Climate change and global warming are impacting the world to a higher level, especially in the 20th century, as the consumption of natural resources and carbon emissions drastically increases. According to studies, the Construction industry and industrial sector have a vast impact in producing billions of tons of CO2 in material extraction and processing to make them refine and others which generate greenhouse emissions. The need to reduce these impacts is to replace conventional building technologies with carbon-negative technologies. Thus, Cellulose aggregate concrete (CAC) or bio concrete, or Hemp concrete has come into studies researchers as a replacement for cement and has many benefits such as low density, low embodied energy, thermal insulation with natural binders like lime, fly ash, slag, rice husk, etc.
In several states now, hemp is becoming allowed after years of being prohibited due to the plant’s 05% THC content. Its woody core portion, which offers a green, sustainable building material as an alternative to cement and aggregates, is the reason it is used extensively.
Hemp and Hempcrete
Hemp is a type of medical plant, abundantly found throughout the environment and has been utilized for more than 50,000 divergent products, including paper, clothes, food, textiles, biofuel, and plastics. One of the biomasses on the globe with the quickest rate of growth is it. Hemp for hempcrete can be grown in a wide range of climates and soils and has the capability of carbon sequestration while flourishing. (Roberts, 2020)
Hempcrete is a bio-composite breathable material made up of Hemp hurd (shives), Lime, water, sand, or pozzolans used in building construction. It was first found in France in the early 1990s during the construction to build non-load-bearing infill walls. Require a minimum 12” thickness of the walls or more. Excellent alternative building material as it has many properties, such as being lightweight due to its hurd/shives and lime mixture, less embodied energy, vapor permeability, and being locally available, which reduces the cost of transportation. Hempcrete can be used in many different methods, such as infilling, screeding, stacking, precast blocks and slabs, sundried blocks, and lintels, to form walls, roofs, floors, and slabs. They come in a range of sizes and shapes, and they feature steel reinforcing to improve the stability of the building.
Hempcrete blocks are independent masonry units that provide no structural function. The key components are lime, hemp chips, and water. The hemp shives have particles that range between 2 and 20 mm in size. The blend contains hemp in at least 80% of its entire composition. The last phases of the procedure—molding, pressing, curing, and drying—are all completed without the use of heat outside. The normal size of hemp-based blocks is usually 60 cm by 30 cm.
Properties of Hempcrete
The dried hemp stem is divided into several categories, including fiber, wool, mat, and other components. Materials from hemp shives/hurds are removed and dry for an extended period to produce hempcrete blocks. Then, hemp bast is processed using a device with a thick blade that separates the fibrous material into pieces according to applications. To manufacture Hempcrete mixture, blocks, and filler, hemp shavings are mostly combined with cement or lime as a binder. (Tarun Jami, 2018)
Depending on the casting procedures, researchers around the world who have worked with hemp concrete have reported varying values for the material’s compressive strength, ranging from 0.2 to 6.94 MPa. It was discovered that as compactness rises, density rises as well. Other elements that influence the hemp concrete mix’s compressive strength are particle size and the chemical makeup of the adhesive. (Tarun Jami, 2018)
Thermal and acoustic performance
It is the most lightweight material with a thermal conductivity ranging from 0.05 to 0.138W/(m. K), depending on the density. It provides thermal mass as well as insulation because of the density of the lime binder once it has been set. The acoustic absorption of hempcrete is excellent due to its lightweight properties which improve the building’s acoustic and insulation performances.
It displays how durable the substance is. Lime and hemp have been used for a period of over 1500 years and have been utilized today to preserve ancient structures, demonstrating the material’s excellent degree of durability since it typically lasts for at least 60 to 80 years. The lime binder ratio plays an important in maintaining the durability of the whole material.
The curves and other shapes with hempcrete blocks or infilling methods can be designed or constructed having no design issues. But the size and thickness of the blocks are defined, which sometimes creates space obstruction in design. Due to its porosity, this material can be proposed in Pavers designs to recharge the Groundwater table. Hempcrete is widely used for walls, slabs, roofing, etc.
Water or vapor permeability helps to facilitate healthier buildings or spaces, which improves the quality of life while improving indoor air and humidity levels. Thus, the porosity of hempcrete material helps in fulfilling this phenomenon, thus reducing the active technologies for cooling and heating indoor spaces. Consequently, water retention may cause the decaying of material if not made with a strong binder or adhesives.
The proportions of hemp, water, and lime in hempcrete should be quite accurate as the structural properties of the material are being impacted by this ratio. Hempcrete, however, performs poorly in tensile characteristics Numerous technologies come into the ground to improve structural aspects to some extent. For example, IsoHemp engineers designed the hempcrete blocks with bioplastic incorporated within, which acts like building block joints, and other companies and engineers are researching and incorporating techniques to improve the structural part of this material.
This property is affected by various factors such as Binder type and ratio, curing condition, production methods, and moldings. Different hemp shiv ratio to the binder ratio is an important aspect of improving the mechanical property of Hempcrete. (Tarun Jami, 2018)
Life cycle assessment test and carbon footprint
A life-cycle assessment (LCA), is used to examine the environmental impact of hemp bricks. The LCA found that 1 m3 of bricks store 76 kg of CO2. The block scrap is entirely recycled back onto the production line during production. No garbage or effluent is discharged. (building, 2021)
Everything in the world has its benefits and drawbacks, depending on how it is being utilized. Hemp materials are characterized by their strengths and weaknesses, and they are less harmful to the environment than other man-made materials. Due to its low carbon footprint or carbon-negative nature, this material is primarily used in mid-rise residential buildings and researchers claim that it is much less carbon-negative than a regular-based concrete house. Hempcrete may be used in various ways and still need research to obtain more structural properties. Hemp has been used historically in Ellora caves, which are over 1500 years old. The summary also shows that the hemp and binder have different qualities, but the binder needs to be more focused to improve the quality of the material. Hempcrete is an essential alternative material for both environmental and construction opportunities that can aid in developing sustainable housing solutions. Materials and methods that don’t degrade the environment’s quality but enhance human existence should be used by the entire world.
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