https://www.engr.psu.edu/ce/courses/ce584/concrete/library/materials/History/DevelopementofPC-main.html

That's dumb and it is patently incorrect. 

The study discusses using coffee to replace some of the sand. It would lower the amount of sand needed and that would be significant. 

Cje95

It's incorrect that they would replace sand with coffee. That's dumb. It's the fly ash that they would replace. Sand is the finer aggregate that needs to fill the void between the larger aggregate of rocks.

Construction_and_Engineering

Scientists Discovered An Amazing Practical Use For Your Leftover Coffee Grounds

It's incorrect that they would replace sand with coffee. That's dumb. It's the fly ash that they would replace. Sand is the finer aggregate that needs to fill the void between the larger aggregate of rocks. 