Introduction: Standard Test Method for Density (unit weight), Yield, and Air Content (Gravimetric) of Concrete –Apparatus –Sample –Procedure 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 i.e. air meter bowl - 10#s for.25 cft.- 40#s (Range of use) - 50#s 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. 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. 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. ACI Certification –Section 4 [ASTM C138]

Apparatus Mallet – A mallet (with a rubber or rawhide head) having a mass of 1.25±0.50lb for use with measures of 0.5 cft or smaller –Mass of 2.25±0.50lb for greater than 0.5 cft. ACI Certification –Section 4 [ASTM C138]

Sample ASTM C172 – 1” nominal max size aggregate –0.2 cft capacity measure ACI Certification –Section 4 [ASTM C138]

Procedure Rod for slumps > 3” Rod or vibrate bet.1”-3” Vibrate < 1” ACI Certification –Section 4 [ASTM C138]

Procedure Rod 25 times <= 0.5 cft Rod 50 times = 1 cft Rod 1 per 3sqin. > 1cft Rod bottom layer not touching the bottom of pale For two top layers penetrate 1 in. into layer below ACI Certification –Section 4 [ASTM C138]

Procedure –After each layer is rodded, tap the sides times –The force should close voids and release air bubble from mix –Add the final layer so as to avoid overfilling 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 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 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 ACI Certification –Section 4 [ASTM C138]