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Hemp Rebar

Low-cost Non-corroding

What is Hemp?

WHAT IS HEMP?

Hemp, or industrial hemp, is a botanical class of Cannabis sativa cultivars grown specifically for industrial or medicinal use. It can be used to make a wide range of products. Along with bamboo, hemp is among the fastest growing plants on Earth. It was also one of the first plants to be spun into usable fiber 50,000 years ago. It can be refined into a variety of commercial items, including paper, rope, textiles, clothing, biodegradable plastics, paint, insulation, biofuel, food, and animal feed.

Hemp as Rebar

Hemp as Rebar

  • Researchers at the USA's Rensselaer Polytechnic Institute have invented an alternative to steel rebar made from hemp, which they claim avoids the problem of corrosion while cutting carbon emissions from construction.

  • At present, steel rebar rusting contributes significantly to the premature decay of structures including bridges, roads, seawalls and buildings, the project leads Daniel Walczyk and Alexandros Tsamis told Dezeen.

HEMP

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HEMP REBAR

HEMP REBAR

The hemp fibre is encased in thermoplastic to make a reinforcing bar.

Rebar life span

HEMP REBAR PROPERTIES

Corrosion, in environments with high salt concentration, concrete structures are given a lifetime of 40 to 50 years.

  • Traditional steel rebar has a relatively low amount of embodied energy, particularly if it is made with recycled content, although the number conceals the impacts of its service life and maintenance needs.
  • However, structural designs in highly corrosive environments will often use alternatives to traditional steel such as glass fibre reinforced polymer (GFRP) rebar, which has a high environmental impact.
  • The team says their preliminary results show the hemp rebar has a significantly lower amount of embodied energy than GFRP rebar while likely being as long-lasting, although the work is yet to be peer-reviewed.

HEMP & TRADITIONAL REBAR

The hemp rebar is made through a pultrusion process in which the fibres are pulled together with thermoplastics into a heated die and melted to form a solid bar.

The first step is to make the hemp into a rope containing a blend of natural and plastic fibres – the exact "recipe" for which the RPI team is still finessing.

HOW TO MAKE A HEMP REBAR

The team from Rensselaer Polytechnic Institute is experimenting with different thermoplastics for the mixture, including polypropylene

Hemp rebar could cut construction time while keeping cost low

HEMP REBAR FORGING MACHINE

Coils of this rope are then fed into a machine created especially for the process. This device, a CNC machine about the size of a small car, sits on-site and forges the rebar on demand, reading from digital files to bend and cut the product to the stipulated shape.

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