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Material properties and full-scale rain exposure of lime-hemp concrete walls

measurements and simulations

de Bruijn, Paulien (2012). Material properties and full-scale rain exposure of lime-hemp concrete walls. Diss. (sammanfattning/summary) Alnarp, Sweden : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2012:68
ISBN 978-91-576-7715-0
[Doctoral thesis]

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Abstract

Lime-hemp concrete (LHC) is a building material consisting of a lime-based binder combined with hemp shiv that is suitable for various building applications. This thesis aimed to elucidate the possibilities for using LHC for exterior walls in a cold, wet climate through investigating mechanical, thermal and moisture-related properties of the material.
The mechanical properties of LHC containing both shiv and fibres of the hemp stalk in combination with different binders were tested in order to find a mixture with increased mechanical strength so that a supporting timber load-bearing structure could be omitted. A larger amount of cement in the binder mix improved compressive strength. However, even when using unseparated hemp (both shiv and fibres) in combination with a high-cement binder, mechanical strength was not sufficient for the material to be load-bearing without additional support.
The moisture properties of LHC were studied in order to determine its robustness and durability in cold, wet conditions. Sorption isotherms and moisture diffusivity were determined over the complete moisture range for two LHC mixes with different lime:hemp ratios. Compared with other building materials (e.g. timber, cellular concrete and lime-based render), LHC showed a high moisture diffusion coefficient in the 35-95% relative humidity (RH) range. The sorption isotherm of LHC appeared quite planar up to 95% RH, but steep between 95 and 100% RH.
The thermal properties of specimens with different relative humidities were found to be influenced by RH. At higher RH values thermal conductivity was higher, whereas differences in thermal diffusivity and specific heat capacity as a consequence of differences in RH were less apparent.
Four full-scale wall sections combining different renders and LHC mixes were exposed to a rain scenario in order to fully understand the hygric performance. Moisture properties were used in computer simulations of these full-scale wall sections and the simulation results compared with measured data. It was found that even after prolonged rain exposure, some wall sections had low moisture levels inside the wall. A lime-cement render allowed rain to penetrate the wall more easily than a cement render and also dried more slowly after exposure to rain. LHC with a larger proportion of hemp absorbed moisture more slowly and dried more quickly after construction than a mix with a larger proportion of lime. This indicates that LHC with more hemp in the mix in combination with a cement render would be more suitable for use in a cold, wet climate.

Authors/Creators:de Bruijn, Paulien
Title:Material properties and full-scale rain exposure of lime-hemp concrete walls
Subtitle:measurements and simulations
Series/Journal:Acta Universitatis agriculturae Sueciae (1652-6880)
Year of publishing :2012
Volume:2012:68
Number of Pages:67
Papers/manuscripts:
NumberReferences
1de Bruijn, P.B., Jeppsson, K-H. & Nilsson, C. (2009). Mechanical properties of lime-hemp concrete containing shives and fibres. Journal of Biosystems Engineering 1003, 474-479.
2de Bruijn, P.B. & Johansson, P.(2012). Moisture transport properties of lime-hemp concrete determined over the complete moisture range. Submitted to an international peer-reviewed journal.
3de Bruijn, P.B. & Johansson, P. (2012). Moisture fixation and thermal properties of lime-hemp concrete. Submitted to an international peer-reviewed journal.
4de Bruijn, P.B., Johansson, P., Jeppsson, K-H. & Nilsson, C. (2012). Measured and simulated hygric performance of lime-hemp concrete walls exposed to rain. Submitted to an international peer-reviewed journal.
Place of Publication:Alnarp, Sweden
Publisher:Dept. of Rural Buildings and Animal Husbandry, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-576-7715-0
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:X Agricola extesions > X60 Technology
Subjects:Obsolete subject words > TECHNOLOGY > Materials science > Construction materials
Agrovoc terms:construction materials, concrete, hemp, limestone, technical properties, simulated rainfall, moisture content
Keywords:lime-hemp concrete, moisture properties, hemp shiv, hydraulic lime, slaked lime, rain exposure, moisture transport, moisture fixation, mechanical properties, lime-hemp
URN:NBN:urn:nbn:se:slu:epsilon-e-596
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-596
ID Code:9007
Department:(LTJ, LTV) > Rural Buildings and Animal Husbandry (until 121231)
External funders:Royal Swedish Academy of Agriculture and Forestry
Deposited By: Paulien de Bruijn
Deposited On:30 Aug 2012 09:23
Metadata Last Modified:02 Dec 2014 10:51

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