Materials News
Recycled plastics take the high road Recycled plastic is reinventing itself as a sustainable, durable and cost-effective material for building bridges and roads that used to be dominated by materials like bitumen, iron, steel and other metals, says Angelica Buan in this article.
P
ost-consumer resin or PCR is no more a buzzword. The ubiquitous word may appear on a flap of a cereal box, at the bottom of a take-out salad pack, or on other plastic packaging. Utilising PCR in packaging and even in household goods is common, but now applications extend to larger structures like bridges and roads. Also, there is a rising demand for PCR, which goes back to how valuable plastic is as a resource. In the US, demand for PCR is forecast to rise 6.5% to 200,000 tonnes in 2016, with PET bottles as the leading source, says a report from Cleveland-based market research firm Freedonia. More rapid gains, however, are forecast for rigid plastics, film, and carpet as well as rLDPE, which will benefit from a rebound in the construction market; with growth also expected for smaller volume resins such as nylon, PP and PS. Meanwhile, PET and HDPE were the two leading resins used in recycled plastic products in 2011, accounting for over 70% of demand, says the firm. VinylPlus, the European PVC industry sustainable development programme, says that 514,913 tonnes of PVC was recycled last year, of which window profiles and related profile products accounted for around 45%. The target is to recycle 800,000 tonnes/year of PVC by 2020 in Europe.
Heavy-duty bridges made of recycled plastics In the 1980s, Ohio-headquartered Axion International (which is currently under Chapter 11 bankruptcy) together with Rutgers University’s Advanced Polymer Centre produced a thermoplastic composite material made of 100% PCR and HDPE. Since then Axion’s Ecotrax composite railroad ties and Struxure composite building products can be found in infrastructures like girders, pilings, railroad ties and bridge substructures, as replacements for traditional materials like wood, steel or concrete.
The 100% PCR and HDPE composite material produced by Axion is used for the Fort Bragg bridge, which could carry a 71-tonne M1 Abrams tank and HS25 loads
Raw material from consumer waste is turned into high performance composite material
6
MAY 2016
Unlike the glass fibre-composite systems, which were commonly used in bridges with decks during the mid-1970s, the TP-based bridge systems have shown to be inherently resistant to rust and spoilage, and require zero to minimal maintenance, says Axion. Trying out the material, the US Army made the first recycled plastic bridge at Fort Bragg in North Carolina in 2009. The bridge could carry a 71-tonne M1 Abrams tank and HS25 loads. The bridge components, including girders, pier caps, decking, railings and pilings, are made from recycled plastics. The following year, the dilapidating railroad timber bridges at Fort Eustis in Virginia were replaced with the TP composite.