Use this to good advantage by extending the use of the

Establish a density to be compacted in the pan

tester to become a good AC content tester for field use.

each time. . this is 135 pounds/cubic feet, a value that

is about 95% of optimum for the region that is going to

Some additional hardware is required

use this test. It will vary, of course, for different parts of

the world.

a. Metal pan, approximately 16" x 16" x 4".

If the desired density is 135 PCF, and if each inch in

b. Compaction plate...5" x 5" x 1/2" with a rod

the pan represents 0.1481 cubic feet then a one inch

welded to it and a sliding weight to slide on the rod and

layer compacted to 135 PCF would actually weigh 19.99

permit a controlled compaction effort on the plate.

pounds.

c. Accurate scale to approximately 30 pounds.

135 PCF x 0.1481 CF = 19.993 pounds.

d. Straight edge and a finely graduated metal ruler.

b. Measure out exactly 19.99 pounds of hot AC mix

.. C-clamp to clamp the ruler to the straight edge. The

and dump this into the pan.

straight edge should be approximately twice as long as

the pan's longest dimension.

Spread it around evenly and then compact it down to

a depth of exactly one inch.

Procedure

A 1/16th inch error in height is equal to a 6% error in

Establish an initial calibration curve in the laboratory.

final compaction. . an error of 8.1 PCF, something not

After that, the same procedure is used in the field to

accepted or calibration work.

establish the desired asphalt content value.

c. Compact a second and third lift in the same

Prepare a sample of asphaltic concrete at a specific

manner.

weight each time. This weight will be selected at the

outset and will be used for the initial calibration as well as

Weigh the final pan of material and it should weigh

for all subsequent field tests.

exactly 3 x 19.99 = 59.97 pounds plus tare.

This weight should be approximately 95% of optimum for

d. Set the pan atop the tester shipping case in the

the typical asphalt weights used in the user's locale.

same manner as you would take a standard count.

Round it off to a practical value for ease of preparation

Remove the reference standard from the case.

and calculations.

e. Take several tester moisture readings on the

Initially prepare a sample at a known density, evenly

compacted surface, revolving the tester 900 each time.

compacted in the pan in one inch thick layers.

Record the readings.

Thereafter prepare the sample in the same one inch

layers for all field work using the same technique exactly.

f. Run an extraction of a sample of the compacted

material to determine asphalt content.

a. Measure the pan and determine precisely the

volume in each inch for the bottom three inches. The

g. Plot the tester reading (in ratio) on the vertical

fourth inch will merely become a catch basin for the light

axis of a calibration sheet similar to that used fur the

material that is compacted into the third inch.

CPN moisture curve, and plot the asphalt content

PERCENTAGE across the bottom.

If a 16" square pan was used, then each inch would

hold precisely 0.1481 cubic feet.

This curve is now an accurate asphalt content curve.

Zero is obtained by compacting a bone dry

Integrated Publishing, Inc. |