Standard Test Method for Density (unit weight), Yield, and Air Content (Gravimetric) of Concrete

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ACI Certification Section 4 ASTM C138

• Introduction
• Standard Test Method for Density (unit weight),
  Yield, and Air Content (Gravimetric) of Concrete
• Apparatus
• Sample
• Procedure

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ACI Certification Section 4 ASTM C138

• Apparatus
• Balance
• 0.1 lbs accuracy or within 0.3 of the test load
• Whichever is greater at any point within the
  range of use.
• Range of use shall be from mass of the measure
  empty to measure plus contents _at_160/cft
• i.e. air meter bowl - 10s
• concrete_at_160/cft for .25 cft.- 40s
• (Range of use) - 50s

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ACI Certification Section 4 ASTM C138

• Apparatus
• Tamping Rod
• A round ,Straight Steel Rod, 5/8 inch dia.
• 24 in. in length
• Tamping end rounded to a hemispherical tip 5/8
  in.

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ACI Certification Section 4 ASTM C138

• Apparatus
• Internal Vibrator
• 7000 vibrations per min.or more
• Outside dimension 0.75in and less than 1.50in.
• The length of the shaft shall be at least 24 in.

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ACI Certification Section 4 ASTM C138

• Apparatus
• Strike-off Plate
• A flat rectangular metal plate at least ¼ in.
  thick or a glass or acrylic plate at least ½ in.
  thick with a length and width at least 2in.
  Greater than the diameter of the measure with
  which it is to be used.

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ACI Certification Section 4 ASTM C138

• Apparatus
• Mallet
• A mallet (with a rubber or rawhide head) having
  a mass of 1.250.50lb for use with measures of
  0.5 cft or smaller
• Mass of 2.250.50lb for greater than 0.5 cft.

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ACI Certification Section 4 ASTM C138

• Sample
• ASTM C172
• 1 nominal max size aggregate
• 0.2 cft capacity measure

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ACI Certification Section 4 ASTM C138

• Procedure
• Rod for slumps gt 3
• Rod or vibrate bet.1-3
• Vibrate lt 1

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ACI Certification Section 4 ASTM C138

• Procedure
• Rod 25 times lt 0.5 cft
• Rod 50 times 1 cft
• Rod 1 per 3sqin. gt 1cft
• Rod bottom layer not touching the bottom of pale
• For two top layers penetrate 1 in. into layer
  below

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ACI Certification Section 4 ASTM C138

• Procedure
• After each layer is rodded, tap the sides 10-15
  times
• The force should close voids and release air
  bubble from mix
• Add the final layer so as to avoid overfilling

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ACI Certification Section 4 ASTM C138

• Procedure
• Fill and vibrate the measure in two approximately
  equal layers
• Do not allow vibrator to touch or rest on bottom
  or sides during bottom layer vibrating
• When vibrating final layer, penetrate only 1 inch
  into layer below.
• No air pockets should be left in mix when
  withdrawing vibrator
• Continue vibration until proper consolidation is
  achieved

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ACI Certification Section 4 ASTM C138

• Procedure
• Concrete must not contain a substantial excess or
  deficiency of concrete
• An excess of concrete protruding approx 1/8 in.
  above the top of the mold
• A small quantity of conc. May be added to correct
  the dificiency
• If there is an excess, remove with a scoop or
  trowel immediately after consolidation but before
  struck -off

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ACI Certification Section 4 ASTM C138

• Procedure
• Strike-off should be pressed on top of surface
  about 2/3 of the surface and withdrawing the
  plate in a sawing motion to finish area
  originally covered
• The place the plate on the top of the measure to
  cover the original 2/3 of the surface and advance
  it with a vertical pressure and sawing motion
  until it slides of the edge
• Several final strokes with the inclined edge of
  the plate will produce a smooth finished surface
• After the strike-off, clean all excess concrete
  from exterior measure and determine mass