permittivity (ε w  ≈ 80) than mineral compounds (ε s  ≈ 4) or air (ε a  ≈ 1). From the measurement of the propagation time of an electromagnetic signal along a wave-guide, the mean relative permittivity, which is among others moisture dependent, of the investigated dielectric material is derived from the reflection picture. Subsequently, the volumetric water content can be determined directly from the mean relative permittivity applying suitable material functions, which relate mean relative permittivity and volumetric moisture content.
Alexander Michel, Henryk Sobczuk, Kurt Kielsgaard Hansen
Chapter 16. Microwave Reflection
Abstract
Electromagnetic methods in the range of microwaves have high sensitivity to moisture condition of building materials. Two methods are available for assessment of moisture according a non destructive way: the radar (Ground Penetrating Radar—GPR) which is a tool developed mainly for detection of internal structures in materials and which knows developments focusing on moisture assessment; and microwave technique specifically dedicated to moisture assessment.
Jean-François Lataste, Arndt Göller
Chapter 17. Neutron Radiography
Abstract
Neutron radiography is in general based on the universal law of attenuation of radiation transmitted through the tested matter. Since the transmission differs for different compositions and thickness, the information on the structure and composition of the tested materials can be obtained by radiographic measurement. Water movement can be detected by neutron imaging with a good contrast between water and the materials. Neutron radiography makes it possible to measure moisture in building materials, such as concrete, stone, mortar, etc. in a qualitative and quantitative way with high sensitivity.
Zhang Peng, Zhao Tiejun
Chapter 18. X-Ray and Gamma-Ray
Abstract
X-ray (and gamma-ray) techniques have been used for many years to determine moisture distribution in laboratory specimens, cf. Shang and Pere (1997) and Hansen and Bentz (1999). The attenuation (loss of intensity) is a measure of the density and the thickness of the object between a source and a sensor. By performing a second measurement on the same, dried, object the moisture content of the object exposed to the beam can be quantified.
Owe Lindgren, Lars-Olof Nilsson

Applications

Frontmatter
Chapter 19. Spatial Distributions
Abstract
In many applications moisture measurements are made to estimate the moisture differences between different points in a structure. Here, it is often more important to use a “simple” method that is easy and rapid to use in many points instead of necessarily obtain the exact moisture level in each point. The objective with “moisture indications” like that could very well be to select points where more accurate moisture measurements are to be made. The measuring principle to apply is of course a trade-off between accuracy and simplicity.
Jean-François Lataste, Kurt Kielsgaard Hansen, Lars-Olof Nilsson, Charlotte Thiel, Angelika Schießl-Pecka, Arndt Göller, Christoph Gehlen
Chapter 20. Moisture Distribution in a Structure/Specimen—General
Abstract
In a lot of applications there is a need to measure the distribution of moisture in a material, i.e. the moisture content or the state of moisture, at a certain, defined position or a series of positions.
Lars-Olof Nilsson
Chapter 21. ND-Methods—From a Surface
Abstract
A complicated application is to measure a moisture distribution with depth from a surface non-destructively. Only a few methods are suitable for such a case.
Kurt Kielsgaard Hansen, Jean-François Lataste, Charlotte Thiel
Chapter 22. Coring, Drilling and Sampling Techniques
Abstract
An obvious method to determine the distribution of moisture in a material or structure is to take a sample from the intended position and then determine the moisture content or state of moisture on that sample.
Lars-Olof Nilsson, Elisa Franzoni
Chapter 23. Installation of Probes
Abstract
The principles of installation of probes to measure moisture in a certain position in a structure or specimen are shown in Fig. 23.1.
Lars-Olof Nilsson, Franck Agostini, Charlotte Thiel
Chapter 24. Specimen or Core; In the Laboratory (Sides Available)
Abstract
When also the sides, of a specimen or a core from a structure, are available during the moisture measurement procedure numerous techniques are applicable compared with when only the exposed surface is available.
Kurt Kielsgaard Hansen, Jean-Francois Lataste, Lars-Olof Nilsson, Charlotte Thiel, Alexander Michel
Chapter 25. Moisture in a Substrate Before Surface Covering
Abstract
A very common application of moisture measurements is to quantify the moisture conditions of a substrate before applying a surface cover.
Lars-Olof Nilsson
Chapter 26. Monitoring, Remote Measurements
Abstract
A special group of applications is “monitoring” where a series of moisture measurements are to be done in the same position at a number of occasions. This kind of application requires certain measures to overcome some special challenges when measurements are done during a longer period of time.
Franck Agostini, Elisa Franzoni, Kurt Kielsgaard Hansen, Hemming Paroll, Lars-Olof Nilsson
Chapter 27. Heterogeneous Materials
Abstract
Measuring moisture in heterogeneous materials in a specimen or in a structure is a delicate task for several reasons. Examples of materials where this is relevant are e.g. bricks, concrete, (historic) masonry, etc.
Lars-Olof Nilsson, Elisa Franzoni

Conclusions

Frontmatter
Chapter 28. Conclusions
Abstract
From the description in the previous chapters of the state-of-art of methods for measuring moisture in building materials these conclusions can be drawn:
Lars-Olof Nilsson
Backmatter
Metadaten
Titel
Methods of Measuring Moisture in Building Materials and Structures
herausgegeben von
Prof. Lars-Olof Nilsson
Copyright-Jahr
2018
Electronic ISBN
978-3-319-74231-1
Print ISBN
978-3-319-74230-4
DOI
https://doi.org/10.1007/978-3-319-74231-1