1. 72
Name: ROSAROS, KENT ARNEL T. Student Number: 20180125966
Activity No. 8
Unit Weight, Yield, and Air Content (Gravimetric) of Concrete
Reference:
AASHTO T 121-97, ASTM C 138-92
Objective:
To determine the unit weight, yield and air content of freshly mixed concrete.
Data/Calculation:
Calculate the unit weight of concrete, W, by dividing the net weight by the
volume of the measure used.
Calculate the yields as follows:
W
W
m
Y l
=
)
( 3
(19-1)
Calculate the air content as follows:
  units)
(SI
100
)
( x
Y
V
Y
A −
= (19-2)
Where:
W = unit weight of concrete, kg/m3
V = total absolute volume of the component ingredients in the batch, m3
Wl = total weight of all materials batched, kg
Y = volume of concrete produced per batch, m3

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Computation:
Empty mass of container, kg 3.55
Mass of container with concrete, kg 20.49
Volume of container, m3
0.0071
Density, kg/m3
2385.915
Unit weight, kN/m3
23.406
Total batch weights, kg 2,384
Yield, m3
1
Discussion/Conclusion:
Mass of concrete = Mass of container with concrete – Empty mass of container Mass of
concrete = 20.49 – 3.55 = 16.94 kg
Density = Mass / Volume of Container = 16.94 kg / 0.0071 m3 = 2385.915 kg/m3
Unit Weight (kN/m3 ) = Density x Acceleration due to Gravity x 1/1000
Unit Weight (kN/m3 ) = 2385.915 kg/m3 x 9.81m/s2 x 1/1000 = 23.406 kN/m3
Yield = Total weight of all materials batched / unit weight of concrete
Yield = 2384 kg / 2385.915 kg/m3 = 0.999 m3 ≈ 1 m
Air content = [(yield – volume)/yield] x 100
Ari content = [(1-0.0071)/1] x 100 = 99.29