Idaho Standards Section 520

IDAHO STANDARD METHOD OF TEST FOR

DETERMINATION OF RECLAIMED ASPHALT PAVEMENT (RAP)

AGGREGATE BULK (DRY) SPECIFIC GRAVITY (Gsb)

Idaho Designation: IT 146-16

2. SCOPE
1.1 This method covers the procedure for determining the Bulk (Dry) Aggregate Specific Gravity,
(Gsb) of a Recycled Asphalt Pavement, (RAP) aggregate from Maximum Theoretical Specific
Gravity (Gmm) tests of the RAP. An Effective Specific Gravity of Aggregate, (Gse) is calculated
and used to determine the Gsb of the RAP after adjusting the Gse for asphalt absorption.

1.2 This standard does not purport to address all of the safety concerns, if any, associated with its
use. It is the responsibility of the user of this standard to establish appropriate safety and
health practices and determine the applicability of regulatory limitations prior to use.

3. REFERENCE DOCUMENTS

2.1 AASHTO Standards

 M 231,Weighing Devices Used in the Testing of Materials
 T 2, Sampling Aggregates
 T 248, Reducing Samples of Aggregate to Testing Size
 T 209, Theoretical Maximum Specific Gravity (Gmm) and Density of Hot Mix Asphalt (HMA)
 T 85, Specific Gravity and Absorption of Coarse Aggregate

2.2 Idaho Standards

 IT-144, Specific Gravity and Absorption of Fine Aggregate Using Automatic Vacuum
Sealing (CoreLok) Method

2.3 Other Documents:

 McDaniel, R. and Anderson, R.M. (2001). Recommended Use of Reclaimed Asphalt
Pavement in the Superpave Mix Design Method: Technician’s Manual, NCHRP Report No.
452, Transportation Research Board, Washington, DC.
 Copeland, A. (2011). Reclaimed Asphalt Pavement in Asphalt Mixtures: State of the Practice,
Publication No. FHWA-HRT-11-021, Turner-Fairbank Research Center, Federal Highway
Administration.
 Advanced Asphalt Technologies, LLC (2011). NCHRP Report 673 A Manual for Design of
Hot Mix Asphalt with Commentary, TRB, National Research Council, Washington DC
 Asphalt Institute MS-2, Asphalt Mix Design Methods. 7th Edition, 2014, Lexington Kentucky

2.4 Standard Specifications, Subsection 720.07.

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4. SUMMARY OF METHOD
4.1. A representative RAP sample is prepared prior to testing by reheating and remixing the reclaimed
material. Determine binder content and gradation, per T 308, and apply the chemical
extraction/ignition furnace correlation factor to the result. Perform a minimum of two maximum
theoretical specific gravity (Gmm) tests so that an effective specific gravity (Gse) can be calculated.
Use the calculated Gse value and the assumed asphalt binder absorption of the RAP to determine
the bulk (dry) specific gravity (Gsb) of the RAP.

5. APPARATUS
5.1. Drying Oven. Oven of sufficient capacity for containing the sample and capable of maintaining a
temperature of 230 ± 9ºF.

5.2. Balance. Of sufficient capacity and conform to the requirements of M 231, Class G2.

5.3. Sample Pans. Large, flat and capable of holding 20,000 grams of RAP material.

5.4. Chopping Utensil – Blade trowel or other utensil used to separate the large conglomerations of a
RAP sample into a loose-flowing condition.

5.5. Vacuum Setup – Associated with AASHTO T 209

5.6.

6. SAMPLING
6.1. Sample the RAP stockpile, in its final usable form, by obtaining a minimum of six representative
locations from the RAP stockpile. Obtain 22 lb (10,000 grams) of RAP from each location.
Thoroughly blend all the samples and reduce per AASHTO T 248 to produce a 20,000-gram
sample.
Note1―NCHRP Report 673 includes a recommended RAP Sampling Plan in Chapter 9.

7. PREPARATION OF SAMPLE
7.1.1. Place the entire 20,000-gram sample into a large flat pan(s).

7.1.2. Place sample into a preheated oven at 230 ± 9° F. and heat for 30 to 45 minutes.

7.1.3. Remove the sample from the oven and begin breaking up the larger conglomerations of RAP with
the chopping utensil.

7.1.4. Blend the heated RAP by mixing the freshly chopped material with the fines in the pan, as the
material begins to soften.

7.1.5. Return the RAP into the oven and continue heating for another 15 - 20 minutes.

7.1.6. Remove the RAP from the oven and repeat the chopping of the conglomerations and blending of
the fines until the RAP sample is homogeneous and conglomerations of fine aggregate complies
with AASHTO T-209.

7.1.7. Thoroughly blend the loose RAP sample and reduce to testing size per T 248. Testing sizes are
stated in Section 7.

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8. PROCEDURE
8.1. Percent Asphalt Binder, Pb using Chemical Extraction/Ignition Furnace Correlation Factor:

8.1.1. Determine the Pb of two dried RAP increments according to T 308. Calculate the uncorrected
asphalt content of the two increments and if the difference exceeds 0.2 perform another pair of T
308 tests. Throw out the high and low values, and average the two remaining results.

8.1.2. Compare the average uncorrected asphalt binder content with the Contractor’s average
uncorrected binder content value from Form ITD 1044 or Mix Design. If the algebraic difference
exceeds 0.33 request new samples from the Contractor and repeat steps 5.1 through 7.1, otherwise
accept the Contractor’s asphalt binder correlation factor (from the average of 6 chemical and 6
ignition furnace tests).

8.1.3. Calculate the RAP asphalt binder content using the average uncorrected T 308 results from step
7.1.1 and apply the Contractor furnished asphalt binder correlation.

8.1.4. Record the Pb and the aggregate gradation.

8.2. Maximum Specific Gravity determination, Gmm:

8.2.1. Split out a minimum of three increments of the prepared RAP sample according to the mass
requirements of T 209.

8.2.2. Dry the sample to a constant mass in an oven at 230 ±9° F. While drying, chop and break up the
sample as you would with a standard Gmm sample. Record as “dry RAP mass”.

8.2.3. Place the sample in 295° ± 5° F. oven for one hour.

8.2.4. Add 2 percent virgin asphalt binder (for example PG 64-28 or PG 58-28) at 295° ± 5° F. based on
the “dry RAP mass” from step 7.2.2, to the RAP and thoroughly mix at 295° ± 5° F. to ensure
uniform coating of all particles.
Note 1―In some instances, more than 2% additional virgin binder may be required to ensure
complete coating.

8.2.5. Determine the Gmm of two of the prepared RAP samples according to AASHTO T209 and keep
the remaining sample(s) in reserve.

8.2.6. Calculate the individual Gmm values. The average result will be used in the calculation provided
the individual results do not vary by more than 0.010. If the individual results vary more than
0.010, repeat steps in 7.2., discard the high and low values and average the remaining individual
results provided they do not vary more than 0.010. If remaining individual results vary more than
0.010 repeat steps in 7.2. until individual results compare within 0.010.

8.2.7. Estimate the asphalt binder absorption of the RAP, Pba from the water absorption of virgin
aggregates used in the project.

9. CALCULATIONS
9.1. Calculate the “adjusted Pb” of the RAP to account for the addition of the 2 percent virgin asphalt
binder as follows:

9.1.1. Calculate “mass of RAP Asphalt Cement (AC)”.

Mass of RAP AC = Dry RAP mass x Pb

9.1.2. Calculate “mass of virgin AC added”

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Mass of virgin AC added = 0.02 x Dry RAP mass

9.1.3. Determine “New RAP mass”:

New RAP mass = Dry RAP mass + Mass of virgin AC added

9.1.4. Calculate “Adjusted Pb”:

𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 𝑜𝑜𝑜𝑜 𝑅𝑅𝑅𝑅𝑅𝑅 𝐴𝐴𝐴𝐴 + 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 𝑜𝑜𝑜𝑜 𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉 𝐴𝐴𝐴𝐴 𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎

𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑃𝑃𝑏𝑏= × 100
𝑁𝑁𝑁𝑁𝑁𝑁 𝑅𝑅𝑅𝑅𝑅𝑅 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀
9.2. Assume the Specific Gravity of Binder, Gb. Use 1.040.

9.3. Calculate the effective specific gravity (Gse) of the RAP:

(100 − 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑃𝑃𝑏𝑏 )
𝐺𝐺𝑠𝑠𝑠𝑠(𝑅𝑅𝑅𝑅𝑅𝑅) =
100 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑃𝑃𝑏𝑏
� − �
𝐺𝐺𝑚𝑚𝑚𝑚 𝐺𝐺𝑏𝑏

9.4. Estimate or assume the asphalt binder absorption of the RAP, Pba

9.4.1. Asphalt absorption of RAP is assumed to be two-thirds of the water absorption of virgin
aggregates used in the project.

9.4.2. Determine the water absorption values by AASHTO T85 and Idaho IT-144 and calculate the total
water absorption for the virgin aggregate by proportionately combining the coarse and fine
absorption by the percent of each aggregate.

9.4.3. Calculate Pba:

𝑃𝑃𝑏𝑏𝑏𝑏 = 𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤 𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 × 0.667

9.5. Calculate the stone bulk gravity (Gsb) of the RAP:

𝐺𝐺𝑠𝑠𝑠𝑠(𝑅𝑅𝑅𝑅𝑅𝑅)
𝐺𝐺𝑠𝑠𝑠𝑠(𝑅𝑅𝑅𝑅𝑅𝑅) = +1
𝑃𝑃𝑏𝑏𝑏𝑏(𝑅𝑅𝑅𝑅𝑅𝑅) × 𝐺𝐺𝑠𝑠𝑠𝑠(𝑅𝑅𝑅𝑅𝑅𝑅)
� �
100 × 𝐺𝐺𝑏𝑏(𝑅𝑅𝑅𝑅𝑅𝑅)

10. EXAMPLE
10.1. Example with 2% virgin asphalt binder added:
10.1.1. Dry RAP mass = 3,000 g
10.1.2. Pb, (% AC) in RAP = 4.9%

10.2. Determine “mass of RAP AC”:

10.2.1. Mass of RAP AC = Dry RAP mass x Pb
=3,000 x 4.9%
=147 grams

10.3. Add 2 percent virgin AC:

10.3.1. Determine “mass of virgin AC added”:

Mass of virgin AC added = 0.02 x Dry RAP mass
= 0.02 x 3,000 grams
= 60 grams

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10.3.2. Determine “New RAP mass”

New RAP mass = Dry RAP mass + Mass of virgin AC added
= 3,000 + 60
= 3,060 grams

10.4. Calculate “Adjusted Pb”:

𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 𝑜𝑜𝑜𝑜 𝑅𝑅𝑅𝑅𝑅𝑅 𝐴𝐴𝐴𝐴 + 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 𝑜𝑜𝑜𝑜 𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉 𝐴𝐴𝐴𝐴
𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑃𝑃𝑏𝑏 = × 100
𝑁𝑁𝑁𝑁𝑁𝑁 𝑅𝑅𝑅𝑅𝑅𝑅 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀

147 𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔 + 60 𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔

= × 100
3,060 𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔
=6.8%
10.5. Calculate Gse:
(100 − 𝑃𝑃𝑏𝑏 )
𝐺𝐺𝑠𝑠𝑠𝑠(𝑅𝑅𝑅𝑅𝑅𝑅) =
100 𝑃𝑃
� − 𝑏𝑏 �
𝐺𝐺𝑚𝑚𝑚𝑚 1.040
Adjusted Pb = 6.8%
Rice Test, Gmm = 2.455
(100 − 6.8)
𝐺𝐺𝑠𝑠𝑠𝑠(𝑅𝑅𝑅𝑅𝑅𝑅) =
100 6.8
� − �
2.455 1.040
93.2
=
(40.73 − 6.54)
=2.726
10.6. Calculate Pba from water absorption of the virgin aggregate:
Water Absorption = 1.2%
𝑃𝑃𝑏𝑏𝑏𝑏 = 1.2 × 0.667
= 0.80% asphalt absorption
10.7. Calculate RAP Gsb:
𝐺𝐺𝑠𝑠𝑠𝑠(𝑅𝑅𝑅𝑅𝑅𝑅)
𝐺𝐺𝑠𝑠𝑠𝑠(𝑅𝑅𝑅𝑅𝑅𝑅) =
𝑃𝑃𝑏𝑏𝑏𝑏(𝑅𝑅𝑅𝑅𝑅𝑅) × 𝐺𝐺𝑠𝑠𝑠𝑠(𝑅𝑅𝑅𝑅𝑅𝑅)
� �+1
100 × 𝐺𝐺𝑏𝑏(𝑅𝑅𝑅𝑅𝑅𝑅)
Gse (RAP) = 2.726
Pba = 0.80%
Gb = 1.040
2.726
𝐺𝐺𝑠𝑠𝑠𝑠(𝑅𝑅𝑅𝑅𝑅𝑅) =
0.80 × 2.726
� �+1
100 × 1.040

𝐺𝐺𝑠𝑠𝑠𝑠(𝑅𝑅𝑅𝑅𝑅𝑅) = 2.670

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