Article

Acoustic absorption of hemp-lime construction

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Abstract

Hemp-lime concrete is a sustainable alternative to standard wall construction materials. It boasts excellent hygrothermal properties in part deriving from its porous structure. This paper investigates the acoustic properties of hemp-lime concrete, using binders developed from hydrated lime and pozzolans as well as hydraulic and cementicious binders. To assess the acoustic absorption of hemp-lime walls, as they are commonly finished in practical construction, wall sections are rendered and the resulting impact on absorption is evaluated. Hemp-concretes with lime-pozzolan binders display superior acoustic properties relative to more hydraulic binders. These are diminished when rendered, as the open surface porosity is affected, however hemp-lime construction offers the potential to meet standard and guideline targets for spaces requiring acoustic treatment.

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... High-quality building blocks are produced by mixing a binder, e.g. lime, clay or cement, with non-fibrous hurds particles (Elfordy et al. 2008;Pretot et al. 2014;Kinnane et al. 2016;Gourlay et al. 2017;Jami et al. 2019). These materials are bio-composites referred to hemp concrete, hempcrete or hemp-lime ( Fig. 2.6). ...
... Due to their low density, elasticity, permeability, and insulating properties, hurds are also used for production of particle boards (Elfordy et al. 2008;Bouloc 2013;Cigasova et al. 2015;Ingrao et al. 2015;Fangueiro and Rana 2016;George et al. 2016;Jonaitiene and Stuoge 2016;Kinnane et al. 2016;Niyigena et al. 2016;Fernea et al. 2017;Gourlay et al. 2017;Kiruthika 2017;Liuzzi et al. 2017;Mirski et al. 2017;Chernova et al. 2018;Kallakas et al. 2018;Nováková 2018;Pichardo et al. 2018;Usmani and Anas 2018). ...
... Hemp-lime is also a cheap and low density material with associated low thermal conductivity depending on the density and moisture level, and it presents an interesting balance between low mass and heat storage capacity compared with classical insulation materials. It is considered as a sustainable, carbon negative and low embodied energy construction material (Zabalza Bribián et al. 2011;Latif et al. 2015;Bouloc 2013;Kinnane et al. 2016). ...
Chapter
Recent trends in natural resources, energy conservation, biomass conversion to chemicals, bioproducts and biofuels have renewed the interest on hemp as a new low-cost, sustainable, ecological, biodegradable, recyclable, and multi-purpose material. Hemp-based materials are indeed suitable substitutes for many fossil-based materials and applications.
... The interior parts of the concrete will not set as a result of this. Hemp concrete's mechanical, thermal, hygrothermal, and acoustic qualities are all affected by the binder used and the dose [28][29][30][31][32]. In hemp concrete, the most common binding agent is hydrated lime (Ca(OH) 2 ). ...
... The type of binder, formulation, and production techniques all play a role. They do, however, have an average sound absorption of 40-50% [28] over a wide frequency range. The surface permeability, which varies based on the texture, influences the absorption coefficient (α). ...
... With increasing binder concentrations, the amplitude of the peaks and the width of their bands diminishes as the pore size shrinks. Sound absorption was higher in concretes made with smaller hemp shives [31] (Fig. 10) and concretes made with lime-pozzolanic binders than in hydraulic binders [28]. ...
Article
A simple mixture of hemp hurd, water, and lime is used to make hemp concrete. It is indeed one of the few materials that can continue to absorb carbon after being employed in construction, storing more carbon in the atmosphere over the building's lifetime than was emitted during construction. Furthermore, hemp can be harvested in as little as 60 days. Hemp concrete is a “carbon-negative” or “better-than-zero-carbon” substance because the hemp plant absorbs more carbon from the atmosphere than it emits during its production and application on site. It is a bio-composite material that can be utilised as an alternative to concrete and standard insulation in building. Hemp concrete is also recyclable at the end of the building's lifespan. This study summarises the fast-developing body of knowledge about hemp concrete, which was recently developed.
... High-quality building blocks are produced by mixing a binder, e.g., lime, clay or cement, with non-fibrous hurds particles (Elfordy et al. 2008;Pretot et al. 2014;Kinnane et al. 2016;Gourlay et al. 2017;Jami et al. 2019). These materials are biocomposites referred to hemp concrete, hempcrete or hemp-lime ( Fig. 6). ...
... Hemp provides all sorts of building materials: blocks and bricks, slabs and paneling, wallboard (Fig. 5), fiberboard, roofing tiles, and insulation products (Fig. 6). Hurds/shives are used to produce light concretes and mortars for different end uses, e.g., wall construction, insulation, underfloor, etc. Due to their low density, elasticity, permeability, and insulating properties, hurds are also used for production of particle boards (Elfordy et al. 2008;Bouloc 2013;Cigasova et al. 2015;Ingrao et al. 2015;Fangueiro and Rana 2016;George et al. 2016;Jonaitiene et al. 2016;Kinnane et al. 2016;Niyigena et al. 2016;Fernea et al. 2017;Gourlay et al. 2017;Kiruthika 2017;Liuzzi et al. 2017;Mirski et al. 2017;Chernova et al. 2018;Kallakas et al. 2018;Nováková 2018;Pichardo et al. 2018;Usmani and Anas 2018). ...
... Hemp-lime is also a cheap and low density material with associated low thermal conductivity depending on the density and moisture level, and it presents an interesting balance between low mass and heat storage capacity compared with classical insulation materials. It is considered as a sustainable, carbon negative and low embodied energy construction material (Zabalza Bribián et al. 2011;Latif et al. 2015;Bouloc 2013;Kinnane et al. 2016). ...
Article
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The hemp plant Cannabis sativa Linn, referring to industrial hemp, is a high-yielding annual industrial crop grown providing fibers from hemp stalk and oil from hemp seeds. Although hemp is a niche crop, hemp production is currently undergoing a renaissance. More than 30 countries grow hemp, with China being the largest hemp producing and exporting country. Europe and Canada are also important actors in the global hemp market. Traditionally, hemp as a fiber plant has been used for the production of apparels, fabrics, papers, cordages and building materials. The hurds, as waste by-product of fiber production, were used for bedding of animals, the seeds for human nutrition, e.g., as flour, and the oil for a wide range of purposes, from cooking to cosmetics. Hemp has also been an important crop throughout human history for medicine. Other more recent applications include materials for insulation and furniture, automotive composites for interior applications and motor vehicle parts, bioplastics, jewelry and fashion sectors, animal feed, animal bedding, and energy and fuel production. Foods containing hemp seed and oil are currently marketed worldwide for both animal and human nutrition. They also find applications in beverages and in neutraceutical products. Hemp oil is also used for cosmetics and personal care items, paints, printing inks, detergents and solvents. It is estimated that the global market for hemp consists of more than 25,000 products. Currently, the construction and insulation sector, paper and textile industries, and food and nutrition domains are the main markets while the cosmetics and automotive sector are growing markets. Innovative applications, e.g., in the medical and therapeutic domains, cosmeceuticals, phytoremediation, acoustic domain, wastewater treatment, biofuels, biopesticides and biotechnology, open new challenges. Hemp is also the object of numerous fundamental studies. This review presents and discusses the traditional and new uses of industrial hemp.
... There are few researchers who also highlighted that different types of binder used in the hemp concrete can influence the acoustic characteristics [42,43]. For example, Gle et al. [43] found that by incorporating lime as binder, better sound absorption coefficient can be obtained compared to the use of cement. ...
... This was attributed to the low grain density of lime (2800 kg/m 3 where 3200 kg/m 3 for cement) and high porosity of the lime matrix (52% for lime and 39% for cement). This also corroborates well with observations by Kinnane et al. [42]. Hence, the sound absorption of lime hemp concrete is considered to be inversely proportional to hydraulic content of the binder used. ...
... Hemp stem with various sizes[42].T.S.Tie et al. ...
Article
Concrete, known as the second most consumed material in the world after water, is a versatile, inexpensive and durable construction material. Due to its high density, concrete is usually employed as rigid walls in buildings and also as sound barrier in highway. Researchers have proposed several methods to treat the concrete to also be capable of absorbing sound and thus improving the sound quality in a room. However, there exists limited information regarding the sound absorbing capability of concrete or more generally the cement-based materials. This paper reviews the sound absorption properties of various modified concrete materials from the existing published works. The influence of aggregate types and alteration of concrete ingredients on the acoustic properties of modified concrete materials are discussed. From the review, it is concluded that the sound absorption of the concrete or cement-based material can be improved by creating porous structures in the materials through different methods, namely incorporating lightweight aggregate, creating physical voids, such as in pervious concrete or by inducing voids with the inclusion of foam in cellular concrete. Another proposed method is also to incorporate large amount of hemp shiv to produce hemp concrete. A linear relationship is found to generally estimate the noise reduction coefficient as the function of the density of the materials using the data available from the published works.
... The intensity of the sound I is the sound power divided by the unit area. The audible threshold occurs at sound intensity I 0 = 10 −12 W/m 2 [4,11,20]. The sound pressure level is calculated in decibels in the following logarithmic relationship: ...
... Porous concrete can absorb sound but has low sound insulation. Thus, plastering or painting porous concrete could help in reducing sound absorption and upsurges its sound insulation features [20]. The sound absorption coefficient for normal concrete is almost 0.02, signifying that around 98% of the sound dynamism is a surface reflection. ...
... Hemp concrete is characterized by a highly porous microstructure and has an open porosity ranging from 60 to 90%, depending on the mixture [105,115]. In [20], the acoustic properties of hemp-lime concrete using hydrated lime and pozzolan binders and hydraulic and cement binders are investigated. The wall sections are visualized to assess the acoustic absorption of hemp-lime concrete walls in real construction and the effect on absorption is evaluated. ...
Article
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Noise is continuously treated as an annoyance to humans and indeed commotion contamination shows up within the environment, causing inconvenience. This is likewise interesting to the engineering tactic that inclines to develop this noise proliferation. The basics of the soundretaining proliferation, sound-absorbing properties, and its variables were rarely considered by previous researchers. Thus, the acoustic performance and sound insulation of constructions have gained significance over the last five decades due to the trend for accommodating inner-city flat and multi-story residential building condominiums. Due to this dilemma, the proliferation of high-driven entertaining schemes has engaged extraordinary demands on building for its acoustic performance. Yet, construction industries worldwide have started to mainly use sound-absorbing concrete to reduce the frequency of sounds in opened-and-closed areas and increase sound insulation. As reported, the concrete acoustic properties generally rely on its density, exhibiting that the lighter ones, such as cellular concrete, will absorb more sound than high-density concretes. However, this paper has an objective to afford a wide-ranging review of sound-absorbing acoustic concretes, including the measurement techniques and insulation characteristics of building materials and the sound absorption properties of construction materials. It is also intended to extensively review to provide insights into the possible use of a typical sound-absorbing acoustic concrete in today’s building industry to enhance housing occupants’ efficiency, comfort, well-being, and safety.
... In response to this scenario, a global research and product trends have put their eyes on natural sources as raw inputs which could be used to different kind of applications, from composite reinforcement to technical nonwovens made for acoustic treatment. In many cases, natural materials could be retrieved from the wastes of the textile sector and agroindustry [7][8][9][10][11][12]. In this sense, acoustic properties of materials composed of natural fibres of protein or lignocellulosic origin have been investigated thoroughly in recent years, in many cases outclassing commercially available products marketed as acoustic absorbers [11,13,14]. ...
... Natural based materials acoustic properties have been tested in the past, employing a variety of methods, most commonly impedance tube measurements and sound absorption coefficient calculation [12,[16][17][18]. In many cases fibres were mixed with binders in different ratios, affecting in some degree the sound absorption coefficients [19,20]. ...
Article
Fique is an endemic agave species and extensively harvested in Colombia. Its fibres are commonly used for low-tech applications like sacks and cords fabrication for food packaging and handicrafts in general. This paper discusses the study of fibres and textiles from fique as an alternative natural thermoacoustic material for potential technological applications. The study was carried out by characterizing the fique fibres morphology, fabricating non-woven samples from raw fique fibres and in-depth thermoacoustic characterization. Fique nonwovens sound absorption was measured and modelled, flow resistivity, dynamic stiffens, and thermal conductivity were measured. It has been demonstrated that the sound absorption performance can be improved by increasing the thickness of the sample and by having a small fibre diameter. Fique nonwovens behaved like an elastic framed material, which makes rigid skeleton models inaccurate to calculate its sound absorption. Overall fique fibres showed to be comparable to synthetic materials in thermal insulation, sound impact reduction and sound absorption above 1000 Hz.
... Cérézo (2005) observed two peaks in the case of hemp concrete, as shown in Figure 24. This observation was consistent with the others results of hemp concrete reported in the literature [163,164]. The first peak corresponding to the coating and roof formulations shifted from 300 Hz to 500 Hz with aggregate contents of 8.3% and 25.1%, respectively. ...
... The properties of aggregates, their size, and porosity may bring these acoustical differences between the composites and are discussed in the following part. Nevertheless, various studies showed that the type and amount of the binder and the degree of compaction are the principal parameters influencing sound absorption [76,163,164,166,167]. ...
Article
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The use of plant aggregates obtained from agricultural co-products mixed with mineral binders to form eco-friendly insulating building materials has been initiated for a few years to bring environmentally friendly solutions to the construction sector. Several studies on different agro-resources have already been carried out, providing various information about the properties of plant aggregates and plant-based concrete. However, the characteristics of the agricultural co-product, which allow it to qualify as a plant aggregate for plant-based concrete, are not yet very clear despite the multitude of data, especially on hemp concrete. Therefore, it is important to gather numerous but very disparate pieces of information available in the literature concerning the properties of plant aggregates and their correlations with composites. This review is based on the results of 120 articles and aims to identify the characterization methods and the multi-physical properties of plant aggregates affecting those of plant-based concrete and to propose additional factors that could influence the properties of the composites. A total of 18 plant aggregates of different origins used for plant-based concrete have been listed in the literature. In France, hemp shiv is the most studied one, but its quantity is quite low unlike cereal or oilseed straws and wood transformation residues. With the existence of several characterization methods, properties like microstructure, particle size distribution, bulk density, water absorption capacity, and chemical composition of aggregates are easily and frequently determined. In contrast, data on the apparent density of particles, the skeleton density, and the hygro-thermal properties of aggregates are rare. The particle size, density, and porosity have been identified as important parameters influencing the properties of the composites. Other parameters related to the behavior of the aggregates under wet compaction and compression of their stacking can also predict the physical and mechanical properties of the obtained plant-based concrete. Dosages of the constituents should be preferred as formulation parameters for future studies assessing the impact of the aggregate properties on the composites.
... [15,16] to other raw materials. Other works focused on highly compressed mixes [17] and on the effects of alternative binders and coatings in Ref. [18]. The case of hemp-clay material (also called light earth) has been addressed later by Ref. [19]. ...
... Compared to the experimental investigation on raw materials cited previously, sound absorption at the wall and building scale is likely to be significantly modified due to the existence of a coating layer. Main coatings are indeed more resistive than hemp concrete and strongly limit acoustic dissipation [18,27]. However, compromise might be found with adequate coating thickness and resistivity in order to maintain this interesting absorption property and this is precisely the focus of another paper to be published soon. ...
Article
This paper focuses on the sound reduction of light earth at the wall scale. It aims at gaining knowledge and providing informations to professional building workers to help them in the acoustic optimization of biobased walls. Experimentations have been performed in controlled conditions using the intensimetry method, on 22 different samples to investigate thickness effect, wood frame effect, coating effect together with different light earth implementations (shuttering, spraying). These data were then confronted to two modelling approaches, the mass law estimate and a Transfer Matrix Method computation. It is shown that light earth performance can be satisfactorily predicted, whatever the wall configuration using the Transfer Matrix Method computation with isotropic elastic and porous layers. The study brings finally a good understanding of the physical phenomena occurring in biobased concretes, depending on the presence of coatings. For light earth, it also appears that mass law yields to a good approximation of the single-number rating for some configurations including at least one coating.
... Additionally, shiv particles of the woody-core are a biobased alternative to mineral aggregates for low-impact concrete. Therefore both the plant fibres and the shiv particles are suitable for developing biobased, environmentally friendly building materials that have been shown to have inherent thermal, hygrothermal and acoustic characteristics (Kinnane et al., 2016;Reilly et al., 2019;Shea et al., 2012). ...
Preprint
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Cannabis sativa is an extraordinarily versatile species. Hemp and its cousin marijuana, both C. sativa, have been used for millennia as a source of fibre, oil and for medicinal, spiritual and recreational purposes. Because the consumption of Cannabis can have psychoactive effects, the plant has been widely banned throughout the last century. In the past decade, evidence of its medicinal properties did lead to the relaxation of legislation in many countries around the world. Consequently, the genetics and development of Cannabis as well as Cannabis-derived products are the subject of renewed attention.Here, we review the biology of C. sativa, including recent insights from taxonomy, morphology and genomics, with an emphasis on the genetics of cannabinoid synthesis. Because the female Cannabis flower is of special interest as the site of cannabinoid synthesis, we explore flower development, flowering time well as the species' unique sex determination system in detail. Furthermore, we outline the tremendous medicinal, engineering, and environmental opportunities that Cannabis bears. Together, the picture emerges that our understanding of Cannabis biology currently progresses at an unusual speed. A future challenge will be to preserve the multipurpose nature of Cannabis, and to harness its medicinal properties and sustainability advantages simultaneously.
... They guarantee greater massiveness than a panel of less thickness. This technique has shown that the load-bearing structure itself guarantees acoustic comfort without further intervention on the wall stratigraphy [30]. ...
Article
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In order to limit the anthropic emissions of CO2, research is currently investigating new materials for the building sector. The main purpose is the reduction in the embodied energy consumption, especially in the residential sector, and consequently the limitation of the direct and indirect utilization of fossil fuels, for the indoor heating, cooling, and ventilation services. Indeed, the residential sector is affected by a high energy demand, thus the choice of improved materials is fundamental to improve the sustainability. All phases: construction, building life, and dismantling are impacting in terms of resource and energy consumption, both associated with the emissions of pollutants in the atmosphere. The aim of this experimental research is to study the thermal insulation and the acoustic absorption of a material composed by natural lime, water, and shives from sativa hemp, a variety of hemp usable for industrial applications. In order to assess the main characteristics of this material, some specimens have been made according to required shapes and sizes to test them in specific machines. The results obtained from the tests are compared with the values of similar lime-based materials already available on the market. The comparison shows how, in certain aspects, the lime and hemp shives materials represent a concrete alternative to conventional materials. This completely natural material would like to achieve thermal and acoustic comfort in indoor environments.
... Polyurethane and mineral wool have a noise reduction coefficient (NRC) that is higher than polystyrene and cellular inorganic materials. Among natural materials, Coconut pith, hemp, and sheep wool exhibit the highest NRC of around 0.75 [12,13,166], whereas wooden and husky materials have the least NRC of 0.4 [164,234]. The use of sheep and vegetable wool in double-leaf walls attenuate noise transmission better than the heavy double-wall insulated with rock wool and polystyrene [147,235]. ...
Article
Building envelope insulation is crucial for an energy-efficient and comfortable indoor environment because the envelope accounts for 50–60% of total heat gain/loss in a building. Previous studies mostly used lifecycle cost as the criteria to select the optimum insulation materials with little or no consideration of embodied energy, emission, and summer overheating potential. This study presents a comparative analysis of building insulation materials properties (thermal, hygroscopic, acoustic, reaction to fire, environmental, and cost) and their performance in different climate zones and proposed an optimization framework. Insulation materials can be primarily categorized as conventional, state-of-the-art and sustainable. State-of-the-art insulation materials have the lowest thermal conductivity value amongst the three insulation types. However, their life cycle cost is higher compared to the other types. Sustainable insulation materials could be useful to delay and minimize indoor peak temperature and reduce overheating risk during the hot summer period. The analysis also showed that building walls with comparatively lower thermal resistance are more cost-effective for the cooling dominated region, but walls with higher thermal resistance are more cost-effective in heating-dominated regions. However, highly insulated and airtight houses may also lead to increased overheating risk and peak cooling demand during a hot summer period. In addition, hygroscopic, acoustic, and fire retardancy properties of insulation materials are critical to control indoor relative humidity in a humid region, to maintain a minimum noise level in a zone, and to reduce fire destruction. Hence, the optimization should include four criteria 1) Energy, 2) Environment, 3) Economic, and 4) Comfort.
... Hemp concrete is a bio-based material composed of hemp shives and a binder (Nozahic et al. 2012;Pretot et al. 2014). Numerous studies have shown that this material has excellent hygrothermal (Bennai et al. 2018c;Collet and Pretot 2012;Rahim et al. 2016a) and acoustic (Degrave-Lemeurs et al. 2018;Kinnane et al. 2016) properties derived in part from its porous structure. ...
Article
Full-text available
Bio-based materials, such as hemp concrete, have been widely recommended to reduce carbon emissions and energy consumption of buildings as a means of addressing current environmental problems. These materials may possess very interesting hygrothermal and acoustic performance. Hemp concrete is composed of hemp particles embedded in a binder that forms a very heterogeneous and porous component. The aim of this paper is to examine the influence of hemp concrete heterogeneity on the mechanisms of heat and mass transfer. The originality of this paper is to consider the real 3D structure of hemp concrete for modelling coupled heat and moisture transfers within the material. These 3D microstructures were obtained using 3D X-ray tomography reconstruction with a voxel size of 31.8 μm. Then, a specific finite element mesh was generated from the real, heterogeneous geometry of hemp shives, binder and interparticle air. A mesoscopic model was developed to simulate coupled heat and mass transfer phenomena within the material. The 3D temperature and relative humidity fields showed high heterogeneity and complex distributions that are governed by the hemp concrete morphology. In addition, the anisotropy of the material led to different effective thermal conductivities in each transfer direction. Numerical comparison with simulations performed on the fictive elementary representative volume of hemp concrete showed that consideration of the real geometry allows a better understanding of coupled heat and moisture transfer phenomena modelling.
... However, the sound absorption of composites compacted at 60% is very poor, which is due to the smooth surface of a composite with negligible pores mainly reflects the sound waves. Kinnane et al. (2016) have studies the acoustic properties of hemp-concretes with limepozzolan binders for construction building wall applications. It has been found that buildings and rooms built by hemp concrete enable exposure of high sound-absorbing surfaces and low reverberation times, and it is not necessary to apply additional acoustical treatments. ...
Article
Compared to the commonly used synthetic fibrous materials, natural fiber represents an eco-friendly solution in various engineering fields. Noise control is an important application of natural fibers due to the unique acoustic characteristics. Studies on the sound absorption of hemp fibers have attracted more and more attention in recent years. Generally, hemp products for sound absorption mainly including nonwoven fabrics and fiber-reinforced composites. This review has gathered the most recent advances on the acoustics of hemp fibers, and also the sound absorption design principles of hemp-based materials. A detailed information related to the improvement of the sound absorption properties of hemp is given, which mainly including the optimization of manufacturing, materials component, bulk density, morphologies, and structural parameters, etc. Hemp fibers exhibit robust acoustical performance, and the present work is beneficial to the development of sound absorption hemp-based materials.
... The Kundt's tube or standing wave tube is a good, albeit affordable, test device for measuring acoustic properties of materials. It is specifically well suited to measure, on the one hand, the absorption coefficient of sound absorbing materials [1], which are intended to reduce the reverberation time of a room, and, on the other hand, the transmission loss of materials intended for sound insulation in mufflers [2]. ...
Article
We explore the limits of the use of the Kund’s tube and the transfer matrix method for the measurement of transmission loss with common building materials. The results of several tests performed in a standing wave tube with two different building materials (concrete and gypsum board) and mounting the samples in the tube using four different sealing methods are presented. With the analysis of the obtained data, it is proved that the “two loads” method in the Kundt’s tube cannot be used to measure the transmission loss of rigid construction materials like the tested ones due to the high variability of the data.
... Another important factor, besides eco-friendliness, seems to be in favor of the hemp-lime composite is its great acoustics properties. We can find many papers related to this issue mostly dealing with the materials acoustic absorption by Kinnane et al. [36], or by Gle et al. [37]. In the last three years, we can also see that a lot of scientists like Bourebrab et al. [38] or Heidari et al. [6] are dealing with the surface coating of hemp-lime composites to increase their resistance to humidity or life cycle. ...
Article
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The main goal of the paper is to calculate the heat conductivity for three experimental hemp–lime composites used for structural construction purposes with the use of the experimental stand inside two compartments. Due to current construction trends, we are constantly searching for eco-friendly materials that have a low carbon footprint. This is the case of the analyzed material, and additional thermographic heat distribution inside the material during a fire resistance test proves that it is also a perfect insulation material, which could be applied in addition of popular isolating materials. This paper presents the results of certain hemp–lime composite studies and the potential for using hemp–lime composite for the structural construction industry. Hemp–lime composite heat transfer coefficient, fire resistance, and bulk density properties are compared to those of other commonly used construction materials. The obtained results show that the material together with supporting beams made of other biodegradable materials can be the perfect alternative for other commonly used construction materials.
... New approaches with hemp shiv-which is regarded as a waste product obtained after the extraction of the fibers for the textile industry-have been taken into consideration in the construction sector. There is a significant number of studies on hemp shiv with lime, which is a composite material named hempcrete [12][13][14], but there are only few studies that concern hemp shiv with cement [15][16][17][18][19]. ...
Article
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Interdisciplinary and sustainability represent the main characteristics of this paper due to the fact that this research is offering a connection between two main areas—agronomy and construction, by using hemp shiv for the design of new building materials, which can increase the sustainability level of the building industry. For this reason, the main scope of this study is based on the investigation of a new category of composite building materials—lightweight mortars based on hemp shiv, volcanic rocks and white cement—which contribute to a positive environmental impact and help to increase indoor comfort. A complex report was carried out on two segments. The first one is focused upon the characteristics of the raw materials from the composition of the new materials, while the second segment presents a detailed analysis of these composites including morphological and chemical investigation, pyrolytic and fire behavior, compression and flexural strengths, and acoustic and thermal characteristics. The proposed recipes have as a variable volcanic rocks, while the hemp and the binder maintain their volumes and properties. The results were analyzed according to the influence of volcanic rocks on the new composites.
... Natural materials and natural materials-based composites have several advantages, such as easy processing [1], use of local materials [2], high availability [3], carbon sequestration during the plant's life [4], and, after the end of service life, they can be introduced into the natural environment without causing damage [5]. Besides these advantages, they also possess a few disadvantages, such as low fibre-matrix compatibility [6], high risk of attack of microorganisms [7], fibre defects, and structural differences that can lead to variable mechanical strengths [8]. ...
Article
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The aim of this paper is to propose a novel sandwich panel, which would be suitable for sound absorption and airborne sound insulation, used as applied cladding or independent lightweight partition wall. As far as the authors are concerned, this is the first sheep wool-based sandwich panel using only natural materials. The structure was prepared using hydrated lime-based composite face sheets and a sheep wool-based core. Several parameters of the sandwich panel were determined, including sound absorption coefficient, airborne sound insulation, thermal conductivity, thermal resistance, compressive strength, and bending strength, respectively. The results indicate that the maximum sound absorption value of 0.903 was obtained at the frequency of 524 Hz in the case of the unperforated sample, 0.822 at 536 Hz in the case of the sample with 10% perforations, 0.780 at 3036 Hz in the case of the sample with 20% perforations, and 0.853 at 3200 Hz in the case of the sample with 30% perforations. The registered airborne sound insulation index of the panel was 38 dB. Based on the obtained data, it can be concluded that the studied panel recorded comparable values with other synthetic noise control solutions, which are suitable as applied cladding or an independent lightweight partition wall, with good acoustic properties.
... Conventional various sound absorbers such as foam-like materials or nonwoven fabrics as low-density porous materials can prevent reflection of the incident sound waves and hence increase sound absorption. The use of nonwovens, as widely accepted porous sound absorbing materials, has been extensively researched [2][3][4][5][6]. ...
... In general, porous materials hold promise for use as raw material for sound absorbing [32]. Fibrous and cellular materials such as rice husk [33], corn cob and palm fiber [28], and hemp [34] have shown good thermal and sound absorption properties. It is well known that porous materials and composites with internal pores have good acoustic absorption properties in high frequency range [35]. ...
Article
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High energy consumption in the building sector appeals for the implementation and the improvement of innovative approaches with low-environmental impact. The development of eco-friendly composites as insulating materials in buildings provides practical solutions for reducing energy consumption. Different mass proportions (2.5%, 10%, and 20%) of untreated and chemically treated palm fibers were mixed with (cement, water and sand) so as to prepare novel composites. Composites were characterized by measuring water absorption, thermal conductivity, compressive strength and acoustic transmission. The results reveal that the incorporation of untreated and chemically treated date palm fibers reduces novel composites’ thermal conductivity and the mechanical resistance. Thermal measurements have proved that the loading of fibers in composites decreases the thermal conductivity from 1.38 W m⁻¹ K⁻¹ for the reference material to 0.31 W m⁻¹ K⁻¹ for composites with 5% of treated and untreated fibers. The acoustical insulation capacity of untreated palm fiber-reinforced composites (DPF) was the highest at 20% fiber content, whereas treated palm fiber-reinforced composites (TPF) had the highest sound insulation coefficient for fiber content lower than 10%. Compressive strength, thermal conductivity and density correlation showed that only chemically treated fiber-reinforced composites (TPF) are good candidates for thermal and acoustic building insulations. Graphic Abstract Open image in new window
... There have been other studies related to the acoustical properties of natural materials. The acoustic properties of hemp concrete with lime pozzolan binders and hydraulic binders have been compared and results have shown that former display superior acoustic property than later [91]. The SAC of vegetable fibers such as coconut, palm, sisal, and acai have also been discussed [92]. ...
Article
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The sound is the pressure disturbance created over air particles above and below atmospheric pressure. It is a mechanical wave which requires a medium to propagate. The sound can generate from a source, then travels through a medium and finally is received by the receiver. The noise is an unpleasant or unwanted sound that is undesired by the receiver. This unwanted sound is absorbed by the sound absorbing (SA) materials. This paper presents a complete comprehensive literature survey for the SA materials and organized the information in the following manner. First, the phenomenon behind SA mechanism is being explained, then the detailed information of existing SA materials with their classification is reported. After that, the factors associated with the sound absorption that influences the sound absorption coefficient (SAC) is being presented. Finally, the theoretical models for porous materials are being discussed followed by the details of price comparison of natural and synthetic fiber-based sound absorbers and the applications of SA materials of various acoustical products. There are a lot of researches going on to develop new acoustic materials and hence this paper will help the researchers to know about the existing SA materials and also help them to develop new acoustic materials by considering significant information related to sound absorption.
... The variation in stiffness with properties has also been measured [3]. As well as good thermal performance, hempcrete exhibits beneficial acoustic properties [4]. ...
... Due to better thermal and acoustic properties, natural fiber composites are used as insulating and soundproofing materials [283]. Hemp/lime/concrete composites have exhibited better sound absorption ability than any other binders [284]. Life cycle assessment, durability properties, and ecological aspects are taken into account before selecting any bio-composite as a construction material. ...
Article
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Increased environmental concerns and global warming have diverted focus from eco-friendly bio-composites. Naturals fibers are abundant and have low harvesting costs with adequate mechanical properties. Hazards of synthetic fibers, recycling issues, and toxic byproducts are the main driving factors in the research and development of bio-composites. Bio-composites are degradable, renewable, non-abrasive, and non-toxic, with comparable properties to those of synthetic fiber composites and used in many applications in various fields. A detailed analysis is carried out in this review paper to discuss developments in bio-composites. The review covers structure, morphology, and modifications of fiber, mechanical properties, degradable matrix materials, applications, and limitations of bio-composites. Some of the key sectors employing bio-composites are the construction, automobile, and packaging industries. Furthermore, bio-composites are used in the field of medicine and cosmetics.
... Additionally, shiv particles of the woody-core are a biobased alternative to mineral aggregates for low-impact concrete. Therefore both the plant fibres and the shiv particles are suitable for developing biobased, environmentally friendly building materials that have been shown to have inherent thermal, hygrothermal and acoustic characteristics (Kinnane et al., 2016;Reilly et al., 2019;Shea et al., 2012). ...
... On the other hand, hemp concrete can cover several uses in buildings, depending on the formulation used [14,15]. The available literature has shown that hemp concrete has very interesting hygrothermal [14,[16][17][18][19] and acoustic [20] properties compared to classic building materials. Indeed, this vegetable particle-based material has a low thermal conductivity [21,22] and, therefore, a significant insulation capacity which could improve the thermal behaviour of buildings. ...
Article
The aim of this paper is to analyse the impact of hemp concrete on the overall hygrothermal behaviour of the building when it used as an infill layer in the envelope of wood-frame structures. Three wall configurations were considered in different climates. Then, a hygrothermal co-simulation approach was used to integrate the model of coupled heat and moisture transfer through multilayered walls in a dynamic thermal simulation tool for the building. The material properties which constitute the input parameters for the model were determined experimentally, according to the hygrothermal state of the material. The results showed that hemp concrete significantly reduces the energy consumption of the building and has better insulation properties than the two conventional building materials: brick and aerated concrete. This is justified by the good hygrothermal properties of this bio-based material, especially its high thermal resistance of 3.08 K.m²/W compared to 0.88 K.m²/W of brick and 2.28 K.m²/W of aerated concrete. In addition, for the three climates considered, the thermal comfort of the hemp concrete envelope is significantly improved. This material also allows stabilisation of relative humidity levels in the ambient air by naturally regulating the hygrometry, to ensure better ambience. The study shows that hemp concrete has interesting hygrothermal properties. Thus, this material can be used massively in the construction field in order to meet the requirements of the current standards which aim to reduce the energy and environmental impacts of dwelling and office building.
... In the same way, Nguyen et al., 2016;Tronet et al., 2016) distinguished the intra-particle porosity (encompassing close and open porosity) and the inter-particle porosity. -Acoustics: the acoustic behaviour of hemp shiv and hemp concrete has also been investigated in (Cerezo, 2005;Glé et al., 2012;Kinnane et al., 2016;Fotsing et al., 2017) at two main scales of porosity: inter-particle pores and intra-particle pores. It has been shown by (Glé et al., 2012) that not all of them contribute to sound dissipation, and a new scale of porosity, called "acoustic porosity" has been proposed. ...
Article
This paper concerns the packing of plant particles (hemp shiv) used for building applications and aims to quantify skeletal, particle and packing densities and associated porosities. These parameters were measured on hemp particles as a case study and were used to assess the physical behaviour of this material in terms of water adsorption and absorption, mechanical compression and thermal and acoustic behaviours. A number of experimental methods have been used to characterise these parameters including fluid and powder pycnometry, mercury intrusion and X-ray computed tomography, leading to robust and complementary results as a function of particle size and level of aging by immersion in water. It was concluded that smaller particles are characterised by higher packing and particle densities, while aged particles present a strong evolution of their microstructure, which is visible through lower packing and particle densities and higher skeletal density. By comparing these experimental results with physical property characterisations, correlations were found between water absorption and open porosity, compression behaviour and the three density scales, and between acoustic dissipation and intra-and inter-particle porosities.
... Hemp is often used in combination with concrete in the concept of green buildings. Combining hemp and concrete and comparing different binders for acoustic purposes were studied in [18][19][20][21]. ...
Article
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The purpose of this research is to investigate the acoustic properties of natural fibres and compare them with the values achieved by common insulation materials used in the construction of buildings. Three materials based on biomass were used for testing, namely cork, hemp and fibreboard. From the group of conventional materials, mineral wool, propylat and polyurethane foam were selected. For the purpose of determining the values of the sound absorption coefficient (α), the absorber specimens were tested using the impedance tube and two microphones method, according to standard ISO 10534-2. The measurement was performed for thicknesses of 20, 40, 60, 80 and 100 mm. The highest sound absorption of all materials was measured with a hemp sample at a frequency of 2000 Hz (α = 0.99) and a thickness of 20 mm. The lowest performance was achieved by cork at the same thickness and frequency of 100 Hz (α = 0.02). Among biomass materials, hemp dominated in the entire frequency range and at all thicknesses. The lowest values were for cork, from 160 to 500 Hz with a tendency to exceed the values of the fibreboard sample. Among conventional materials, mineral wool achieved the best results, while the lowest values were recorded for propylat with the occasional exception of the highest frequencies from 1600 to 2500 Hz.
... Many works have already been devoted to assess the properties of plant-based concretes [14][15], including mechanical properties [16][17], heat conductivity [16], hygrothermal properties [3,17], acoustic properties [18][19] or environmental impact [20][21]. Some papers have focused more particularly on earth-hemp [19,[22][23] or gypsum-hemp concretes [24][25][26]. ...
Article
Greenhouse gas emissions from cement manufacturing account for about 8 to 10 percent of total CO2 emissions worldwide. To reduce these emissions, researchers are developing new concrete manufacturing techniques and processes to reduce high energy consumption and environmental impacts. Biobased concretes are eco-friendly insulating materials for building industry that can respond to this problem. However, there is a lack of knowledge regarding how these plant-based fillers ignite and contribute to heat release in case of fire. In this work, the fire behaviour of a series of hemp-based earth and/or gypsum concretes covering a large range of densities (180–1500 kg/m³) is investigated using the cone calorimeter at an incident heat flux of 50 kW/m². The fire performances are mainly monitored by the thermal inertia of the materials. Only the lightest concretes ignite with a density threshold for ignition occurrence around 500 kg/m³. For a density of 261 kg/m³, the critical heat flux of an earth-hemp concrete was found to be close to 27 kW/m². The flaming period remains very short in all cases.
... Le béton de chanvre est présent en France depuis les années 80, mais il a vécu son essor à partir des années 90. C'est un mélange de broyat de tige de chanvre (chènevotte), d'eau et d'un liant (classiquement ciment de Portland (Sedan et al., 2008) ou chaux (Kinnane et al., 2016)), dont le rôle est de maintenir l'agrégat (le broyat) collé (cf. Figure 0.10). ...
Thesis
In France, thermal regulations for buildings are changing to face the climatic challenges. The “Grenelle 2” law and the “Plan de Rénovation Energétique de l'Habitat” strategy establish requirements that motivate the search for innovative solutions for the insulation of buildings with high thermal losses. This is the case of national heritage, whose bio-energy retrofit is at the heart of this thesis project. In this context, the agroconcrete industry is currently experiencing an upturn driven by the economic and environmental benefits of the exploitation of agricultural waste and of the local production of resources. This work seeks to characterize lime-based concretes made from sunflower pith and maize pith, two agricultural by-products available in large quantities and whose properties have been scarcely studied. To this end, a study of the mechanical, hygrothermal and acoustical characteristics, compared to the properties of hemp concrete, is carried out, focusing on the impact of the binder-aggregate couples. This experimental campaign has the double objective of exploring new methods of characterization of macroscopic properties. In addition, a mathematical model, which considers the coupling of thermal and hygroscopic effects, is proposed in order to describe the hygrothermal response of the concretes studied at the wall scale. The experimental study has corroborated that lightweight pith concretes show relatively low mechanic characteristics, which place them in the limit of the threshold for “wall”-type applications according to the “Règles Professionnelles Construire en Chanvre” guideline. However, its interesting hygrothermal properties, whose variation with humidity was determined, make it suitable for use as interior insulation, which is the main application envisioned by the project. The campaign also highlighted the extent of the impact of the interactions between the pith and the binder on the properties and the importance of studying the compatibility between aggregates and binders when developing new concretes. During this campaign, a new device for measuring the thermal conductivity of walls was conceived. The cross study of the properties resulted in a contribution to the determination of thermal conductivity and water vapour permeability from acoustic measurements. On the other hand, the results of the numerical study underline the influence of climate on the response of the wall, which determines the choice of the insulating material, and revealed that the presence of pith does not guarantee a greater degree of hygroscopicity of the concrete than the presence of hemp shiv. This hygroscopicity has been proven to have a significant impact on surface heat flows. Lastly, the proposed numerical model is used to quantify the impact of the presence of several kinds of thermal flowmeters on the heat flow passing through a wall during a laboratory test under controlled hygrothermal solicitations.
... Natural fibers are relatively low cost, biodegradable, easily available, eco-friendly, and show good sound absorption characteristics [6][7][8]. Some researchers have used vegetative and animal fibers such as cotton, flax, kenaf, sisal, coir, wool, etc. [9][10][11][12][13], and some have used agricultural by-products and wastes [14][15][16][17] as natural sound-absorbing materials. ...
Article
Full-text available
An increasing interest in the possibilities of converting agricultural wastes to value-added products has emerged. Annually, 200,000 tons of date palm waste are generated, which are charred or released as agricultural wastes. This work describes the efforts to fabricate low-cost sound-absorbing panels from date palm waste fibers and assess their performance for sound absorbing applications. Samples of different thicknesses (25, 35, 45, and 55 mm) and densities (125 and 175 kg/m3) were produced. The normal-incidence sound absorption coefficient was measured using the impedance tube and was modeled using both the Johnson-Champoux-Allard and the Attenborough models. The findings show that the samples with a thickness of 55 mm and a density of 175 kg/m3 have the highest sound absorbing performance. The acoustic behavior of this new material was investigated in a reverberation room. Moreover, the acoustic performance of the panels in a conference hall was modeled, assessing the improvements in its reverberation time (RT), early decay time (EDT), speech transmission index (STI), clarity (C80), and definition (D50). Finally, this paper shows that the acoustic performance of this material can be used to enhance room acoustics properties.
... 226 Hemp fiber/lime concrete composites have proven to be 40-50% better sound absorption than other binders. 227 Kenaf fiber-reinforced composite is an alternative to synthetic fiber-based materials mainly used in building and construction applications because of its lightweight and cost-effectiveness. 228 A study was conducted on coir fiber-reinforced polyester resin biocomposites. ...
Article
The growing awareness of socioeconomic and environmental issues and the high percentage of petroleum resources consumed and new environmental regulations have fueled efforts to develop innovative, cutting-edge, environmentally friendly materials with a wide range of applications. Due to environmental and sustainability concerns, the advancement of biocomposites has resulted in tremendous breakthroughs in green materials in this century. Their primary goal is to replace current synthetic petroleum-based composites with natural resources. Materials derived from nonrenewable petroleum-based sources are hazardous and expensive to produce; on the other hand, biocomposites derived from natural sources are biodegradable, recyclable, non-abrasive, and compostable and have properties comparable to synthetic fiber composites. Natural fibers are low-cost, lightweight, biodegradable, renewable, and environmentally friendly alternatives to synthetic fibers like glass and carbon fiber. The long-term viability of natural fiber-based composite materials has led to increased use in various production industries. However, the manufacturing process of natural fiber-based biocomposites is still plagued by some difficulties, such as poor adhesive propensity, moisture absorption, poor fire resistance, low impact strength, and low durability. This review provides a panoramic view to provide insight into different aspects of biocomposites based on natural fibers and polymers in terms of properties and applications, which will pave the way for future biocomposites research in academic and commercial contexts.
... However, the main problem of building materials incorporating organic fibers is a lack of information about their durability. In this work, the studied material is hemp mortar, that is known for their functional performances: acoustic [8], hygrothermal [7] and mechanical [9]. Nevertheless, hemp mortars as all biobased materials representing anisotropic behavior, heterogenic microstructure and hygroscopicity. ...
Conference Paper
Full-text available
The use of hemp mortar as a bio-based insulation composite is widely promoted in the construction sector in France due to its environmental and hygrothermal advantages and the availability and low price of hemp fibers. Nevertheless, the use of such materials claims the consideration of the microbiological contamination that could lead to its degradation. Molds are known for their ability to modify locally the composition of hemp mortar by decreasing the pH level. That's why the main objectives of the present work are, first, to expose the hemp mortar favorable conditions for mold growth, secondly, to investigate the proliferation of the mold filaments inside the hemp mortar sample and, then, to analyze the crystallographic composition. Experimentally, hemp mortar samples were exposed to high level of relative humidity during one year until the mold growth. The SEM observation allowed to follow the internal growth and identify the depth of the mold growth. Finally, the composition of the contaminated hemp mortar was studied by X-ray diffraction. The obtained results reveal that molds growth occurs not only on the surface but also in the depth. Nevertheless, as the mold growth started only after one year of high humidity exposure, a good resistance of studied hemp mortar towards molds was noted. Furthermore, the mineralogical composition analysis of the contaminated samples shows that the hydrates responsible for durability remained. These results provide data to better predict the durability of hemp mortars.
... Le béton de chanvre est présent en France depuis les années 80, mais il a vécu son essor à partir des années 90. C'est un mélange de broyat de tige de chanvre (chènevotte), d'eau et d'un liant (classiquement ciment de Portland (Sedan et al., 2008) ou chaux (Kinnane et al., 2016)), dont le rôle est de maintenir l'agrégat (le broyat) collé (cf. Figure 0.10). ...
Thesis
Full-text available
En France, la réglementation thermique pour les bâtiments évolue pour faire face aux enjeux climatiques. La loi Grenelle 2 et le Plan de Rénovation Energétique de l’Habitat établissent des exigences qui motivent la recherche de solutions novatrices pour l’isolation de bâtiments à fortes déperditions thermiques. C’est le cas du patrimoine vernaculaire, dont la bio-rénovation énergétique est au coeur de ce projet de thèse. Dans ce contexte, la filière des agro-bétons connaît actuellement un essor poussé par les avantages économiques et environnementaux de l’exploitation de déchets agricoles et de la production locale de ressources. Ce travail cherche à caractériser des bétons à base de chaux et de moelle de tournesol et de maïs, deux sous-produits agricoles disponibles en grande quantité et dont les propriétés ont été peu étudiées. A cette fin, une étude des caractéristiques mécaniques, hygrothermiques et acoustiques, comparées aux propriétés du béton de chanvre, est menée, en mettant l’accent sur l’impact des couples liant-granulat. Cette campagne expérimentale a le double objectif d’explorer de nouvelles méthodes de caractérisation des propriétés macroscopiques. En outre, un modèle mathématique, qui prend en considération le couplage des effets thermiques et hygroscopiques, est proposé afin de décrire la réponse hygrothermique des bétons étudiés à l’échelle paroi. L’étude expérimentale a permis de constater que les bétons de moelle à faible densité présentent des caractéristiques mécaniques relativement faibles, les classant à la limite du seuil pour les applications de type « mur » des Règles Professionnelles Construire en Chanvre. Toutefois, ses propriétés hygrothermiques intéressantes, dont la variation avec l’humidité a été déterminée, le rendent apte à l’utilisation en tant qu’isolant intérieur, qui est l’application principale envisagée par le projet. La campagne a également mis en évidence l’ampleur de l’impact des interactions entre la moelle et le liant sur les propriétés et l’importance d’étudier la compatibilité entre agrégats et liants lors du développement de nouveaux bétons. Lors de cette campagne, un nouveau dispositif de mesure de la conductivité thermique des parois a été mis en place. L’étude croisée des propriétés a débouché en une contribution à la détermination de la conductivité thermique et de la perméabilité à la vapeur à partir de mesures acoustiques. D’autre part, les résultats de l’étude numérique soulignent l’influence du climat sur la réponse de la paroi, qui détermine le choix du matériau isolant, et ont révélé que la présence de moelle ne garantit pas un degré d’hygroscopicité du béton plus important que la présence de chènevotte. Cette hygroscopicité a été prouvée avoir un impact non négligeable sur les flux thermiques en surface. Enfin, le modèle numérique proposé est utilisé pour quantifier l’impact de la présence de différents types de fluxmètres sur le flux thermique traversant une paroi lors d’un essai au laboratoire sous des sollicitations hygrothermiques maîtrisées.
... Theoretical approaches to the design and creation of traditional concretes are not entirely applicable to multicomponent composites either in composition or in operational loads, although the methodology for selecting the composition of heavyweight concrete, taking into account the energy performance of the components, can be taken as a basis [36][37][38][39][40]. Composite binders are often used in the most severe conditions, so the main requirement for them is high density and strength [41][42][43]. ...
Article
The use of composite binders instead of cement with the use of highly effective types of mineral raw materials, which has gone through the path of multi-stage natural activation due to deep geological processes, is a promising direction of modern construction materials science. The paper is devoted to the development of a resource-saving technology for obtaining high-strength composite binders for energy-efficient construction. The significance of this study is to focus on expanding the raw material base of polymineral binders at the expense of technogenic and substandard materials. The work is aimed at studying the nature of the joint interaction of alumina, silicate and carbonate components from natural and technogenic raw materials, taking into account its genesis in the processes of structure formation of multicomponent hardening systems. The novelty of the work lies in the establishment of regularities for the regulation of the structure and properties of the composite binders with powdered mineral modifiers. Comprehensive researches of natural raw materials included the study of its energy performance and particle sizes parameters after grinding. The synthesized polymineral binders were compared in terms of heat of hydration, rheological and physical-mechanical properties, as well as their microstructure. The developed modified cementitious pastes have a water-binding ratio of no more than 0.3; compressive strength of 81 MPa, flexural strength of 12 MPa. Accordingly, the cement composites have great potential for use in civil engineering.
... However, the main problem of building materials incorporating organic fibers is a lack of information about their durability. In this work, the studied material is hemp mortar, that is known for their functional performances: acoustic [8], hygrothermal [7] and mechanical [9]. Nevertheless, hemp mortars as all biobased materials representing anisotropic behavior, heterogenic microstructure and hygroscopicity. ...
Article
Full-text available
The use of hemp mortar as a bio-based insulation composite is widely promoted in the construction sector in France due to its environmental and hygrothermal advantages and the availability and low price of hemp fibers. Nevertheless, the use of such materials claims the consideration of the microbiological contamination that could lead to its degradation. Molds are known for their ability to modify locally the composition of hemp mortar by decreasing the pH level. That’s why the main objectives of the present work are, first, to expose the hemp mortar favorable conditions for mold growth, secondly, to investigate the proliferation of the mold filaments inside the hemp mortar sample and, then, to analyze the crystallographic composition. Experimentally, hemp mortar samples were exposed to high level of relative humidity during one year until the mold growth. The SEM observation allowed to follow the internal growth and identify the depth of the mold growth. Finally, the composition of the contaminated hemp mortar was studied by X-ray diffraction. The obtained results reveal that molds growth occurs not only on the surface but also in the depth. Nevertheless, as the mold growth started only after one year of high humidity exposure, a good resistance of studied hemp mortar towards molds was noted. Furthermore, the mineralogical composition analysis of the contaminated samples shows that the hydrates responsible for durability remained. These results provide data to better predict the durability of hemp mortars.
Article
This article aims to study the mechanical strength and fire resistance of polyurethane/cement (PuCem) composites containing glass sludge and sludge from aluminum anodizing. Scanning electron microscopy (SEM) results showed that the replacement of 24.5% of the cement with sand (San), aluminum anodizing (Aas), or glass-polishing sludge (Gla) maintained the alveolar structure in the composites. Also, energy-dispersive X-ray spectroscopy and FTIR analyses showed that the cement hydration reaction forms hydrated aluminates and silicates. ANOVA–Tukey tests showed that the PuCemAas composites’ areas are significantly different from those of PuCemGla and PuCemSan, which are similar to each other. The compressive strength decreases upon replacing cement with the aggregates. The TGA thermograms were similar for the four composites and the polyurethane matrix. The specimens were declassified in the vertical and horizontal position (UL-94). Thus, the composites were an alternative for reducing the use of raw materials from non-renewable sources.
Article
This article investigates the sound absorption coefficient of materials manufactured from natural wastes. Fruit stones from some crops are one of the most available natural wastes in the Mediterranean Region. Recycled and vegetable products are becoming an interesting alternative to traditional materials to be used as sound-absorbing panels. Fruit stones can be profitable for a number of applications, such as biomass to produce energy. This research work intends to demonstrate that one of their applications can be ecological sound absorbers in building acoustics. Different four fruit stone samples, with different air gap volume percentages, display similar behaviour to multiple Helmholtz resonators (MHRs). By adding a 40 mm-thick rockwool layer, the sound absorption coefficients are compared for each sample. The experimental results allow establishing some analogies between MHRs and the new absorbing materials according to thickness, fruit type and the air gap volume. These fruit stones have been demonstrated as a good choice from acoustic and sustainable points of view.
Article
The development of more sustainable construction materials is a crucial step toward the reduction of CO2 emissions to mitigate climate change issues and minimize environmental impacts of the associated industries. Therefore, there is a growing demand for bio-based binders which are not only safer toward human and environmental health but also facilitate cleaner disposal of the construction materials and enable their compostability. Here, we summarize the most relevant bio-based polymers and molecules with applications in the construction sector. Due to the biologic nature of these materials, the existing biotechnological processes, including synthetic biology, for their development and production have been evaluated. Full text available in the following link: https://www.cambridge.org/core/journals/mrs-communications/article/synthetic-biology-for-the-development-of-biobased-binders-for-greener-construction-materials/C3866B4A1E01DBD09423627EA9960C1A/share/5adc3023f22e494d30a36f1eb62ec31d0477c290
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Bagasse from sugar cane waste is an important agriculture waste and the byproduct of the sugar industry. Generally, bagasse is used as a fuel for many industries which causes environmental pollution while it can be used as a good sound-absorbing material. The acoustic absorption coefficient of the bagasse is investigated in this research work. Three different samples with different thicknesses (t = 10 mm–30 mm) and different stages are considered to conduct the experimental test. Two acoustic parameters viz. 1. The airflow resistivity and 2. The acoustic absorption coefficient is measured to investigate the performance of the bagasse fibrous material in the different frequency ranges. The influence of material thickness and air gap on the acoustical performance of bagasse material samples is discussed. The results obtained from tests show the acoustic absorption coefficient and flow resistivity increase with the increase in bagasse material thickness. Keywords: Acoustic absorption, Bagasse, Natural fibrous material, Sound absorption coefficient.
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Noise pollution caused by urbanization and industrial development must be effectively controlled to provide a pleasant living atmosphere. Different synthetic fiber materials have good acoustic performance, yet synthetic fiber materials have a high cost and have adverse effect on the environment. Natural fibers are a good alternative to synthetic fibers in terms of acoustic properties and they are also less expensive and have less environmental impact. Several factors affects the acoustic behavior of natural fiber reinforced polymer composites (NFRPCs). The present article focuses on the effect of different processing methods, reinforcement architecture, fiber diameter, laminate thickness and density on the acoustic performance of NFRPCs. Reinforcement architecture has been proved to be the best option in order to tailor the various acoustic properties of the composite laminates without even changing other physical properties. The challenges, future scope and potential applications of natural fibers in acoustic applications (home theaters, offices, cinema halls, automobiles, etc.) have also been discussed.
Article
New energy-efficient materials are increasingly used in architecture and civil engineering today. Many of these are based on the reuse of plants and plant residues from industry and agriculture for the production of bio-sustainable insulation materials, and as aggregates in concretes. This paper presents the results of our study of research into hemp concrete, an emerging material in the green building sector, since it first appeared about twenty-five years ago to the present day. The study centres on a growing bibliography over this period, emphasizing some fundamental parameters of hemp raw materials and related building materials, the binders used in the production of hemp aggregate concretes and assessments of different aspects of their performance. The most important properties of hemp concrete vary according to the quality of the plant aggregates, the choice of binders (typically aerial or hydraulic lime), the proportions of the raw materials and the application techniques. Organic aggregates are less stable than inorganic aggregates and are therefore more difficult to use in a concrete mix with both inorganic and organic binders. Among other reasons, this is due to the disproportionate amount of water required in the mixing of plant-based concretes and to the release of organic compounds, which can have serious effects on the hardening process. This problem was identified in scientific studies on the use of hemp concrete in sustainable, bioclimatic construction, whether applied as a semi-liquid mass or as a precast element. This new biomaterial offers excellent results in terms of its application on site and has important physical properties, such as high durability and easy conservation. This study seeks to provide a useful tool for future research into sustainable building materials, better use of available energy and plant-based resources and more efficient recycling of the waste produced by human activities.
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The purpose of this study is to determine the key properties of Australian hemp particles which are used for manufacturing hempcrete. Hemp characteristics have a wide variability due to the influence of the environment conditions in various farmed areas. This study focuses on the measurements of the mechanical, thermal and acoustic performances of three Australian hemp: unretted hemp hurd, retted hemp hurd, and hemp fines. Hemp hurd is usually used in non-load bearing building walls, and hemp fine, which is the by-product of hemp manufacturing industry, is usually incorporated into a render. The experimental results show that the main impact of the retting process is a decrease in bulk density and leading to an improvement in thermal and acoustic properties. Without compaction, the bulk density is ranged from 97 and 118.8 kg.m⁻³, the max sound absorption coefficient from 0.88 and 0.99, and the thermal conductivity from 64 to 97 mW.m⁻¹. K⁻¹. Hemp fines have excellent thermal and acoustic properties and appear to be an efficient aggregate to produce an insulating render. Australian hemps investigated in this study have shown very similar characteristics to European hemps.
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Concrete is the most common building material; therefore, when designing structures, it is obligatory to consider all structural parameters and design characteristics such as acoustic properties. In particular, this is to ensure comfortable living conditions for people in residential premises, including acoustic comfort. Different types of concrete behave differently as a sound conductor; especially dense mixtures are superior sound reflectors, and light ones are sound absorbers. It is found that the level of sound reflection in modified concrete is highly dependent on the type of aggregates, size and distribution of pores, and changes in concrete mix design constituents. The sound absorption of acoustic insulation concrete (AIC) can be improved by forming open pores in concrete matrices by either using a porous aggregate or foam agent. To this end, this article reviews the noise and sound transmission in buildings, types of acoustic insulating materials, and the AIC properties. This literature study also provides a critical review on the type of concretes, the acoustic insulation of buildings and their components, the assessment of sound insulation of structures, as well as synopsizes the research development trends to generate comprehensive insights into the potential applications of AIC as applicable material to mitigate noise pollution for increase productivity, health, and well-being.
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Bio-based materials have been extensively studied in recent decades. These materials based on vegetable aggregates are highly heterogeneous, and their complex behaviour depends on the behaviour of the constituents as well as their spatial distribution, size, and shape. Classically, homogenization methods are used for the prediction of the behaviour of heterogeneous materials because they allow to take into-account the microscopic phenomena and characteristics governing the macroscopic behaviour at a considered scale. In the case of composite materials, the use of this prediction approach allows to optimize the properties according to some criteria while limiting often expensive and time-consuming experimental tests. This paper aims to predict the effective thermal conductivity and model the mechanical behaviour of a bio-composite based on lime and cereal straw. A numerical homogenization approach was adopted to consider the complex microstructure of these biobased materials. An experimental characterization of the composites was carried out to describe the microstructure of the material (size, orientations, and shape of aggregates). X-Ray micro tomography observation was performed to determine volume fraction of the different phases of the biocomposite. A statistical approach was also used to determine the size of the Representative Volume Element (RVE) of the studied material for different distributions of heterogeneities. Then, numerical simulations of the thermal and mechanical behavior of composite was carried out. The results show the need to take into account an interphase between the straw aggregates and the matrix as well as the effect of the vegetal aggregates on the hydration of the binder to accurately predict the effective properties of the material.
Chapter
Hemp is used for a wide variety of products, from cannabidiol oil to food, furniture, textiles, construction materials, or even animal bedding. The growing need for sustainable materials and the comeback of hemp made many companies interested in the fast-growing crop. Hence, many new hemp products are being introduced to the market. Some of the most promising innovative hemp products are hemp biofuel, medicine, cosmetics, acoustic panels, and soil contamination treatments. The current uses and opportunities of these hemp products in current, promising, and innovative industries will be further discussed in this chapter. The bottlenecks in material durability, costs, and the need for specialised machines need to be tackled to stimulate hemp growth even further.
Chapter
Cannabis sativa is an extraordinarily versatile species. Hemp and its cousin marijuana, both C. sativa, have been used for millennia as a source of fibre, oil, and for medicinal, spiritual, and recreational purposes. Because the consumption of Cannabis can have psychoactive effects, the plant has been widely banned throughout the last century. In the past decade, evidence of its medicinal properties did lead to the relaxation of legislation in many countries around the world. Consequently, the genetics and development of Cannabis as well as Cannabis-derived products are the subject of renewed attention. Here, we review the biology of C. sativa, including recent insights from taxonomy, morphology, and genomics, with an emphasis on the genetics of cannabinoid synthesis. Because the female Cannabis flower is of special interest as the site of cannabinoid synthesis, we explore flower development, flowering time well as the species' unique sex determination system in detail. Furthermore, we outline the tremendous medicinal, engineering, and environmental opportunities that Cannabis bears. Together, the picture emerges that our understanding of Cannabis biology currently progresses at an unusual speed. A future challenge will be to preserve the multi-purpose nature of Cannabis, and to harness its medicinal properties and sustainability advantages simultaneously.
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Background Environment-friendly materials attract attention whilst the construction sector causes excessive global energy consumption and emission of greenhouse gas. Renewable plant-based biomaterials, which have a low environmental impact, are very beneficial in order to prevent environmental pollution and to preserve natural resources. Hempcrete provides environment-friendly construction materials as well as thermal and hygroscopic properties. Objective This paper presents a review of hempcrete research about understanding the environmental effects and construction methods of hempcrete; moreover, the benefits and innovations it has provided throughout its life cycle, have been investigated. Methods For this purpose, experimental studies of hempcrete were compared to each other in all aspects in order to determine density, thermal conductivity, vapor permeability, hygrometric behavior, durability, acoustic absorption, mechanical properties and life cycle analysis. Moreover, binder characteristics, hemp shiv proportions, water content, curing conditions and results have been focused on to explain the benefits of hempcrete. Results The results obtained show that hempcrete has high porosity and vapor permeability, medium-low density, low thermal conductivity, Young’s modulus and compressive strength. Conclusion Based upon the findings of the studies reviewed, hempcrete is an advantageous material in buildings with its extraordinary thermal and hygrometric behaviour. Hemp is also an eco-friendly and economical plant-based raw material for the construction industry.
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Bio-based building materials are composites of vegetal particles embedded in an organic or mineral matrix. Their multi-scale porous structure confers to them interesting thermal, hygroscopic and acoustic properties. These performance properties have spurred research on these materials as alternative building materials with low embodied energy. This review contains a comprehensive critical analysis of mechanical, thermal, and acoustic properties of bio-based building materials with a particular focus on the interactions of various constituents and manufacturing parameters. Alkali-activated binders are reviewed for their potential use in high strength bio-based composites. A detailed physico-chemical characterisation of the aggregates and compatibility analysis allow a comprehensive understanding of fundamental phenomena affecting mechanical, thermal, and acoustic properties of bio-based building materials. A wide range of biomass materials is available for building composites, and hemp shives remain the most prevalent bio-aggregate. In the context of England, the farming of industrial hemp remains limited, due in part to the long, costly licencing process and the abandonment of processing subsidy as part of the EU common agricultural policy in 2013. On the other hand, Miscanthus (elephant grass) is a perennial, low-energy, and well-established crop in the England which is gaining interest from farmers in the South West region. Its development aligns with actual agricultural, land management and environmental policies with potential to fuel innovative industrial applications. This review performs a critical assessment of the performance of bio-based materials in an attempt to identify potential frameworks and opportunities to develop building insulating materials from miscanthus.
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Background: Environment-friendly materials attract attention whilst the construction sector causes excessive global energy consumption and emission of greenhouse gas. Renewable plant-based biomaterials, which have a low environmental impact, are very beneficial in order to prevent environmental pollution and to preserve natural resources. Hempcrete provides environment-friendly construction materials as well as thermal and hygroscopic properties. Objective: This paper presents a review of hempcrete research about understanding the environmental effects and construction methods of hempcrete; moreover, the benefits and innovations it has provided throughout its life cycle, have been investigated. Methods: For this purpose, experimental studies of hempcrete were compared to each other in all aspects in order to determine density, thermal conductivity, vapor permeability, hygrometric behavior, durability, acoustic absorption, mechanical properties and life cycle analysis. Moreover, binder characteristics, hemp shiv proportions, water content, curing conditions and results have been focused on to explain the benefits of hempcrete. Results: The results obtained show that hempcrete has high porosity and vapor permeability, medium-low density, low thermal conductivity, Young's modulus and compressive strength. Conclusion: Based upon the findings of the studies reviewed, hempcrete is an advantageous material in buildings with its extraordinary thermal and hygrometric behaviour. Hemp is also an eco-friendly and economical plant-based raw material for the construction industry.
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The growing world population and urbanization have worsened noise pollution, driving the development of sound absorption (SA) research across the globe. This study aims to analyse the SA global research trends and discover the opportunities for future development or collaboration using systematic bibliometric analysis. A total of 2970 articles since 1913 were systematically retrieved. Results reveal that the most productive journal had taken 10.3 % of the total publications. A high correlation r = 0.87 was found between the number of co-authorship and the h-index of a scholar. China has the highest number of publications 55.3 % and most research focused on porous materials. Present findings could be helpful to further develop SA from a global level perspective.
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1 and the transfer function method 2 . The standing wave method measures pressure maxima and minima of standing waves set up in a tube (with the sample at the end) and calculates the reflection factor from the resulting standing wave ratio and the complex acoustic impedance can also be determined with phase data from the position of the first pressure minimum from the sample surface. This technique is very reliable but can be time consuming as it must be done frequency by frequency; a more time efficient method was therefore introduced that provides easy determination of the acoustic impedance and hence absorption coefficient of samples over a continuous frequency range. This method is often called the transfer function method as it makes use of multiple frequency response measurements at discrete points in the tube and uses the transfer function between these measurements to calculate the complex reflection factor of the sample from equation 1 from which the surface impedance and absorption coefficient of the sample can be determined. The theory of impedance tube measurements is well known and an overview covering both of these measurement techniques can be found in Acoustic Absorbers and Diffusers by Cox and D'Antonio 3 .
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Book
Low Impact Building: Housing using Renewable Materials Tom Woolley ISBN: 978-1-4443-3660-3 252 pages February 2013, Wiley-Blackwell Buy Paperback £63.50 €79.40 Add To Cart Buy E-book ? £57.99 €71.99 Add To Cart Norton Shopping Guarantee Low Impact Building: Housing using Renewable Materials (1444336606) cover image Description This guide to the designs, technologies and materials that really make green buildings work will help architects, specifiers and clients make informed choices, based on reliable technical information. Low Impact Building: Housing using Renewable Materials is about changing the way we build houses to reduce their ‘carbon’ footprint and to minimise environmental damage. One of the ways this can be done is by reducing the energy and environmental impact of the materials and resources used to construct buildings by choosing alternative products and systems. In particular, we need to recognise the potential for using natural and renewable construction materials as a way to reduce both carbon emissions but also build in a more benign and healthy way. This book is an account of some attempts to introduce this into mainstream house construction and the problems and obstacles that need to be overcome to gain wider acceptance of genuinely environmental construction methods. The book explores the nature of renewable materials in depth: where do they come from, what are they made of and how do they get into the construction supply chain? The difference between artisan and self-build materials like earth and straw, and more highly processed and manufactured products such as wood fibre insulation boards is explored. The author then gives an account of the Renewable House Programme in the UK explaining how it came about and how it was funded and managed by Government agencies. He analyses 12 case studies of projects from the Programme, setting out the design and methods of construction, buildability, environmental assessment tools used in the design, performance in terms of energy, air tightness, carbon footprint and post-occupancy issues.
Chapter
This chapter re-contextualizes the lifecycle analysis (LCA) study performed by the authors on hempcrete in 2005, and gives the reader certain indications to help understand the working hypotheses made at the time and the results of the investigation. In addition, this chapter affords us the opportunity to place the 2005 LCA in perspective in relation to the present-day context in the domain of hempcrete. The chapter revisits the main results of the LCA on the banked hempcrete wall on a wooden skeleton, and the reflection carried out in order to perform this work on the evaluation of the environmental benefits of hempcrete.
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This study presents an analysis of a 30 000 strong data matrix derived from 227 studies originating from 35 countries since 1968. Similar to the fly ash effect, the carbonation of concrete increases with the incorporation of ground granulated blast-furnace slag (GGBS), but the rate increases as GGBS content is increased. This effect is greater for concrete designed on an equal water/cement (w/c) basis to the corresponding Portland cement (PC) concrete than on an equal strength basis. The Eurocode 2 specification for XC3 carbonation exposure in terms of the characteristic cube strength of concrete (or its w/c ratio) may need to be increased (or decreased) with the addition of GGBS. Other influencing factors, including GGBS fineness, total cement content and curing, were also investigated. In some cases, the carbonation of in-service GGBS concrete has been estimated to exceed the specified cover before 50 years of service life. Measures to minimise the carbonation of GGBS concrete are proposed. Fully carbonated reinforced GGBS concrete is assessed to show a higher corrosion rate. In relation to PC concrete, the carbonation of GGBS concrete is essentially similar when exposed to 3–5% carbon dioxide accelerated or indoor natural exposure, and the conversion factor of 1 week accelerated carbonation equal to 0·6 year is established.
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This paper presents the acoustic performance of small scale crumb rubber concrete (CRC) panels in terms of the sound absorbance and insulation at low (63, 125, 250 and 500 Hz) and high (1000, 2000, 4000 and 5000 Hz) frequencies. Acoustic tests were conducted with differing levels of fine aggregate replacement with crumb rubber (7.5% and 15%) with four different grades following freezing and heating. Analysis of the workability, compressive strength and density are also presented. The results found that CRC performed well in terms of sound absorbance particularly with higher proportions (15% here) and grades of crumb rubber. As an insulator, the CRC was comparable with plain concrete with only marginal differences observed. Effects of freezing and heating were shown to have no significant influence on the insulation properties. The insulation performance for all concretes was found to improve at high frequencies. The results demonstrate that CRC has potential as an external building cladding to absorb sound around high-rise urban structures but requires full-scale testing on site. This approach offers an environmental friendly solution to the ongoing problem of used tyres.
Conference Paper
Hemp concrete is nowadays an attractive alternative to traditional materials used in building construction and for noise barriers. As filling material associated with a timber frame, hemp concrete has a very low environmental impact and it is characterized by very interesting performances in hygro-thermal insulation and sound absorption. In order to control and optimize its acoustical behavior, it is important to predict the performance of this material as a function of several fabrication parameters such as the particle size distribution of the shiv (hemp aggregates), the hemp, water and binder mass contents, and the binder type. The effect of these fabrication parameters on acoustical properties was investigated by measuring sound absorption and transmission loss of various hemp concretes. However, hemp concrete is a highly porous material, having porosity distributed throughout three different scales. Moreover, the shape of its hemp aggregates is parallelepiped. These two particularities make the modelling of such material quite complicated. It was found out that semi-phenomenological models can be used to predict accurately these acoustical properties, by using a multiple porosity approach. Besides it was shown that the acoustical behaviour of this material is mainly due to the bigger pores existing between particles.
Article
Direct reanalyses of over 57 000 interview responses to 35 noise sources in 20 social surveys and reviews of publications for over 12 000 additional responses to 16 noise sources in 13 social surveys show that residents' reactions to an audible environmental noise (a target noise) an only slightly or not at all reduced by the presence of another noise source (ambient noise) in residential environments. The direct reanalyses account for type of noise source (aircraft, road traffic, railway, impulse noise), type of noise reaction question, type of activity disturbance, quality of noise data, type of regression analysis model (linear, legit, probit), two noise metrics (DNL, L-Aeq), and ten personal characteristics. Although there is considerable variation from survey to survey, the best direct estimate is that approximately a 20-dB increase in ambient noise exposure (95% confidence interval of 15-50 dB) has no more impact than approximately a 1-dB decrease in target noise exposure. Tabulations of 12 findings from laboratory studies in which subjects rated periods of multiple noise events also found that target noise annoyance is not consistently reduced by ambient noise. (C) 1998 Acoustical Society of America. [S0001-4966(98)06809-X].
Article
In a context of sustainable development and energy sparing, a life cycle assessment (LCA) may be useful to make good choices. Thus, this study concerns the LCA of an environmentally friendly material used for building construction, hemp concrete. The functional unit is first defined per square such that the wall may provide the function of bearing wall meter and its thermal performance is described by a thermal resistance of 2.78 m².K/W. The results then showed that the production phase of raw materials is mainly responsible for the environmental impact of the wall, mostly due to the binder production. It was also shown that, compared to traditional construction materials, hemp concrete has a low impact on environment. Moreover, hemp concrete contributes to reduce climate change as photosynthesis-mediated carbon sequestration and carbonation serve to reduce atmospheric carbon dioxide. A sensitivity analysis is performed on three criteria: wall thickness, renewal of coatings and compounds of the indoor coating. Our results show that environmental indicators evolve with wall thickness, except for the climate change indicator. It improves with thickness due to carbon sequestration and carbonation. Moreover the increase in the wall's thermal resistance with wall thickness is not taken into account in such an LCA performed at the material level. The renewal of coating slightly impacts the environmental indicator for small numbers of renewals but it leads to negative effects if they are too numerous. It appears that hemp-lime coating has a greater impact than sand-lime coating as it embeds more binder.
Article
This paper focuses on the acoustical properties of mixes of hemp particles. A physical analysis of the experimental data revealed that acoustical dissipation in this material is governed by inter-particle pores in the tested frequency range. The evolution of the acoustical parameters of mixes of hemp particles is studied as a function of density and it was found that these parameters are strongly affected by the parallelepipedal shape of the particles. The relationships existing between these acoustical parameters and basic parameters of the material, such as the apparent density of the mix, the particle apparent density, the characteristic dimension of the particles and their shape factor are investigated. It is shown first that these basic parameters can be directly used to model the acoustical properties of the mixes, then that acoustical data can be very useful to characterize the shape and microstructure of these hemp aggregates.
Article
Hemp concrete is a multifunctional ecological material used in buildings. Due to its high porosity (about 80% in volume), it presents an “atypical” mechanical behavior and its thermal and acoustic properties are particularly interesting. It is today possible to design this material according to the required use. This paper focuses on the mechanical properties of hemp concrete. It is shown that extreme curing conditions (30%, 75% and 98% RH) are prejudicial to the mechanical setting of the hydraulic binders whereas only high relative humidity disrupts the one of the air lime-based binder. It is also established that the binder content hugely influences the setting and hardening of the material. Finally, according to the hemp particle size, it appears that small particles (about 3 mm in length) lead to reduce the porosity and consequently the setting process of hemp concrete as compared to concrete manufactured with large particles (about 9 mm).
Book
IntroductionViscosity effectsThermal effectsEffective density and bulk modulus for cylindrical tubes having triangular, rectangular and hexagonal cross-sectionsHigh- and low-frequency approximationEvaluation of the effective density and the bulk modulus of the air in layers of porous materials with identical pores perpendicular to the surfaceThe Biot model for rigid framed materialsImpedance of a layer with identical pores perpendicular to the surfaceTortuosity and flow resistivity in a simple anisotropic materialImpedance at normal incidence and sound propagation in oblique poresAppendix 4.A Important expressionsReferences
Article
This study performed an evaluation of the physical and mechanical properties and sound absorption characteristics of porous concrete. Design was based on the target void ratio and the content of recycled aggregate. The objectives are to reduce noise generated in roads, railroads, residential and downtown areas as well as to utilize recycled waste concrete aggregate. The test results demonstrated that the difference between the target void ratio and the measured void ratio was less than 1.7%. The compressive strength reduced rapidly when the target void ratio and the content of the recycled aggregate exceeded 25% and 50%, respectively. The sound absorption characteristics of the porous concrete using recycled waste concrete aggregate showed that the Noise Reduction Coefficient (NRC) was optimum at the void ratio of 25% but the percent content of the recycled aggregate had very little influence on the NRC. Therefore, the optimum void ratio is 25% and the recycled aggregate is 50%.
Article
This article illustrates the value of incorporating psychological principles into the environmental sciences Psychophysiological, cognitive, motivational, and affective indices of stress were monitored among elementary school children chronically exposed to aircraft noise We demonstrate for the first time that chronic noise exposure is associated with elevated neuroendocrine and cardiovascular measures, muted cardiovascular reactivity to a task presented under acute noise, deficits in a standardized reading test administered under quiet conditions, poorer long-term memory, and diminished quality of life on a standardized index Children in high-noise areas also showed evidence of poor persistence on challenging tasks and habituation to auditory distraction on a signal-to-noise task They reported considerable annoyance with community noise levels, as measured utilizing a calibration procedure that adjusts for individual differences in rating criteria for annoyance judgments
Article
This paper demonstrates that by understanding how energy is consumed in the manufacturing of reinforced concrete, designers can significantly reduce the overall embodied energy of structures. Embodied energy of products can vary from country to country. Therefore, to accurately estimate the embodied energy of reinforced concrete structures, data specific to the country where they are being constructed must be used. This paper presents the assessment of embodied energy in typical RC building structures in Ireland.The most common methods used to calculate EE are evaluated in this paper and the most suitable method was applied to reinforced concrete. The EE of a typical 30MPa concrete mix in Ireland is calculated to be 1.08MJ/kg. Notably cement is credited with 68% of the total EE. The major contributors of energy consumption are identified, which should aid to minimise energy consumption and optimise efficiency.A case study is presented which compares the EE of a typical reinforced concrete structure in Ireland using two concrete mix designs. The first uses Ordinary Portland Cement, while the second uses GGBS replacing half of the cement content. As expected, the EE of the GGBS mix is significantly lower (30%) than that of its counterpart.
Article
Results are presented of an investigation into the acoustical properties of a range of fibrous absorbent materials. Measured values of characteristic impedance and propagation coefficient are shown to normalise as a function of frequency divided by flow-resistance and can be represented by simple power-law functions. Absorption coefficients of thin layers of material over a range of flow-resistance values are also shown. Supplementary data provide a basis for estimating the flow-resistance of a material from its bulk density.