2021-06-10

MIT scientists introduce the observation plan of concrete hydration process based on Raman spectroscopy

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MIT scientists introduce the observation plan of concrete hydration process based on Raman spectroscopy

Molecular scale observation/visualization of concrete hydration (picture from: MIT)

As shown in the picture above It shows that during hydration, white tricalcium silicate (alite) forms blue hydrated calcium silicate (CSH) and red silicate (portlandite). The remaining green part is belite, while the yellow part is calcite.

With the support of Raman imaging technology with high temporal and spatial resolution, researchers are expected to answer the historical questions about cement chemistry that have lasted for thousands of years, and help them find ways to make concrete more sustainable Sexual approach.

The research co-author, Franz-Josef Ulm, a faculty member of the MIT Center for Sustainable Concrete Development and a professor of civil and environmental engineering at the school, said that this research can be described as “the Lumiere in the field of concrete science.” Brother Moment”.

It is reported that the brothers used a video camera to take the world’s first (black and white) movie. And this new research by MIT brings us a glimpse of the early cement hydration process (comparable to the birth of color films).

MIT scientists introduce the observation plan of concrete hydration process based on Raman spectroscopy(1)

Researchers pointed out that the cement used in concrete , Which accounts for about 8% of the total global carbon dioxide emissions, which is already comparable to the emissions produced by most countries. Associate Professor of Civil and Architecture Admir Masic explained:

“With the in-depth understanding of the chemical properties of cement, scientists will be able to improve the production process or formula composition, so that the concrete produces less emissions, or add Other ingredients that can actively absorb carbon dioxide”.

As a materials scientist at Black Buffalo 3D, Hyun-Chae Chad Loh, a graduate student in Masic’s laboratory, added: Next-generation technologies such as concrete 3D printing are also expected to benefit from the new results of this imaging technology. Benefit.

MIT scientists introduce the observation plan of concrete hydration process based on Raman spectroscopy(2)

To achieve this goal, Loh and his Colleagues used a technique called “Raman microscopic spectroscopy” to carefully observe the dynamic process of specific chemical reactions that occur during concrete hydration.

Raman spectroscopy needs to irradiate a high-intensity laser onto a material, and measure its intensity and wavelength when it is scattered by the molecules of the material to create a special image.

Because different molecules and molecular bonds have their own unique scattering “fingerprints”, this technology can also be used to create images of the internal molecular structure and dynamic chemical reactions of materials.

Previously, this technology was often used to characterize materials in the field of biology and archaeology, just as Masic had done in the study of nacre and other biomineralized materials, as well as ancient Roman concrete.

During the study, MIT scientists used this device to observe an ordinary concrete sample placed under water. During the period, efforts were made to simulate the real-world environmental conditions and did not interfere with or artificially stop the hydration process.

The team concluded: Under normal circumstances, the hydration process of concrete is The disordered phase of the hydration product called silicate begins, after which it penetrates the entire material and crystallizes.

Previously, scientists could only study concrete hydration snapshots with average volume characteristics or at a certain time node. But with the blessing of new technology, they were able to observe all changes almost continuously, and improved their image resolution on time and space scales.