Article

Structural benefits of hempcrete infill in timber stud walls

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Abstract

Hempcrete is a bio-composite mix made up of hemp shives, lime, cement and water. Extensive research has shown that it has good thermal and acoustic insulation properties, and can passively regulate humidity in a built environment. However it has low compressive strength and modulus of elasticity and so cannot be used as a direct load bearing material. It is often used as an infill material in timber stud walls. The objective of this study was to determine if the hempcrete infill has sufficient strength and stiffness to act as lateral bracing and prevent weak-axis buckling of the timber studs.Seven timber walls were constructed (both half scale – 1200 mm high; and full scale - up to 2133 mm high) with varying column dimensions. Five of the walls were infilled with hempcrete of two different densities (313 kg/m3 and 715 kg/m3). Two walls were not infilled and were baseline tests. All walls were tested in compression. It was found that high density hempcrete (715 kg/m3) not only prevents weak-axis buckling of columns but also carries some direct load. Low density hempcrete was also successful in preventing weak-axis buckling of the infilled walls. Infilled walls failed in strong-axis buckling at a load twice (for half scale walls with 38 × 89 mm columns) or four times (full scale walls with 38 × 235 mm columns) that of the unfilled walls. An analytical model (based on buckling of a strut on an elastic foundation) was proposed to predict the maximum capacity of hempcrete as a continuous lateral support for a column.

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... This, too, has strong negative effects for energy bills. Anyone who lives in a modern home and has observed how easily the room temperature drops when the heating is switched off is frustrated [20] . ...
... The raw material for hempcrete will become more readily available as hemp cultivation spreads around the world and processing plants made easy [20] . If textile manufacturers can shift away from cotton and toward hemp, the hemp market can grow quickly, allowing the price of hemp shiv to remain steady. ...
Article
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Concrete one of the important building material and day by day the utilization of concrete increasing to meet the infrastructure development requirement. On one hand it is unavoidable but some alternative to be explored to reduce the global environmental impact caused by the concrete. To overcome this from the last decade the world is looking towards the fact of sustainability due to rapid industrialization. The growth in the construction industry increased the demand of concrete as construction material. This concrete produces significant amount of greenhouse emission in the environment. There is a need to find an alternative solution to minimize the greenhouse emission emitted from the concrete manufacturing plant.
... This, too, has strong negative effects for energy bills. Anyone who lives in a modern home and has observed how easily the room temperature drops when the heating is switched off is frustrated [20] . ...
... The raw material for hempcrete will become more readily available as hemp cultivation spreads around the world and processing plants made easy [20] . If textile manufacturers can shift away from cotton and toward hemp, the hemp market can grow quickly, allowing the price of hemp shiv to remain steady. ...
Conference Paper
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Construction industry is one of the main sectors contributing for the growth of countries economy and also it is one of sector releasing huge amount of carbon emission in the atmosphere. Several measures are taken in this sector by adopting new trends in the construction industry with respect to the use of evolving material such as low carbon cement, fast setting concrete, Self-healing concrete and more, has left us with a high need for research in the area of sustainable materials. As most of the building material used in construction like concrete and cement are high carbon dioxide emitting material that can be a hazard (in a longer run) to the environment and people working in such buildings. To overcome this situation an alternative sustainable material has to be used for the construction of eco-friendly buildings. Hempcrete is a bio-composite material and also it is one of the prospective materials to reduce greenhouse gas emissions. It can be used in Construction and Insulation activities by Hemp hurds and lime. Hemp is the fastest growing plant and has one of the strongest plants fibers and due to its fastest and rapid growing nature it can lock up more carbon in it. This has been used in France since the 1990s for construction of non-weight bearing insulating infill walls. A meter cube of hempcrete has the capability to absorb 165 kg of carbon dioxide and has excellent fire resistance. Resistance to crack under movement being the core property of hempcrete makes it most appropriate for use in earthquake-prone areas. In this research, an initiative was taken up to check the feasibility of hempcrete as an alternative to conventional concrete. Few feasibility studies were carried to highlight application and access the properties of the same. The main aim to suggest the application of hempcrete with admixture like fine aggregate and testing of its strength under Universal Testing Machine (AIMIL) make. Though, Hempcrete does not have adequate strength as par with the conventional concrete but can be used for the construction of substructure. It can be concluded that it can be highly beneficial for non-load bearing structures for its property like lightweight breathability, energy efficiency etc.
... In view of their properties, it makes sense to consider that plant-based concretes could contribute to the mechanical performance of the structure. In particular, some authors [29][30][31][32] have shown that LHC provides in-plane racking strength to the timber frame. According to Munoz and Pipet [29], the mechanical behaviour of a timber stud frame with LHC infill is enhanced compared to that with diagonal bracing. ...
... An illustration of the racking strength test and failure of timber wall is presented in Fig. 1. Another author [32] has found that hemp concrete prevents weak axis buckling of timber columns by acting as a continuous lateral elastic support. Regarding high density LHC (715 kg m À3 ), it is stated that the latter can add strength to the wall by partly contributing to its load-bearing capacity. ...
... The interface between straw fiber and cement in HRCC is improved and the negative effect of hemp straw fiber on hydration reaction is alleviated. [4][5][6] 。秸秆纤 维作为重要的生物质可再生材料 [7][8] ...
... The term bio-aggregate concretes refers to the mixture of binders (lime, clay, plaster, and cement) and natural fibers (hemp, straw, flax, bamboo, and animal hairs) [1]. In this context, the use of eco-friendly concrete such as hempcrete [2], wood-concrete [3], papercrete [4], and mud-concrete [5] has been growing considerably. Hempcrete is most widely used in the field of green construction owing to its remarkable environmental quality as a non-CO2 producer [6,7]. ...
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Construction materials made of renewable resources have promising potential given their low cost, availability, and environmental friendliness. Although hemp fibers are the most extensively used fiber in the eco-friendly building sector, their unavailability hinders their application in Iraq. This study aimed to overcome the absence of hemp fiber in Iraq and develop a new sustainable construction material, strawcrete, by using wheat straw and traditional lime as the base binder. A comparable method of developing hempcrete was established. The experimental program adopted novel Mixing Sequence Techniques (MSTs), which depended on changing the sequence of mixed material with fixed proportions. The orientation of the applied load and the specimen's aspect ratio were also studied. The mixing proportion was 4:1:1 (fiber/binder/water) by volume. Results showed that the developed strawcrete had a dry unit weight ranging from 645 kg/m3 to 734 kg/m 3 and a compressive strength ranging from 1.8 MPa to 3.8 MPa. The enhanced physical and strength properties varied with the MST and loading orientation. The properties of the developed hempcrete were compared with those of strawcrete.
... Hempcrete insulation possesses the structural capacity to help restrain the studs from bending or buckling under loaded conditions. Results of tests conducted at Queen's University in Canada showed that a 610 mm  1830 mm timber stud wall with 313 kg/m 3 hempcrete infill could support three to four times the compressive loading of a standard stud wall due to the support that hempcrete provides to the timber stud in weak axis bending (Mukherjee and MacDougall, 2013). ...
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... Hempcrete is a more elastic material in comparison to traditional building materials and can allow walls to sustain lateral earthquake motion. 28 Hempcrete is a so-called zero carbon material but also acts as a carbon sink for the lifetime of the building, providing an environmentally safe and green home for its dwellers. ...
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... walls, failing at more than twice the load as compared to unfilled timber walls (Mukherjee, 2012). ...
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... It was found that the addition of hemp fiber resulted in a high performing construction material. [3] But is hemp really an environmentally friendly material? This paper explores answers to this question, using both published literature and on site experience. ...
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In the Climate Change Act of 2008 the UK Government pledged to reduce carbon emissions by 80% by 2050. As one step towards this, regulations are being introduced requiring all new buildings to be ‘zero carbon’ by 2019. These are defined as buildings which emit net zero carbon during their operational lifetime. However, in order to meet the 80% target it is necessary to reduce the carbon emitted during the whole life-cycle of buildings, including that emitted during the manufacture of materials and components, and during the processes of construction, refurbishment and demolition. These elements make up the ‘embodied carbon’ of the building. 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There is also a particular shortage of data across the construction sector in the energy used and carbon emitted during transport to site (part of stage 1 in prEN 15804), stages 2 (construction), 3 (in use) and 4 (end of life). The commercial and in-house analysis tools also vary in the databases they use, in their LCA methods and in the boundaries assumed in analysis.Taking each of the missing calculations in turn, the calculation of the reduced impacts of transport to site of local construction materials will inform and support the European standard BS EN 15643 parts 3 and 4, which considers the social and economic sustainability of construction works.Some construction projects last for several years and have hundreds of workers on site carrying out energy intensive activities. The accurate prediction of energy use and carbon emissions during standard site operations for stage 2 of the life cycle is therefore a fundamental part of the calculation for whole life embodied energy. Separately the development of off-site construction systems has been heralded as a ‘sustainable’ solution; this can only be verified with the development of an accurate ‘carbon costing’ method for both on-site and off-site construction activities, enabling the accurate comparison of different techniques and materials. Furthermore there is a lack of general data on the carbon and energy savings to be made by site management operations such as reuse of subgrade rather than the import of new materials.While ongoing maintenance and repair can be considered as part of the operational energy requirements, as suggested by the Strategic Forum for Construction (SFfC) [15], the impacts of major retrofit and refurbishment works form part of stage 3 of the whole life embodied impacts of a building. 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It is hoped that the forthcoming standardisation of EPDs should ensure that all manufacturers produce equivalent information for their products within a few years. However the diversity of products used within construction will mean that the LCA of individual buildings will remain complex.This review will guide the future development of a consistent and transparent database and software tool to calculate the embodied energy and carbon of buildings within the specific context of the UK. The research is being carried out as part of a project led by BLP Insurance, and with the support of the Technology Strategy Board and the Engineering and Physical Sciences Research Council (EPSRC).In the Climate Change Act of 2008 the UK Government pledged to reduce carbon emissions by 80% by 2050. As one step towards this, regulations are being introduced requiring all new buildings to be ‘zero carbon’ by 2019. These are defined as buildings which emit net zero carbon during their operational lifetime. However, in order to meet the 80% target it is necessary to reduce the carbon emitted during the whole life-cycle of buildings, including that emitted during the processes of construction. These elements make up the ‘embodied carbon’ of the building. While there are no regulations yet in place to restrict embodied carbon, a number of different approaches have been made. There are several existing databases of embodied carbon and embodied energy. Most provide data for the material extraction and manufacturing only, the ‘cradle to factory gate’ phase. In addition to the databases, various software tools have been developed to calculate embodied energy and carbon of individual buildings. A third source of data comes from the research literature, in which individual life cycle analyses of buildings are reported. This paper provides a comprehensive review, comparing and assessing data sources, boundaries and methodologies. The paper concludes that the wide variations in these aspects produce incomparable results. It highlights the areas where existing data is reliable, and where new data and more precise methods are needed. This comprehensive review will guide the future development of a consistent and transparent database and software tool to calculate the embodied energy and carbon of buildings.
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Hemp-lime is an insulating low carbon dioxide material that is produced from sustainable natural resources. The use of hemp-lime within the construction industry is a relatively recent development. Currently within the UK hemp-lime is used to form solid wall insulation in conjunction with structural timber studwork. Current design practice generally assumes that the hemp-lime does not contribute towards the structural capacity of the wall. This paper details research that has been undertaken to establish the compressive load enhancement provided to timber studs by encasement in hemp-lime. Laboratory testing was carried out on timber studs with and without hemp-lime and the results compared. It was found that the hemp-lime significantly increases the compressive capacity of the studs and prevents buckling from occurring.
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The building industry accounts for up to 40% of the earth's energy usage from material extraction through building operation; housing constitutes roughly 30% of energy use in North America. Owners and consumers are looking for more efficient building systems that would decrease this use of energy. The material chosen to construct the structure of a building has the potential to reduce the building's initial environmental impact and its life cycle energy use. However, this is rarely considered during conceptual design. Sustainable construction materials that have low embodied energy include earthen construction and straw bale construction. However, these materials are not widely accepted alternatives in North America because they are included only in select building codes in North America and around the world. In this paper, an extensive review of the current construction practice of sustainable construction materials is summarized. Durability concerns and limitations of the methods of construction are discussed, and areas of future research are identified. DOI: 10.1061/(ASCE)MT.1943-5533.0000241. (C) 2011 American Society of Civil Engineers.
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The Centre for Excellence is being designed as a highly innovative, two–storey multi-purpose facility that will provide essential trades and technology training and professional development to students in British Columbia, Canada and beyond. The building will support a syllabus with a focus on sustainable building technologies and processes, and the development and application of alternative and renewable energy. Design work and construction will be completed in time for the building to open in April 2011. The Centre for Excellence will also host an incubator organization to provide tenancy space for start–up innovation and research companies specializing in sustainable technologies. This building project is unique from a number of perspectives. It is aimed at attaining the highest standard of sustainable building design, namely the Living Building Challenge. Further, the building itself will become an essential element of the educational programs that will reside there, mainly focused on building trades and engineering technologies. In addition, the Okanagan Research Innovation Centre will be incorporated into the building, providing opportunities for start–up companies to develop and prototype new green technologies in a supportive and synergistic environment. Finally, this building is being constructed in the somewhat challenging climatic regime of the Okanagan region of Canada. The most important element of this project is that is will demonstrate that the Living Building Challenge is achievable at a cost comparable to conventional building design. The paper will focus on how this ambitious goal will be attained along with the numerous unique aspects that have been incorporated into the building design.
Book
Abstract The first half of the Review focuses on the impacts and risks arising from uncontrolled climate change, and on the costs and opportunities associated with action to tackle it. A sound understanding of the economics of risk is critical here. The Review ...
Article
The effect of using different binding agents in combination with hemp shives and fibres in Lime–Hemp Concrete (LHC) building material was examined. LHC is a light composite building material with building lime as binding agents and hemp (Cannabis sativa) as a renewable raw material from agriculture. Contemporary LHC only uses the woody core part of the hemp, the shive. However, using both hemp shives and fibres may improve the mechanical strength, eliminating the need for a fibre separation process. The aim was to elucidate the feasibility of using the entire fragmented hemp stalk in an LHC, and to determine some important material properties such as compressive strength, splitting tensile strength, water sorption and frost resistance. LHC with varying inclusions of the lime-based binders were tested, as were five mixes using the binding agents hydrated lime, hydraulic lime, and cement. Specimens were cured for 12 weeks at room temperature and 40 days in a carbonation room (4.5 vol% CO2), and tested for mechanical properties, water sorption and frost resistance. Using both shives and fibres in LHC may be advantageous for countries such as Sweden where facilities for separating hemp from shives are not commercially available.
Article
Timber column design methods have now to take account of a body of research work on timber properties from in-grade tests and on strength considerations using notions of stressed volume. This paper gathers results from this body of work and proposes a design formula for timber columns which is convenient to use and represents true behaviour. It includes, in particular, a material strength effect related to the length of the column. The proposed formula has been incorporated into the new Canadian code “Engineering design in wood.” Key words: timber, buckling, columns, design, size effects.
Article
Combined bending and axial loading is often encountered in lumber and timber members. Existing design methods are based on studies carried out many years ago, and are no longer appropriate because they do not recognize that wood with defects behaves in compression as a nonlinear ductile material and in tension as an elastic brittle material subject to size effects.This paper summarizes the findings of a comprehensive investigation into the behaviour of lumber subjected to eccentric axial loading, which was carried out at two Canadian universities. The study included analytical modelling and an extensive experimental program using full-size lumber.The results of the investigation have been used in this paper to propose improved design methods, using design charts and approximate formulae for in-plane behaviour. The discussion is extended to general loading cases and biaxial behaviour. Input information required for the design process is also discussed.
Article
Concrete blocks, made of a mixture of lime and hemp shives (also called “hemp hurds”), have been manufactured by a recently developed projection process. Lime carbonatation kinetics is determined by X-ray diffraction. Density measurements are made within blocks, and thermal and mechanical properties are measured (flexural strength, compression strength and hardness). The main observations are moderate density variations within a given block, and an influence of the projection distance on density. Both thermal conductivity and mechanical properties increase with the mortar density, which is well described by existing theoretical models. Compression tests induce a compaction, or densification, of the material.
Mechanical and Thermal properties of hemp mortars and wools: experimental and theoretical approaches
  • L Arnaud
Arnaud, L. Mechanical and Thermal properties of hemp mortars and wools: experimental and theoretical approaches. Proceedings of the third International symposium, bioresource, hemp and other fibre crops, Germany: Wolfsburg: 2000.
Innovative building material based on line and hemp particles: From ecological and technical interests
  • L Arnaud
  • D Samri
Arnaud, L. and Samri, D. Innovative building material based on line and hemp particles: From ecological and technical interests. International conference on Sustainability in the Cement and Concrete Industry, Lillehammer, Norway, September 16-19, pp. 580-592, 2007.
Hemp and lime composites in sustainable construction
  • I Pritchett
I. Pritchett, Hemp and lime composites in sustainable construction, Convention on Non-Conventional Materials, NOCMAT 2009 Proceedings, 2009, Bath, England.
ASTM D143 -09 for Small Clear Specimens of Timber
  • P A Usa
ASTM D143 -09 for Small Clear Specimens of Timber, P.A,USA 2010.
ASTM D 1621 -Standard Test Method for Compressive Properties of Rigid Cellular Plastics-Determination of Compression Properties
ASTM D 1621 -Standard Test Method for Compressive Properties of Rigid Cellular Plastics-Determination of Compression Properties. P.A,USA 2008
The Wales Institute for Sustainable Education(WISE): Non-conventional materials in Mainstream Construction
  • R Harris
  • J Shanks
  • T Hodsdon
  • Borer
Harris. R., Shanks. J., Hodsdon. T., Borer., The Wales Institute for Sustainable Education(WISE): Non-conventional materials in Mainstream Construction. Proceedings of the 11 th International Conference on Non-conventional Materials and Technologies (NOCMAT 2009)6-9 September 2009, Bath, UK.
Structural Behavior of Timber
  • B Madsen
Madsen, B., Structural Behavior of Timber. Timber Engineering Ltd., First Edition, 1992.
Wood Design Manual 2005-A complete reference for wood design in Canada-Canadian Wood Design Council
  • D J White
  • W A Take
  • M Bolton
White, D. J., Take, W. A, and Bolton, M. D, Soil deformation measurement using particle image velocimetry (PIV) and photogrammetry. Geotechnique 53, No. 7, 619-631,2003. Wood Design Manual 2005-A complete reference for wood design in Canada-Canadian Wood Design Council.