Designing and Proportioning Normal Concrete Mixtures

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Designing and Proportioning Normal Concrete
Mixtures

• ACI 211

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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

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SLUMP

• Normally specified
• Choice based type of construction shown on Table
  9-6

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Slump
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WATER CONTENT

• Approximation based on slump, maximum size of the
  coarse aggregate, and type of concrete
  (air-entrained, or non air-entrained)- see Table
  9-5
• Air contents for AE concrete are normally
  specified but can also be determined by exposure
  conditions based on Table 9-5

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WATER-TO-CEMENT RATIO

• Concrete strength is specified by the design
  engineer.
• Based on specified concrete strength and type of
  concrete (AE or non AE) see Table 9-3.
• W/C ratio may be modified due to certain
  environmental conditionssee Tables 9-1 and 9-2.
• Concrete strength may also be modified due to
  special conditions-see Table 9-11

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Water/Cement Ratio
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Cementitious Content

• Cement Content Recommended water content (Table
  9-5) / the recommended water-to-cement ratio
  (Table 9-3 or 9-1 or 9-2)
• Cementitious Material Portland cement, fly ash,
  blast furnace slag, and silica fume.

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Coarse and Fine Aggregate Contents

• How much does 1 cy of portland cement concrete
  (PCC) weigh?
• What is the volume of 1 cy of PCC?

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COARSE AGGREGATE

• Coarse aggregate size specified
• Determination of VOLUME of CA recommended per
  unit volume of concrete
• Volume based on maximum size of CA and fineness
  modulus of sand Table 9-4
• Weight of CA volume of CA x dry rodded unit
  weight of CA x 27 cf.

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Volume Formulas

• Vol. of water wt. of water/62.4 pcf
• Volume of portland cement wt. of PC/(3.15 x
  62.4)
• Vol. of CA wt. of CA/(SG(ca) x 62.4)
• Volume of Air (Air content x 100)/27

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FINE AGGREGATE

• Fine Aggregate Content 27 cu. ft. - Volume of
  water - Volume of Cement - Volume of Coarse
  Aggregate Volume of Air
• Weight of FA volume of FA x specific gravity of
  FA x 62.4

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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.
• Dont forget about correcting for water content
  also.

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Trial Batch

• Slump should be within ¾-inch of maximum design
  value.
• Air content should be within 0.5 of maximum
  design value.
• Avg. required compressive strength (psi)
• _at_ 28 days must be equal to or greater than
• f(cr) f(c) 1.34S
• f(cr) f(c) 2.33S -500

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Mix Proportioning Absolute Volume Method
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Moisture
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Additions