Simple chemical reaction creates ecofriendly concrete
Siobhan Treacy | April 15, 2021Researchers from the University of Tokyo created a new method that can produce concrete without harmful materials and chemicals.
To synthesize the new concrete the team directly bonded sand particles using a simple chemical reaction in alcohol with a catalyst. This process could slash carbon emissions and be the key to constructing buildings and structures on the moon or Mars.
Concrete is made of two parts. The first is an aggregate, which is typically made of sand or gravel. The second part is cement which is responsible for 8% of the total global carbon dioxide emissions. The availability of the sand used to create concrete is limited because the sand particles need to be a specific size distribution to provide flowability to concrete. Cement is used to bind sand and gravel.Researchers at the Institute of Industrial Science at The University of Tokyo examined a new method of producing concrete via direct bonding of sand particles, which may help reduce greenhouse emission. Source: Institute of Industrial Science, the University of Tokyo
Researchers have been looking to replace cement with other materials, like fly ash, but these are unsustainable because of their decreasing supply. The team set out to create concrete from inexhaustible materials with a lighter environmental load.
Tertraalkoxysilane can be produced from sand through a chemical reaction with alcohol and a catalyst by removing water, which is a by-product of the reaction. The team built on this idea by leaving the water to shift the reaction back and forth from sand to teraalkoxysilane to bond sand particles with each other. A cup made of copper foil was placed in a reaction vessel with sand and other materials. Researchers systematically varied reaction conditions in the cup, including the amount of sand, alcohol, catalyst, dehydration agent, heating temperature and reaction time.
The right proportion of sand and chemicals is critical to creating a product with the right strength to be made into concrete. The products that were proven strong enough were silica sand, glass beads, desert sand and simulated moon sand. The new product is likely to have better durability than conventional concrete because cement paste is relatively weak against chemical attacks and has large volume changes due to temperature and humidity that is not included in the product.
A paper on the new concrete will be published in Seisan Kenkyu.