Making buildings from plant fibres
Bâtiments en fibres végétales
De nouveaux matériaux de construction innovants et non polluants.
Pour parer au réchauffement climatique, chercheurs et industriels tentent depuis quelques années d’élaborer des dispositifs de construction et des matériaux moins polluants, et ils se montrent aujourd’hui plus créatifs que jamais... Le plastique confectionné à partir de fibres de bois et le béton à base de fibres de carottes sont-ils les matériaux du futur ?
Using carrots to create concrete, turning wood into plastic, or even compressing it into a “super wood” that is as light and strong as titanium might sound like a series of almost Frankensteinish experiments. Yet all three are among the latest examples of employing natural fibres from 1. concrete béton / to turn sth into transformer qch en / even même / strong résistant, rigide / to sound like ressembler à / experiment expérience scientifique / yet cependant, et pourtant / to be among(st) faire partie de, figurer parmi / latest dernier (en date), plus récent / plants as eco-friendly additives or alternatives to man-made materials.
2. Materials-science researchers are finding that plant fibres can add durability and strength to substances already used in the construction of buildings and in goods that range from toys and furniture to cars and aircraft. A big bonus is that, because plants lock up carbon in their structure, using their fibres to make things should mean less carbon dioxide is emitted. The production of concrete alone represents some 5% of man-made global CO2 emissions, and making 1kg of plastic from oil produces 6kg of the greenhouse gas.
3. Start with the carrots. These are being investigated by Mohamed Saafi at Lancaster
eco-friendly respectueux de l'environnement, écologique. 2. goods produits, articles, biens / to range from... to aller de... à / furniture (inv.) meubles, mobilier / aircraft (inv.) avion(s) / bonus ici, avantage / to lock up contenir (sans libérer), renfermer / global mondial / oil pétrole / greenhouse gas gas à effet de serre. 3. to investigate ici, étudier / University, in England. Dr Saafi and his colleagues do not use whole carrots, but rather what they call “nanoplatelets” that have been extracted from carrots discarded by supermarkets or as waste from foodprocessing factories. Sugar-beet peelings are also a useful source of nanoplatelets. The researchers are working with CelluComp, a British firm that produces such platelets for industrial applications, including as an additive that helps toughen the surface of paint as it dries.
A POWERFUL COMPOSITE
4. Each platelet is only a few millionths of a metre across. It consists of a sheet of stiff cellulose fibres. Although the fibres are minute, they are strong. By combining platelets whole entier / rather plutôt / platelet plaquette / to discard jeter / waste déchets / food processing transformation alimentaire, agro-alimentaire / sugar beet betterave à sucre / peelings épluchures, pelures / such ici, de telles / to toughen renforcer, solidifier, durcir / to dry sécher. 4. across de diamètre/large / sheet feuillet, plaquette, couche / stiff rigide / although bien que / minute infime, minuscule /
with other materials, a powerful composite can be produced. Dr Saafi is mixing the platelets into cement which is made by burning limestone and clay together at high temperature. (The chemical reaction between them releases carbon dioxide from the limestone.)
CARROT SOUP FOR STRONGER CONCRETE
5. To turn cement into concrete, it is mixed with aggregates such as sand, stones and crushed rocks, which act as reinforcement, and with water, which reacts with the chemicals in the cement to form a substance called calcium silicate hydrate. This starts off as a thick gel, but then hardens into a solid matrix that binds the aggregates together.
6. By adding vegetable platelets to the mix, Dr Saafi and his colleagues can make con-
into ici, à / limestone (roche) calcaire / clay argile / to release libérer. 5. to crush concasser / to act as agir en tant que, servir/faire office de / chemical substance/composé chimique / thick épais / to harden se durcir/solidifier / to bind, bound, bound lier. 6. mix mélange / to make, made, made ici, rendre / crete stronger. This is useful in itself, but it also permits a reduction in the ratio of cement to aggregates that is required to achieve a given level of strength. Reducing the amount of cement in this way consequently reduces CO2 emissions.
7. The group is still exploring exactly how strong it can make concrete by adding platelets, but initial studies suggest that the impact could be considerable. Just 500 grams of platelets can reduce the amount of cement needed to make a cubic metre of concrete by about 40kg—a saving of 10%. Dr Saafi and his team have now embarked on a two-year study to investigate the process in more detail and to perfect the best mix for use by the construction industry.
WOOD FIBRES IN PLASTIC GOODS
8. Unlike cement, wood is already a composite material. It is made of cellulose fibres embedded in a matrix of lignin, an organic polymer that serves a number of purposes, including providing woody plants with their rigidity. In May, Stora Enso, a Finnish forestry-products company, launched a wood-derived alternative to oil-based plastics.
9. This material, called DuraSense, looks a bit like popcorn. It consists of wood fibres, including lignin, obtained from pulping and other operations. The fibres are mixed with oil-based polymers and other additives, such as colouring agents. The resulting granules can be melted and moulded in the same way as plastic is in factory processes. Adding wood fibres, the company says, can reduce the amount of plastic needed to make goods with plastic parts by 60%. to achieve parvenir à, atteindre, obtenir / amount quantité / way façon. 7. to explore ici, étudier / about environ / saving ici, réduction / to embark on se lancer dans, entamer / process processus, mécanisme, fonctionnement. 8. unlike contrairement à, à la différence de / to be embedded in être fixé à, faire partie intégrante de / a number of plusieurs / purpose fin, utilité / to provide sth with ici, assurer/garantir à qch / woody plant plante ligneuse (dont la structure repose principalement sur le bois) / Finnish finlandais / forestry- ici, dérivé du bois / to launch lancer (sur le marché). 9. to look like ressembler à (visuellement) / to pulp ici, transformer en pâte / to melt fondre / to mould mouler, modeler, façonner / part pièce (détachée), composant.
Plant fibres can add durability and strength to substances already used in the construction of buildings.