20-07-2012, 04:23 PM
ACI Mix Design
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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
ACI Mix Design
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.
ACI