Could nano-engineered concrete cut CO2 emissions?
مطلبی که میخوانید مربوط به كاهش انتشار CO2 ناشي از ساخت سيمان با كمك فناورينانو میباشد که بزودی متن فارسی آنرا در وبلاگ قرار خواهم داد.
Could nano-engineered concrete cut CO2 emissions?
Studying the nanostructure of concrete could help reduce carbon dioxide (CO2) emissions during its manufacture, according to work by engineers at the Massachusetts Institute of Technology (MIT). Around 2.35 billion tons of concrete are produced each year and producing cement, the main component of concrete, accounts for 5–10% of the world's total CO2 emissions – an important contribution to global warming.
Franz-Josef Ulm and Georgios Constantinides of MIT have found that concrete is strong and durable thanks to the way in which the nanoparticles making up the material are organized. "If everything depends on the organizational structure of the nanoparticles that make up concrete, rather than on the material itself, we can conceivably replace it with a material that has concrete's other characteristics – strength, durability, mass availability and low cost – but does not release as much CO2 into the atmosphere during manufacture," explains Ulm.
Cement is the oldest engineered construction material in the world, dating back to Roman times or earlier. It is made by crushing its constituents, limestone and clay, to a powder and heating them to temperatures of around 1500 °C. At these high temperatures, the material undergoes a transformation and energy is stored in the powder – the process in which most of the CO2 is emitted. When the powder is then mixed with water, the energy is released into chemical bonds to form the elementary building blocks of cement: calcium-silicate-hydrate (C-S-H).
The MIT engineers studied a wide range of cement pastes from around the world using a novel nano-indentation technique that involves probing hardened cement paste with a nano-sized needle. An atomic force microscope then allowed them to calculate the nanostructure and strength of each paste by measuring the indentations created by the needle. This technique has been used on homogenous materials before now but never on a heterogeneous material, such as cement.
The researchers say that world CO2 emissions could be cut by up to as much as 10% if scientists could find, or nano-engineer, different minerals to use in cement paste. Such minerals would have the same packing density of cement but would not need the same high temperatures to produce.
The team reported its work in the Journal of the Mechanics and Physics of Solids.www.mh.coo.ir
0 نظرات:
ارسال یک نظر