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.
(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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