Concrete is the most commonly used building material in the world, but unfortunately the cement used to make it carries quite a carbon footprint. Now, scientists at the University of Tokyo have created a cement-free alternative that directly bonds sand particles together using a reaction between alcohol and a catalyst.
Concrete is made up of an aggregate material, usually sand and gravel, and cement, which acts like glue to hold it all together.
Portland cement is the most common type, but making it is a pretty environmentally unfriendly affair – between the high heating temperatures and the limestone outgassing, about 1 kg (2.2 lb) of carbon dioxide is produced for every kilogram of cement. Considering just how much of the material is made every year, cement production accounts for around eight percent of global CO2 emissions.
With that in mind, scientists are working on greener alternatives, most commonly substituting the cement for waste materials like fly ash or steel slag. But for the new study, the researchers developed a new recipe that directly bonds the sand particles together.
“Researchers can produce tetraalkoxysilane from sand through a reaction with alcohol and a catalyst by removing water, which is a byproduct of the reaction,” says Yuya Sakai, lead author of the study. “Our idea was to leave the water to shift the reaction back and forth from sand to tetraalkoxysilane, to bond the sand particles with each other.