Feb 15, 2020· A mixture of a very rigid concrete would use 1 part of cement, 3 parts of sand and 4 parts of gravel. A recipe for a more practical lot would be 1 part of cement, 2 parts of sand and 2 ¼ parts of gravel. Sag test. To adjust your mixing ratio for best results, perform a drop test on a test lot. Cut the bottom of a styrofoam cup.