Effective thermal conductivity of porous building materials – analysis and verification

Wyrwał, Jerzy; Marynowicz, Andrzej; Świrska, J.

doi:10.1002/bapi.200810056

Cited by 20 publications

(6 citation statements)

References 5 publications

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“…Several analytical formulas for two-phase mixtures have been used to compute the effective conductivity of foams [17,19,24,[44][45][46][47][48][49], the most popular ones being those of Maxwell [13] and Bruggeman [21], defined for foamed concretes as…”

Section: Comparison To Analytical Formulasmentioning

confidence: 99%

“…Maxwell published the formula (32) in 1873 to compute the electrical resistance of a medium with Fig. 11 thermal conductivity of 21 foamed concretes: comparison between results using the simplified model and experiments [17] dispersed spherical inclusions; in 1940, Eucken [50] proposed to apply it to determine the thermal conductivity (inverse of the resistance) in such medium, reason why it is also called the Eucken formula [51] or, more frequently, the Maxwell-Eucken formula [44,45,48,52]. Further, note that the Maxwell formula gives the Hashin-Shtrikman upper bound for isotropic conductivity [53].…”

Section: Comparison To Analytical Formulasmentioning

confidence: 99%

“…Similarly, Bruggeman formula (33) was proposed in 1935 to compute the dielectric constant of a medium with disordered spherical aggregates; in 1952, Landauer [54] derived an identical formula for the thermal conductivity using the effective medium theory (EMT), so Eq. ( 33) is referred to as EMT by several authors [17,19,44,45,48,49,55].…”

Section: Comparison To Analytical Formulasmentioning

confidence: 99%

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Automatic generation of high-fidelity representative volume elements and computational homogenization for the determination of thermal conductivity in foamed concretes

Fachinotti,

Peralta,

Toro

et al. 2023

Mater Struct

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Foamed concretes are highly porous materials with excellent insulation properties. Their thermal conductivity is strongly dependent on the pore structure, characterized by the porosity as well as the shape and size distribution of pores. To define the representative volume element (RVE) of foamed concretes with high fidelity, we develop NRGene, an automatic generator of cubic samples with spherical air inclusions whose number and size obey a given distribution. We compute the effective thermal conductivity tensor for a given RVE using finite-element-based computational homogenization. The hi-fi RVE of foamed concretes may contain hundreds of millions of finite elements, making it better suited for benchmarking than for everyday engineering applications. Then, having the hi-fi model as benchmark, we propose a simplified model consisting of the hi-fi model called with a truncated histogram as input, which is largely cheaper while keeping a satisfactory accuracy. We model 21 different foamed concretes with a wide range of porosities and different compositions of the cement paste. Further, we demonstrate that it is the volume of all the pores of a given size, and not its quantity, what affects the effective thermal conductivity of foamed concretes.

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Section: Comparison To Analytical Formulasmentioning

confidence: 99%

Section: Comparison To Analytical Formulasmentioning

confidence: 99%

Section: Comparison To Analytical Formulasmentioning

confidence: 99%

See 1 more Smart Citation

Automatic generation of high-fidelity representative volume elements and computational homogenization for the determination of thermal conductivity in foamed concretes

Fachinotti,

Peralta,

Toro

et al. 2023

Mater Struct

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“…Several studies indicated that the thermal conductivity of cement-based materials is related to the pore structure [19][20][21][22] and can be predicted by assuming a two-phase material, i.e., solid phase and void phase [23][24][25][26][27]. Also, different models were proposed to estimate the effective thermal conductivity based on the thermal conductivity and the volume of the solid and gas phases [28][29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

Evaluating the Effective Thermal Conductivity of Cement Mortar Through X-Ray Scanning

Asadi¹,

Ji²,

Baghban³

2022

SSRN Journal

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“…Aside from studies constituting a review of thermal conductivity measurement techniques [ 13 , 14 ], the assessment of the possible application of existing models to predict thermal conductivity of cement-based composites is also conducted. For example, in Reference [ 15 ], the selected models describing the heat conductivity coefficient in porous, dry and damp building materials were analyzed. The values obtained from the models were compared with the measured parameters.…”

Section: Introductionmentioning

confidence: 99%

The Thermal Parameters of Mortars Based on Different Cement Type and W/C Ratios

Stolarska

Strzałkowski

2020

Materials

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This study examines the thermal parameters of mortars based on different cement type and water-cement W/C ratios. The presented relationships are important from the point of view of thermal insulation of the entire building component, of which the mortar is a part. The thermal properties of the mortar, and in particular its dependence on the degree of moisture, is important information from the point of view of hygrothermal simulations of building components. The moisture effect on the thermal properties was tested using nine mortar types. The study consisted of producing nine types of mortar on the basis of three cements (CEM I 42.5R, CEM II A-S 52.5N, CEM III A 42.5N). For each cement type, three variants of specimens were prepared which differed according to their water/cement ratio (0.50, 0.55 and 0.60). The main research of thermal parameters was carried out using a non-stationary method based on the analysis of changing heat flux readings. The thermal conductivity, volume-specific heat and thermal diffusivity values were analyzed. The tests performed allowed for determination of the density of specimens, water absorbability and thermal parameters in three water saturation states: dry, natural and wet. Additional microstructural tests were performed using mercury intrusion porosimetry. The obtained parameters were used to determine the relationship between the measured properties. An adverse effect of dampness on the thermal insulation of the studied materials was confirmed. In extreme cases, the increase in thermal conductivity due to material high moisture was 93%. The cement used affects the relationship between the total specific surface area and the W/C ratio. As expected, the total porosity of specimens was higher for mortars with higher W/C ratios. A strong correlation has been demonstrated between the total surface area and thermal conductivity. The opposite results were obtained when assessing the relationship between the total specific surface area and water absorbability. In case of specimens CEM II A-S 52.5N, the relation was the proportional, and in specimens CEM III A 42.5N, the relationship was inversely proportional to the W/C ratio.

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Effective thermal conductivity of porous building materials – analysis and verification

Cited by 20 publications

References 5 publications

Automatic generation of high-fidelity representative volume elements and computational homogenization for the determination of thermal conductivity in foamed concretes

Automatic generation of high-fidelity representative volume elements and computational homogenization for the determination of thermal conductivity in foamed concretes

Evaluating the Effective Thermal Conductivity of Cement Mortar Through X-Ray Scanning

The Thermal Parameters of Mortars Based on Different Cement Type and W/C Ratios

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