Shives Research Articles

A STUDY OF HEMPCRETE PROPERTIES USING NATURAL HYDRAULIC LIME – MIX DESIGN, MECHANICAL PROPERTIES, AND MICROSTRUCTURE

In the article, an analysis of tensile strength fiber hemp and hemp fiber linkage analysis in the cement matrix is presented. The average tensile strength of the fibers of untreated hemp amounts to 764 MPa and the calculated modulus of elasticity amounts to 30 GPa. A test of pulling fibers from the cement matrix has shown that when increasing the length linkage, the maximum pulling force increases while the clamping strength does not significantly change. In the laboratory, a mixture of hemp concrete where a portion of mineral aggregate was replaced with hemp hurd was prepared. Results of the examination of the microstructure of hardened lime binder have shown that the hardened NHL mixture is porous and vapor-permeable while the hardened HL mixture is thick and compact. The goal was to create a prototype hemp concrete mixture that can be used for production of prefabricated elements with tensile strength between 10 and 25 MPa.

Flax Shive and Hemp Hurd Residues as Alternative Raw Material for Particleboard Production

Flax shive and hemp hurd residues were characterized, and the feasibility of manufacturing three-layered particleboards was evaluated using 2.5% and 5% polymeric diphenyl methane diisocyanate resin loadings. The flax shive and hemp hurd residues had lower bulk densities and higher aspect ratios compared with the wood residues. Their higher aspect ratios offered greater overlap in bonding, which led to consistently higher bending properties that exceeded the American National Standards Institute (ANSI) requirements for low-density (LD2) particleboard and, in some cases, medium-density (M2) particleboard. Because of their particle geometry, the flax shive and hemp hurd particleboards also showed minimal linear expansion with changes in the moisture content at 20 ± 3 °C and between 50% and 90% relative humidity. The high absorption capacity of the flax shive and hemp hurd residues resulted in higher thickness swell and water absorption properties than the wood residues. The results indicated that low-density flax shive and hemp hurd particleboards (500 to 620 kg/m3) can be manufactured using isocyanate resin quantities as low as 2.5% to produce panels that conform to ANSI specifications with a greater mechanical performance than that of wood residue particleboards.

Thermal insulation materials from renewable resources: thermal and hygric performances

The European ISOBIO project aims to develop new bio-based building insulating materials which contribute to reduce environmental impacts of buildings. The developed materials shall have low embodied energy and low carbon footprint and shall contribute to reduce energy needs of buildings ant to ensure high hygrothermal comfort of users. This study investigates the valuation of agro-resources as bio-based aggregates and as binding material to produce wholly bio-based composites. Two types of aggregates: hemp shiv and corn cob residues (obtained after alkali treatment on the corn cob), and five types of green binders are investigated. Specimens are produced to characterize thermal and hygric properties of developed composites and to identify the best mixture between aggregate and binder. They show interesting thermal and hygric properties. They have low thermal conductivity ranging from 0.067 to 0.148 W/(m.K) and depending on the mix (aggregate with binder). They are excellent hygric regulators (MBV >2 g/(m².%RH)). These results suggest that developed composites can be used as building materials but not for the same types of use. In fact, some composites would be more suitable for thermal insulating products and others would be better suited to indoor facing panels.

Calcium phosphate bonded wood and fiber composite panels: production and optimization of panel properties

AbstractThe development of phosphate bonded composites with properties comparable with those of current Portland cement bonded products has been investigated. More precisely, the focus of the study was the optimization of calcium phosphate cements in combination with wood processing residues slash pine (Pinus elliottiiEngelm.) planer shavings, Black wattle (Acacia mearnsiiDe Wild.) residues, Blue gum (Eucalyptus globulusLabill.) residues, hemp (Cannabis SativaL.) hurds and dried crushed sugarcane bagasse (Saccharum officinarumL.) as well as pulp mill sludge and waste paper. A central composite design (CCD) for the response surface methodology (RSM) was applied for selection of the proper parameters. Mechanical tests were conducted on the composite products and the effect of the processing variables was evaluated based on the Pareto analysis of variance. The density of the wood-based panels ranged from 0.68 to 1.21 g cm−3, that of the agricultural fibers from 0.59 to 1.15 g cm−3and that of the paper pulp panels from 0.81 to 1.21 g cm−3. The modulus of elasticity (MOE) data of the panels ranged from 1.63 to 4.92 MPa for wood, from 0.37 to 3.28 MPa for agricultural fibers and from 0.65 to 3.87 MPa for paper-pulp-based fibers. The physical properties of the composite products met the requirements for Portland-cement-bonded particleboards (EN 634-2, 2007).

Recommendation of the RILEM TC 236-BBM: characterisation testing of hemp shiv to determine the initial water content, water absorption, dry density, particle size distribution and thermal conductivity

This recommendation is the outcome of research conducted by a working group within the RILEM Technical Committee 236-BBM ‘Bio-aggregate-based building Materials’. The work of the group related to the study of construction materials made from plant particles. The major raw material utilised being renewable, recyclable and easily available plant particles. These particles are obtained from the processing of hemp, flax, miscanthus, pine, maize, sunflower, bamboo and other plants. In this report, the outcome of the Round Robin Testing is centred on hemp because hemp shiv is the bio-aggregate that is the most widely used in building materials and the most studied in the literature. The first round robin test of the TC-BBM published in the State of The Art Report of Technical Committee 236-BBM ‘Bio-aggregate-based building Materials’ was carried out to compare the protocols in use by the different laboratories (labs) to measure initial water content, bulk density, water absorption, particle grading and thermal conductivity. The aim was to define a standardised characterisation protocol developed from those used by the different labs. The different methodologies used by 7 labs constitute a set of statistically representative data which have been analysed to develop this recommendation for the characterisation of hemp shiv.

Lightweight Composites Based on Technical Hemp Hurds in Construction Industry

This article discusses about the possibility of using technical hemp as a source of natural fibres for purpose of construction. The technical hemp (Cannabis Sativa) is the source of two types of fibres; bast fibres (used mainly in the paper and textile industries) and woody fibres - hurds. In recent decades hemp hurds have experienced a renaissance in use in the construction industry. This material is waste resulting from the processing of hemp stem on bast fibres. For the purposes of construction, it has potential thanks to their exceptional thermal insulation, antiseptic, acoustic and mechanical properties. One of the aspects of using hemp products in building industry is its environmentally friendly properties in comparison to the conventional materials (such as insulating materials with polymer matrix or based on mineral wool). Due to the low density and high porosity of the hemp fibres, the combination of hemp and binder creates high-quality products such as hemp concrete, fibre boards and lightweight composites. In this paper, the physical and mechanical properties of lightweight composites based on pre-treated hemp hurds and alternative binder MgO-cement are studied after their hardening in indoor condition for 28 days. The results of the parameters (density, density changes after thermal stress, water absorbability, thermal conductivity coefficient, compressive and tensile strength) of composites presented with emphasis on their usage as thermal insulation material show some differences which are determined by properties of modified filler (hemp material) as well as by properties of filler/binder interface.

Lightweight Composite Building Materials with Hemp (Cannabis Sativa L.) Additives

The scope of our research was to evaluate the potential of the content of fibre and shives in the biomass of industrial hemp cultivars grown under different nitrogen fertiliser rates to use them for increasing the energy efficiency as a thermal insulation and acoustic material. The aim of the research was to find out the production technology, properties of the thermal conductivity for lightweight concrete made from hemp shives and sapropel or gypsum as a binder to be used for thermal and sound insulation material. The hemp cultivar 'Bialobrzeskie' was used for lightweight composite materials and lightweight composite materials were obtained with hemp shive additives with heat transfer coefficient 0.046÷0.15 W mK-1 and sound insulation index R`=35 dB. The obtained composite materials can be used as sound and heat insulation materials for building envelope in residential buildings, office buildings and factories.

Characterization of Barley Straw, Hemp Shiv and Corn Cob as Resources for Bioaggregate Based Building Materials

Expanding the use of low-environmental impact materials in the field of building materials is a major aim in a context of sustainable development. These alternative materials should be non-polluting, eventually recycled, and locally available. Bioresources are already used in some building materials but few studies have investigated their relevance in such applications. The aim of this paper is to evaluate the suitability of three kinds of vegetal aggregates: barley straw, hemp shiv and corn cob. The availability of these bioresources, extracted from a French database, is discussed, as are their physical properties and chemical compositions. Their microstructure is described with SEM images and their particle size distributions are provided through image analysis. Sorption–desorption isotherms are measured by a Dynamic Vapour Sorption system. Bulk density, thermal conductivity and water absorption are also quantified. The results highlight a tubular structure for the three different aggregates, with low bulk density and thermal conductivity (0.044, 0.051 and 0.096 W m−1 K−1 respectively for straw, hemp shiv and corn cob) and high water absorption, especially for barley straw and hemp shiv (414 and 380% vs. 123% for corn cob). Their hygric regulation capacity is also sufficiently good, with a water sorption of between 20 and 26% at 95% of relative humidity. These plant aggregates could therefore be used as additions in an earth matrix, or a hydraulic, pozzolanic, air lime or gypsum binder, or just as loose-fill insulation material. However, future research should focus on their resistance to fire and bacterial growth to validate this approach.

Glycidyl methacrylate-compatibilized poly(lactic acid)/hemp hurd biocomposites: Processing, crystallization, and thermo-mechanical response

Poly(lactic acid)-based biocomposites were developed with hemp hurd (Cannabis sativa L.) with grafting-based interfacial compatibilization. Poly(lactic acid) was extruded with hemp hurd and glycidyl methacrylate as the polymer/hurd interfacial compatibilizer, and injection molded. Interfacial compatibility between poly(lactic acid) and hemp hurd increased with grafted glycidyl methacrylate in comparison to the non-compatibilized control, as corroborated by scanning electron microscopy fractography and mechanical analysis, which showed increases in the glycidyl methacrylate-grafted 20% (w/w) hemp hurd/poly(lactic acid) biocomposite, retaining 94% of the neat polymer strength, with increases in crystallinity, and showing a range of thermo-mechanical properties desirable for rigid biocomposite applications.

Physical and Mechanical Property Characterization of Hemp Shive Reinforced Gypsum Composite Board

Known and used since Antiquity, the hemp plant comes back to the attention of the researchers focused on making new ecological products used to reduce the environmental impact in the construction sector. A sustainable building environment needs to develop relations with renewable raw materials. This study aims to make an investigation in the products based on gypsum and hemp shives, where hemp shives are an agricultural plant and gypsum a natural resource produced by burning gypsum plaster. Using the multicriterial analysis, the best performing formula is identified, in order to satisfy thermal insulation, sound insulation, mechanical and fire related requirements and in which the variable is the hemp shives percentage in the composite material. The three recipes prepared were compared with the normative and other studies. The results presented at the end of this study shows that in terms of acoustic absortion and thermal conductivity, the insulating materials are best when the volume of hemp grows. Meanwhile the positive aspect of growing the volume of hemp for insulation materials becomes a disadvantage from the mechanical point of view, where to have high values of strength is recomanded a low volume of hemp.

The Application of Raw Materials Obtained from the Cultivation of Industrial Hemp in Various Industries

Abstract Subject and purpose of work: The raw materials which are the purpose of the current hemp cultivation (<0.2% THC) are fibre, seeds and shives. This study describes the characteristics the raw materials obtained from the industrial hemp and described in detail the possibilities of their applications in pulp and paper, textile, pharmaceutical, construction and food industries. Analysis of the issues: Hemp straw consists of a porous ligneous core, which may be cut into smaller pieces, called hemp shives and of the fibre around the core. Hemp cellulose is used to produce paper pulp or plastics. In the construction sector, hemp fibre is used to produce, among other things, thermal insulation materials. Hemp shives is used as a filler for a composite based on lime binder, which is used as a wall material with good hygrothermal conditions confirmed by proprietary research. Hemp seeds are used for the production of cooking oil. Hempseed oil is also used in the pharmaceutical industry, e.g. to produce skin creams. Conclusions: Raw materials obtained from industrial hemp have a variety of applications. Currently, new directions in hemp application are being sought and tested, like for example hemp lime composite and bio-composites. The positive environmental impact resulting from the cultivation of hemp should be the main reason for simplifying the procedures for the commencement of its cultivation in many countries, e.g. in Poland.

Improving the performance of hemp hurd/polypropylene composites using pectinase pre-treatments

The potential for using pectinase as a pretreatment to improve the properties of hemp hurd for use in a hemp/polypropylene composite was compared with the addition of a silane coupling agent. Pectinase pre-treatment reduced pectin levels in the hemp hurd (p=0.0014) and this reduction was associated with improved tensile strength, modulus of rupture, modulus of elasticity and resistance to water uptake (p<0.0001). Pre-treatment had no consistent effect on thickness swell. Addition of a coupling agent to non-modified hemp/polypropylene panels produced similar improvements to panel properties (p<0.0001) and also markedly reduced thickness swell (p=0.01). The results indicate that pectinase pretreatment can enhance panel strength properties but did not affect moisture behaviour.

Hygrothermal Assessment of a Prefabricated Timber-frame Construction Based in Hemp

In this paper, an assessment is made on a pre-fabricated timber framed hemp-based building envelope system. The hemp-lime mixture within the envelope is produced by mixing the hemp shiv with a lime formulated solution, which acts as a binder, and provides thermal insulating and moisture buffering capacity to the resulting construction.Hemp, by its natural origin, is a fixative of CO2 and can result in a negative carbon footprint helping to reduce the global impact of a building. In addition the hemp-lime layer absorbs and expels heat and humidity in relation to the environment and acts as a thermal storage by reducing the flow of energy through the wall. The presented system targets at the generation of an innovative building system focused on the expansion of the market for structural products, sustainable, ecological and low carbon footprint.As part of its development its thermal insulation and moisture buffering properties have been assessed, and case studies and outcomes of full scale experimental studies are presented.

Properties of Hemp–Flax Composites for Use in the Building Industry

ABSTRACTThis article presents the results of research concerning lightweight composites produced on the basis of lime, cement, and clay binders, with the addition of perlite, hemp shives, and flax straw. Tests of physical and mechanical properties of composites were performed and their basic characteristics were determined, i.e. absorptivity, density, thermal conductivity coefficient, and compressive and flexural strength. The study was conducted to determine the use of hemp and flax composites to fill the frames of a wooden house. The results prove that the composites have low thermal conductivity, apparent density, and low strength properties compared with conventional building materials.

Thermal degradation of natural and treated hemp hurds under air and nitrogen atmosphere

Sustainability goals are essential driving principles for the development of innovative materials in the construction industry. Natural fibers represent an attractive alternative as reinforcing material due to good mechanical properties and sustainability prerequisites. The study has been focused on the comparative investigation of chemical and physical treatments of hemp hurds and their influence on the thermal behavior of main hemp constituents in air and nitrogen atmosphere. Thermal decomposition of hemp hurds involves several parallel reactions related to heat and mass transfer processes. A comparison of DSC and TG/DTG results of hemp hurds samples before and after treatments demonstrates a better thermal stability for treated samples. It is caused by changes in chemical composition due to a partial removal of non-cellulosic components from hemp hurds structure, an increase in cellulose content and decrease in its degree of polymerization. The results show different thermal behavior of the hurds samples heated under nitrogen and air atmosphere. Based on DTG records, several-stage process of mass loss has been found for the samples under air, whereas only two-stage process under nitrogen.

Formosolv fractionation of hemp hurds

Effects of the main variables of the Formosolv fractionation of hemp hurds (formic acid and hydrochloric acid concentrations and treatment time) on delignification and hemicellulose solubilisation were quantified. The conditions that provided a pulp with low lignin content and high cellulose content, while recovering the maximum possible amount of lignin by precipitation, are 30min of treatment time, 86.6%w formic acid, and 0.095%w hydrochloric acid. Under these conditions, 93.2% hemicellulose removal and 72.1% delignification were achieved. The residual solid from the Formosolv treatment contained a high proportion of formate groups (8.7%w). Four total chlorine-free treatments were used to eliminate the formate groups. Only alkaline treatments (oxygen and sodium hydroxide) completely removed the formate groups. However, the ozone treatment produced a solid with the highest delignification rate (34.7%, 80.1% global) and crystalline index.

Design and multi-physical properties of a new hybrid hemp-flax composite material

An experimental investigation was conducted in order to study the properties of a hybrid hemp-flax composite material in term of capillary water absorption, mechanical strength, thermal conductivity and shrinkage. The hemp-flax composite material is made with 90% hemp shives and 10% flax fibers. Hemp aggregates have a high water absorption capacity, which led to a reduction of the hemp concrete mechanical performances. Four mixes were made for: shuttered walls, external coating, floor insulation and roof insulation. Firstly, bio-based aggregates were characterized in term of particle size distribution and water absorption. Then, the compressive strength of these four mixes was determined to compare the mechanical behavior of the hybrid composite material with hemp concrete. The capillary absorption and the total shrinkage of these bio-based materials were also measured. Finally, we measured the thermal conductivity coefficient of these materials. The results of the compressive strength show a significant improvement due to the incorporation of flax fibers. Flax fibers improve the compactness of the material, thus increasing its density, which leads to a greater mechanical strength. It was observed that the capillary absorption of hemp concrete seems to be related to the aggregates/paste ratio. Finally, flax fibers have reduced hempcrete shrinkage of about 15%.

Adsorption of acid-extractable organics from oil sands process-affected water onto biomass-based biochar: Metal content matters

The impact of biochar properties on acid-extractable organics (AEO) adsorption from oil sands process-affected water (OSPW) was studied. Biochar from wheat straw with the highest ash content (14%) had the highest adsorption capacity (0.59 mg/g) followed by biochar from pulp mill sludge, switchgrass, mountain pine, hemp shives, and aspen wood. The adsorption capacity had no obvious trend with surface area, total pore volume, bulk polarity and aromaticity. The large impact of metal content was consistent with the carboxylates (i.e., naphthenate species) in the OSPW binding to the metals (mainly Al and Fe) on the carbon substrate. Although the capacity of biochar is still approximately two orders of magnitude lower than that of a commercial activated carbon, confirming the property (i.e., metal content) that most influenced AEO adsorption, may allow biochar to become competitive with activated carbon after normalizing for cost, especially if this cost includes environmental impacts.

Thermal Stress Effect on Density Changes of Hemp Hurds Composites

Abstract The aim of this article is to study the behavior of prepared biocomposites based on hemp hurds as a filling agent in composite system. In addition to the filler and water, an alternative binder, called MgO-cement was used. For this objective were prepared three types of samples; samples based on untreated hemp hurds as a referential material and samples based on chemically (with NaOH solution) and physically (by ultrasonic procedure) treated hemp hurds. The thermal stress effect on bulk density changes of hemp hurds composites was monitored. Gradual increase in temperature led to composites density reduction of 30-40 %. This process is connected with mass loss of the adsorbed moisture and physically bound water and also with degradation of organic compounds present in hemp hurds aggregates such as pectin, hemicelluloses and cellulose. Therefore the changes in the chemical composition of treated hemp hurds in comparison to original sample and its thermal decomposition were also studied.

Study of Inorganic Pollutants Removal from Acid Mine Drainage by Hemp Hurds

Abstract Sulphates in wastewaters have an origin as the by-products of a variety of industrial operations. A specific and major producer of such effluents, which contained sulphates and heavy metals, is the mining industry. These contaminants should be removed from wastewater using an adequate process of treatment. The paper deals with selected heavy metals (iron, cooper, and manganese) and sulphate removal from acid mine drainage outflowing from an abandoned mine in Smolnik (Slovakia) using the modified biosorbent - Holland hemp hurds. Pre-treatment of acid mine drainage was based on oxidation of ferrous cations from acid mine drainage by hydrogen peroxide and subsequent precipitation. The precipitate were analysed by infrared spectrometry which found the precipitate containing hydroxide and sulphate functional groups. During this process the concentration of sulphate decreased by 43.8 %. Hemp hurds modified by NaOH decreased concentration of Cu2+ in solution by about 70 %