# ACI Method of Mix Design Outline

The most common method used in North America is that established by ACI Recommended Practice 211.1

Any mix design procedure will provide a first approximation of the proportions and must be checked by trial batches

Local characteristics in materials should be considered

The following sequence of steps should be followed:

(1) determine the job parameters – aggregate properties, maximum aggregate size, slump, w/c ratio, admixtures,

(2) calculation of batch weight, and

(3) adjustments to batch weights based on trial mix.

Water/cement ratio (w/c ratio) theory states that for a given combination of materials and as long as workable consistency is obtained, the strength of concrete at a

given age depends on the w/c ratio

The lower the w/c ratio, the higher the concrete strength.

Whereas strength depends on the w/c ratio, economy depends on the percentage of aggregate present that would still give a workable mix.

The aim of the designer should always be to get concrete mixtures of optimum strength at minimum cement content and acceptable workability.

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