Aci Concrete Mix Design
¨The most common method used in North America is established by American Concrete Institute.
A good mix design must be capable of being placed & compacted with minimal bleeding & segregation & be finishable.
Strength & Durability
¨Possible requirements for resistance to freeze-thaw and chemical attack must be considered.
Required material information
Sieve analyses of both fine and coarse aggregates, unit weight, specific gravities, and absorption capacities of aggregates.
Choice of slump —
Generally specified for a particular job. However, if not given, an appropriate value may be chosen from Table 1. As a general rule, the lowest slump that will permit adequate placement should be selected.¨Once the water content and the w/c ratio is determined, the amount of cement per unit volume of the concrete is found by dividing the estimated water content by the w/c ratio.
¨weight of cement = weight of water /(w /c)
¨However, a minimum cement content is required to ensure good finishability, workability, and strength.
Adjustment for moisture in the aggregate.
¨Decrease/Increase the amount of water required by surface moisture content of the weight of the fine aggregate