Mixture proportioning is more critical for high-strength concrete than for normal-strength concrete. High strength concrete is defined as concrete that has a specified compressive strength f'c of 6000 psi or greater. When proportioning high-strength concrete mixtures, the basic considerations are to determine the ingredient quantities required to produce a concrete with the desired plastic properties (such as workability and finishability) and hardened properties (such as strength and durability) at the lowest cost. Before starting the proportioning, review project specifications. The procedure described in ACI 211.1, "Standard Practice for Selecting Proportions for Normal, Heavy Weight and Mass Concrete," for proportioning normal-strength concrete is similar to that required for high-strength concrete. The following steps should result in a set of adjusted high-strength concrete laboratory trial proportions. (1) Select slump and required concrete strength. (2) Select maximum aggregate size. (3) Select optimum coarse aggregate content. (4) Estimate mixing water and air contents. (5) Select w/c+p. (6) Calculate content of cementitious material. (6) Proportion basic mixture with no other cementitious material. (7) Proportion companion mixtures using fly ash. (8) Produce trial mixtures. (9) Adjust trial mixture proportions. (10) Select optimum mixture proportions.