Cement serves an adhesive role in the makeup of concrete. Without cement, the rest of the substances in the concrete will disintegrate under the tiniest pressure. However, manufacturing cement results in high carbon emissions, not to mention the fact that massive amounts of cement are used each year. Further compounding the issue is the irreplaceability of cement. However, students from the Institute of Industrial Science at the University of Tokyo recently had the idea of forming a cement-less concrete by bonding various aggregates together using the chemical reaction that results from mixing alcohol with catalysts.
Concrete is composed of, for the most part, water, cement, sands, and rocks – all of which are inexpensive materials found on earth in abundance. Of these materials, cement is responsible for bonding various aggregates and is manufactured from limestone and soil, both of which are likewise plentiful and cheap. It therefore makes sense that cement is the most used construction material in the world. Incidentally, while cement was invented more than a century ago, no suitable new materials have emerged to take its place.
However, manufacturing cement is a process with massive carbon footprint. For instance, producing one kilogram of cement also results in one kilogram of carbon dioxide as a waste byproduct. That is why the production of cement now accounts for about 8% of the global carbon emission. As climate change intensifies going forward, industries have begun to undertake energy transitions and carbon emission cuts, and various countries are not only requiring their electricity providers to reduce carbon footprints, but also gradually phasing out coal-burning facilities in favor of renewable energies, thereby placing further pressure on certain industries, including steel, chemical products, and construction materials, to cut down on carbon emissions.
Therefore, scientists have been hard at work looking for a suitable substitute for cement, such as using fly ash or blast furnace slag to reduce the amount of cements used in a given volume of concrete. However, students from the University of Tokyo took an approach diametrically opposed to conventional paradigms. They decided to leapfrog cement and investigate the possibility of bonding aggregates directly. The lead author of the investigation, Yuya Sakai, indicates that tetraalkoxysilane can be manufactured with the chemical reaction of dehydration resulting from mixing alcohol with certain catalysts.
The research team had the idea of creating a shift reaction between aggregates and tetraalkoxysilane once dehydrated, resulting in bonded aggregate particles. The investigators combined silica sand, alcohol, potassium hydroxide, and 2,2-dimethoxypropane in a copper container and heated the resultant mixture. After several tens of attempts with swapping out materials, changing the proportions of ingredients, adjusting the temperature, and adjusting the heating time, the investigators were ultimately able to create cement-less concrete.
Unfortunately, the resultant concrete falls far short of industrial requirements in terms of stress resistance. The new material could not even manage to pass a squeeze test done with bare hands – a far cry from traditional concretes with respect to strength and durability. As such, the research team has yet to conduct more stringent tests, as they are instead focusing on investigating additional ways of strengthening the cement-less concrete.
Even so, the team still believes their new material is not without merit, since it is still relatively more durable and more resistant to chemicals, temperatures, and humility, compared to a host of other materials. Furthermore, the new material is compatible with various aggregates, including sand particles of various sizes and other easily inflated materials. According to the research’s second author, Ahmad Farahani, products of acceptable strength levels can be manufactured from silica sands, marbles, desert sands, or simulated moon sand. This means that no specific sand is required to produce sufficiently strong concrete.
(Image: Institute of Industrial Science, the University of Tokyo)