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Acoustic absorption of hemp-lime construction
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.
... This wide density variability is reflected in the different compressive strength performances achieved by the composites, which go from 0.10 MPa to almost 4 MPa [4]. These composites also have good acoustic properties, fire resistance and durability to salt exposure and biological deterioration [4][5][6]. Hemp concrete can also be prefabricated through vibro-compaction by using hemp shiv with lime-metakaolin binders [7]. Alternative binders such as silica and polysaccharide can be used to confer to this hemp-material water resistance, vapor permeability and superior moisture buffering capacity [8]. ...
... There are no references in the literature to such mixtures. Usually, insulating mixtures use binders and natural fibers (without aggregates), thus obtaining low mechanical strengths [6,7,15]; other works analyze concretes with natural fibers added as partial replacements for sands, with poor thermal performance [15,16,20]. ...
... Flexural strengths of cement-reed and lime-reed (Calce Fiore + cement) mixtures are, respectively, 0.483 MPa and 0.826 MPa. The ratio between compressive and flexural strength for these mixes is, respectively, equal to 1.76 and 1.82; in the literature, ratios around 1.83 were found [6] for lightweight lime-hemp mixtures, while higher ratios were found for denser hemp materials (around 4.95 in [6]), for reed reinforced lime mortars (around 3.10 in [20]) and for reinforced cement mortars (5.35 in [15] and 6.42 in [16]. ...
The growing concern for the reduction of energy needs and the environmental impact of the building sector has placed emphasis on the possibilities offered by natural materials. The adoption of agricultural by-products seems to be promising and in line with the circular economy paradigm. Materials such as hemp and straw have been extensively adopted in contemporary construction , but nevertheless, the potential use of giant reed has not been sufficiently investigated despite being a common infesting plant abundantly available all over the planet. This work focuses on the performances assessment of lime/cement-reeds mixtures as base materials to design a new line of building components (bricks, blocks, panels and loose insulation) that can be used both in new bio-based construction and in existing buildings for energy-efficiency retrofit. The main materials used in the experimental campaign are giant reed by-products, lime, cement and local and recycled aggregates. The evaluation of the physical, mechanical and thermal properties of lime-reed and cement reed composites are presented. The results of thermal conductivities (between 0.245 and 0.191 W/m K) and mechanical properties (compressive strengths between 0.848 and 1.509 MPa, and flex-ural strengths between 0.483 and 0.829 MPa) allow meeting the requirements for non-bearing and thermal building blocks. The outcomes show how blocks made with the abovementioned lime-reed mixture have good mechanical performance and thermo-physical behavior when compared to conventional building materials such as hollow clay or hemp blocks with the same thickness.
... 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]. ...
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.
... 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. ...
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.
... Nonetheless, the addition of those fibers could hardly affect the sound insulation properties. In another study, Kinnane et al. [32] examined the acoustic behavior of hemp-lime concrete made from various binders including hydrated lime (CL90), hydraulic lime (NHL 3.5), cement (type-I), and different pozzolans (metakaolin and ground granulated blast furnace slag). The results revealed that the composite continuing hydrated lime-pozzolan had a higher sound absorption coefficient than those incorporating cement or hydraulic lime, due to the lower density of the lime-pozzolan concrete. ...
... [31]. Furthermore, the NRC for several hemp lime mortars and concretes were reported to be less than 0.5 [32,76]. ...
In the search of more environmentally-friendly construction materials, the use of natural-based fibers has gained much attention as reinforcement in the inorganic-based matrix. In this paper, the nonwoven flax fabric reinforced lime composites are created using a dewatering technique, and the serviceability parameters –thermal conductivity, sound absorption coefficient, and residual flexural resistance after exposure to elevated temperature– are determined experimentally. The tests are carried out on two different lime composites prepared under two distinct curing regimens, i.e., accelerated carbonation in a CO2 chamber and natural carbonation in laboratory conditions, to evaluate the effect of forced carbonation. In addition, the experimental results of the serviceability parameters are included in the MIVES model (Integrated Value Model for Sustainability Assessment) to evaluate the social sustainability of the developed material as an interior drywall panel. MIVES, a type of multi-criteria decision-making method, is based on the value function concept and seminars with experts. According to the results of experimental tests, the accelerated cured sample has higher thermal conductivity (~4 times) and lower sound absorption coefficients (~20%) than the naturally cured one. Nonetheless, the flexural performance of the former is 50% (at room temperature) and 100% (at elevated temperature) better. As for the social sustainability index assessed by the MIVES-based multi-objective approach, it ranges between 0.65 and 0.75 (out of 1.0) for both lime composite panels, at least 20% higher than the control lime panel with no reinforcement. The sustainability model designed for this research can be used for assessing the social sustainability performance of other materials although the weights assigned by the experts could be adapted to reflect the perceptions and local preferences.
... Hemp concrete is considered a green building material not only because of its low carbon content but also because of its ability to regulate heat, humidity, and relative humidity [4]. Hemp concrete is also known to exhibit acoustic insulation [5]. Response to fire is an important factor to consider as it relates to building safety. ...
... Particle size distribution[5] ...
Polypropylene, steel, and carbon fibers are used to increase the ductility and toughness of concrete materials. In recent years, studies on the use of natural fibers have increasingly continued. Among natural fibers, hemp fiber has the highest tensile strength value. The aim of this study was to discuss and present the results of the experimental study on the use of cement-based hemp shives and fibers to increase the ductility of mortars. Another aim is to increase the use of hemp in the construction field by using more economical and natural fibers. Various binders and different amounts of fibers and shives were added and their effects on flexural strength were investigated. Water absorption and flexural tests and scanning electron microscope and X-ray diffraction analysis were performed on the produced samples. Particle and hole size distributions and stereo microscope images of the samples are given. The use of hemp fibers was observed to improve flexural strength, while shives were not significantly improved flexural strength.
... The order in which these ingredients are added is very important as the reactions occur rapidly (21). Some hempcrete producers choose to mix the hurds using a mortar mixer (or by hand) with the limebased binder, followed by misting water until the desired consistency is reached (30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48). A chemical reaction known as "bonded cellulose insulation" occurs between the water and the lime-based binder, which adheres to the hurd particles together . ...
... 9) The thermal storage capacity of hempcrete allows it to store the generated interior heat and release it to the interior later (e.g., at night) when outside is colder (during winter) . On the other hand, during the summer, it will absorb the outside heat and does not release it to the interior immediately (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40). This will help to avoid overheating, and therefore can reduce energy bills (21). ...
This review paper highlights about the Industrial hemp (fiber type) used as a plant based building construction material, Hempcrete. Industrial hemp (Cannabis sativa L.) is an emerging food and fibre crop. It is a non-drug variety of Cannabis sativa with low Δ9-tetrahydrocannabinol (THC) content of less than 0.3 per cent. The use and performance of hempcrete suggested that hempcrete can be considered as an environmentally friendly material. In a first of its kind in India, an architect couple, Namrata Kandwal and Gaurav Dixit have built a house made of using hemp fibre-hempcrete in Uttarakhand state, India. Industrial Hemp (fiber-type) is both an agricultural and industrial commodity and stem supplies both cellulosic and woody fibers. Hempcrete is a construction material made from hemp fibres, lime and water. Hemprete showed a negative carbon footprint making it a suitable material in the construction industry. This composite, hempcrete breathes, as well as having a good thermal and acoustic-insulation properties. However, hempcrete does have several key drawbacks that make it less than ideal as a building material. In addition to poor mechanical performance, hempcrete also has a high capacity to absorb and retain water. Therefore, future in detail study is warranted for the commercialization of hempcrete as a building material.
... An experimental study showed that hemp fiber/lime concrete composite binders absorb sound 40-50% better than other binders [354]. According to research findings, kenaf fiber-reinforced composite is a lightweight, ecologically friendly, and cost-effective alternative to synthetic composite materials primarily employed in building and construction applications [355]. ...
... Yahaya et al. [385] designed woven kenaf/Kevlar hybrid composites and compared their energy absorption and ballistic limit velocity to non-hybrid Kevlar composites (V50). The results showed that kenaf/Kevlar composites absorbed Fig. 20 Application of plant fibers in construction a Hemp fiber-based chair [351], b Wood veneer reinforced elastic composite [352], c Off-site roofing components in building construction [354], d wood fiber-based construction wall [351], (Creative Commons CC-BY-NC-ND), e Jute based underground pipes [353]. Copyright©2018 Elsevier Ltd less specific energy than non-hybrid Kevlar. ...
Reducing energy consumption and minimizing environmental impacts have been significant factors in expanding the applicability of plant fiber-reinforced composites across a variety of industries. Plant fibers have major advantages over synthetic fibers, including biodegradability, light weight, low cost, non-abrasiveness, and acceptable mechanical properties. However, the inherent plant fiber properties, such as varying fiber quality, low mechanical properties, moisture content, poor impact strengths, a lack of integration with hydrophobic polymer matrices, and a natural tendency to agglomerate, have posed challenges to the development and application of plant fiber composites. Emphasis is being placed on overcoming this limitation to improve the performance of plant fiber composites and their applications. This study reviews plant fiber-reinforced composites, focusing on strategies and breakthroughs for improving plant fiber composite performance, such as fiber modification, fabrication, properties, biopolymers, and their composites with industrial applications like automotive, construction, ballistic, textiles, and others. Furthermore, Pearson rank correlation coefficients were used in this review to assess the relationship between the chemical composition of plant fibers with their physical and mechanical properties. If researchers study the behavior of plant fibers using correlation coefficients, it will be easier to combine plant fibers with a polymer matrix to develop a new sustainable material. Through this review study, researchers will learn more about the strategic value of these materials and how well they work in different real-world situations.
Graphical abstract
... Natural fiber composites are employed as insulating and soundproofing materials because of their superior thermal and acoustic qualities. Hemp/lime/concrete composites have outperformed all other binders in terms of sound absorption [307]. The thermal characteristics of the concrete can be improved by adding hemp. ...
... In addition, many countries are using biocomposite materials to combat environmental challenges. Due to future demand, many companies are investing in biocomposites [307]. ...
Global environmental concerns, as well as the rapid depletion of non-renewable fossil
fuel-based resources, have prompted research into the development of sustainable, environmentally
friendly, and biodegradable materials for use in a variety of high-end applications. To mitigate the
environmental setbacks caused by nonbiodegradable materials, the development of biocomposites
with improved mechanical performance is gradually gaining momentum. Natural fibers such as
hemp, flax, and sisal have been well incorporated into biocomposite development. Nonetheless,
the impact of functional moieties in their life cycle cannot be underestimated. In this review paper,
a detailed discussion of the characteristics and components of biocomposites is presented. The
treatment of composite materials (alkali and acetylation), as well as several manufacturing processes
(hand layup, 3D printing, extrusion, etc.) and the applications of biocomposites, which are not limited
to the aerospace industry, packaging, biomedicine, etc., are presented. Biocomposites with excellent
durability, performance, serviceability, and reliability must be produced to expand their applications.
... Binder is the most crucial component of a concrete-like substance, because of its availability and minimal emissions during manufacturing. Because of the high amount of silica contents present in the woody parts of the hemp plant, it can bond easily with lime (Kinnane et al. 2016). ...
... Hemp-based concrete has been proven to provide high permeability and acoustic insulation (Kinnane et al. 2016). The researchers argued that walls of the concrete made of hemp have greater sound absorption capacities as compared to conventional concrete walls. ...
Cannabis is the most versatile species. Hemp and marijuana have been used for fibre, oil, medicinal and recreational purposes from millennia. Throughout the last century, the plant has been generally outlawed because of its psychotropic effects in many nations. In recent past, the studies on cannabis revealed the evidence of its high medicinal properties and its uses in treating life threatening diseases, which leads to the relaxation of legislation in many counties. Now, the genetic and genomics as well as the cannabis derived products enjoys renewed attention. In this chapter, the discussion was made on the advent of genomics and breeding strategies to improve various traits of cannabis. This will bring insights on future direction of cannabis breeding.
... 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]. ...
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. ...
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.
... Bio-based composite materials are receiving much attention for their hygrothermal properties [14][15][16][17], and acoustical properties [18][19][20]. Although thermal insulation performance results of these materials are often approved as a main priority, mechanical properties are also essential to guarantee the present safety, stability, and quality level during use and environmental conditions. ...
This study investigates the mechanical and energy absorption properties of an eco-friendly straw-lime composite. Compression tests were performed to explore the effect of the straw-to-binder ratio (S/B = 0.2, 0.3, and 0.4), as well as the influence of compression speed, and test direction, on the mechanical properties and capabilities to dissipate energy. The Digital Image Correlation (DIC) technique was applied to analyze strain field homogeneity during the deformation process and to evaluate Young’s modulus and Poisson’s ratio. Results show decreasing strength and energy absorption with higher straw to binder ratios. Samples tested orthogonal to straw fiber orientation exhibited an increase of over 100% in absorbed energy per unit volume compared to parallel samples. Physical properties are sensitive to strain rate, with values up to 0.72 MPa for the plateau stress and 300.40 kJ/m3 for the absorbed energy, for a 0.2 S/B ratio at a loading speed of 100 mm/min. The material has shown greater energy absorption than lightweight foam concrete of equivalent density. These results are promising for the development and new use of straw-lime biocomposites as energy absorbing protective materials.
... Different applications are being studied to use hemp stalk, taking advantage of its low price, such as using it as insulation in buildings and adding lime to form non-structural blocks [58,59]. Seeking a sustainable substitute for traditional walls, researchers carried out a study of the acoustic absorption properties of lime and hemp stalk walls, obtaining an average of between 40-50% acoustic absorption, obtaining better results with the less hydric binders and which can be manufactured on-site or placed as prefabricated units [60]. The main advantages of hempcrete are the insulating properties provided by the hemp stalk, and the lime binder provides protection against moisture, fungi, and fire [61]. ...
There has been increasing interest in green and recyclable materials to promote the circular economy. Moreover, the climate change of the last decades has led to an increase in the range of temperatures and energy consumption, which entails more energy expenditure for heating and cooling buildings. In this review, the properties of hemp stalk as an insulating material are analyzed to obtain recyclable materials with green solutions to reduce energy consumption and reduce noise to increase the comfort of buildings. Hemp stalks are a low-value by-product of hemp crops; however, they are a lightweight material with a high insulating property. This study aims to summarize the research progress in materials based on hemp stalks and to study the properties and characteristics of the different vegetable binders that could be used to produce a bio-insulating material. The material itself and its microstructural and physical aspects that affect the insulating properties are discussed, as is their influence on durability, moisture resistance, and fungi growth. Research suggests using lignin-based or recyclable cardboard fiber to develop a bio-composite material from hemp stalk, but long-term stability requires further investigation.
... These conditions are also important to observe the possible degradation of hygroscopic natural fibers which are also sensitive to fungal growth. Meanwhile, as the natural fiber, hemp (Cannabis Sativa L.), is well known as one of the oldest textile fibers, nowadays hemp aggregates (shiv) are often used in heat [25] and sound insulation [26] issues disregarding strength concern. As for this study, hemp was used as fiber similar to the other cellulosic ones such as sisal or jute, not as bio-aggregate, combined with cement and SCMs in different ratios. ...
Concrete with cellulosic fibers should preserve the microstructural and functional properties with less degradation and without micro-organisms for several years. This study focuses on the usability of hemp fibers in a mixture combined with lightweight aggregates (LWA) and cementitious materials. Unlike mostly mortar based current literature, this study addresses the hemp fiber reinforced lightweight concrete (HRLWC) in which coarse aggregates are also used, and these aggregates are volcanic pumice aggregates (VPA). In order to mitigate fiber degradation induced by alkali attack, supplementary cementitious materials (SCM) e.g. metakaolin, blast furnace slag and fly ash were used. Total binding materials and water to binder ratio were taken constant, and the hemp fiber ratio was chosen as Vf = 1.0%. In this scope, compressive strength, flexural behavior, energy absorption, crack width, density, and water absorption were experimentally investigated. Herein, two important exposures on samples are under consideration, one is the natural moisture curing due to LWAs which resemble water reservoir gradually releasing water, the first time for cellulosic fibers in the current literature. The second one is the accelerated aging test to provoke alkali release by immersing in hot water for 10 days. The findings from test results and micro photographs reveal that the pumice aggregates combined with proper SCMs are suitable to contribute sustainable HRLWC design.
... The thermal conductivity ranged from 0.05 W/m⋅K to 0.138 W/m⋅K for a variety of dry densities from 220 to 1000 kg/m 3 (Arnaud and Gourlay, 2012;Bevan and Woolley, 2008;Elfordy et al., 2008;Fazio et al., 2020;Arnaud, 2000;Nguyen et al., 2010). Additionally, due to high porosity (more than 70%), hempcrete has a very high specific heat (Walker and Pavía, 2014), strong thermal mass, and excellent acoustic absorption (Fernea et al., 2017;Glé et al., 2011;Kinnane et al., 2016). This combination of low thermal conductivity and high heat storage capacity proposes an increase in the building's envelope energy-efficient performance, even in hot and arid conditions. ...
Hempcrete is a bio-composite material with excellent environmental and thermal properties. This material has
been increasingly adopted in Europe as an alternative to concrete and traditional insulation. However, hemp
hurds, as the raw materials for hempcrete, are discarded in the world’s largest producer (Morocco) and
considered biomass waste due mainly to their association with marijuana production. Thus, research on
hempcrete remained limited in Morocco, with fewer stakeholders aware of the benefits of hempcrete in green
buildings. The objective of this paper is to assess the potential use of Moroccan hemp biomass in the construction
industry using a life-cycle assessment comparison of a residential house in Marrakech (Morocco) with three
different exterior walls systems, two insulated conventional wall systems (i.e., double hollow clay brick (DHB),
composite wall (CW) with extruded polystyrene (XPS) insulation), and a bio-composite material (i.e., hempcrete)
to identify environmentally preferable wall systems. Our study demonstrated that hempcrete is advantageous
over other comparable conventional wall systems in terms of embodied energy and performs best in terms of the
environmental performance associated with its entire life cycle achieving relatively low carbon emissions
(484.42 tCO2) compared to insulated DHB and CW systems (546.27 tCO2 and 546.55 tCO2 for DHB and CW,
respectively) over a lifetime of 100 years. Significant savings (i.e., 61.85–62.13 tCO2 if hempcrete is used instead
of DHB and CW) can be made from the exterior wall choice for a single house. These savings become much more
significant if scaled up to the national level of Moroccan homes. Consequently, by exploiting the hemp biomass
currently available in Morocco, results show a reduction of 1.91 MtCO2–1.92 MtCO2, equivalent to 2.81%–2.83%
of overall Moroccan emissions. Thus, strong policy support and hemp legalization in Moroccan are essential to
boost and expand hempcrete utilization for a greener construction industry
... 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]. ...
Lightweight concrete (LWC) panels are becoming popular in buildings because of being lightweight, which allows easy transportation, handling, and installation. They provide the opportunity for modular construction. They also have insulating properties with thermal conductivity of 0.026-1.0 W/m-K. However, they have low thermal mass, which causes overheating during the heatwave period in Mediterranean and temperate climates. Therefore, Phase Change Materials (PCM) are integrated into LWC panels to increase thermal storage, mitigate overheating, and increase energy efficiency. However, the integration of PCM in LWC panels also increases their thermal conductivity, which is not favorable for a sustainable building. There is a need to reduce the thermal conductivity of PCM-integrated LWC panels. Thus, this study aimed to develop new lightweight heat-resistive and thermal storage panels (HRSPs) using porous fillers and PCM for energy-efficient building applications.
First, the optimum PCM melting point for cool temperate climates of Melbourne was identified through parametric analysis considering a typical Victorian house as a case study. The result showed that the optimum PCM melting point for free-running and air-conditioned houses is 30°C and 25°C, respectively. Based on these findings, capric acid (CA) PCM with a 29-32°C melting point was selected. The integration of PCM in cementitious composites may suffer from leakage issues during mixing with cement and other aggregates. The leaked PCM, such as fatty acids, may acidify concrete and reduce its compressive strength. The traditional leakage test proposed by previous researchers was insufficient to identify the microscopic leakage of PCM and its potential acid attack on concrete. Moreover, the conventional Form Stable PCM (FSPCM) synthesis procedures are energy-intensive, increasing the embodied energy of FSPCM. This study proposed a new FSPCM synthesis procedure to reduce energy use, eliminate acid attacks and increase PCM absorption capacity in porous material for energy-efficient buildings. The proposed method was energy-efficient, with CA absorption of 75% in porous hydrophobic expanded perlite (HEP). However, due to acid attack, the compressive strength and thermal conductivity at 75% CA absorption were lower than one with 60% CA.
Hence, the absorption of PCM should not be the only criterion for developing FSPCM. More indicators should be considered to develop an optimum FSPCM.
This study proposed six indicators, including absorption, thermal conductivity, strength, thermal inertia, latent heat storage, and thermal storage, to select the best porous materials to absorb PCM. American Society for Testing and Materials (ASTM) standards were adopted to measure proposed indicators. A comparative study was conducted to select the best porous materials amongst Silica Aerogel Granules (SAG), Hydrophobic Expanded Perlite (HEP), Nano-clay (NC), Recycled Expanded Glass (REG), and Silica Fume (SF) to absorb CA and develop FSPCM. In this study, the FSPCM-integrated concrete panels were named thermal energy storage panels (TESP). The comparative analysis revealed that SAG-based TESP was meeting all five indicators accept compressive strength (3.66 MPa), which was lower than the
minimum compressive strength (4.14 MPa) criteria for non-structural applications. However, HEP-based TESP had acceptable compressive strength and thermal conductivity with the second-best thermal inertia and heat storage, making it a suitable porous material for absorbing polar PCM for buildings. However, the thermal conductivity of TESPs was still higher than LWC because of the higher thermal conductivity of PCM and concrete, although the TESPs have higher thermal storage. Thus, there is a need to develop a TESP with high latent heat storage, low thermal conductivity, and acceptable mechanical properties.
To reduce the thermal conductivity of TESP, sand was volumetrically replaced with SAG to prepare Heat Resistive and Storage Panels (HRSP) using the proposed particle-density-based approach. The developed SAG-based HRSP had lower thermal conductivity than TESP with similar thermal storage. Although HRSP had higher thermal conductivity than SAG-based LWC, it resulted in higher energy savings (9%), emission (24%), and comfort than SAG-based LWC because of higher thermal inertia and storage. Moreover, the HRSPs had lower embodied energy and carbon than SAG-based LWC. However, the SAG-based HRSP still had higher embodied energy than normal concrete panels. Consequently, the SAG was replaced entirely with REG particles to develop eco-friendly HRSP for buildings. Results revealed that REG based HRSP had 27% lower thermal storage then SAG-based HRSP due to high thermal conductivity and slightly lower latent heat storage. The compressive strength of REG-based HRSP (17.77 MPa) was very close to the minimum compressive strength for the structural application of concrete. Applying REG-based HRSP in a building envelope had slightly higher discomfort hours than SAG-based HRSP, and it also reduced annual energy use and CO2 emission by 8.24% and 20% lower than SAG-based HRSP in a typical Victorian house, respectively.
In conclusion, the REG-based HRSP was the best eco-friendly material for buildings with acceptable structural properties and moderate energy savings potential. However, the SAG based HRSP was the most energy-efficient material with acceptable mechanical and thermal properties of the non-load-bearing structure.
... Hemp composite typically includes high volume of hemp shiv, wooden part of hemp stalk, which is highly porous and lightweight unique component (De Bruijn & Johansson, 2013). Thus, hemp composites become a lightweight insulation material having excellent thermal (Hussain et al., 2019;Somé et al., 2018), acoustical (Degrave-Lemeurs et al., 2018;Kinnane et al., 2016), and hydric (Latif et al., 2015;Walker & Pavía, 2014) properties. In addition, hemp composites were found to be carbon-negative construction materials which store higher amounts of CO2 than they emit through their service life (Arehart et al., 2020). ...
This study investigated the production and properties of lightweight hemp composites produced using waste industrial hemp stems cultivated in Turkey. Hemp stems were separated from their fibers and fragmented to obtain hemp shiv aggregates in the laboratory. Twelve mixtures were prepared with varied volumetric ratios of hemp: cement (H:C) and hemp: water (H: W) using different sizes of hemp shiv. The influence of mix proportions on the physical and mechanical properties of hemp composites were investigated. Besides, microstructure of hemp composites was examined. The hemp composites produced were in the apparent density range of 312 to 928 kg/m3 and exhibited 0.20 to 1.24 MPa compressive strength. The water absorptions of samples were in the range of 3.47 and 8.50 kg/m2.h1/2. The apparent density and compressive strength of hemp composites decreased with the increase of H:C ratio, but this situation is the opposite for increase of H: W ratio and hemp shiv size. Besides, increase in H:C ratio or hemp shiv size caused higher water absorptions.
... A structure of different kinds of porous materials microscopic images are depicted in Figures 2 and 3. The presence of passages, cracks, and cavities on surfaces of porous materials eases the entry and absorption of sound waves as sound waves travel through cavities, the friction of air with the pore wall and vicious loss contribute to thermal losses and result in the dissipation of sound by heat (Berardi and Iannace 2015), (Kumar 2012), (Kinnane et al. 2016). To obtain a larger band of frequency for sound absorption the above principles of energy consumption are majorly contributed (Sagartzazu, Hervella-Nieto, and Pagalday 2008). ...
Over the last couple of decades, there is an increasing demand to control interior noise occurring in aircraft, automobiles, railways, and construction works. Interior noise could impair people’s health, affecting passenger comfort and active safety performance. One of the contemporary noise control technologies is the use of sound-absorbing materials. Traditionally, mineral fibers, foams, and composites are used as sound-absorbing materials. However, they are expensive and energy consumptive as they add to the structure’s weight and affect structural integrity. Natural fibers could contribute to the replacement of conventional mineral fibers with decreased environmental impact, carbon neutrality, and improved sound-absorbing qualities. Also, previous research proved that sound-absorbing materials having natural fiber possess better acoustic properties comparable to those of synthetic fibers. However, high water absorption, termite attack, low fire resistance, and low strength are some of the issues restricting natural fibers usage. Here, an attempt is made to present the potential of natural fibers for acoustic absorbers by understanding the benefits of their inherent porous and tortuous structure. This paper involves a review study of experimental methods and parameters used to regulate the acoustic performance of natural fibers. Natural fibers seem a proven alternative as an acoustic absorber, thereby reducing sustainability concerns related to synthetic materials in acoustics applications.
... 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]. ...
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]. ...
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.
... 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. ...
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.
... 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). ...
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.
... 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. ...
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.
... 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. ...
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.
... 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]. ...
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. ...
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.
... 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. ...
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.
... 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). ...
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.
... 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. ...
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.
... 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. ...
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). ...
... 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). ...
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.
This paper aims to study the possibility of valorizing hemp residues in order to develop new local bio-composites from Moroccan hemp shiv and epoxy. The goal is to use them as thermal and acoustical insulation panels since these hemp residues exist in large quantities in landfills and present a national concern due to a lack of waste management technologies. For this purpose, several samples were prepared for different densities and two sizes of hemp shiv; crushed shiv (CS) and fibred shiv (FS). The results revealed that the increase of density resulted in an increase in thermal conductivity and a decrease in thermal diffusivity. However, the thermal conductivity of composites is still lower than 0.1 W/mK for the most studied samples. The samples show values of acoustic absorption coefficients varying between 0.2 and 0.59 for crushed shiv composites (CSC) at the frequency range (578-1396 Hz) and between 0.2 and 0.73 at the frequency range (662-1396 Hz) for Fibred shiv composites (FSC). It has been observed that the density has a significant effect on the sound absorption coefficient. Increasing the density shifts the acoustic absorption curve towards the low frequencies. Also, decreasing the particle size enhances the sound absorption in the medium frequency range (300-600 Hz). The obtained results are satisfactory for manufacturing these new composites that can be used as thermal and acoustic insulators. Moreover, it offered the best solution for hemp waste management.
Composites made of annual plants, based on polymer matrix reinforced with ligno-cellulosic material, have been extensively used in construction, automotive industry, marine etc. due to their tailored properties and acceptable costs. Petroleum-based adhesives (most of them based on methane and formaldehyde), a principal matrix for lignocellulosic-based composites, include more than 85% from all the resins used yearly in the world. Their utilization can cause air pollution and health damages for humans because of the toxic substances (e.g. formaldehyde). Considering the scarcity of gas and petroleum reserves and the environmental concerns on high-emission and non-recyclable materials, researchers are trying to develop new alternative resins based on biomass or by-products of many industries. This chapter includes the use of alternative adhesives for composites with annual plants derived from food industry, as casein, polylactic acid, starch and soybean, pharmaceutical industry, as chitosan and cement industry as mineral binders, including here cement, lime, gypsum and geopolymers.KeywordsAdhesivesCaseinPolylactic acidStarchSoybeanChitosanCementLimeGypsumGeopolymers
Magnesium binder is an alternative to lime binder in the technology of hemp-based composites. The advantage of using this binder is an increase in mechanical strength compared to those based on lime. These composites are mainly used as an insulating wall material, as a filling of a wooden frame structure. During compaction of the mixture, hemp shives tend to lay with fibers perpendicular to the compaction direction. The direction of the fibers in the shives, as well as the direction of the capillary pores affect the properties of the composite. The performance characteristics of a building partition insulated with a composite will vary depending on the direction of the shives in relation to the direction of the external factor. The outer wall is exposed to heat flow and water transport, e.g. by capillary action. The article presents the results of tests of the thermal conductivity and capillary rise of a composite densified in the direction perpendicular and parallel to the heat flux and moisture flow. Composites samples with a bulk density of about 370 kg/m ³ were tested. Compaction of the mixture in the direction parallel to the heat flow decreased the thermal conductivity. Due to the reduced value of the thermal conductivity of the composite compacted parallel to the heat flux, such a technique can be used in prefabrication, e.g. in the production of wall blocks. This direction of compaction - perpendicular to the wall surface, and thus to the direction of capillary rise, also reduced the amount of uptaken up water and changed the course of water rising over time.
Purpose
This paper aims to characterize and develop a new ecological lightweight concrete reinforced by addition of palm plant fibers (from vegetal waste) to be used in the thermal and acoustical insulation of local constructions. The date palm plant fibers are characterized by their low sensitivity to chemical reactions, low cost and large availability in local regions. Therefore, the newly obtained lightweight concrete may suggest a great interest, as it seems to be able to achieve good solutions for local construction problems, technically, economically and ecologically.
Design/methodology/approach
The experimental program focused on developing the composition of palm-fiber-reinforced concrete, by studying the effect of the length of the fibers (10, 20, 30 and 40 mm) and their mass percentage (0.5%, 1%, 1.5% and 2%), on the mechanical and acoustical properties of the composite. The main measured parameters were the compressive strength and flexural strength, sound absorption coefficient, noise reduction coefficient (NRC), etc. These tests were also borne out by the measure of density and water absorption, as well as microstructure analyses. To fully appreciate the behavior of the material, visualizations under optical microscope and scanning electron microscope analyses were carried out.
Findings
The addition of plant fibers to concrete made it possible to formulate a new lightweight concrete having interesting properties. The addition of date palm fibers significantly decreased the density of the concrete and consequently reduced its mechanical strength, particularly in compression. Acceptable compressive strength values were possible, according to the fibers content, while better values have been obtained in flexion. On the other hand, good acoustical performances were obtained: a considerable increase in the sound absorption coefficient and the NRC was recorded, according to the content and length of fibers. Even the rheological behavior has been improved with the addition of fibers, but with short fibers only.
Originality/value
Over the recent decades, many studies have attempted to search for more sustainable and environmentally friendly building materials. Therefore, this work aims to study the possibility of using waste from date palm trees as fibers in concrete instead of the conventionally used fibers. Although many researches have already been conducted on the effect of palm plant fibers on the mechanical/physical properties of concrete, no information is available neither on the formulation of this type of concrete nor on its acoustical properties. Indeed, due to the scarcity of raw materials and the excessive consumption of energy, the trend of plant fibers as resources, which are natural and renewable, is very attractive. It is therefore a major recycling project of waste and recovery of local materials.
Sustainable fiber reinforced polymer (FRP) composites from renewable and biodegradable fibrous materials and polymer matrices are of great interest, as they can potentially reduce environmental impacts. However, the overall properties of such composites are still far from the high-performance conventional glass or carbon FRP composites. Therefore, a balance between composite performance and biodegradability is required with approaches to what one might call an eco-friendly composite. This review provides an overview of sustainable FRP composites, their manufacturing techniques, and sustainability in general at materials, manufacturing, and end-of-life levels. Sustainable plant-based natural fibers and polymer matrices are also summarized, followed by an overview of their modification techniques to obtain high-performance, multifunctional, and sustainable FRP composites. Current state-of-the-art mechanical and functional properties of such composites are then surveyed and provide an overview of their potential applications in various industries, including automobile, aerospace, construction , medical, sports, and electronics. Finally, future market trends, current challenges, and the future perspective on sustainable natural FRP composites are discussed.
The growing apprehensions about increasing carbon emissions have made global leaders take robust action to prevent catastrophic climate change and global warming. Building construction is one of the many factors responsible for the increase in global pollution. Therefore, in this area, green construction is the most important step to reduce carbon emissions and other factors that cause the increased global pollution level. Hence, the revival of eco-friendly green materials could be a steppingstone in this way. Vegetal concrete construction materials based on biomass will be able to offer the beneficial solution of carbon sequestration in addition to the low embodied. These vegetal-based concretes are composed of an organic or inorganic binder and biomass derived from agroforestry industries such as rice husk, straw bale, hemp, kenaf, cork, and others. One of the vegetal concretes is hemp concrete, which has been extensively explored and researched, making it one of the best green materials for other purposes, such as an alternative to plastics and fuel in the form of biofuel. This chapter provides an overview of hemp-based concrete research, which is rapidly increasing in the green building sector, as well as plastic and fuel.KeywordsHemp concreteLimeGreen building applicationFuelPlasticPolymersBiodegradableCarbon dioxide (CO2)
The building and construction sector is responsible for global energy consumption and greenhouse gas emissions. Hence the use of environmental-friendly building materials is becoming increasingly important. Several studies have stated that Hempcrete is an enviro-friendly building material that reduces waste and decreases natural resources and energy use. Despite its many benefits, Hempcrete does have a few disadvantages that make it less than ideal as a building material. For instance, the porous structure of the Hempcrete decreases its mechanical performance and increases its ability to retain water. Though these issues are not so befouling as to prevent the use of Hempcrete within the construction sector altogether, they do provide substantial limitations regarding what it can be used for. Although Hemp does not increase structural strength by what we had assumed, it does exhibit structural properties like fiberglass. The paper examines the opportunities and challenges associated with using hempcrete as a building material. The paper is based on secondary sources and gives an overview of hempcrete research and identifies the gaps, thereby suggesting a further area of research.
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.
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.
Geleneksel betonun çevresel etkisini düşürmek için kullanılan yöntemlerden bir tanesi bitki-bazlı agregaların kullanılmasıdır. Kenevir betonu mineral bağlayıcıların kenevir sapı parçaları ile birleştirilmesi ile elde edilmektedir. Bu çalışmada, Türkiye’de yetiştirilen atık endüstriyel kenevir saplarının kenevir betonu üretiminde değerlendirilmesi amaçlanmıştır. Çalışmada, üç farklı bağlayıcı (çimento, hidrolik kireç ve kireç) ile yedi farklı bağlayıcı kombinasyonu oluşturulmuştur. Kütlece bir kısım kenevir, iki kısım bağlayıcı ve iki onda bir kısım su içeren kenevir betonlarının birim hacim ağırlığı, basınç dayanımı, kapiler su emme gibi fiziksel ve mekanik özellikleri araştırılmıştır. Üretilen numunelere laboratuvar sıcaklığında açık kür uygulanmıştır. 28 günlük kür sonrasında birim hacim ağırlığı 401-455 kg/m3, basınç dayanımları 0,08-0,28 MPa ve kapiler su emme katsayıları 2,45-4,47 kg/m2⋅s1/2 aralığında değişen kenevir betonları üretilmiştir. Karışımlarda hidrolik bağlayıcı miktarının azalması ile basınç dayanımının ve birim hacim ağırlıklarının azaldığı tespit edilmiştir.
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.
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.
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.
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.
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.
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.
Acoustic and thermal comfort play an important role in the building environment. This study investigates ultra-lightweight concrete incorporating Miscanthus fibers as lightweight aggregates to improve sound absorption and thermal insulation properties. Miscanthus fibers (MF) is a kind of sound absorption biomass that can dissipate sound noise thanks to its porous and flexible inner structures and fibrous shape. However, its acoustic absorption performance in cement-based materials is rarely investigated. Therefore, the acoustic absorption and thermal insulation of ultra-lightweight Miscanthus concrete (ULMC) is investigated using two different kinds of Miscanthus fibers. Meanwhile other mechanical properties were characterized, including bulk density and flexural strength. Results showed ULMC with 30% 2–4 mm MF obtained an ultra-low density (554 kg/m³), thermal conductivity (0.09 W/(m·K)) and high acoustic absorption coefficient (0.9) at low frequencies. It is found that the acoustic performance of ULMC can be improved by optimizing the dosage and shape of Miscanthus fibers. The developed green and sustainable bio-based ULMC possesses an excellent acoustic absorption and thermal insulation and is very suitable to use as indoor ceiling boards and in non-structural walls to make indoor living environment comfortable and energy-saving.
The study has been carried out in the context of a working group within the RILEM Technical Commitee 236-BBM 'Bio-aggregate-based building Materials'. It focusses on statistical analysis of hemp concrete properties. The objective is to determine statistically the variability for material density, compressive strength and Young's modulus. The considered parameters are: the testing laboratory equipment, the hemp shiv type, the batch and the specimen size. Two types of hemp shiv have been used with two batches for each one. Two specimen sizes were used: 11x22 cm and 16x32 cm. Specimens were manufactured in one laboratory in order to ensure the homogeneity of studied material. After 90 days of drying under the same conditions, they were transported to ten different laboratories for compressive testing. A drying protocol during 48 hours was applied by all laboratories. Then, a unique protocol for compressive testing has been applied by each laboratory. Finally, data have been collected together for statistical analysis. The obtained results show an accurate repeatability for the compressive strength and the dry density; however, the Young's modulus results show a large variability.
This paper outlines a forensic method for analysing the energy, environmental and comfort performance of a building. The method has been applied to a recently developed event space in an Irish public building, which was evaluated using on-site field studies, data analysis, building simulation and occupant surveying. The method allows for consideration of both the technological and anthropological aspects of the building in use and for the identification of unsustainable operational practice and emerging problems. The forensic analysis identified energy savings of up to 50%, enabling a more sustainable, lower-energy operational future for the building. The building forensic analysis method presented in this paper is now planned for use in other public and commercial buildings.
Sound-absorbing materials absorb most of the sound energy striking them, making them very useful for the control of noise. They are used in a variety of locations - close to sources of noise, in various paths, and sometimes close to receivers. Although all materials absorb some incident sound, the term "acoustical material" has been primarily applied to those materials that have been produced for the specific purpose of providing high values of absorption. The major uses of absorbing materials are almost invariably found to include the reduction of reverberant sound pressure levels and, consequently, the reduction of the reverberation time in enclosures, or rooms. A wide range of sound-absorbing materials exist. In the 1970s, public health concerns helped change the main constituents of sound-absorbing materials from asbestos-based materials to new synthetic fibers. Although, these new fibers are much safer for human health, more recently, issues related to global warming may increase the use of natural fibers instead of synthetic ones.
Over the last few years, a number of researchers have been involved in investigating the exploitation of
natural fibres as load bearing constituents in composite materials. The use of such materials in composites
has increased due to their relative cheapness, their ability to recycle and their mechanical and physical
properties. Composites based on natural fibbers have many advantages over their synthetic counterparts
owing to their low cost, low density, high specific strength and stiffness, excellent sound- absorbing and
high impact energy absorption. The technical hemp as fast-growing plant has prospect in the construction
field in accordance with the principles of sustainable development. A special attention is paid to the use of
fibrous hemp as well as hemp hurds (nonfibrous fraction hemp stalk) in the building materials preparing in
various forms, such as insulation boards, mass-spraying hempcrete for the production of lightweight
composites, where it is in the role of filler.
The presence of surface impurities and the large amount of hydroxyl groups make plant fibbers less
attractive for reinforcement of composites. Incompability of interface between fibres and matrix, the
tendency to form aggregates during processing and poor resistance to moisture can be eliminated by
physical/chemical treatments of fibbers and/or matrix or the use of coupling agents.
In this paper, some aspects of durability of hardened composites based on chemically modified of hemp
hurds slices and MgO-cement as binding agents after long termed storage in deionised water by testing on
some important material properties as water absorbability, thermal conductivity coefficient, apparent
density and compressive strength was studied.
Hemp concrete is an attractive alternative to traditional materials used in building construction. It has a very low environmental impact, and it is characterized by high thermal insulation. Hemp aggregate particles are parallelepiped in shape and can be organized in a plurality of ways to create a considerable proportion of open pores with a complex connectivity pattern, the acoustical properties of which have never been examined systematically. Therefore this paper is focused on the fundamental understanding of the relations between the particle shape and size distribution, pore size distribution, and the acoustical properties of the resultant porous material mixture. The sound absorption and the transmission loss of various hemp aggregates is characterized using laboratory experiments and three theoretical models. These models are used to relate the particle size distribution to the pore size distribution. It is shown that the shape of particles and particle size control the pore size distribution and tortuosity in shiv. These properties in turn relate directly to the observed acoustical behavior.
The main findings from the Probe occupant surveys are assessed. The emphasis is on the consequences for strategic thinking on how best to design and manage buildings to improve conditions for occupants and users, taking examples from the Probe studies. Comfort, health and productivity of occupants are positively associated statistically; and all are easily undermined by chronic, low-level problems. Improvement may not necessarily require raising overall environmental standards - particularly if this requires more energy or reduces perceived control, which occupants think has been falling steadily in recent years. Noise-related problems are also growing with today's trend to more open, more diverse and often more reverberant environments. For the occupant, 'satisficing' may be better than optimizing; and big benefits can come from minimizing the main causes of discomfort, ill health and low productivity - for example by designing and managing to help individuals to choose how to overcome local problems when they occur. Perhaps the greatest enemy of occupant satisfaction is where a building and its systems have become too complicated for its managers - even if this has often occurred initially at their request. Its greatest friends are simplicity, intelligibility, managed feedback, respect for people's comments and rapid response.
Lime-hemp concrete (LHC) is a sustainable building material that combines hemp shiv and building limes. Moisture fixation and thermal properties of LHC were determined so as to gain knowledge about the material's behaviour in a cold, wet climate. Sorption isotherms were produced over the whole moisture range for two LHC mixes by means of glass jar tests and a pressure plate apparatus. Thermal properties were determined for the mixes at different relative humidities using a transient plane source method. The results showed relatively low thermal conductivity and a steep sorption isotherm in the interval between 95% and 100% RH.
This article is devoted to the acoustical properties of hemp concrete, a “green” building material. In the study, hemp concretes made of different binders and different kinds of particles were characterised, and then modeled using equivalent-fluid models. Further, it is shown that the sound absorption of these materials can be controlled and significantly enhanced by means of suitable constituents and fabrication processes. Finally, good results are provided by the models.
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 .
Lime hemp concrete is a sustainable, carbon negative building material that can be used in certain applications lowering the environmental impact of construction. Hemp absorbs large quantities of mixing water (325% of its own weight at 24hours), and this may not leave sufficient moisture in the binder for hydration or carbonation to take place adversely affecting curing and strength development. This paper investigates the effect of using water retainers to ensure that sufficient water is available for proper curing. Hemp concrete including a lime: pozzolan (either GGBS or metakaolin) binder and three water retainers (methyl cellulose and two commercial water retainers one of which is methyl cellulose based) were investigated. This paper studies the impact of the water retainers on strength, drying, setting and microstructure. It was found that the three water retainers delayed setting and drying. The commercial binders did not significantly affect strength however the methyl cellulose improved the compressive strength of both lime:pozzolan pastes and hemp concrete at later ages (100 days). The increase in compressive strength is partially attributed to an enhanced binder water retention that improves hydration. This assumption is based on the increase in the amount of pozzolanic cements, evidenced with SEM at the hemp interface, in the composite with methyl cellulose.
Acoustical sustainable materials, either natural or made from recycled materials, are quite often a valid alternative to traditional synthetic materials. The production of these materials generally has a lower environmental impact than conventional ones, though a proper analysis of their sustainability, through Life Cycle Assessment procedures, has to be carried out.Airborne sound insulation of natural materials such as flax or of recycled cellulose fibres is similar to the one of rock or glass wool. Many natural materials (bamboo, kenaf, coco fibres) show good sound absorbing performances; cork or recycled rubber layers can be very effective for impact sound insulation. These materials also show good thermal insulation properties, are often light and they are not harmful for human health. Furthermore, many of these materials are currently available on the market at competitive prices.There is however a need to complete their characterization, both from an experimental and a theoretical point of view, and especially to propose a standard and unique procedure to evaluate their sustainability.The paper presents an updated survey on the acoustical properties of sustainable materials, both natural and from recycled materials, including mixed and composite materials and systems such as green roofs and green walls, and is completed by a wide selection of recent related bibliography.
Natural fibers are emerging as low cost, lightweight and apparently environmentally superior alternatives to glass fibers in composites. We review select comparative life cycle assessment studies of natural fiber and glass fiber composites, and identify key drivers of their relative environmental performance. Natural fiber composites are likely to be environmentally superior to glass fiber composites in most cases for the following reasons: (1) natural fiber production has lower environmental impacts compared to glass fiber production; (2) natural fiber composites have higher fiber content for equivalent performance, reducing more polluting base polymer content; (3) the light-weight natural fiber composites improve fuel efficiency and reduce emissions in the use phase of the component, especially in auto applications; and (4) end of life incineration of natural fibers results in recovered energy and carbon credits.
This work analyses acoustic qualities of autoclaved aerated concrete (AAC). Three the most widely used types of AAC are chosen for the analysis: gas cement concrete, gas cement concrete with combined binder (Portland cement and lime), and foam cement concrete. The procedure and technique of the materials’ formation is presented in this work. The evaluation of acoustic qualities of AAC is based on the material’s air permeability and porosity (i.e., ratio of the volume of the interconnected pores to the total volume of pores). For this purpose the measurements obtained by an acoustic interferometer are used. The results of the experiment show that regression equations for the AAC types, which density ranges from 250 to 500 kg/m3, may be used to estimate the materials’ normal incidence absorption coefficient values, which depend on the air permeability and porosity. Results show that absorption coefficient of not specially treated AAC is rather low. According to the measurements obtained in a special reverberation room of 202 m3, a sound absorption coefficient may increase up to 0.6, provided that slits of Helmholtz resonator’s type are made in the slabs of AAC gas cement concrete with combined binder.
Low Impact Building: Housing using Renewable Materials
Tom Woolley
ISBN: 978-1-4443-3660-3
252 pages
February 2013, Wiley-Blackwell
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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.
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.
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.
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.
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.
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].
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.
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.
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).
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
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%.
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
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.
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.