Cementless concrete holds potential for decarbonization and lunar buildings

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Researchers from the University of Tokyo have developed a new method of producing concrete without cement. Their technique offers the construction industry a way to reduce carbon emissions, as well as the potential for construction on the Moon and Mars.

Concrete consists of two parts: an aggregate (usually composed of sand and gravel) and cement. Cement is estimated to be associated with 8% of global carbon emissions, making it difficult for the construction industry to reduce its impact on the climate. Another problem facing the industry is the limited availability of sand suitable for the production of concrete, which must have a specific particle size distribution to provide the correct properties.

“In concrete, cement is used to bind sand and gravel together,” said study lead author Yuya Sakai. “Some researchers are investigating how more cement can be replaced with other materials, such as fly ash and blast furnace slag, to reduce CO2 emissions, but this approach is not sustainable as the supply of these materials is dwindling due to reduced use of thermal energy systems and increased use of steel from electric furnaces.

A new approach will be needed to produce concrete from more abundant materials with less environmental impact. “Researchers can produce tetraalkoxysilane from sand through a reaction with alcohol and a catalyst by removing water, which is a byproduct of the reaction,” Sakai said. “Our idea was to let the water move the reaction back and forth from the sand to the tetraalkoxysilane, to bind the sand particles together.

The researchers placed a copper foil cup in a reaction vessel with sand and other materials. They varied the reaction conditions (such as the amount of each material, the heating temperature and the reaction time) to find the right conditions to obtain a sufficiently strong product.

The product is likely to have greater durability than conventional concrete due to the absence of cement paste, which is relatively weak against chemical attack and undergoes growth and contraction with changes in temperature and humidity. humidity.

Ahmad Farahani, second author of the study, said: “We obtained sufficiently strong products with, for example, silica sand, glass beads, desert sand and simulated moon sand. These discoveries can support a move towards a greener and more economical construction industry everywhere on Earth. Our technique does not require specific sand particles used in conventional construction; it will also help solve the problems of climate change and spatial development.

It is hoped that – since it does not require the specific type of sand required in conventional construction – this technique could help solve climatic problems and provide a potential means of constructing buildings in desert regions and even on the Moon and Mars.

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