ISABEL RUBIO ARROYO | Tungsteno
Since 1950 some 8.3 billion tonnes of plastic have been manufactured, according to Greenpeace. That's the weight of about one billion elephants. Only 9% of all the plastic produced to date has been recycled, while 12% has been incinerated and the vast majority, 79%, has ended up in landfills or in the environment. A huge amount of this material ends up in seas and oceans, even at depths reaching 10,000 metres. Plastics can take hundreds of years to disintegrate. Therefore, giving them a second life has become one of the environmental challenges of the 21st century.
The reuse of this waste in the construction sector, in addition to contributing to the circular economy, improves the resistance of buildings to the external action of water and provides greater elasticity and lower thermal conductivity. There are companies and research groups that are experimenting with new building materials that take advantage of the qualities of these materials. "Plastics can become secondary raw materials incorporated into the matrixes of so-called 'traditional materials' such as plaster, cement or concrete," explains María Alejandra Vidales, professor and researcher at the Faculty of Building Construction at the Polytechnic University of Madrid (UPM).
Although structures built with these materials may have lower mechanical strength, their use does bring multiple benefits. The undoubted advantage of using this type of material is its contribution to the sustainable development of the planet. "On the one hand, the amount of this type of waste in landfills is minimized and, on the other, the use of raw materials in the manufacture of the item is reduced, which leads to a reduction in water use," says Vidales. Improvements can also be achieved thanks to the properties of these new materials: "Lower coefficients of thermal conductivity, lightness, lower porosity or greater elasticity."
The plastic waste from the recycling of electrical cables is already being reused with plaster to form a new compound, more elastic and resistant to external elements such as water. Credit: Lyrsa Álava.
Polymers to replace cement or plaster
There are certain sustainability certifications, such as BREEAM, that value the reuse of this type of material in construction. There are different examples and numerous patents, both Spanish and foreign, that breathe a second life into plastic. Two young Mexicans have developed polycrete, a construction material made from recycled synthetic polymers that replaces conventional cement. There are companies such as Platio from Budapest that makes solar paving stones for exteriors using recycled plastic and glass, others like Ecore that makes flooring with recycled rubber, or Presanella from Italy that transforms recycled plastic into bricks.
Vidales’ team at UPM has developed a plaster panel or sheet containing plastic waste from the recycling of electrical cables. "The waste is collected directly from the recycling plant and, without going through any kind of treatment, is introduced into the plaster matrix. The water is then added and the mixture is kneaded, poured into moulds and set," she explains.
The notable features of this material are its behaviour in the presence of water and its greater elasticity, which reduces "the appearance of moisture and cracks". In addition, according to Vidales, it has been possible to reduce the use of water and gypsum stone (the raw material used to make plaster) by between 25% and 30%. This material has not yet been marketed, but ideally it would be used "in the areas of buildings most exposed to water, such as basements, ground floors on screeds or surfaces with holes."
Vidales says that these materials could be used "in any type of construction," including, for example, simple buildings such as JD Composites houses, made only with recycled material, or Lego houses. They can also give shape to larger buildings such as the EcoArk building in Taiwan, a megastructure constructed from recycled plastic bottles. Additional uses include the manufacture of floorboards, bricks and other building materials, tunnels and bridges, railings, floors, paving stones and street furniture.
The flexibility and strength of plastic allows to improve the resistance of the road surface, making polymers a viable alternative to traditional asphalt. Credit: Plastic Road.
Asphalt made with old tires and caps
Plastic materials at the end of their useful life can also be integrated into the asphalt for road surfaces. This is not a new idea. In India, there are already more than 20,000 kilometres of roads made from plastic waste, according to National Geographic. Companies such as Plastic Road are investigating how to harness the qualities of plastic to build roads from this recycled material alone.
In Spain, the Polymix project, in which the Instituto Tecnológico del Plástico (AIMPLAS) is participating, stands out. Belén Monje, the project's main researcher, explains that the new asphalt contains unused tires and waste from caps, packaging and hangers. It has already been used to asphalt two kilometres of a stretch of road at the accesses to Alcalá de Henares.
The results have been promising. The researchers have concluded that this new material exhibits a remarkable improvement in resistance to plastic deformation compared to the conventional asphalt mix. This allows for better performance against the appearance of rutting (a groove left by a wheel on the ground as it passes), which is especially useful in high temperatures or slow heavy traffic.
There are countless possibilities to extend the life of plastic and reduce its impact on the planet. But Monje insists that "it is necessary to establish policies that will propel this type of development forward so it can reach the market." "It is also important that its benefits are known throughout the value chain and that its possibility of introduction is taken into account from the design of the product so that, if necessary, any modification can be made from the beginning," she concludes. If the plastic is going to take more than 100 years to degrade, it is better to have it on walls, buildings or roads than in nature or on the ocean floor.
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Tungsteno is a journalism laboratory to scan the essence of innovation. Devised by Materia Publicaciones Científicas for Sacyr’s blog.