Coffee grounds offer performance boost for concrete
https://techxplore.com/news/2023-08-coffee-grounds-boost-concrete.html
I wish they explained a bit more about how coffee grounds do this. Maybe its the nitrogen?
During WWII the UK & Canada were considering making giant aircraft carriers made from ice and wood pulp, apparently adding wood pulp to ice makes it much stronger.
https://en.wikipedia.org/wiki/Project_Habakkuk