Coffee Grounds make Concrete Stronger when ...

Okay, this is too good to miss; I have to post it. Scientists in Australia took a different approach to adding waste coffee grounds to concrete ...

Previous studies have looked at using SCG as a replacement for fine aggregate (also known as sand) in the making of concrete, but it was generally found to decrease the strength of the finished product.

The solution the scientists hit upon was to heat the SCG in an oxygen-free environment (a process called pyrolysis), breaking down some of its organic components and converting it into activated carbon.

In that form, the grounds were found to actually increase the strength of the finished concrete.

https://nationalpost.com/news/coffee-grounds-concrete

EDIT:
Well shoot, it's the same study noted here: https://permies.com/t/224264/Coffee-Grounds-Biochar-Strengthens-Concrete

The only thing new here is that ... once again ... pyrolysis and biochar are finding their way into mainstream media.

Albert Bates, who is a permaculturalist in Tennessee, wrote about many uses of biochar in his book, "Burn".  Making concrete stronger was one of the uses, but there were a whole bunch of them.

John S
PDX OR