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Materials

Polymer rebar may find use in much more durable concrete structures

By Ben Coxworth
July 02, 2019
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Deakin's Dr. Kazem Ghabraie, Austeng Engineering's Ross George and Deakin's Dr. Mahbube Subhani, with samples of the rebar
Deakin University
Deakin's Dr. Kazem Ghabraie, Austeng Engineering's Ross George and Deakin's Dr. Mahbube Subhani, with samples of the rebar
Deakin University

While many of us might think that concrete structures such as bridges simply stand unaided for decades at a time, the fact is that they require maintenance as often as once every five years. An experimental new type of rebar, however, could drastically change that.

The problem with existing concrete structures lies in the steel rebar rods that are embedded within them for support. As these rust over time, the rust occupies more space than the original non-corroded rebar. The rusted steel thus pushes out against the surrounding concrete, leading to spalling, a process in which concrete cracks and falls away from the main structure.

According to Dr. Mahbube Subhani, who is a Lecturer in Civil Engineering at Australia's Deakin University, reinforced concrete structures typically require some maintenance every five years or so, along with major rehabilitation every 20 years. This state of affairs prompted Subhani and Dr. Kazem Ghabraie to produce a new non-rusting rebar, made of a carbon and glass fiber-reinforced polymer.

The material is reportedly stronger than rebar made of regular steel, and is one-fifth the weight of reinforced-steel rebar. Additionally, it requires only a quarter as much energy to produce.

It is now about to be used in the construction of a pedestrian bridge in the Australian city of Geelong. The researchers believe that once the bridge is constructed, it should require no maintenance for the rest of its planned 100-year lifespan.

Additionally, instead of cement, the concrete used for the bridge will incorporate fly ash obtained from coal combustion – cement production is one of the major sources of manmade carbon dioxide emissions. Deakin researchers have previously developed eco-friendly concrete in which waste glass was used as aggregate.

"We have replaced the steel reinforcing bar normally used in steel reinforced concrete with more durable carbon and glass fiber reinforced polymer," says Subhani. "This bridge should not require any maintenance for the whole of its design life."

Source: Deakin University

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Ben Coxworth
Based out of Edmonton, Canada, Ben Coxworth has been writing for New Atlas since 2009 and is presently Managing Editor for North America. An experienced freelance writer, he previously obtained an English BA from the University of Saskatchewan, then spent over 20 years working in various markets as a television reporter, producer and news videographer. Ben is particularly interested in scientific innovation, human-powered transportation, and the marine environment.
11 comments
Er Joginder Singh
Replacement of steel reinforcing bars with carbon & glass fibre reinforced bars is a valuable invention to society. As per your research, bridges so constructed with these bars doesn't require any Maintance for the whole of its design life. Induction of this new material will probably reduce the maintenance cost .
windykites
This is a very good product. Think how much weight will be saved in construction. It should be cheaper, so it may quickly replace steel rebar. I think ground up plastic could be used as an addition to sand as a filler for concrete.
Pierre Latour
Basalt rebar has been around for years. Extruded from volcanic rock, it is cheap, impervious to rust, available in braided rope, etc. Polymer rebar is recycled? Cost?
Username
The convenient thing about steel is that it had the same temperature contraction/expansion rate as concrete. If this polymer does too, then it's a winner.
Gordien
This is exciting news. I read about basalt rebar, and geopolymer concrete a few years ago to be used for building oceanic structures - cities on the sea. I learned about it through New Atlas (Gizmag) when they did a story on the Seasteading Institute. I wish them the best of luck.
paul314
Epoxy coatings on rebar will in theory reduce rusting rates substantially, but the coatings don't appear to be that durable in the real world.
jocco
In Bangkok, I saw them using Bamboo in place of rebar.
Neal H.
I agree with everyone but what's the cost compared to rebar. Contractors and owners will be hard-pressed to switch if the change comes with a price. Also - I believe there's one mistake with the article. At the end it's stated that the cement was substituted with fly ash. I don't believe this to be the case. Fly ash is added to the concrete mix to cut down on the amount of cement needed. Cement is the binder (maybe the greatest glue of all time). Fly ash is not the same. It's basically a filler. But if you add fly ash you can REDUCE the amount of cement needed to obtain the same strength. Also - it should reduce cracking as the particulate size of fly ash is very small and fills in micro spaces within the concrete.
lasharela
ridiculous... do you have an idea how many decades ago the mass-production of fiberglass-polymer rebars began and how many million tons of them are produced annually, or how many bridges and other structures are built using solely that type of rebar?
tomtoys
All to the good. Beautifying concrete is a bit of a problem, it's not the most attractive material. Glass has been added to replace sand. I wonder could beams be given a coat of glass on the outside. Grind glass to suitable size, glue it into the mould, pour the concrete. My simple experiment showed an increase in attractiveness. Coloured glass good.
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