Ingredient Proportions

The ingredient proportions for the concrete on a particular job are usually set forth in the specifications under CONCRETE – General Requirements. See Table 4 for examples of normal concrete mix design and the number of bags of cement used in the mixing specifications.

In Table 4, one of the formulas for 3,000 psi concrete is 5.80 bags of cement per cubic yard, 233 pounds of sand (per bag of cement), 297 pounds of coarse aggregate (per bag of cement), and a water-cement ratio of 6.75 gallons of water to each bag of cement. These proportions are based on the assumption that the inert ingredients are in a saturated surface dry condition, meaning that they contain all the water they are capable of absorbing, but no additional free water over and above this amount.