Air Content of Concrete by Volumetric Method (ASTM C - 173)

 Air Content of Concrete by Volumetric Method

ASTM C - 173


Introduction

In this test, we will determine the air content in normal and heavy-weight concrete

If the air content increases 1% above the design value  the strength reduction will be 3 to 5%

Apparatus

Air Meter, Bowl diameter equal to 1 to 1.25 times, Capacity of bowl 0.075 cubic feet, Top section 20% larger than a bowl
Temping Rod, Hemispherical tip, diameter 16 + 2 mm, height 100 mm greater than the bowl

Isopropyl Alcohol,

Calibrated Cup,

Funnel,

Rubber Syringe,

Mallet,

Procedure

Dampen the bowl with water, fill the fresh concrete in the bowl with two equal layers

First Layer, fill the half bowl of its volume, rodding 25 times through its depth, and distribute over the cross-section, 10 to 15 times tap with the mallet outside of the bowl

Second Layer, fill the remaining bowl, rodding 25 times to penetrate the previous layer about 25 mm, and distribute over the cross-section, 10 to 15 times tap with the mallet outside of the bowl

Surface Leveling

Remove all excess concrete from the top of the bowl with a strike-off bar, and clean the exterior of the bowl 

Top Section Air Meter


Dampen the top section of the air meter from the inside, and attached it top of the bowl with a water-tight seal

Insert the funnel in the top section of the meter and fill the water with at least 0.5 liter

Select the amount of isopropyl alcohol from the given table



Continue adding water until it appears on the neck of the air meter

Remove the funnel and adjust the water level from the rubber syringe until the level is up to the zero mark on the scale

Attached is the cap, producing water tight seal

Shaking Process

quickly invert the meter shake the base and return to the upright position, do not invert the meter for more than 5 seconds

Repeat the shaking process minimum of 45 seconds or until the concrete free from the bottom of the bowl

Using the hand to rotate the meter vigorously, quickly starting and stop the meter several times

Turn the base and repeat the rolling process for about 1 minute, while listening to the aggregate sliding in the meter

Liquid Level

Set the meter upright position and loosen the cap to allow the liquid level to stabilize

The liquid level is stable when it does not change more than 0.25% within 2 minutes

If the liquid level does not stable within 6 minutes, discard the test

Initial Reading & Final Reading

when the liquid level is stable read the level nearest 0.25%, it is the initial meter reading

Re-tighten the cap and repeat the previous shaking steps

If the second reading does not change more than 0.25% the second record as a final reading

If the second reading changes by more than 0.25% the second reading record as an initial reading

If the third reading does not change by more than 0.25% the third reading is recorded as a final reading otherwise discard the test

Valid or Invalid Test

Disassemble the meter, dump out the concrete from the base, and examine the base portion of undisturbed tightly packed concrete

If such a material is present the test is invalid

Calculation

Air Content = Final Reading - Correction Factor from Table





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