Recycled plastic bridges

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Introduction

In addition, the United Kingdom uses over 5 million tonnes of plastic each year, of which only 24% is recovered or recycled (ref 2)

Plastics are recycled and used for construction because they are price-competitive and have a low cost for installation and replacement. Recycled plastics come in many different forms, and produce strong and versatile products, allowing them to be used for a wide range of applications:

• Fencing
• Pipes and ducting
• Water drainage
• Scaffolding planks
• Decking and flooring products

In the London 2012 Olympics, recycled plastics were used in the construction of the Water Polo Arena. The silver-coloured wrap is made of recycled plastics, and the sloping roof of the Arena is made from air-inflated recyclable plastic cushions.

Traditionally, bridges have been constructed using materials such as concrete, masonry, steel, timber and so on. Recently however, engineers have started to consider using recycled plastic to overcome some of the problems of instability that can be found in such materials. For example, concrete can suffer problems such as chloride penetration, carbonation, alkali silica reactions, structural cracks, and damage due to accidents and explosions. Masonry bridges can suffer from scouring, rainwater damage, cracking and so on. Timber bridges can suffer insect attack and rot.

Advantages of recycled bridges

• They do not need regular maintenance.
• The plastic can be recycled on demolition of the bridge.
• Most of the plastics used are chemically inert, prolonging their life span.
• They are stable under UV radiation.
• They are stable in saltwater.
• They are resistant to rot and damage from insects.
• They have high strength to weight ratio.
• They can reduce the amount of non-biodegradable plastics being sent to landfill.
• The can help educate people about recycling plastics.

Possible challenges of constructing recycled bridges

Cost effectiveness

Since there are not many pioneers at constructing plastic bridges, they are not as yet competitive when compared to the construction costs of other materials. Future developments, such as composite recycled plastics; for example, plastic I-beam sections reinforced with steel, may offer lower costs in the long term.

Mechanical properties may be reduced after recycling processes

Recycled plastics are ground and moulded during the recycling process. This may cause the glass fibre chain length to decrease, and mechanical properties such as ultimate tensile strength (UTS) may decrease as a result. (ref 11) More attention may need to be paid to the mechanical properties of recycled plastics, such as Young's modulus, ultimate tensile strength (UTS) and compressive strength.

Size

More research may be necessary to determine how best to maximise the mechanical properties of mixed recycled plastics so that longer span structures can be created. Most examples of plastic bridges have low heights and small spans. This may be due to the relatively low strength of recycled plastics when compared to other materials as well as the price of recycled plastics after processing.

Examples of plastic bridges

Bridge across the Tweed River, Scotland, United Kingdom

A Welsh company called Vertech built a bridge across the Tweed River. The bridge is 30 metres in length and made entirely out of waste plastic products. It is the world's longest and sturdiest recycled bridge. (ref 6) The installation process was relatively simple. It was designed by engineers from Rutgers and Cardiff Universities, then constructed off-site. It was then taken to the site and assembled in four days. The entire process of putting the bridge together took less than two weeks. (ref 12)

Bridge at Fort Bragg, North Carolina, USA

Axion International Holdings, Inc. built a bridge made of recycled plastic at Fort Bragg, in North Carolina. The bridge consists of 94 percent recycled materials, including glass, vehicle bumpers and about 85,000 pounds of high-density polyethylene plastic. (ref 13) The bridge can carry the weight of a tank of 68.7 tons.

Footbridge at Santa Rosa Valley, California, USA

The pedestrian bridge at Santa Rosa Valley is 25 feet long and 10 feet across. It was constructed across the Arroyo Santa Rosa to help connect a portion of a trail that was washed out during heavy rains. (ref 15) The bridge is made of recycled plastic, and is particularly useful in the area because of saltwater concentrations in the environment, since steel rusts, concrete cracks and wood rots. (16)

Bridge at York, Maine, USA

The bridge at York is 26 feet by 15 feet, and is the first recycled-plastic vehicular bridge in Maine and the first plastic bridge used on a public highway application in the United States. The materials cost were $USD70,000 and the construction cost was $USD25,000.

Related articles

• Sustainability
• Sustainable materials
• Timber
• Whole-life costs

External references

1. History World HISTORY OF BRIDGES http://www.historyworld.net/wrldhis/plaintexthistories.asp?historyid=ab97
2. British Plastics Federation Plastics Recycling http://www.bpf.co.uk/sustainability/plastics_recycling.aspx
3. CONTEC Aps Concrete Bridges and Viaducts
4. Universidade do Minho STRENGTHENING OF STONE MASONRY ARCH BRIDGES
5. J Page (1993) Masonry Arch Bridges. HMSO
6. CNN World's longest recycled bridge spans Scottish river http://edition.cnn.com/2011/12/06/world/recyclable-bridge
7. WORLDNETDAILY THE ARMY'S FIRST PLASTIC BRIDGE http://www.wnd.com/2009/09/110770/
8. The Waste & Resources Action Programme (WRAP) Using recycled plastic products in construction http://www.wrap.org.uk/sites/files/wrap/ReConstructPlastic.2031.pdf
9. The Telegraph (2012) London 2012 Olympics: Water Polo Arena construction completed http://www.telegraph.co.uk/sport/olympics/water-polo/9181116/London-2012-Olympics-Water-Polo-Arena-construction-completed.html
10. Energy Efficiency News (2008) Recycled plastic has future in construction.
11. Harold Cornier-Rios (2003) EFFECT OF RECYCLING ON MATERIAL PROPERTIES OF POLYETHYLENE TEREPHTHALATE AT VARIOUS RECYCLING RATIOS AND RECYCLING GENERATIONS. University of Puerto Rico.
12. Duncan Geere (2011) Recycled plastic bridge spans Welsh river http://www.wired.co.uk/news/archive/2011-10/26/recycled-plastic-bridge
13. USAEC (2009) FORT BRAGG TESTS RECYCLED PLASTIC BRIDGE
14. WORLDNETDAILY THE ARMY'S FIRST PLASTIC BRIDGE http://www.wnd.com/2009/09/110770/
15. Michele Willer-Allred (2011) Arroyo Santa Rosa's plastic bridge project moves ahead. Scripps Interactive Newspapers Group.
16. Michele Willer-Allred (2012) Pioneering plastic bridge opens in Santa Rosa Valley. Scripps Interactive Newspapers Group.
17. Heritage Pioneer (2012) A Recycled Plastic Bridge in York, Maine. Packaging Phoenix
18. Vince Bond (2012) Recycled plastics used to form Maine bridge. Crain Communications Inc.