Hemp concrete: creating holistic sustainability with plant-based building materials
Courtesy of GoHemp
Hemp is one of the oldest plants domesticated by humans. With its wide variety of uses and uses, it’s easy to see why it has been a desirable product throughout history. Hemp seeds and flowers are used in natural foods, medicines, and organic beauty products. The fibers and stems of the hemp plant are used in clothing, paper, and biofuel. Today, even a waste product from hemp fiber processing called hemp shives is used to make sustainable building materials like hemp concrete.
Hemp concrete is a bio-aggregate concrete in which the hemp shives – small pieces of wood from the stem of the plant – are mixed with either lime or mud cement to obtain a durable, environmentally friendly building material. Hemp concrete is lightweight and not structural, but can instead be incorporated into traditional building construction systems. Similar to conventional concrete, it can either be poured on site or prefabricated into components such as blocks or sheet metal.
Courtesy of GoHemp
The high silica content naturally found in the woody parts of the hemp plant means that it combines well with lime. The lime binder used in hemp concrete is in the form of calcium hydroxide, which then begins to absorb carbon dioxide from the atmosphere to produce calcium carbonate or limestone. This means that hemp concrete is not only durable, but actually a carbon negative material. After pouring, hemp concrete requires significantly less water to harden than conventional cement, which helps to preserve this valuable natural resource.
Cast hemp wall with traditional stone masonry. Image courtesy of GoHemp
Since hemp is made from natural waste, its entire life cycle as a construction product is environmentally friendly, right through to possible reuse or recycling in the event of a demolition. Even growing the hemp plant requires less water, pesticides and fertilizer than other crops. Hemp can be grown easily and quickly in almost any part of the world and delivers two harvests a year. As it grows, it binds CO2, prevents erosion, naturally stops weeds from growing around it, and also detoxifies the soil. What is left after harvest breaks down into the soil, provides valuable nutrients and makes hemp a desirable crop rotation for farmers.
Once hemp becomes hemp, its benefits remain. In the event of a fire, the lime jacket offers sufficient fire resistance for evacuating the residents. It also reduces the spread of fire and the risk of smoke inhalation as it burns locally and without smoking. Hemp concrete does not cause skin or breathing problems and is also vapor permeable, which creates a healthy indoor climate. Due to its light structure and the air pockets created between the particles, hemp concrete is both earthquake-proof and an efficient thermal insulator.
Courtesy of GoHemp
Hemp is naturally resistant to both mold and pests, and people used these special properties as recently as 1,500 years ago. In the sacred Ellora Caves of India, works of art from the 6th century AD have been preserved due to the ancient people’s use of hemp plaster. A research team led by Indian scientist MR Singh found that these artists had chopped up the hemp plant and mixed it with lime to form a plaster of paris. Hemp’s ability to naturally repel pests and regulate humidity means that the artwork in these caves has withstood the test of time whereas that of the Ajanta Caves, built before those of Ellora, does not have hemp in theirs Plaster of paris, eventually mainly destroyed by silverfish insects.
Today companies like GoHemp work in India, inspired by the late Dr. Prem Jain, known as the “Father of Green Building in India”, is researching and developing the potential of hemp as a sustainable building material and working with local governments to farm the hemp land and create prototype structures. With India’s agricultural economy, making hempcrete into a widely accepted and used building material could have economic and social benefits as well as environmental benefits. As Dr. Jain once said, “If we change the way we think about buildings, what you build may change the world.”
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