We made it to the front page of https://www.thingiverse.com/ - congrats, team π
My plan for the next concrete mix. https://tun.sika.com/dms/getdocument.get/a8b219c4-161c-44d6-b310-b7932fb5eb68/sikagrout-234.pdf - said to be resistant to shock and vibration, allows for small gravel to be added for volume, 70MPa