One of the most crucial aspects of environmental awareness is understanding how it is not just one area of our modern ways of living that needs to be changed; it’s a whole myriad of different industries, sectors, and systems that need to be changed. These different systems play into each other and rely on each other to function.
This means that many changes in different areas must be made to reduce the total carbon output to our atmosphere for example. Some areas contribute more than others, though; one of these industries is concrete manufacturing. Making concrete produces large amounts of carbon dioxide as a chemical byproduct of manufacturing and the energy required to produce it. Every year, about 8% of the total carbon dioxide emissions into our atmosphere are represented by concrete. However, potential change is on the horizon as MIT researchers have discovered new additives for concrete, making it more mechanically sound and green.
Roughly half of the emissions associated with concrete manufacturing come from burning fossil fuels to heat up the mixture of limestone and clay that ultimately is turned into ordinary Portland cement. While the energy provided could be substituted by renewable energy sources like wind and solar, the other half of the emissions are inherent to the material itself. As the mixture is heated, the calcium carbonate and clay are turned into a mixture of clinker (mainly calcium silicates) and carbon dioxide, which is then released into the air.
This is in spite of the fact that cured concrete has the potential to sequester carbon in itself; however, this is a problem for the material’s mechanical performance. As carbonation occurs in the late stage, over decades, it lowers the internal alkalinity of the concrete. It weakens it accelerating the corrosion of the rebar and reducing the load-bearing capacity of the concrete. The new process discovered by the researchers calls for adding sodium bicarbonate, also known as baking soda. It can mineralize up to 15% of the carbon dioxide emitted by the manufacturing process into the material in the early stages of production.
This method also does not impact the mechanical properties of concrete and actually benefits the construction industry in other ways. This new concrete sets significantly quicker than conventional concrete, meaning that structures like buildings and bridges could be built significantly faster than before. This is combined with new research into Roman concrete, which was created using chunks of calcium carbonate. These chunks were initially thought to be a result of poor mixing techniques, but it might have been intentional; it has been found that the calcium carbonate actually acts as a self-healing mechanism, as when water comes into contact with the calcium carbonate, it creates new concrete that seeps into the cracks created by the aging process.
When thinking about the materials we use globally to create, it’s vital to remember that what we use and how we use it has consequences outside of what is immediately recognizable. Concrete has been and continues to be one of the most widely used and cheapest available materials to build with. It is unreasonable to propose that we ban concrete and go back to building only stick and timber buildings, as much as it is unreasonable to ban cars and go back to horses and buggies.
However, the research shows that we can change the material to suit the new green world we are transitioning to while retaining the same properties that have made concrete such a widely used and praised building material. While the research is still in its beginning stages, what has been published is incredibly promising. Green concrete is no longer just a fantasy; it is fast becoming a reality. A reality that could very well be industry standard within our lifetimes.