Measuring and Calculating the Thermal and Hygric Properties of Insulating Building Materials Over Wide Temperature and Moisture Ranges

Long-term assessment of degradation processes is a very useful tool for an analysis of building materials performance. Since computational techniques are mostly used for this purpose, hygric properties of involved materials are required as substantial input data. Unfortunately, some construction details or heterogeneous materials have to be solved by means of multi-dimensional modelling which is demanding on computing power and thus the calculations may take a lot of time. The presented paper aims at determination of effective hygric properties of heterogeneous materials which would allow one-dimensional transformation. The parameter identification process is carried out on the basis of results of multi-dimensional modeling, using genetic algorithms. The main objective is to find such effective global moisture transport and accumulation functions that provide in one-dimensional modeling as similar results to multidimensional modeling as possible. The obtained functions give a very good agreement; the investigated relative humidity profiles differ only by 1.48 percentage points in average. The correctness of obtained results is also verified using the Lichtenecker's mixing rule as homogenization technique. The transformation of the original multidimensional problem into one-dimensional is found to substantially contribute to minimization of computational time, which is reduced from weeks to minutes.

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A round robin campaign on the hygric properties of porous building materials

MATEC Web of Conferences ◽

10.1051/matecconf/201928202011 ◽

2019 ◽

Vol 282 ◽

pp. 02011 ◽

Cited By ~ 1

Author(s):

Chi Feng ◽

Ana Sofia Guimarães ◽

Nuno Ramos ◽

Lixin Sun ◽

Dariusz Gawin ◽

...

Keyword(s):

Building Materials ◽

Round Robin ◽

Capillary Absorption ◽

Reliable Determination ◽

Porous Building Materials ◽

Vacuum Saturation ◽

Experimental Protocols ◽

Hygric Properties ◽

Data Processing Methods

The reliable determination of the hygric properties of porous building materials is important. In earlier round robin campaigns large discrepancies of measured hygric properties were found among different labs. Later studies indicated that differences in lab conditions and more importantly, personnel’s operation procedures and data processing methods, might have the greatest impact. To gain further insight, a new round robin campaign has been launched by KU Leuven (Belgium), to which another eight institutes contributed. A relatively stable and homogeneous ceramic brick is tested, and 3 standard tests are performed: the vacuum saturation test, the capillary absorption test and the cup test. During the campaign, two rounds of measurements are performed. In the 1st round, tests are performed according to participants’ respective experimental protocols. Next, a strict and detailed common protocol is prescribed. This paper reports on the results obtained in the 1st round of measurements. Results show that not much progress has been made since the EC HAMSTAD project: the vacuum saturation test leads to the most consistent results, while the cup test produces the largest discrepancies, most probably originating from sample sealing and humidity control.

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Validation of pore network model for hygric property calculation

MATEC Web of Conferences ◽

10.1051/matecconf/201928202024 ◽

2019 ◽

Vol 282 ◽

pp. 02024

Author(s):

Muhammad Islahuddin ◽

Chi Feng ◽

Steven Claes ◽

Hans Janssen

Keyword(s):

Moisture Content ◽

Pore Structure ◽

Network Model ◽

Building Materials ◽

Pore Space ◽

Pore Network ◽

Pore Network Model ◽

Pore Scale ◽

Structure Information ◽

Hygric Properties

Hygric properties can be estimated directly from pore structure information, represented by a network of regularly shaped pores, extracted from a pore structure image to conserve the real topology. On this network, pore-scale models of moisture behaviour determine the hygric properties of moisture storage and transport. The reliability of this approach is validated with a sintered-glass filter. Despite its more limited heterogeneity and pore size range relative to typical porous building materials, it provides a good basis for validating crucial pore-scale moisture processes. Measured storage data compare well to the estimated ad- and desorption moisture retention curves as well as to the saturated and capillary moisture content. Furthermore, the simulated whole-range moisture permeability curve agrees acceptably with measured data. The variation in modelling the pore space as a pore network model is also analysed by considering two distinct pore network extraction methods. The measured and simulated moisture contents agree well for the whole capillary range. Moreover, the resulting transport properties are generally accurate for the whole moisture content range. On the other hand, the estimated vapour permeabilities show notable variations between the two pore network models.

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Straw Based Materials for Building Retrofitting and Energy Efficiency

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.678.50 ◽

2016 ◽

Vol 678 ◽

pp. 50-63 ◽

Cited By ~ 1

Author(s):

Stefania Liuzzi ◽

Simona Rigante ◽

Francesco Ruggiero ◽

Pietro Stefanizzi

Keyword(s):

Energy Efficiency ◽

Thermal Properties ◽

Wheat Straw ◽

Thermal Insulation ◽

Water Glass ◽

Building Materials ◽

Hygric Properties

This work aimed to measure the hygrothermal properties of some different straw-based mix that could be used as building materials (panels or bricks). Straw is used to improve the hygrothermal performances of the final products. Several mix were produced adding different percentages of straw. Two types of fibers were used: wheat straw and bean straw. The results indicated that increasing the percentages of straw greater effects on the change of thermal properties can be appreciated. Furthermore the results also reveal that the specimen produced by water glass and straw, without binder, has the highest values of hygric properties and thermal insulation.

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Hygric properties of porous building materials (V): Comparison of different methods to determine moisture diffusivity

Building and Environment ◽

10.1016/j.buildenv.2019.106344 ◽

2019 ◽

Vol 164 ◽

pp. 106344 ◽

Cited By ~ 1

Author(s):

Peng Ren ◽

Chi Feng ◽

Hans Janssen

Keyword(s):

Building Materials ◽

Moisture Diffusivity ◽

Porous Building Materials ◽

Hygric Properties

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Stochastic generation of multiscale 3D pore network models of building materials

E3S Web of Conferences ◽

10.1051/e3sconf/202017208002 ◽

2020 ◽

Vol 172 ◽

pp. 08002

Author(s):

Steven Claes ◽

Hans Janssen

Keyword(s):

Building Material ◽

Building Materials ◽

Spatial Scales ◽

Network Models ◽

Pore Network ◽

Scale Invariant ◽

Network Modelling ◽

Stochastic Generation ◽

Pore Network Modelling ◽

Hygric Properties

The current experimental determination of hygric properties of porous building materials are demanding in time and effort, merge ad- and desorption techniques, fuses static and dynamic methods, and finally do not yield complete nor robust results. Therefore, numerical pore-scale-based prediction of the hygric properties of building materials is on the rise as an alternative. For building materials, this is mostly based on pore network modelling (PNM), given that these are more efficient compared to lattice Boltzmann or particle hydrodynamic methods. Pore network modelling however requires data of the complete pore network for the building material. With the currently available characterization and visualization techniques, this cannot be readily obtained, as the pore sizes in building materials often span several spatial scales. The aim of this paper is to present a scale invariant stochastic generation. To realize this objective, distributions of direct parameters (pores’ sizes, shapes, positions, connections, ...) as well as indirect parameters (overall pore size distribution and open porosity value) are derived from the input data obtained by micro-CT and FIB-SEM and subsequently applied to generate a complete pore network of the porous building material. The quality of the generated PNMs is assessed by comparing them to the original PNMs.

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