Concrete carbon emissions can be reduced with visualization technique
Concrete can be made more durable by using a new method to visualize the reaction with water during mixing.
Cement in concrete contributes about eight percent of the world’s total carbon dioxide emissions, dwarfing the emissions of most individual countries.
With a better understanding of cement chemistry, scientists could potentially “change production or change ingredients so that concrete has less impact on emissions, or add ingredients that are able to actively absorb carbon dioxide,” said Professor Admir Masic, an expert in civil engineering.
Technic. engineering at MIT. The team developed a technique called Raman microspectroscopy to view the specific and dynamic chemical reactions that take place when water and cement mix.
Raman spectroscopy creates images by shining high-intensity laser light onto material and measuring the intensities and wavelengths of the light as it is scattered by its molecules.
Different molecules and molecular bonds have their own unique scattering “fingerprints,” so the technique can be used to create chemical images of molecular structures and dynamic chemical reactions in a material.
The MIT researchers used it to observe a sample of ordinary Portland cement placed under water without disturbing it or artificially stopping the hydration process, mimicking the real-life conditions of concrete use.
One of the hydration products (portlandite) usually starts out as a disordered phase, seeps through the material and then crystallizes, the researchers concluded.
Before that, “scientists could study cement hydration only with medium bulk properties or with a single time point snapshot,” said Hyun-Chae Loh, a doctoral student and first author on the study.
“But this allowed us to observe all the changes almost continuously and improve the resolution of our image in space and time.”
Their work could help researchers experiment with new additives and other methods to reduce greenhouse gas emissions from concrete.
“Knowing when the concrete will set is the most critical question everyone in the industry is trying to understand,” Loh said. “We do a lot of trial and error to optimize a design.
But monitoring the underlying chemistry in space and time is critical, and this science-backed innovation will impact the concrete printing capabilities of the construction industry.
” Next-generation technologies, such as 3D printing of concrete, could also benefit from the study’s new imaging technique, the team suggests.