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Steel was once the primary material used in construction, but now, engineers have made strides forward with the development of new materials. Researchers have focused on creating substances that are stronger, more durable, and reliable, to replace older materials. As bridges weaken through steel corrosion, engineers are looking into the use of plastic for repairs.
Plastic Ushers in a New Era for Bridge Construction
A new material has been established - fibre-reinforced polymers (FRP). FRP is a composite material that is constructed of a polymer matrix reinforced with fibres. The incorporated fibers are commonly glass, carbon, aramid, or basalt but can also be paper or wood.
The materials’ impressive properties include being lightweight, strong, corrosion-resistant and relatively cheap. These characteristics has allowed the material to become popular in the construction industry, particularly in bridge construction and repair.
Nowadays, FRP is one of the most commonly used materials for repairing concrete infrastructure such as bridges, which can be repaired at half the cost when compared to steel. Construction companies are also turning to the material to build bridges from scratch. We are seeing pedestrian bridges, highway bridge decks and girders made of only FRP components, as well as highway bridges being made of a mixture of hybrid reinforced concrete and FRP components.
McKinleyville Bridge, Brooke County, USA
In 1988, engineers shunned the traditional steel rebar in favor of FRP rebar to reinforce its concrete decking, making the McKinleyville Bridge in Brooke County the very first vehicular bridge to incorporate this material. After a few decades, the bridge remains in good condition.
Market Street Bridge, West Virginia, USA
In 1993, FRP was also chosen to be used as the main construction material in the Market Street Bridge in West Virginia due to it being four times lighter than concrete and five to six times stronger. This bridge has also stood the test of time.
Rotterdam, Netherlands
Today, Rotterdam is a city that has completely embraced the use of plastic in constructing bridges. The city, like Amsterdam, is characterized by its many canals, resulting in the need for around 850 bridges to connect the city. Over time, the bridges are wearing out, but instead of replacing them with conventional steel, concrete, or wood, the city is opting for plastic-based bridges.
Although feedback suggests that the structures feel ‘wobbly’, they are designed to withstand 100 years of use. Builders are instantly seeing the benefits of constructing the bridges with FRP over alternatives, as bridges are being put up over a few hours rather than weeks. The city is also enjoying the environmental benefit of using FRP, as the alternative material of steel takes twice as much energy to make, additionally, they are experimenting with recycled plastic.
Replacing Wood with Plastic
The US military has been testing new bridges made from plastic that are looking to replace worn-out wooden ones. Results have shown that the bridges can withstand the weight of a tank crossing it, require little maintenance, and can be expected to endure around 50 years of use before they require replacement. Therefore, we may see the US follow in the footsteps of Rotterdam soon.
Overall, FRP is beginning to make a name for itself in the area of bridge construction. With its benefits of being stronger and lighter than steel, durable, relatively cheap and quick and easy to work with, as bridges age and as new ones are put up engineers are looking at how they can use this material over traditional steel, wood and concrete.
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