In 1991,the American Concrete Institute(ACI) published guidaelines for normal, heavyweight and mass concrete mix design. The absolute volume method of mix design as described by ACI committee 211 is presented.
ACI Method Of Concrete Mix Design
It has the advantages of simplicity that it:
Applies equally well with more or less identical procedure to rounded or angular aggregate.
To regular or light weight aggregates.
To air entrained or non-air-entrained concretes.
ACI 211
A Properly Proportioned Concrete Mix Should Posses These Qualities.
Acceptable Workability of Freshly Mixed Concrete
Durability, Strength and Uniform Appearance of the Hardened Concrete
Economy
DATA REQUIRED
Class of concrete to be designed.
Fine aggregate:
Specific gravity
Fineness modulus
Coarse aggregate:
Maximum size aggregate
Specific Gravity
Unit Weight (dry rodded unit weight)
From Code Specifications:
Cement factor (minimum cement content).
W/C ratio (maximum W/C ratio)
Air content (mean air content).
Nominal Maximum size of aggregate.
The standard ACI mix design procedure can be divided into 9 basic steps:
Compressive strength.
Water cement ratio.
Air content selection.
Choice of slump
Water content selection.
Cement content
Coarse aggregate content.
Fine aggregate content.
Adjustments for aggregate moisture
Dry Weights vs. Actual Weights
Batch weights calculated from volumes assume dry CA and dry FA.
Actual weight of CA and FA are NOT dry
Adjustment based on moisture contents for both CA and FA.
Correction for the water content is must.
CONCLUSION
The mix proportions for the actual materials to be used must be checked and adjusted by means of laboratory trials consisting of small batches.Fresh concrete should be tested for slump, workability, unit weight and air content; specimens of hardened concrete cured under standard conditions should be tested for strength at the specified age.
ACI Method Of Concrete Mix Design
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