Science Corner: What Makes Toothpaste And Cement Become Solid Over Time?

Have you ever wondered why toothpaste and cement can turn into a solid material after a period of time exposed to the air?

This is totally an intriguing question; however, the answer that can explain what is making these pastes’ structures to change has not been verified.

With the aspiration for finding a plausible key to this phenomenon, an international group, comprised of a team from the Ecole des Ponts as well as the Université Paris-Est in France and a professor from the University of Delaware, has been working on the solidification of toothpaste and cement and eventually had their exact answer, which was publicized in Nature Materials.

These paste materials are also known as ‘dense colloidal suspensions’, which can become hard when time flies. This change partly stems from the structural dynamics or their adjustment of loads under a period of time. However, it took scientists many years to finally understand what exactly led to the transformation of these pastes. 

It was explored that there exists another process that is called contact-controlled aging is happening in these materials. This process helps the global team to fully understand the age-related changes inside the pastes. 

>>> Sniffing Your Partner's Fart Can Reduce Aging, Study Shows

They found some connections between particles in the paste that can stabilize their microstructure in the end. After that, these contacts solidify and make the whole material become a hard one. 

Based on the explanation provided by Professor Eric Furst from the University of Deleware, the mechanism of these pastes has been overwhelmed by changes in the material’s organization or microstructure when it is regarded as an aging process in materials, especially in rheology or the study of how things operate.

This finding is considered as a very useful exploration of the century. It will apparently help those who have to work with these pastes to create better ways to estimate and minimize unexpected changes as they age. The materials mentioned should include cement, clays, soils, inks, and so on - common materials used in many industries all over the world. 

>>> Man Broke Into Museum Amid COVID-19 To Take Selfies With Dinosaurs