Limestone and clay are combined to make cement, which is then crushed up after being heated to extremely high temperatures. Around 8% of the world's CO2 emissions originate from the production of cement, which is one of the factors contributing to greenhouse gas emissions.
Because of this, low-carbon cement will be required to pave the way to net zero. A study group at Rice University may have a partial solution.
Chemist James Tour and his team began their research with fly ash, a fine-grained residue produced by coal-fired power plants that are commonly used in concrete mixtures.
They utilized a technique called flash Joule heating, which involves passing an electric current through carbon-containing materials to rapidly heat them to approximately 3,000 degrees Celsius within milliseconds, to extract harmful heavy metals from the fly ash.
This approach is significantly more energy-efficient compared to traditional methods resulting in purified fly ash being subsequently incorporated into cement.
In a recent study, the researchers discovered that a batch of concrete became significantly stronger and more elastic when 30% of the cement was replaced with purified coal fly ash.
Additionally, it decreased emissions of heavy metals and glasshouse gases by 40% and 30%, respectively. This is because the process requires less energy and allows for the absorption of vapourised heavy metals before they are released into the atmosphere.
Any strategy to get net zero must incorporate cement due to its widespread use, which is one of the factors driving the intense interest in enhancing its sustainability. Recent advancements in this field include the use of non-recyclable plastic trash to make lightweight concrete blocks and carbon-negative Portland cement.