Humboldt H-1449 Vacuum Extractor - Manual (Page 4)

CALCULATIONS
Calculate the percentage of bitumen extracted as follows:
Bitumen extracted, percent of gross test specimen weight
Where:
S= Weight of test specimen
A= Weight of extracted mineral aggregate
Add the retention factor (note 2), previously determined for the job mix, to the percent
bitumen extracted and report total as percentage of bitumen in the mix (note 3).
Note 2: see section 8 for procedure for determining the retention factor.
Note 3: procedure as detailed in section 4.4 does not require a moisture correction. If
the moisture in the bituminous mixture being tested is over 0.6 percent, then routinely,
the amount of moisture shall be determined by standard test procedures. In this case the
extracted aggregate shall be dried to a constant weight at 230°F, ± 9.
The percentage of bitumen extracted shall be calculated as follows:
Bitumen Extracted, percent of dry mixture
Where:
S= Weight of test specimen
A= Weight of extracted mineral Aggregate,
W= Weight of water in specimen
Add the retention factor to the percent bitumen extracted and report as the percentage
of bitumen in the dry mix.
5. Retention Factor
SCOPE
Certain types of aggregate will retain a small amount of bitumen after being tested by
the vacuum extractor; this should be taken into consideration in calculating the final
percent bitumen in the mix. The following procedure is used to determine the retention
factor.
Note 4: where the retention factor is known to be 0.04 or less it may be disregarded.
PROCEDURE
5.1 The test procedure as outlined in the following paragraphs shall be performed
separately on at least two specimens of aggregate representative of the material to
be used in the mix. Test specimen size shall conform to the requirements of Table 1.
The aggregate specimen shall be dried to a constant weight at 275°F, plus or minus
five.
5.2 Place specimen in a tare metal beaker and weigh to the nearest 0.1 gm.
5.3 Immediately add asphalt cement of the amount and type called for by the job mix
formula. The asphalt cement shall be preheated to 300°F to 350°F. Calculate the
exact percentage of bitumen added to the nearest 0.01 percent.