Hemp-Lime Building Blocks Could Revolutionize Construction
Humans have used the hemp plant for thousands of years, with the first evidence of human use dating back to 8,000 BCE in modern-day Taiwan, where archeologists found pottery remains containing hemp cord. Humans have also used hemp as a source for medicine since at least 2,800 BC, with the hemp plant being listed in the Chinese Emperor Shen Nung’s pharmacopoeia.
These days, hemp is still used for fiber and making various textiles, and is a source for medical products on a level never witnessed before in human history. However, hemp is also used for a wide array of other things, including bioremediation to clean up toxic sites around the world, for creating batteries, and to create the building material hempcrete.
The latter of those, hempcrete, is a bio-composite made of the inner woody core of the hemp plant mixed with a lime-based binder. The inner woody core or ‘shiv’ is high in silica content, and that allows it to naturally bind really well with lime. It is a property that is seemingly unique to hemp among all of the known natural fibers.
Currently, hempcrete is primarily used as an insulating and fill-in material. It weighs about a seventh or an eighth of the weight of concrete, floats in water when fully cured, has a negative CO2 footprint, and is nearly fireproof (at least compared to other popular building materials). One limitation of hempcrete is that it is not used as a structural element because it is not a load-bearing material.
The limitation of hemp as a source for load-bearing construction material could soon become a thing of the past, with the Cologne University of Applied Sciences reportedly having developed new hemp-lime building blocks potentially capable of being used as a material for load-bearing structures.
“These zones, like conventional hemp limestone blocks, are to be composed exclusively of biomass and mineral binders. According to the project participants, the aim is to create a climate-positive alternative to aerated concrete blocks or lightweight vertically perforated bricks, enabling single-shell masonry construction from rapidly renewable raw materials.” reported Allgemeine Bauzeitung in its local coverage (translated from German to English).
The Institute for Construction and Agricultural Machinery Technology at the Cologne University of Applied Sciences is reportedly developing a device that will be designed to produce compacted bricks made of hemp on a large scale. The resulting bricks will undergo testing to further explore their efficiency and application feasibility.
“In the second half of our project, we will devote ourselves to practical tests with our masonry blocks. We will erect several wall modules and examine their structural properties. In addition to properties such as load-bearing capacity, thermal insulation, and moisture behavior, we want to determine which materials, such as plaster and mortar, are compatible with the blocks and demonstrate that the blocks can be easily processed using conventional tools,” said project leader Prof. Dr. Arne Künstler from the Faculty of Architecture at the Cologne University of Applied Sciences according to Allgemeine Bauzeitung.
If the project’s research can prove that hemp-lime building blocks can be used as a load-bearing construction material, it would revolutionize the construction industry. Producing hemp is exponentially more sustainable compared to the production of most traditional construction materials. Cement production, for example, is a significant source of pollution around the globe.