MAY 27, 2022 11:30 AM PDT

Strong as Steel: Hemp Reinforcing Bar

WRITTEN BY: Kerry Charron

Can hemp building materials prevent dangerous crises such as the recent Surfside building collapse in Miami, or crumbling MICA homes in Ireland? Rensselaer Polytechnic Institute researchers believe that hemp fiber could have a significant impact on the construction industry. They have developed hemp reinforcing bar or “rebar” made from hemp fiber coated with resin or bioplastic, and they claim this hemp rebar is just as strong as the steel rebar often used in cement structures. 

Hemp rebar could replace steel rebar used in construction of bridges, buildings, roadways, and water dams. Hemp rebar is a safe substitute for steel because it has a similar strength to steel in weight ratio. Steel rebar is susceptible to moisture which can cause corrosion and compromise the building’s stability, and it can be warped by extreme heat. Hemp fiber is safe, durable, and moisture resistant. The RPI research team uses production technology similar to 3D printing to create hemp rebar, which requires both a filament and a machine to form it. Hemp rebar filament is extracted hemp fibers wrapped in a thermoplastic. It is spun into a rope-like coil, and the machine heats and consolidates the filament into hardened bars.

Using hemp rebar is gaining more architectural attention, but builders have been using another hemp building product called hempcrete for many years. Hempcrete is fire-resistant, energy efficient, and carbon-negative. It is made by mixing hemp hurd taken from the stalk with lime and pouring the mixture into a rectangular block mold. Hempcrete can withstand the same load bearing capacity of a high-performance concrete. Hempcrete and hemp rebar demonstrate the versatility and durability of this building material. 

Researchers also believe hemp rebar can last longer than steel and has less or no carbon emissions. Assistant professor of architecture, and associate director of RPI’s Center for Architecture Science and Ecology, Alexandros Tsamis explains the environmental benefits of using hemp over steel rebar: “By switching the material used in one object from steel to a composite of fibers, you can drastically reduce the carbon footprint of the building industry, because you extend the lifetime of structures.” Hemp construction materials have great potential to promote sustainability, minimize building costs, and optimize safety structures. 

Professor Tsamis also said in the report that concrete structures “in environments with high salt concentration” have an expected lifetime of “40-50 years” due to the corrosion of steel-based rebar.

Source: Times Union


About the Author
Bachelor's (BA/BS/Other)
Kerry Charron writes about medical cannabis research. She has experience working in a Florida cultivation center and has participated in advocacy efforts for medical cannabis.
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