Engineers Discovered the Spectacular Secret to Making 17x Stronger Cement
(www.popularmechanics.com)
Yes, I didn't read the article.
Having now read it, I was a bit concerned that they were going to be harvesting mother of pearl in some horrendous twist of "we can use less concrete! But we have to industrialise the harvesting of molluscs".
Thankfully it's the micro-pattern in polymers inspired by nature.