Concrete Without Cement?

November 3, 2021

Researchers from the Institute of Industrial Sciences, belonging to the University of Tokyo, have developed a new method to produce concrete without cement. They have directly bonded the sand particles through a simple reaction in alcohol with a catalyst. This can help both to reduce carbon emissions and to build buildings and structures in desert regions, even on the Moon or Mars.

Concrete is made up of two parts: aggregate (normally made of sand and gravel) and cement (responsible for 8% of total CO2 emissions in the world). Although there is an enormous amount of sand in the world, the availability of sand for concrete production is quite limited because the sand particles must have a specific size distribution to provide flowability to concrete.

“In concrete, cement is used to bind sand and gravel. Some researchers are studying how to substitute more cement for other materials, such as fly ash and blast furnace slag, to reduce CO2 emissions, but this approach is unsustainable because the supply of these materials is declining due to reduced use of blast furnace systems. thermal energy and increased use of steel from electric furnaces, ”explains lead author Yuya Sakai.

Therefore, a new approach is needed to produce concrete from inexhaustible materials with less environmental burden. ‘Researchers can produce tetraalkoxysilane from sand by reacting with alcohol and a catalyst removing water, which is a by-product of the reaction. Our idea was to leave the water for the reaction to pass from the sand to the tetraalkoxysilane, to bind the sand particles together. ‘

The researchers placed a copper foil beaker in a reaction vessel with sand and materials, and systematically varied the reaction conditions, such as the amounts of sand, alcohol, catalyst, and dehydrating agent; heating temperature and reaction time. Finding the right proportion of sand and chemicals was essential to obtain a product with sufficient resistance.

“We produced sufficiently strong products with, for example, silica sand, glass beads, desert sand and simulated moon sand,” says second author Ahmad Farahani. “These discoveries can advance the move towards a greener and more economical construction industry anywhere on Earth. Our technique does not require the specific sand particles used in conventional construction. This will also help address the problems of climate change and spatial development. ‘

In addition, the product is likely to have greater durability than conventional concrete because it does not include cement paste, which is relatively weak to chemical attack and exhibits large volume changes due to temperature and humidity.

Dr. Loony Davis5
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Born and raised in Brussels in an English family, I have always lived in a multicultural environment. After several work experiences in marketing and communication, I came to Smart Water Magazine, which I describe as the most exciting challenge of my career.
I am a person with great restlessness and curiosity to learn, discover what I do not know, as well as reinvent myself daily, someone who is curious about life and wants to know. I enjoy sharing knowledge.
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