Hemp could never replace steel … but wait. Could it?

Hemp could never replace steel … but wait. Could it?

Architect-engineer team thinks hemp construction rebar has the potential to replace steel.

An architect and mechanical engineer say they’ve developed a hemp‐based rebar for cement construction that could replace steel, reports Hemp Today.

The pair of collaborators are working together at Rensselaer Polytechnic Institute, a New-York-based private research university, to develop the rebar — and the machines that could turn it from raw plant material to an end product that performs as well as steel.

The Team

The architect: Alexandros Tsamis, assistant professor of architecture and associate director of the Center for Architecture Science and Ecology at Rensselaer.

The engineer: Dan Walczyk, professor of mechanical engineering and director of the institute's Manufacturing Innovation Center.

Tsamis and Walczyk have developed a thermoplastic rebar reinforced with hemp fiber they say could replace steel in concrete buildings and infrastructure.

The Strengths of Hemp for Rebar

Concrete is strong but has relatively low tensile strength, meaning it can’t withstand a great deal of stretching or pulling. That's where rebar comes in, reinforcing cement in construction to increase tensile strength.

There is some precedent for non-steel rebar. For instance a fiberglass rebar exists, called glass fiber reinforced polymer or GFRP. It’s more expensive, so is selectively used for projects that demand rebar that won’t corrode or is non-magnetic. And GFRP rebar actually outperforms steel rebar in measures of tensile strength and yield strain. So, it can be done.

The hemp-reinforced rebar would:

  • reduce corrosion, which is a common problem with steel rebar
  • extend the useful lifetime of structures built with it
  • reduce the carbon footprint of construction by emitting a lower volume of greenhouse gasses during processing
  • possibly create a carbon-neutral product, because hemp also sequesters carbon as it’s grown

Is It Strong Enough?

The most important question: Is it strong enough?

Preliminary results of working with the material have shown “strength characteristics comparable to steel,” according to a press release from Rensselaer.

A key part of Tsamis and Walczyk’s work is developing machines that can separate hemp's fiber from its woody inner core without degrading the strength of the raw material.

Cost is also a consideration, and the research team is working to ensure the hemp machines and methods they're developing are cost effective.

To streamline processing and keep costs low, they envision strategically placed barns — made of hemp, of course — equipped to process hemp plants after harvest. Once the plants are broken down into various parts, the components would be shipped to end-product manufacturers.

The researchers believe this network would minimize the hemp industry’s carbon footprint and optimize its supply chains. They’re also developing a “sustainable degumming method” and new ways to process hemp bio-composite materials.

Meeting of the Minds

The hemp-rebar development is one of the first projects to come out of Rensselaer’s new Institute for Energy, Built Environment, and Smart Systems (EBESS). This branch of the institute taps talent from Rensselaer in design, engineering and business, bringing them together to innovate.

This particular innovation shows what’s possible when experts in different disciplines come together. It also demonstrates how hemp, as a material, fits with the Institute's larger mission to bring carbon-neutral, climate-resilient infrastructure from dream to reality.