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Standard Practice for

Emulsified Asphalt Content

of Cold Recycled Mixture Designs

AASHTO Designation: PP 86-20 (2021)1

Technically Revised: 2020 Reviewed but Not Updated: 2021

Technical Subcommittee: 2a, Emulsified Asphalts

American Association of State Highway and Transportation Officials

555 12th Street NW, Suite 1000
Washington, DC 20004
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Standard Practice for

Emulsified Asphalt Content of

Cold Recycled Mixture Designs
AASHTO Designation: PP 86-20 (2021)1
Technically Revised: 2020 Reviewed but Not Updated: 2021

Technical Subcommittee: 2a, Emulsified Asphalts

1. SCOPE
1.1. This standard for mix design evaluation is used to determine the amount and composition of
emulsified asphalt and other additives when using cold recycling (CR) of asphalt mixtures, which
includes cold in-place recycling (CIR) or cold central plant recycling (CCPR). The mix design is
based on strength and other performance properties.

2. REFERENCED DOCUMENTS
2.1. AASHTO Standards:
 MP 31, Materials for Cold Recycled Mixtures with Emulsified Asphalt
 R 90, Sampling Aggregate Products
 R 97, Sampling Asphalt Mixtures
 T 11, Materials Finer Than 75-µm (No. 200) Sieve in Mineral Aggregates by Washing
 T 27, Sieve Analysis of Fine and Coarse Aggregates
 T 30, Mechanical Analysis of Extracted Aggregate
 T 164, Quantitative Extraction of Asphalt Binder from Hot Mix Asphalt (HMA)
 T 166, Bulk Specific Gravity (Gmb) of Compacted Asphalt Mixtures Using Saturated Surface-
Dry Specimens
 T 209, Theoretical Maximum Specific Gravity (Gmm) and Density of Asphalt Mixtures
 T 245, Resistance to Plastic Flow of Asphalt Mixtures Using Marshall Apparatus
 T 269, Percent Air Voids in Compacted Dense and Open Asphalt Mixtures
 T 283, Resistance of Compacted Asphalt Mixtures to Moisture-Induced Damage
 T 308, Determining the Asphalt Binder Content of Asphalt Mixtures by the Ignition Method
 T 312, Preparing and Determining the Density of Asphalt Mixture Specimens by Means of the
Superpave Gyratory Compactor
 T 331, Bulk Specific Gravity (Gmb) and Density of Compacted Asphalt Mixtures Using
Automatic Vacuum Sealing Method

TS-2a PP 86-1 AASHTO

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2.2. ASTM Standards:
 D3549/D3549M, Standard Test Method for Thickness or Height of Compacted Asphalt
Mixture Specimens
 D7196, Standard Test Method for Raveling Test of Cold Mixed Emulsified Asphalt Samples

2.3. Other Documents:

 LTPP Seasonal Asphalt Concrete Pavement Temperature Models, LTPPBind 3.1
 Basic Asphalt Recycling Manual, Asphalt Recycling and Reclaiming Association and
FHWA-HIF-14-001, Annapolis, MD.

3. TERMINOLOGY
3.1. cold central-plant recycling (CCPR)—the process in which the asphalt recycling takes place at a
central location using a stationary cold mix plant. The resulting pavement serves as a base layer
overlaid with a surface treatment or asphalt mixture overlay.

3.2. cold in-place recycling (CIR)—the on-site recycling process to a typical treatment depth of
75-100 mm (3-4 in.), using a train of equipment (tanker trucks, milling machines, crushing and
screening units, mixers, pavers, and rollers) and an emulsified asphalt with or without a
combination of additives (lime, cement, aggregate), generating and re-using 100 percent of the
milled material, with the resulting pavement serving as a base layer overlaid with a surface
treatment or asphalt mixture overlay.

3.3. reclaimed asphalt pavement (RAP)—removed and/or processed pavement materials containing
asphalt binder and aggregate.

4. SIGNIFICANCE AND USE

4.1. The procedure described in this standard is used to produce CIR or CCPR that satisfies mix design
requirements.

4.2. Specifying an emulsified asphalt alone for CIR or CCPR may not be satisfactory in producing a
good-performing mixture. The mix design described in this standard practice has been used
successfully in many projects.

5. OBTAINING AND PREPARATION OF MATERIALS

5.1. Sampling Existing Pavement for CIR and CCPR:

5.1.1. Obtain cores from the areas to be recycled. The material provided must be representative of the
material to be recycled.
Where visual differences in the pavement surface are noted or where construction or maintenance
records indicate differences, obtain additional cores to evaluate the difference. If these additional
cores show significant material differences, perform a separate mix design for each identified
pavement segment.
Note 1—Take cores using a pattern that results in a representative sample of the pavement to be
recycled including at or near lane lines, within and between wheel paths, at the pavement edge and
within shoulders if shoulders are to be recycled. Provide at least 180 kg (400 lb) of RAP per
design, more if asphalt content or binder properties or recovered aggregate gradation analysis of
the RAP are desired.

TS-2a PP 86-2 AASHTO

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5.1.2. Crush cores at ambient temperature or colder to obtain materials for the mix design.
Note 2—A jaw crusher, laboratory milling machine, or other suitable method is recommended for
modeling the particle shape and gradation expected during recycling.

5.1.3. As an alternative to obtaining and crushing cores, obtain RAP by milling. Mill the pavement from
areas to be recycled to the specified depth.
Note 3—Consider a cold planer if the pavement section is uniform and a representative section is
milled. Obtain samples provided the cold planer (milling machine) produces sufficient coarse
material to conduct a mix design. Fine millings may not be acceptable if they are not coarse
enough to represent the construction-produced millings. Only millings that represent the pavement
to be recycled shall be collected. If the existing pavement surface is planned to be milled and
removed during construction, the pavement shall be milled in a similar manner and removed prior
to milling for sampling purposes. Milling and sampling shall only be to the planned recycle depth.
The material may be taken from one test location for each mix design to be performed. For
example, if a pavement change exists within the limits of the roadway, one test location should be
designated separating each area.

5.2. Sampling Existing Stockpiles for CCPR:

5.2.1. Remove the crust of the stockpile in accordance with R 97 and then sample the RAP in accordance
with R 90.

5.2.2. Provide at least 180 kg (400 lb) of RAP per design, and obtain more if asphalt content, binder
properties, or recovered aggregate gradation analysis of the RAP are desired.

5.3. Processing of Recycled Asphalt Pavement (RAP) Materials:

5.3.1. Sieve the RAP according to T 27, with the exception that drying the RAP to constant mass shall be
performed at 40 ± 2°C (104 ± 4°F). If a significant amount of fine uncoated particles is present,
perform washed sieve analysis on a representative sample in accordance with T 11.
Process RAP materials to model the gradation expected during recycling. As an alternative,
combine RAP materials to meet two of the gradation bands in MP 31.
Note 4—Adjustment of the gradation bands to local conditions and construction equipment is
recommended. The selected gradations shall be chosen to match the expected field gradation as
closely as possible, with the exception that a greater top size on the project is expected. Gradations
on a project will vary from sample to sample. Slight adjustments in the field to the design
emulsified asphalt content are often necessary to obtain optimum mixture performance.
Performing the mix design at two gradations can determine an acceptable range of emulsified
asphalt contents for the project. Ensure all materials pass the 25-mm (1-in.) sieve for 100-mm
(4-in.) diameter specimens.

5.3.2. Obtain two representative samples of processed RAP for T 308 or T 164 testing for Section 6.

6. DETERMINE ASPHALT CONTENT AND GRADATION OF EXTRACTED

AGGREGATE FROM RAP
6.1. Perform either T 308 or T 164 on two representative samples set aside from Section 5.3.2.

6.2. Determine the average asphalt content according to whichever method was used in Section 6.1.
Note 5—It is not possible to accurately determine an asphalt content and/or aggregate correction
factor for RAP materials. One may be applied if the correction factor of the original RAP
materials is known or can be based on experience with local aggregate materials.

TS-2a PP 86-3 AASHTO

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6.3. Sieve the extracted aggregate and determine the gradation according to T 30.
Note 6—Consider corrective aggregate meeting agency requirements if the amount passing the
4.75-mm (No. 4) sieve in the extracted mineral aggregate gradation is greater than 65 percent or if
the asphalt content is greater than 5.5 percent, or both. Lab-prepared cold recycle mixture
properties may also indicate the need for corrective aggregate in lieu of the T 308 and T 30 test
results, such as low voids, low dry strength, or low retained strength.

7. EMULSIFIED ASPHALT AND ADDITIVES FOR MIX DESIGN

7.1. Select an emulsified asphalt in accordance with MP 31:

7.1.1. Obtain 7.6 L (2 gal) of the emulsified asphalt that will be used to produce the cold recycled
mixture. Include the name and location of the supplier in the mix design report. Include the grade
and properties of the emulsified asphalt in the mix design report.

7.2. Samples of Other Additives:

7.2.1. Obtain 2.3 kg (5 lb) of quicklime, hydrated lime, or cement if needed for the mix design.
Note 7—Dry additives are sometimes used to improve early cohesion, strength, and moisture
resistance. To limit brittle behavior, the quantity of cement is normally limited to one-third the
quantity of new residual asphalt from the emulsified asphalt and the quantity of lime should be
limited to a maximum of 1.5 percent.

7.2.2. Obtain a sufficient amount of other additives (i.e., add stone) that will be used to complete the mix
design. List the name and source of all additives in the mix design report.

8. DETERMINATION OF STRENGTH OR STABILITY AND STRENGTH

RATIO
8.1. Batching RAP Material:

8.1.1. Select a minimum of three emulsified asphalt contents in 0.5 percent to 1.0 percent increments
covering a range typically between 1 percent and 4.0 percent by dry weight of RAP. Batch RAP
material for each specimen conforming to the gradation expected in the field or to at least two of
the three gradation bands shown in MP 31. Batch aggregate at the appropriate percentage, if
required. Prepare six specimens for each emulsified asphalt content selected. As an option,
additional specimens may be batched, compacted, and tested that have varying percentages of
other additives such as quicklime.

8.1.1.1. For indirect tensile strength testing from T 283, determine the amount of RAP material required to
produce a 150 mm (6 in.) diameter and 95 ± 5 mm (3.75 ± 0.2 in.) tall specimen when compacted
in the gyratory compactor at 30 gyrations.
For Marshall stability testing from T 245, determine the amount of RAP material required to
produce a 100-mm (4-in.) diameter and 63.5- ± 3-mm (2.5- ± 0.1-in.) tall specimen. Exclude plus
25-mm (1-in.) material from 100-mm (4-in.) specimens.
Note 8—Compact to 30 gyrations if using gyratory compaction. Compact at 75 blows per side if
using the Marshall compaction apparatus.
Note 9—Choose only one strength or stability test.

TS-2a PP 86-4 AASHTO

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8.2. Preparing Lime Slurry:

8.2.1. Prepare slurry by adding the required quantity of additive to water using the ratio expected for the
project.

8.2.2. Minimize the amount of additive lost in the form of dust.

8.2.3. Stir until thoroughly mixed, and continuously mix the slurry until it is used to prevent settling.

8.2.4. Cover to reduce water evaporation.

8.3. Mechanical Mixing:

8.3.1. Mix samples for testing using a mechanical bucket mixer or laboratory-sized pugmill. Add
moisture that is expected to be added at the milling head, typically 1.5 to 2.5 percent, and mix
thoroughly. If any dry additives are in the mixture, add the additives to the dry RAP and mix
thoroughly before adding the water. If slurry is used, add at the desired solids content by weight of
dry RAP and mix thoroughly.

8.3.2. Mix RAP conditioned at room temperature between 20 and 25°C (68 and 77 °F), thoroughly mix
RAP with water, additives and water, or slurry then mix with emulsified asphalt at the expected
delivery temperature. One specimen will be mixed at a time. Mixing time with emulsified asphalt
should not exceed 60 s.
Note 10—RAP conditioned at temperatures higher than 25°C (77°F) can be mixed and
compacted to better simulate hot-weather field conditions. If ambient air temperatures are
expected to be 29°C (85°F) or greater, then condition RAP and mold to 40°C (104°F) for
compaction. Higher-temperature conditioning will likely have the effect of lowering the design
emulsified asphalt content. If construction conditions are cooler, the field emulsified asphalt
content demand could increase; however, it is impractical to mix and compact the RAP at cool
temperatures in the laboratory.
Note 11—Before mixing the design samples, prepare trial blends with expected moisture,
additives and add stone, if any, to determine that the emulsified asphalt disperses throughout the
blend. If an improvement is needed, adjust moisture content, going no higher than 3 percent. If an
improvement is still needed, an emulsified asphalt formula change may be needed.

8.4. Compacting:

8.4.1. Immediately after mixing, compact the specimens. Compact the specimens at 25 ± 2ºC (77 ± 4ºF)
(see Note 10 for higher-temperature conditioning).

8.4.2. Compact the specimens according to T 312 compaction procedures with the exception that the
materials and the molds are not heated unless desired as described in Note 10.

8.4.3. Compact six specimens at each emulsified asphalt content for strength or stability testing; three for
unconditioned (dry) strength on cured samples and three for conditioned strength on cured
samples for moisture conditioning.

8.5. Curing:

8.5.1. Extrude the specimens from the molds after compaction. Handle specimens carefully as to not
disturb or damage. Carefully remove the paper disks from the top and bottom of the specimens.

8.5.2. Place specimens in 60 ± 1°C (140 ± 2°F) forced draft oven with ventilation on sides and top. Place
each specimen in a small container to account for material loss from the specimens. Cure
compacted specimens at 60 ± 1°C (140 ± 2°F) to constant mass but do not heat for more than

TS-2a PP 86-5 AASHTO

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48 h and not less than 16 h. Constant mass is defined as 0.05 percent change in mass or less in 2 h.
After curing, cool specimens at 25 ± 2°C (77 ± 4°F) for a minimum of 12 h and a maximum of
24 h.

8.6. Sample Conditioning and Testing:

8.6.1. After curing of specimens, determine the bulk specific gravity of each compacted, cured, and
cooled specimen according to T 166 Method A or T 331, if required. Since the specimens have
already been cured to constant weight under heat, additional drying of the specimens as discussed
in Section 6.1 of either T 166 (Method A) or T 331 is not required.

8.6.2. Determine specimen heights according to ASTM D3549/D3549M. Alternatively, the height can be
obtained from the Superpave gyratory compactor readout.

8.6.3. Determine air void contents of the compacted and oven-cured samples at each emulsified asphalt
content according to T 269 using the maximum theoretical specific gravity as determined in
Section 9.

8.6.4. For each emulsified asphalt content tested, separate the specimens into two subsets of three
specimens each so the average air void contents of the two subsets are approximately equal.

8.6.5. Perform moisture conditioning on three compacted samples at each emulsified asphalt content by
applying a vacuum of 10 to 26 in. of Hg partial pressure (13 to 67 kPa absolute pressures) for a
time duration required to vacuum saturate samples to 55 to 75 percent. Saturation calculation shall
be in accordance with T 283.

8.6.5.1. For the tensile strength test, soak the moisture-conditioned samples in a 25 ± 1°C (77 ± 2°F) water
bath for 24 ± 1 h.

8.6.5.2. For the Marshall stability test, soak the moisture-conditioned samples in a 25 ± 1°C (77 ± 2°F)
water bath for 23 h, followed by a 1-h soak in a 40 ± 1°C (104 ± 2°F) water bath.

8.6.6. Dry samples are tested after a minimum of 2 h temperature conditioning by immersing in a 25 ±
1°C (77 ± 2°F) water bath for tensile strength or a 40 ± 1°C (104 ± 2°F) water bath for Marshall
stability. Place dry specimens in a leak-proof bag to prevent samples from coming in contact with
water. Alternatively, the Marshall stability specimens can be conditioned in an oven at 40 ± 1°C
(104 ± 2°F) for a minimum of 2 h. This testing is performed at the same time that moisture-
conditioned specimens are tested.

8.6.7. If the tensile strength test was performed, calculate the tensile strength ratio by dividing the
average conditioned tensile strength by the average dry strength for each emulsified asphalt
content. If the Marshall stability test was performed, calculate the Marshall stability ratio by
dividing the average conditioned Marshall stability by the average dry Marshall stability for each
emulsified asphalt content.

9. DETERMINING THE THEORETICAL MAXIMUM SPECIFIC GRAVITY

9.1. Batch two RAP material samples according to the gradation used for each mix design for use in
determining the theoretical maximum specific gravity value according to T 209.

9.2. Mix samples according to Section 8.3 using the highest emulsified asphalt content in the design.

TS-2a PP 86-6 AASHTO

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9.3. Follow T 209 with the exception that loose RAP mixtures are cured in a forced draft oven at
60 ± 1°C (140 ± 2°F) to constant mass. Cure for no more than 48 h and no less than 16 h. Constant
mass is defined as 0.05 percent change in mass or less in 2 h.

9.4. Do not break any agglomerates that will not easily reduce with a flexible spatula.

9.5. Test both specimens at the highest emulsified content in the design.

9.6. Use the Supplemental Procedure for Mixtures Containing Porous Aggregate of T 209 to account
for uncoated particles.

9.7. Back calculate the theoretical maximum specific gravity for the lower emulsified asphalt contents
using the following formulas. Calculate the effective specific gravity of the RAP from the average
measured Gmm as:
(100 − Pbr )
GRAP = (1)
 100   Pbr 
 − 
 Gmm   Gb 
where:
GRAP = Effective specific gravity of RAP
Pbr = Percent residual asphalt content from the emulsified asphalt in the mix
Gb = Specific gravity of the residual asphalt

Calculate the theoretical maximum specific gravity for the lower emulsified asphalt contents using
the following formula:
100
Gmm = (2)
(100 − Pbr )  Pbr 
+ 
GRAP  Gb 
where:
Gmm = Theoretical maximum specific gravity at desired emulsified asphalt content
Pbr = Percent residual asphalt content at desired emulsified asphalt content
Gb = Specific gravity of the residual asphalt

10. RAVELING TEST

Note 12—The use of the raveling test in combination with other tests in this procedure may be
protected by one or more of the following U.S. patents: 6,599,057, 7,275,890, and 7,455,476. For
more information, contact Road Science at www.roadscience.net or call 918-960-3800.
Alternatively, do not perform the raveling test, or replace it with an alternative test determined by
the agency.

10.1. Batch RAP material at the medium gradation band in MP 31 Table 1 or other desired gradation.

10.2. Mix and compact specimens at the desired emulsified asphalt content at temperatures noted in
Section 8.3.2 or Note 10. Refer to Method B of ASTM D7196.

10.3. Cure the specimens for 4 h at 10°C (50°F) and 50 percent relative humidity.
Note 13—Consider alternate curing conditions if the ambient temperature during construction is
expected to be above 29°C (85°F). In that case, cure for 4 h at 25°C (77°F) and 50 percent relative
humidity.

TS-2a PP 86-7 AASHTO

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10.4. Abrade the specimens for 15 min according to ASTM D7196.

10.5. Record the percent mass loss according to ASTM D7196.

11. EMULSIFIED ASPHALT CONTENT SELECTION

11.1. Choose the design emulsified asphalt content that meets the CIR requirements listed in the
specification for CIR and CCPR mixtures. Report the range of contents that meet the specification
requirements. Report the values for each of the gradations if two or more RAP gradations are used.
Note 14—The designer may choose a content that is above the minimum value that meets all the
criteria based on knowledge of local construction conditions and sound engineering judgment and
experience.

12. REPORT
12.1. Report the following information in the mix design report:

12.1.1. Gradation of RAP;

12.1.2. Recommended water content range as a percentage of dry RAP;

12.1.3. Amount of additive as a percentage of dry RAP;

12.1.4. RAP conditioning temperatures;

12.1.5. Theoretical maximum specific gravity of the mixture at each emulsified asphalt content, Gmm;

12.1.6. Average air voids and bulk specific gravity at each emulsified asphalt content of T 245 or T 283
samples;

12.1.7. Dry tensile strength or Marshall stability at each emulsified asphalt content;

12.1.8. Level of saturation and conditioned tensile strength or Marshall stability value at each emulsified
asphalt content;

12.1.9. Tensile strength ratio or Marshall stability ratio at each emulsified asphalt content;

12.1.10. Theoretical maximum specific gravity, air void content, dry tensile strength, or Marshall stability,
and tensile strength ratio or Marshall stability ratio at recommended moisture and emulsified
asphalt contents;

12.1.11. Optimum emulsified asphalt content as a percentage of dry RAP, and provide a range of contents
that meets the requirements;

12.1.12. Emulsified asphalt and additive designation, supplier company name, and location;

12.1.13. Emulsified asphalt residue content;

12.1.14. Emulsified asphalt penetration of residue;

12.1.15. Notes for the field inspector regarding field construction temperatures compared to the mix design
temperatures, including notes suggesting the possibility of increasing emulsified asphalt content
for cooler weather conditions; and

TS-2a PP 86-8 AASHTO

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12.1.16. Notes for the field inspector regarding the possibility of increasing the emulsified asphalt content
for finer RAP field gradations or decreasing the content for coarser RAP field gradations
compared to mix design gradation.

12.2. Optional report information:

12.2.1. RAP asphalt content;

12.2.2. Mineral gradation of extracted aggregate;

12.2.3. Raveling test results; and

12.2.4. Certificates of compliance for emulsified asphalt and additive.

13. KEYWORDS
13.1. CCPR; CIR; cold central plant recycle; cold in-place recycle; cold recycled; emulsified asphalt;
RAP; reclaimed asphalt pavement.

1
This provisional standard was first published in 2017.

TS-2a PP 86-9 AASHTO

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