- Email: [email protected]
Water vapour permeability of innovative building materials from different waste
Journal Pre-proofs Water vapour permeability of innovative building materials from different waste C. Buratti, E. Belloni, F. Merli PII: DOI: Reference:
S0167-577X(20)30164-6 https://doi.org/10.1016/j.matlet.2020.127459 MLBLUE 127459
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
8 November 2019 14 January 2020 31 January 2020
Please cite this article as: C. Buratti, E. Belloni, F. Merli, Water vapour permeability of innovative building materials from different waste, Materials Letters (2020), doi: https://doi.org/10.1016/j.matlet.2020.127459
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2020 Published by Elsevier B.V.
WATER VAPOUR PERMEABILITY OF INNOVATIVE BUILDING MATERIALS FROM DIFFERENT WASTE C. Buratti a*, E. Belloni a, F. Merli a a
Department of Engineering – University of Perugia. Via G. Duranti 67. 06125 Perugia (Italy)
*Corresponding author: [email protected]; tel. +39 075 5853993; fax. +39 075 5853916
ABSTRACT The hygrothermal performance of building materials is a very important issue for indoor comfort. The aim of this study is to measure the water vapour resistance factor μ of recycled waste materials. Leather cuttings, rice husk, and coffee chaff were used in order to manufacture innovative panels for thermal-noise building insulation. The permeability measurements were carried out by the dry cup method in compliance with the Standard EN ISO 12572. In the experimental campaign, conventional gypsum plaster and expanded polystyrene were also considered, whose hygrothermal characteristics are known from the Literature, in order to verify the reliability of the method. The moisture transfer properties of the innovative panels are higher than the values available in the Literature for other vegetable and mineral fibers-based panels (sheep wool, wood, cork, expanded vermiculite and perlite, glass or stone wool, and so on). However, the high μ-value obtained for coffee chaff panels (equal to 392) could involve an increase in heat loss and acoustically weak points.
Keywords: permeability performance, water vapour resistance factor, building insulation, recycled waste materials.
1. INTRODUCTION In the modern society, energy efficiency and environmental issue aspects are becoming central. The building sector can be considered the major responsible for energy resources, water consumption, and for carbon dioxide emissions [1]. In this context, a lot of constructive solutions and insulation materials based on renewable resources or waste are developed. In the Literature the development, experimental thermal-noise insulation properties, lower environmental impact, embodied energy, resource consumption, and pollution emissions of these materials are subject of many studies [2-5]. Air tightness of the building envelope is another very important aspect in order to reduce energy consumptions, but it is necessary to balance the walls breathability, which on one hand ensures a greater durability of the materials avoiding condensation problems, and on the other one involves reduction in thermo-acoustic performance, with a decrease in indoor comfort. Few authors in the scientific literature take into account this aspect by measuring the water vapour diffusion resistance factor of different materials, such as Moso bamboo [6] or plasters with different compositions [7]. In other studies these properties are in relationship with other ones, for example with porosity [8]. In this work, the hygrothermal performance of innovative panels consisting of recycled materials are evaluated, in compliance with Standard prescriptions [9]. Scraps resulting from industrial processing, such as leather cuttings, rice husk, and coffee chaff are glued and pressed, in order to fabricate panels. In the last years the
1
Authors started a systematic study on the influence of these materials on the thermal, acoustic, mechanical, and environmental aspects [4, 5]. This paper aims to evaluate their water vapour resistance factor μ, which represents the resistance of the material to be crossed by water vapour with respect to an equally thick layer of stationary air at the same temperature. In order to validate the procedure, also gypsum plaster [10] and conventional insulating panels of expanded polystyrene [11] were considered in the study. The measured values were finally compared with other insulation materials available on the market and with their technical sheet data. 2. MATERIALS AND TESTING METHOD 2.1. Samples description The permeability performance of traditional insulating materials for building applications, such as gypsum from the Safi region (in south-western Morocco), expanded polystyrene, and new recycled ones (glued and pressed leather cuttings waste, rice husk, and coffee chaff) were investigated. For each material, two cylindrical 100mm diameter samples (Figure 1) were purposely fabricated for the study; they were weighed with an electronic precision balance and their thicknesses were measured by a centesimal caliber. In particular: -
leather cuttings waste (1A and 1B) provided by an Italian company in the province of Viterbo were obtained from leather sheets wasted in bags production process. Raw material was chipped and added to Polyvinylacetate glue (5% by weight), along with distilled water (at a ratio of 12% by weight); a hydraulic press allowed the panels fabrication. The 1A and 1B samples were 18-mm thick with a weight of 0.074 kg and 0.091 kg, respectively (estimated densities 570 and 650 kg/m3);
-
2A and 2B panels [5] (both 0.026 kg) consisting of rice husk produced by gluing and pressing the raw material provided by a company based in Lombardy (Italy) were 18-mm thickness. The material is originated by the paddy rice husking process; after threshing the rough rice (unpolished), rice husk was added to a cold-water-based polyurethane glue (percentage 2.5% of the total weight) and pressed as a panel;
-
glued and pressed 3A (0.034 kg) and 3B (0.037 kg) samples 5-mm thick [4,5] were made of coffee chaff, originated by the roasting process of a factory from northern Italy (Pavia);
-
gypsum plasters [10] (4A and 4B, 50-mm thick) were manufactured by mixing Safi (Morocco) natural rock powder with water (mass ratio water/gypsum of 0.8) and dried, according to the thermal stability of the samples. Their weight were 0.375 kg and 0.372 kg, respectively;
-
conventional insulating samples consisting in expanded polystyrene (5A and 5B, 30-mm thick and 0.004 kg weight) [11] were analysed as reference. Water vapour resistance factor μ was in the 20 – 40 range, as suggested by the technical sheet of the material.
In compliance with EN ISO 12572 Standard [9] prescriptions, the samples were preconditioned in a climatic chamber (Mazzali C330G5), characterized by 600 x 700 x 680 mm internal dimensions, - 40°C – 150°C temperature range, and 15% - 100% relative humidity range, available at the University of Perugia. The conditions considered for the tests are 23±5 °C and 50±5% relative humidity. This conditioning lasted for 3 days, until three successive daily determinations of the samples’ weight was within 5%.
2
1A
2A
3A
4A
5A
1B
2B
3B
4B
5B
Fig. 1. The investigated samples for hygrothermal measurements.
2.2. Hygrothermal measurement method Water vapour resistance factor μ-values of the different samples were measured with the dry cup method, according to [9]. The preconditioned samples were placed and sealed in transparent plastic cups containing silicagel as desiccant; transparent cups allow to control the colour change of the salt solution when absorbing water vapour (Figure 2 a). A minimum depth of 15-mm silicagel (granules diameter in the 1 – 3 mm range) with colour indicator was put at the bottom of each cup, leaving an air space of 15 ± 5 mm between the desiccant and the sample. The assembled specimens were then placed in the temperature and relative humidity controlled test chamber, with environmental conditions suggested in [9] (Figure 2 b). A vapour flow occurs through the permeable samples, due to the different partial vapour pressure between the test cup and the chamber. Every 24 hours the samples were weighed, in order to evaluate the rate of water vapour transmission in the steady-state conditions and the mass change rate 𝑚12 was calculated as:
𝑚12 =
𝑚2 ― 𝑚1 𝑡2 ― 𝑡1
[𝑘𝑔 𝑠]
(1)
where: 𝑚1 [kg] and 𝑚2 [kg] are the masses of the test assembly at successive times of weighings 𝑡1 [s] and 𝑡2 [s], respectively. The mean of five consecutive determinations of 𝑚12 was named G; final G-value is obtained when each of the last five consecutive determinations of 𝑚12 is within ± 5 % of G. Considering the water vapour permeability of air δair equal to 2.05 ∙ 10 ―10 kg/(msPa), with a measured barometric pressure of 985 hPa at 23°C inside the apparatus, the water vapour resistance factor μ can be calculated as follows:
𝜇=
𝛿𝑎𝑖𝑟 𝛿
(2)
The water vapour permeability 𝛿 is obtained by multiplying the thickness of the sample d by the water vapour permeance W:
𝛿 =𝑊∙𝑑
(3)
W is given by:
3
𝑊 =
𝐺 𝐴 ∙ 𝛥𝑃
(4)
where A is the average value of the free upper and lower surface areas of the sample and P is the water vapour pressure difference across sample, equal to 1404 Pa for the selected test conditions [9].
(a)
(b)
Fig. 2. Hygrothermal measurements with dry cup method [9]: (a) samples preparation and (b) positioning in the climatic chamber.
3. RESULTS AND DISCUSSION The trend of the weight of the selected samples vs time is reported in Figure 3; data were used to calculate the water vapour resistance factor values shown in Table 1. The stability of permeability tests was achieved in different times for each sample, up to a maximum of 2 months from the starting of the experimental campaign. μ-values in the 31-33 range were obtained for expanded polystyrene (samples 5A and 5B), in agreement with data in the technical sheet of the material (20-40). Despite technical sheets were not available for gypsum plasters, the permeability performance of the 4A and 4B samples (μ = 7-9) are comparable with data relating to traditional gypsum plasters, generally in the 5-10 range [12]. Furthermore, it is possible to observe that the water vapour resistance properties obtained for the leather cutting waste panels (1A and 1B, μ = 27 – 30) and rise husk one (2B, μ = 41, 2A-test was stopped due to the non-perfect sealing of the sample to the cup) are higher than the values found for other vegetable fibers, such as wood (μ = 3 – 10), cork (μ = 5 – 10), hemp, flax, corn, and coir (μ = 1 – 3), and mineral fibers (μ = 5 – 8 for expanded vermiculite and perlite and μ = 1 – 5 for glass or stone wool) [13]. Excellent moisture transfer properties are allowed with coffee chaff (μ = 392); however only one sample (3A) achieved the stability during the test and it was considered in the final results. Data about porosity are available for coffee chaff and rice husk from a previous paper [5]: the porosity of coffee chaff (45.1%) is lower than the one of rice husk (59.7%), according to the higher vapour resistance of coffee chaff (392 vs. 41).
4
waste leather_1A rice husk_2B gypsum plaster_4A polystyrene_5A
waste leather_1B coffee chaff_3A gypsum plaster_4B polystyrene_5B
0.750 0.700
Weight [kg]
0.650 0.600 0.550 0.500 0.450 0.400 0.350 0.300 0.250
Fig. 3. The weight trends vs. time of the samples.
5
polystyrene
gypsum plaster
coffee chaff
rice husk
waste leather
Table. 1. Permeability measurements results. Sample
Stability
1A
after 2 months
1B
after 1 month
2A
not achieved
2B
after 6 weeks
3A
after 3 months
3B
not achieved
4A
after 3 weeks
4B
after 5 weeks
5A
after 1 month
5B
after 1 month
𝑚12 [kg/s] 4.17 ∙ 10 ―9 4.17 ∙ 10 ―9 4.17 ∙ 10 ―9 4.17 ∙ 10 ―9 4.05 ∙ 10 ―9 4.49 ∙ 10 ―9 4.55 ∙ 10 ―9 4.86 ∙ 10 ―9 4.63 ∙ 10 ―9 4.67 ∙ 10 ―9 3.14 ∙ 10 ―9 3.11 ∙ 10 ―9 3.11 ∙ 10 ―9 3.04 ∙ 10 ―9 3.09 ∙ 10 ―9 1.13 ∙ 10 ―9 1.13 ∙ 10 ―9 1.21 ∙ 10 ―9 1.13 ∙ 10 ―9 1.16 ∙ 10 ―9 6.43 ∙ 10 ―9 6.67 ∙ 10 ―9 6.37 ∙ 10 ―9 6.25 ∙ 10 ―9 6.48 ∙ 10 ―9 4.86 ∙ 10 ―9 4.86 ∙ 10 ―9 4.95 ∙ 10 ―9 4.75 ∙ 10 ―9 4.71 ∙ 10 ―9 2.61 ∙ 10 ―9 2.43 ∙ 10 ―9 2.43 ∙ 10 ―9 2.31 ∙ 10 ―9 2.55 ∙ 10 ―9 2.29 ∙ 10 ―9 2.21 ∙ 10 ―9 2.23 ∙ 10 ―9 2.32 ∙ 10 ―9 2.27 ∙ 10 ―9
G [kg/s]
𝑊 [s/m]
d [m]
𝛿 [s]
μ [-]
4.14 ∙ 10 ―9
3.76 ∙ 10 ―10
0.018
6.76 ∙ 10 ―12
30
4.63 ∙ 10 ―9
4.21 ∙ 10 ―10
0.018
7.57 ∙ 10 ―12
27
-
-
-
3.09 ∙ 10 ―9
2.76 ∙ 10 ―10
0.018
4.96 ∙ 10 ―12
41
1.15 ∙ 10 ―9
1.05 ∙ 10 ―10
0.005
5.23 ∙ 10 ―13
392
-
-
-
6.44 ∙ 10 ―9
5.84 ∙ 10 ―10
0.05
2.92 ∙ 10 ―11
7
4.82 ∙ 10 ―9
4.34 ∙ 10 ―10
0.05
2.19 ∙ 10 ―11
9
2.47 ∙ 10 ―9
2.10 ∙ 10 ―10
0.03
6.31 ∙ 10 ―12
31
2.26 ∙ 10 ―9
2.05 ∙ 10 ―10
0.03
6.15 ∙ 10 ―12
33
-
-
4. CONCLUSIONS Hygrothermal properties of building materials are a key parameter in indoor comfort. Data about water vapour permeability are often lacking in the scientific literature, especially for innovative solutions. In this paper the water vapour diffusion resistance factors of innovative building materials were measured by a dry cup method,
6
according to EN ISO 12572 [9]. The performance of gypsum plaster from the Safi region (Morocco) and expanded polystyrene were also evaluated, in order to ensure the validity of the measurements procedure. μvalues measured for these two samples are in agreement with Literature data and the material technical sheet, respectively, therefore the method can be considered reliable. Three innovative panels consisting of recycled waste from different industrial processes (leather cuttings, rise husk, and coffee chaff) were analysed. The water vapour resistance factor for the leather cutting waste (μ = 27 – 30) and rise husk (μ = 41) panels are higher than the values measured for other mineral fibres-based panels, such as sheep wool, wood, and cork (values of about 3 – 10). Much higher value is measured for the coffee chaff (392). This last material, characterized by excellent moisture transfer, has to be carefully checked, because it could incur increase in heat loss and acoustically weak points, so that it deserves a more deepen study.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements Authors wish to thank dr. Francesca Baldassarri for her precious contribution during the experimental campaign.
REFERENCES [1]
United
Nation
Environment
Programme,
Environment
for
development.
http://www.unep.org/sbci/AboutSBCI/Background.asp (accessed 10 July 2019). [2] C. Leiva, C. Arenas, L.F.Vilches, B. Alonso-Farinas, M. Rodriguez-Galan, Development of fly ash boards with thermal, acoustic and fire insulation properties, Waste Manage. 46 (2015) 298–303. [3] M. Pedroso, J. de Brito, J.D. Silvestre, Characterization of eco-efficient acoustic insulation materials (traditional and innovative), Constr. Build. Mater. 140 (2017) 221-228. [4] P. Ricciardi, F. Torchia, E. Belloni, E. Lascaro, C. Buratti, Environmental characterisation of coffee chaff, a new recycled material for building applications, Constr. Build. Mater. 147 (2017) 185–193. [5] C. Buratti, E. Belloni, E. Lascaro, F. Merli, P. Ricciardi, Rice husk panels for building applications: Thermal, acoustic, and environmental characterization and comparison with other innovative recycled waste materials, Constr. Build. Mater. 171 (2018) 338–349. [6] P. Huang, E. Latif, W.S. Chang, M.P. Ansell, M. Lawrence, Water vapour diffusion resistance factor of Phyllostachys edulis (Moso bamboo), Constr. Build. Mater. 141 (2017) 216–221. [7] Š. Nenadálová, L. Balík, M. Rydval, T. Bittner, Laboratory verification of water vapour permeability of plaster compositions, Procedia Eng. 151 (2016) 50 – 57. [8] L. Casnedi, M. Cappai, A. Cincotti, F. Delogu, G. Pia, Porosity effects on water vapour permeability in earthen materials: Experimental evidence and modelling description, J. Build. Eng. 27 (2020) 100987.
7
[9] EN ISO 12572. Hygrothermal performance of building materials and products – Determination of water vapour transmission properties – Cup method, 2016. [10] S. Bouzit, S. Laasri, M. Taha, A. Laghzizil, A. Hajjaji, F. Merli, C. Buratti, Characterization of Natural Gypsum Materials and Their Composites for Building Applications, Appl. Sci. 9 (2019) 2443. [11]
Expanded
polystyrene
technical
sheet.
https://www.fortlan-dibi.it/prodotti/polistirene-espanso-
sintetizzato/dibipop-136-.htm (accessed 3 June 2019). [12] Hygrothermal performance of building components. http://www.docente.unicas.it/useruploads/000370/files/prestazioni_igrotermiche_dei_componenti_in_edilizia_ .pdf (accessed 8 July 2019). [13] http://www.iuav.it/SISTEMA-DE/Archivio-d/approfondi/materiali-/Materiali_Isolanti.pdf (accessed 8 July 2019).
8
WATER VAPOUR PERMEABILITY OF INNOVATIVE BUILDING MATERIALS FROM DIFFERENT WASTE C. Buratt*, E. Belloni, F. Merli Department of Engineering – University of Perugia. Via G. Duranti 67. 06125 Perugia (Italy)
Author Contributions: Conceptualization: Cinzia Buratti Methodology: Cinzia Buratti, Elisa Belloni, Francesca Merli Investigation: Elisa Belloni, Francesca Merli Writing—original draft preparation: Elisa Belloni, Francesca Merli Writing—review and editing: Cinzia Buratti Supervision: Cinzia Buratti
9
Declaration of interests
☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
The corresponding Author (on behalf of all the Authors) Prof. Cinzia Buratti
10
Highlights:
innovative thermal insulation panels based on waste materials were developed;
dry cup method was validated with known permeability values;
hygrothermal performance of panels made of waste materials was evaluated;
water vapour resistance factor was experimentally measured.
11
S0167-577X(20)30164-6 https://doi.org/10.1016/j.matlet.2020.127459 MLBLUE 127459
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
8 November 2019 14 January 2020 31 January 2020
Please cite this article as: C. Buratti, E. Belloni, F. Merli, Water vapour permeability of innovative building materials from different waste, Materials Letters (2020), doi: https://doi.org/10.1016/j.matlet.2020.127459
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2020 Published by Elsevier B.V.
WATER VAPOUR PERMEABILITY OF INNOVATIVE BUILDING MATERIALS FROM DIFFERENT WASTE C. Buratti a*, E. Belloni a, F. Merli a a
Department of Engineering – University of Perugia. Via G. Duranti 67. 06125 Perugia (Italy)
*Corresponding author: [email protected]; tel. +39 075 5853993; fax. +39 075 5853916
ABSTRACT The hygrothermal performance of building materials is a very important issue for indoor comfort. The aim of this study is to measure the water vapour resistance factor μ of recycled waste materials. Leather cuttings, rice husk, and coffee chaff were used in order to manufacture innovative panels for thermal-noise building insulation. The permeability measurements were carried out by the dry cup method in compliance with the Standard EN ISO 12572. In the experimental campaign, conventional gypsum plaster and expanded polystyrene were also considered, whose hygrothermal characteristics are known from the Literature, in order to verify the reliability of the method. The moisture transfer properties of the innovative panels are higher than the values available in the Literature for other vegetable and mineral fibers-based panels (sheep wool, wood, cork, expanded vermiculite and perlite, glass or stone wool, and so on). However, the high μ-value obtained for coffee chaff panels (equal to 392) could involve an increase in heat loss and acoustically weak points.
Keywords: permeability performance, water vapour resistance factor, building insulation, recycled waste materials.
1. INTRODUCTION In the modern society, energy efficiency and environmental issue aspects are becoming central. The building sector can be considered the major responsible for energy resources, water consumption, and for carbon dioxide emissions [1]. In this context, a lot of constructive solutions and insulation materials based on renewable resources or waste are developed. In the Literature the development, experimental thermal-noise insulation properties, lower environmental impact, embodied energy, resource consumption, and pollution emissions of these materials are subject of many studies [2-5]. Air tightness of the building envelope is another very important aspect in order to reduce energy consumptions, but it is necessary to balance the walls breathability, which on one hand ensures a greater durability of the materials avoiding condensation problems, and on the other one involves reduction in thermo-acoustic performance, with a decrease in indoor comfort. Few authors in the scientific literature take into account this aspect by measuring the water vapour diffusion resistance factor of different materials, such as Moso bamboo [6] or plasters with different compositions [7]. In other studies these properties are in relationship with other ones, for example with porosity [8]. In this work, the hygrothermal performance of innovative panels consisting of recycled materials are evaluated, in compliance with Standard prescriptions [9]. Scraps resulting from industrial processing, such as leather cuttings, rice husk, and coffee chaff are glued and pressed, in order to fabricate panels. In the last years the
1
Authors started a systematic study on the influence of these materials on the thermal, acoustic, mechanical, and environmental aspects [4, 5]. This paper aims to evaluate their water vapour resistance factor μ, which represents the resistance of the material to be crossed by water vapour with respect to an equally thick layer of stationary air at the same temperature. In order to validate the procedure, also gypsum plaster [10] and conventional insulating panels of expanded polystyrene [11] were considered in the study. The measured values were finally compared with other insulation materials available on the market and with their technical sheet data. 2. MATERIALS AND TESTING METHOD 2.1. Samples description The permeability performance of traditional insulating materials for building applications, such as gypsum from the Safi region (in south-western Morocco), expanded polystyrene, and new recycled ones (glued and pressed leather cuttings waste, rice husk, and coffee chaff) were investigated. For each material, two cylindrical 100mm diameter samples (Figure 1) were purposely fabricated for the study; they were weighed with an electronic precision balance and their thicknesses were measured by a centesimal caliber. In particular: -
leather cuttings waste (1A and 1B) provided by an Italian company in the province of Viterbo were obtained from leather sheets wasted in bags production process. Raw material was chipped and added to Polyvinylacetate glue (5% by weight), along with distilled water (at a ratio of 12% by weight); a hydraulic press allowed the panels fabrication. The 1A and 1B samples were 18-mm thick with a weight of 0.074 kg and 0.091 kg, respectively (estimated densities 570 and 650 kg/m3);
-
2A and 2B panels [5] (both 0.026 kg) consisting of rice husk produced by gluing and pressing the raw material provided by a company based in Lombardy (Italy) were 18-mm thickness. The material is originated by the paddy rice husking process; after threshing the rough rice (unpolished), rice husk was added to a cold-water-based polyurethane glue (percentage 2.5% of the total weight) and pressed as a panel;
-
glued and pressed 3A (0.034 kg) and 3B (0.037 kg) samples 5-mm thick [4,5] were made of coffee chaff, originated by the roasting process of a factory from northern Italy (Pavia);
-
gypsum plasters [10] (4A and 4B, 50-mm thick) were manufactured by mixing Safi (Morocco) natural rock powder with water (mass ratio water/gypsum of 0.8) and dried, according to the thermal stability of the samples. Their weight were 0.375 kg and 0.372 kg, respectively;
-
conventional insulating samples consisting in expanded polystyrene (5A and 5B, 30-mm thick and 0.004 kg weight) [11] were analysed as reference. Water vapour resistance factor μ was in the 20 – 40 range, as suggested by the technical sheet of the material.
In compliance with EN ISO 12572 Standard [9] prescriptions, the samples were preconditioned in a climatic chamber (Mazzali C330G5), characterized by 600 x 700 x 680 mm internal dimensions, - 40°C – 150°C temperature range, and 15% - 100% relative humidity range, available at the University of Perugia. The conditions considered for the tests are 23±5 °C and 50±5% relative humidity. This conditioning lasted for 3 days, until three successive daily determinations of the samples’ weight was within 5%.
2
1A
2A
3A
4A
5A
1B
2B
3B
4B
5B
Fig. 1. The investigated samples for hygrothermal measurements.
2.2. Hygrothermal measurement method Water vapour resistance factor μ-values of the different samples were measured with the dry cup method, according to [9]. The preconditioned samples were placed and sealed in transparent plastic cups containing silicagel as desiccant; transparent cups allow to control the colour change of the salt solution when absorbing water vapour (Figure 2 a). A minimum depth of 15-mm silicagel (granules diameter in the 1 – 3 mm range) with colour indicator was put at the bottom of each cup, leaving an air space of 15 ± 5 mm between the desiccant and the sample. The assembled specimens were then placed in the temperature and relative humidity controlled test chamber, with environmental conditions suggested in [9] (Figure 2 b). A vapour flow occurs through the permeable samples, due to the different partial vapour pressure between the test cup and the chamber. Every 24 hours the samples were weighed, in order to evaluate the rate of water vapour transmission in the steady-state conditions and the mass change rate 𝑚12 was calculated as:
𝑚12 =
𝑚2 ― 𝑚1 𝑡2 ― 𝑡1
[𝑘𝑔 𝑠]
(1)
where: 𝑚1 [kg] and 𝑚2 [kg] are the masses of the test assembly at successive times of weighings 𝑡1 [s] and 𝑡2 [s], respectively. The mean of five consecutive determinations of 𝑚12 was named G; final G-value is obtained when each of the last five consecutive determinations of 𝑚12 is within ± 5 % of G. Considering the water vapour permeability of air δair equal to 2.05 ∙ 10 ―10 kg/(msPa), with a measured barometric pressure of 985 hPa at 23°C inside the apparatus, the water vapour resistance factor μ can be calculated as follows:
𝜇=
𝛿𝑎𝑖𝑟 𝛿
(2)
The water vapour permeability 𝛿 is obtained by multiplying the thickness of the sample d by the water vapour permeance W:
𝛿 =𝑊∙𝑑
(3)
W is given by:
3
𝑊 =
𝐺 𝐴 ∙ 𝛥𝑃
(4)
where A is the average value of the free upper and lower surface areas of the sample and P is the water vapour pressure difference across sample, equal to 1404 Pa for the selected test conditions [9].
(a)
(b)
Fig. 2. Hygrothermal measurements with dry cup method [9]: (a) samples preparation and (b) positioning in the climatic chamber.
3. RESULTS AND DISCUSSION The trend of the weight of the selected samples vs time is reported in Figure 3; data were used to calculate the water vapour resistance factor values shown in Table 1. The stability of permeability tests was achieved in different times for each sample, up to a maximum of 2 months from the starting of the experimental campaign. μ-values in the 31-33 range were obtained for expanded polystyrene (samples 5A and 5B), in agreement with data in the technical sheet of the material (20-40). Despite technical sheets were not available for gypsum plasters, the permeability performance of the 4A and 4B samples (μ = 7-9) are comparable with data relating to traditional gypsum plasters, generally in the 5-10 range [12]. Furthermore, it is possible to observe that the water vapour resistance properties obtained for the leather cutting waste panels (1A and 1B, μ = 27 – 30) and rise husk one (2B, μ = 41, 2A-test was stopped due to the non-perfect sealing of the sample to the cup) are higher than the values found for other vegetable fibers, such as wood (μ = 3 – 10), cork (μ = 5 – 10), hemp, flax, corn, and coir (μ = 1 – 3), and mineral fibers (μ = 5 – 8 for expanded vermiculite and perlite and μ = 1 – 5 for glass or stone wool) [13]. Excellent moisture transfer properties are allowed with coffee chaff (μ = 392); however only one sample (3A) achieved the stability during the test and it was considered in the final results. Data about porosity are available for coffee chaff and rice husk from a previous paper [5]: the porosity of coffee chaff (45.1%) is lower than the one of rice husk (59.7%), according to the higher vapour resistance of coffee chaff (392 vs. 41).
4
waste leather_1A rice husk_2B gypsum plaster_4A polystyrene_5A
waste leather_1B coffee chaff_3A gypsum plaster_4B polystyrene_5B
0.750 0.700
Weight [kg]
0.650 0.600 0.550 0.500 0.450 0.400 0.350 0.300 0.250
Fig. 3. The weight trends vs. time of the samples.
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polystyrene
gypsum plaster
coffee chaff
rice husk
waste leather
Table. 1. Permeability measurements results. Sample
Stability
1A
after 2 months
1B
after 1 month
2A
not achieved
2B
after 6 weeks
3A
after 3 months
3B
not achieved
4A
after 3 weeks
4B
after 5 weeks
5A
after 1 month
5B
after 1 month
𝑚12 [kg/s] 4.17 ∙ 10 ―9 4.17 ∙ 10 ―9 4.17 ∙ 10 ―9 4.17 ∙ 10 ―9 4.05 ∙ 10 ―9 4.49 ∙ 10 ―9 4.55 ∙ 10 ―9 4.86 ∙ 10 ―9 4.63 ∙ 10 ―9 4.67 ∙ 10 ―9 3.14 ∙ 10 ―9 3.11 ∙ 10 ―9 3.11 ∙ 10 ―9 3.04 ∙ 10 ―9 3.09 ∙ 10 ―9 1.13 ∙ 10 ―9 1.13 ∙ 10 ―9 1.21 ∙ 10 ―9 1.13 ∙ 10 ―9 1.16 ∙ 10 ―9 6.43 ∙ 10 ―9 6.67 ∙ 10 ―9 6.37 ∙ 10 ―9 6.25 ∙ 10 ―9 6.48 ∙ 10 ―9 4.86 ∙ 10 ―9 4.86 ∙ 10 ―9 4.95 ∙ 10 ―9 4.75 ∙ 10 ―9 4.71 ∙ 10 ―9 2.61 ∙ 10 ―9 2.43 ∙ 10 ―9 2.43 ∙ 10 ―9 2.31 ∙ 10 ―9 2.55 ∙ 10 ―9 2.29 ∙ 10 ―9 2.21 ∙ 10 ―9 2.23 ∙ 10 ―9 2.32 ∙ 10 ―9 2.27 ∙ 10 ―9
G [kg/s]
𝑊 [s/m]
d [m]
𝛿 [s]
μ [-]
4.14 ∙ 10 ―9
3.76 ∙ 10 ―10
0.018
6.76 ∙ 10 ―12
30
4.63 ∙ 10 ―9
4.21 ∙ 10 ―10
0.018
7.57 ∙ 10 ―12
27
-
-
-
3.09 ∙ 10 ―9
2.76 ∙ 10 ―10
0.018
4.96 ∙ 10 ―12
41
1.15 ∙ 10 ―9
1.05 ∙ 10 ―10
0.005
5.23 ∙ 10 ―13
392
-
-
-
6.44 ∙ 10 ―9
5.84 ∙ 10 ―10
0.05
2.92 ∙ 10 ―11
7
4.82 ∙ 10 ―9
4.34 ∙ 10 ―10
0.05
2.19 ∙ 10 ―11
9
2.47 ∙ 10 ―9
2.10 ∙ 10 ―10
0.03
6.31 ∙ 10 ―12
31
2.26 ∙ 10 ―9
2.05 ∙ 10 ―10
0.03
6.15 ∙ 10 ―12
33
-
-
4. CONCLUSIONS Hygrothermal properties of building materials are a key parameter in indoor comfort. Data about water vapour permeability are often lacking in the scientific literature, especially for innovative solutions. In this paper the water vapour diffusion resistance factors of innovative building materials were measured by a dry cup method,
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according to EN ISO 12572 [9]. The performance of gypsum plaster from the Safi region (Morocco) and expanded polystyrene were also evaluated, in order to ensure the validity of the measurements procedure. μvalues measured for these two samples are in agreement with Literature data and the material technical sheet, respectively, therefore the method can be considered reliable. Three innovative panels consisting of recycled waste from different industrial processes (leather cuttings, rise husk, and coffee chaff) were analysed. The water vapour resistance factor for the leather cutting waste (μ = 27 – 30) and rise husk (μ = 41) panels are higher than the values measured for other mineral fibres-based panels, such as sheep wool, wood, and cork (values of about 3 – 10). Much higher value is measured for the coffee chaff (392). This last material, characterized by excellent moisture transfer, has to be carefully checked, because it could incur increase in heat loss and acoustically weak points, so that it deserves a more deepen study.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements Authors wish to thank dr. Francesca Baldassarri for her precious contribution during the experimental campaign.
REFERENCES [1]
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http://www.unep.org/sbci/AboutSBCI/Background.asp (accessed 10 July 2019). [2] C. Leiva, C. Arenas, L.F.Vilches, B. Alonso-Farinas, M. Rodriguez-Galan, Development of fly ash boards with thermal, acoustic and fire insulation properties, Waste Manage. 46 (2015) 298–303. [3] M. Pedroso, J. de Brito, J.D. Silvestre, Characterization of eco-efficient acoustic insulation materials (traditional and innovative), Constr. Build. Mater. 140 (2017) 221-228. [4] P. Ricciardi, F. Torchia, E. Belloni, E. Lascaro, C. Buratti, Environmental characterisation of coffee chaff, a new recycled material for building applications, Constr. Build. Mater. 147 (2017) 185–193. [5] C. Buratti, E. Belloni, E. Lascaro, F. Merli, P. Ricciardi, Rice husk panels for building applications: Thermal, acoustic, and environmental characterization and comparison with other innovative recycled waste materials, Constr. Build. Mater. 171 (2018) 338–349. [6] P. Huang, E. Latif, W.S. Chang, M.P. Ansell, M. Lawrence, Water vapour diffusion resistance factor of Phyllostachys edulis (Moso bamboo), Constr. Build. Mater. 141 (2017) 216–221. [7] Š. Nenadálová, L. Balík, M. Rydval, T. Bittner, Laboratory verification of water vapour permeability of plaster compositions, Procedia Eng. 151 (2016) 50 – 57. [8] L. Casnedi, M. Cappai, A. Cincotti, F. Delogu, G. Pia, Porosity effects on water vapour permeability in earthen materials: Experimental evidence and modelling description, J. Build. Eng. 27 (2020) 100987.
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[9] EN ISO 12572. Hygrothermal performance of building materials and products – Determination of water vapour transmission properties – Cup method, 2016. [10] S. Bouzit, S. Laasri, M. Taha, A. Laghzizil, A. Hajjaji, F. Merli, C. Buratti, Characterization of Natural Gypsum Materials and Their Composites for Building Applications, Appl. Sci. 9 (2019) 2443. [11]
Expanded
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https://www.fortlan-dibi.it/prodotti/polistirene-espanso-
sintetizzato/dibipop-136-.htm (accessed 3 June 2019). [12] Hygrothermal performance of building components. http://www.docente.unicas.it/useruploads/000370/files/prestazioni_igrotermiche_dei_componenti_in_edilizia_ .pdf (accessed 8 July 2019). [13] http://www.iuav.it/SISTEMA-DE/Archivio-d/approfondi/materiali-/Materiali_Isolanti.pdf (accessed 8 July 2019).
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WATER VAPOUR PERMEABILITY OF INNOVATIVE BUILDING MATERIALS FROM DIFFERENT WASTE C. Buratt*, E. Belloni, F. Merli Department of Engineering – University of Perugia. Via G. Duranti 67. 06125 Perugia (Italy)
Author Contributions: Conceptualization: Cinzia Buratti Methodology: Cinzia Buratti, Elisa Belloni, Francesca Merli Investigation: Elisa Belloni, Francesca Merli Writing—original draft preparation: Elisa Belloni, Francesca Merli Writing—review and editing: Cinzia Buratti Supervision: Cinzia Buratti
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Declaration of interests
☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
The corresponding Author (on behalf of all the Authors) Prof. Cinzia Buratti
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Highlights:
innovative thermal insulation panels based on waste materials were developed;
dry cup method was validated with known permeability values;
hygrothermal performance of panels made of waste materials was evaluated;
water vapour resistance factor was experimentally measured.
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