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Lime, cement and concrete
Published in Arthur Lyons, Materials for Architects and Builders, 2019
The material is also used as a solid infill for timber frame construction. In this case, the combination of the moisture-absorbing properties of the hemp with the nature of lime, affords some protection to the timber-framing that it encloses. Hemp-lime should not be used below ground level. The porous and hygroscopic properties of hemp-lime give rise to higher thermal efficiencies than are calculated for the material based on conventional thermal transmittance data. To build a conventional house of hemp-lime would require approximately 40 m3 of the material containing 7–10 tonnes of hemp, produced from about 1 ha of land. More recent developments include construction with precast hempcrete panels, eliminating the on-site curing period. Hempcrete is a carbon-negative material as the natural growth of hemp to about 4 m in four to five months absorbs more carbon dioxide than is emitted in its subsequent conversion to hempcrete on site. The hemp plant is naturally pest-resistant and a weed-suppressant, so no chemical fertilisers or weedkillers are required in its agricultural production. The rough surface of hempcrete is usually finished with a lime or clay render (Fig. 3.3). The material is non-combustible.
Bonding agents
Published in Jill L. Baker, Technology of the Ancient Near East, 2018
An additional use for lime plaster has been rediscovered in a sixth-century bridge abutment in France. Merovingian bridges used a hemp mortar known as hempcrete, which construction industries in Europe, Australia, and the United States have been producing and using since this discovery in the 1980s. Hempcrete is a bio-composite material made from the inner woody core of the hemp plant, called the shiv, which is high in silica and binds well with lime and pozzolana (volcanic ash). When combined with lime, hempcrete forms a lightweight cement (it weighs one-seventh or one-eighth that of concrete) with excellent insulating properties. It is also fire resistant. Hempcrete can only be used as fill between supportive and structural components. Nevertheless, those who have built modern homes using this material have seen a significant reduction in heating/cooling bills. Hemp is very easy to grow, is a renewable resource, and does not need fertilizer, weed killer, pesticide, or fungicide. This is a case where the rediscovery of an ancient technology may prove to be useful for our own present and future. Certainly, these natural materials can be grown and found in less industrialized countries and could help provide inexpensive housing and buildings (Chaban 2015; see also American Limetechnology, www.americanlimetechnology.com/ and Hemp Technologies Global, https://hemptechglobal.com. Accessed 3 May 2018).
Thermal/Acoustical Insulation and Interior Wall/Ceiling Materials
Published in Kathleen Hess-Kosa, Building Materials, 2017
Natural fibers include, but are not limited to, cotton, sheep's wool, straw, and hemp. Cotton is generally a recycled material (e.g., old blue jeans) and generally treated with a fire retardant (e.g., boric acid and ammonium sulfate). Water-resistant sheep's wool is generally moth proofed and treated with a fire retardant (e.g., disodium octaborate). Straw and the woody component of hemp are also treated with a fire retardant (e.g., HempCrete®: lime is resistant to fire, insects, and mold).
Occupational health and safety in cannabis production: an Australian perspective
Published in International Journal of Occupational and Environmental Health, 2018
Maggie Davidson, Sue Reed, Jacques Oosthuizen, Greg O’Donnell, Pragna Gaur, Martyn Cross, Gary Dennis
Hemp concrete (hempcrete), an example of an emerging hemp product and industry, is produced by mechanically refining the woody fibres (shiv). The mixture of hemp and lime-based binders is consolidated with water and then tamped down into the formwork in layers. This process would expose worker to potentially hazardous mixtures of organic and inorganic dust. Hemp is grown for both seed and fibre. The seed used to for oil, therapeutic products and as food source, fibre for textiles and building materials amongst many other products. Hemp seed oil may be extracted through cold pressing of seeds [2], while cannabidiol oils containing less than 2% THC require more complex processes such as solvent or carbon dioxide-based extraction [1,22].
Bio-based and recycled-waste materials in buildings: A study of energy performance of hemp-lime concrete and recycled-polyethylene terephthalate façades for office facilities in France and Italy
Published in Science and Technology for the Built Environment, 2018
Tala Moussa, Chadi Maalouf, Carlo Ingrao, Flavio Scrucca, Georges Costantine, Francesco Asdrubali
Hemp plant is cultivated worldwide from the equator to about 60°N latitude. In Europe, hemp cultivation areas expanded from 8000 ha in 2011 to almost 33,000 ha in 2016, which shows a quadruple increase in 5 years of which 16,000 ha was estimated only in France (Carus et al. 2017). It is a multi-use plant which produces oil, and proteins for food, and feed production, and fibers for textile industry (Ingrao et al. 2015). Besides, hemp hurds are introduced in the building industry to form “hempcrete” or “hemp-concrete” (HC) prepared namely with mixing hemp hurds with lime-based binder (Arnaud and Gourlay 2012; Collet et al. 2013; Ingrao et al. 2015; Pretot et al. 2014) or clay binder (Busbridge and Rhydwen 2010; Mazhoud et al. 2017). Other vegetal binder can also be added to the hemp hurds to form an agro-material, for instance hemp-starch composite, prepared using wheat starch (Moussa et al. 2016; Umurigirwa et al. 2015). Numerous investigations (Amziane and Arnaud 2013; Arizzi et al. 2015) showed that hemp concrete density varies from 200 to 800 kg.m−3 coupled with low thermal conductivity (0.09–0.18 W.K−1.m−1) depending on the application. As a result, enhancement of thermal insulation and reduction of heat diffusion through the walls were observed leading to a moderation of the hot waves in summer and a reduction of the heat losses during winter (Maalouf et al. 2011). Accordingly, the hemp additives yield relatively lightweight materials with low Young modulus (Bledzki 1999) and limited compressive strength (less than 2 MPa) compared to other materials used in construction (Shea et al. 2012). Thus, the hemp concrete is not suitable for applications as load-bearing material and, indeed, is generally associated with other structural wooden walls.