ABSTRACT
Once quality materials have been selected, as discussed in Chapter 5, it is necessary to design a concrete mixture for the project that will meet the requirements for fresh and hardened concrete properties, while keeping economy in mind. The concrete must meet project requirements in both the fresh and hardened state. In the fresh state, the chief characteristic is workability. In the hardened state, requirements for strength and durability must be met. If the fresh concrete properties are not satisfactory, the concrete will not be placed, consolidated, and finished properly, and the hardened properties will not matter. The most commonly used method for proportioning concrete mixtures
is the ACI Committee 211 Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete, 211.1-91 absolute volume method (ACI 211 1991). This method is discussed in Chapter 10 of Mindess et al. (2003: 221-242) and Chapter 9 of Kosmatka et al. (2002: 149-177). This procedure uses the following steps (Mindess et al. 2003: 227-236):
• Assemble the required information. This includes: sieve analysis (gradation distribution) of coarse and fine aggregates; dry rodded unit weight of coarse aggregate; bulk specific gravities and absorption capacities of coarse and fine
aggregates; slab thickness (since the maximum coarse aggregate size must be
less than or equal to one-third of the least dimension); w required strength; exposure conditions.
