Humboldt H-1686 User Manual

H-1686_man_06.09

product manual

H-1686

Void Content Apparatus

for Coarse Aggregate

INTRODUCTION

The void content of coarse aggregate measurement provides an indication
of angularity, sphericity and surface texture compared to other aggregates of
the same grading. The test aggregate is allowed to free fall 115mm from the
funnel bottom of a cylindrical hopper into a 154mm diameter by 160mm high
cylindrical measure. Excess heaped aggregate is struck off using a bar, and the
miss is measured.
Uncompacted void content is computed as the difference between the
volume of the cylindrical measure and the absolute volume of tho coarse
aggregate collected in the measure (Based on bulk dry specific gravity
as determined by AASHTO T85). Higher void content in samples of
equal size gradation by this procedure indicate, a combination of greater
angularity, less sphericity. or rougher surface texture.

CALIBRATION OF CYLINDRICAL MEASURE

Apply a light coat of grease to the top edge of the dry, empty, cylindrical
measure. Determine the mass of measure, grease and glass plate. Fill
the measure with freshly boiled, deionized water at 18 to 24°C. Record
water temperature. Place the glass plate on the measure, taking care
that no air bubbles remain. Dry all outer surfaces and determine the
mass of the measure, glass plate, grease, and water to the nearest 0.1g.
Also determine the mass of the clean. dry, empty measure. for
subs equant tests.
Calculate the volume of the measure as follows:
v =1000 (MID)
Where:

v = volume of cylinder, ml
M = net mass of water, g
D = density of water at temperature used. kg/m3
(see table in AASHTO T19)
Determine the volume to the nearest 0.1 ml.

PROCEDURE

AASHTO TP·56 provides three methods of void content measurement,
the differences in method differing by the type of sample used:

Method A: Sample is of standard grading made up from several specified

gradations in specific masses totaling 5000g.

Method B: Separate 5000g samples are tested for each of three sieve

Gradations, then averaged.

Method C: An as-received 5000g sample is used, taken after

removing material finer than the #4 (4.75mm) sieve.

Refer to AASHTO TP56 for details of above Methods A, B and C.
The method of using the H-1686 Void Content Apparatus is the same
for all methods and proceeds as follows:

1. Position the cylindrical measure under the cylindrical hopper, being sure
that the measure is rested on the centering pin. Piece entire apparatus
in a suitable overflow pan

2. Close and lock the gate of the hopper.

3. Mix the sample until it appears homogeneous. Then pour it into the
hopper. The H-4308 Material Handling Pan works well for weighing
sample fraction makeup, mixing and pouring into hopper.

4. The sample must fall freely from the hopper by rapidly opening the
hopper gate, and the gate doors must swing away quickly and remain
out of the flow of sample. The operator should develop a technique of
accomplishing this result. It may be helpful to hold the gate shut while
releasing the latch, then releasing the gate manually.

5. Strike off excess heaped aggregate from the cylindrical measure being

careful to avoid vibration or other disturbance that could cause
compaction of sample in the cylinder. Insert strike-off bar across cylin­der diameter at center of heap and work to sides. When a large piece
of aggregate must be removed leaving an unusual void below the rim,
replace it with one or more smaller pieces that fit below the rim.

NOTE: This replacement procedure is not mentioned in AASHTO TP56,

but is recommended.

6. Determine the mass of the cylindrical measure and contents to the
nearest 0.1g. Also record the mass of the empty measure.

7. Recover all aggregate particles for a second test run. Repeat as above,

since reported void contents will be an average of two tests.

8. Calculate uncompacted voids percent to the nearest one tenth percent
for each determination as follows:

U = (V - F/G) ~ x 100

Where: V = volume of cylindrical measure, ml
F = net mass of coarse aggregate in measure, g
G = bulk dry specific gravity of coarse aggregate
(by AASHTO T85 procedure)
U = uncompacted voids, percent in the material

Warranty

Humboldt Mfg. Co. warrants its products to be free from defects in material or
workmanship. The exclusive remedy for this warranty is Humboldt Mfg. Co.,
factory replacement of any part or parts of such product, for the warranty of this
product please refer to Humboldt Mfg. Co. catalog on Terms and Conditions
of Sale. The purchaser is responsible for the transportation charges. Humboldt
Mfg. Co. shall not be responsible under this warranty if the goods have been
improperly maintained, installed, operated or the goods have been altered or
modified so as to adversely affect the operation, use performance or durability
or so as to change their intended use. The Humboldt Mfg. Co. liability under
the warranty contained in this clause is limited to the repair or replacement of
defective goods and making good, defective workmanship.

Humboldt Mfg. Co.

875 Tollgate Road
Elgin, Illinois 60123 U.S.A.

Testing Equipment for

HUMBOLDT

www.humboldtmfg.com

U.S.A. Toll Free: 1.800.544.7220

Voice: 1.708.456.6300

Fax: [phone]

Email: [e-mail]

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