The production of cement is a major source of carbon emissions, so the less of it that's used, the better. A new study could help, as it shows that cement can be made much stronger with the addition of material derived from waste shrimp shells.
Led by Assoc. Prof. Somayeh Nassiri, scientists from Washington State University and Pacific Northwest National Laboratory started by extracting a compound known as chitin from shrimp shells that would otherwise have been discarded.
Chitin is the world's second-most abundant natural biopolymer (after cellulose), and is found in the shells of various crustaceans. Among other things, it has recently been used in the production of compostable food wrap, mosquito-killing nanoparticles, and an antibacterial coating.
In this latest study, the researchers obtained chitin nanocrystals and nanofibers, each one of which was about one one-thousandth the width of a human hair. When these were added to conventional cement paste at a .05 weight percentage, the resulting hardened cement was up to 40 percent stronger when bent, and 12 percent stronger when compressed.
Additionally, as compared to regular cement, it took about one hour longer to set. This is actually a desirable quality in some scenarios, such as when wet, premixed concrete is being transported long distances to construction sites. The longer setting time is likely due to the fact that the chitin fibers and crystals repel individual cement particles, changing their hydration properties.
More research still needs to be conducted – in particular, the scientists want to see how the cement affects the performance of concrete in which it's used. Ultimately, it is hoped that by making cement stronger, less cement would have to be used, reducing the construction industry's carbon footprint.
A paper on the study was recently published in the journal Cement and Concrete Composites.
Source: Washington State University
