Suggested Polymer Modified Asphalt Specifications
XXX.010 General
XXX.020 Materials and Manufacture
XXX.030 Performance
XXX.040 Storage
XXX.050 Requirements for PGM Binder
XXX.051 Sampling of PGM Binder
XXX.052 Mix Design for PGM Binder
XXX.053 Quality Control for PGM Binder
XXX.010 General. The
requirements of AASHTO MP1-98 shall apply, deviations from these are as
follows.
PG Binders with the suffix
“M” (e.g., PG 70-22M, PG 76-22M) shall meet the requirements for a PGM
Binder.
For this specification, the
Owner's Department of Engineering shall be the known as the Department
. The Department's Laboratory shall be known as the Laboratory and the
Monitoring Team shall consist of appointed representatives of the Department.
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XXX.020 Materials and
Manufacture. The
requirements of the AASHTO MP1-98 “Materials and Manufacture” Section shall
be completely replaced with the following:
5.1 The PG Binder
shall be an asphalt cement from the refining of crude petroleum, or combination
of asphalt cements from the refining of crude petroleum, or asphalt cements
and suitable liquid from the refining of crude petroleum, and possible
organic modifiers for performance enhancement. Material from the crude
refining stream will be considered neat. Liquid from crude refining may
be used for adjustments, but shall not be used for the purpose of substitution
of crude refined asphalt cement in a PG Binder. In the event of a failure
investigation where binders exhibit unusual properties a supplier may be
requested by the Laboratory to supply information about the makeup of a
PG Binder. Failure to cooperate will mean removal from the certification
list.
5.2 A modifier may
be any organic material of suitable manufacture that is proven compatible
with asphalt cement (does not separate appreciably in routine storage),
and that is dissolved, dispersed or reacted in asphalt cement to improve
its performance. Performance enhancement is defined as a decrease in the
temperature susceptibility of the asphalt cement while maintaining or improving
desirable properties in a neat asphalt cement such as coatability, adhesiveness
and cohesiveness. The use of modifiers shall be limited to 6.0 percent
by PG Binder weight.
5.3 The use of previously
used materials must be approved by the Department. Since no standard test
procedures exist for reprocessed materials (and original tests were not
developed with the use of such materials in mind), appropriate test methods
may be chosen by the Department for review. Department approval does not
relieve the binder supplier from full responsibility for content and use
of any previously used material nor guarantee suitable performance enhancement
as defined above. The detected presence in a PG Binder sample of any unapproved
previously used material will mean immediate removal from the certification
list. Approved reprocessed materials will be limited to 6.0 percent by
PG Binder weight.
5.4 The PG Binder
shall be homogeneous, free from water and deleterious materials, and shall
not foam when heated to 350F (175C). The asphalt binder (before modification
or after modification if liquid modifier used) shall be proven fully compatible
with a negative result by means of the Spot Test per AASHTO T 102 using
standard naphtha solvent. If standard naphtha shows a positive result,
a retest using 35 percent Xylene/ 65 percent Heptane (volume) may be used.
5.5 The PG Binder
shall be at least 99.0 percent soluble as determined by ASTM D 5546 or
D 2042. Any insoluble component shall be substantially free of fibers and
have discrete particles less than 75µm.
5.6 Flash point shall
be 500F (260C) min. Mass loss on RTFO of final PG grade binder shall be
0.5 percent max.
5.7 PG 58-28 shall
have a minimum Viscosity (ASTM D2171 @ 60C) of 800 poise and PG 64-22 shall
have a Penetration ( ASTM D5) between 55 and 75.
5.8 Direct Tension
testing is not required, unless otherwise required in this specification.
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XXX.030 Performance. Should
excess fat spots, regular random areas of flushing, or excess drainage
occur on a project and not be attributable to over rolling, plant operation,
or mix quality compared to the JMF, the PG Binder will be rejected. This
rejection includes any PGM Binders with an incompatible polymer or that
have been improperly handled. The Contractor will not be allowed to use
any of the rejected PG Binder. Correction of problem areas will be at the
Department's discretion depending on the problem severity, but if an unsafe
condition exists, the area in question will be removed and replaced. Before
work is resumed, the Contractor or PG Binder supplier shall show to the
Laboratory the material properties and compatibility of another PG Binder,
by reporting actual test data, and that proper binder production equipment
is in use.
The Contractor has a responsibility
to ensure traffic is not released early on the mat, unless overridden by
the Department. This Contractor responsibility includes allowing sufficient
cooling time when night paving before morning rush hour release of traffic.
Should traffic be on the mat in a manner leading to flushing or excess
surface/tire adhesion and tracking of binder, the mat area in question
shall be evaluated for removal and replacement or repair. Any removal and
replacement or repair shall be at the Contractor's expense, unless the
responsibility was overridden by the Department.
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XXX.040 Storage. PG
Binder storage shall be in accordance with Contractor's Plant Operation
Quality Control Plan, with the following additions:
A separate storage tank shall
be used whenever a Contractor is providing a binder other than a PG Binder
to customers other than the Department (excepting winter carryover work)
or switching between different PG Binders because of alternating mix types.
When the Contractor switches
between two different binder grades and is going to use the same storage
tank, the storage tank shall be at least 90 percent empty by tank height.
When the Contractor is switching to a PGM Binder or a PG Binder used to
make a PGM Binder, the storage tank shall be at least 95 percent empty
by tank height.
PGM Binder shall not be stored
at the asphalt concrete mixing plant over the winter. No PG Binder to be
used in producing a PGM Binder at the asphalt concrete mixing plant will
be stored at the facility over the winter. SBR polymer shall be stored
in a heated area over winter, but shall not exceed supplier requirements.
The Monitoring Team representing
the Department shall be notified before the delivery of the first load
of each type of PG Binder with sufficient lead time to allow for verification
of the storage tank condition and if the storage tank meets handling requirements
of the binder supplier. The Monitoring Team may sample the first storage
tank load or give the Contractor permission to proceed with no tank verification.
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XXX.050 Requirements for
PGM Binder. A
PGM Binder shall meet the requirements of Table A and shall be obtained
through modification of a non-oxidized, neat asphalt binder by using a
styrene butadiene latex rubber compound (SBR polymer) or a styrene butadiene
styrene polymer block copolymer (SBS polymer). The polymer supplier shall
certify to the refiner and Contractor that the polymer used meets a minimum
68 percent by weight butadiene content. SBS polymer modification shall
be performed prior to shipment to the asphalt concrete mixing plant (preblend).
SBR polymer modification shall be performed at the asphalt concrete mixing
plant. Asphalt plants utilizing SBR modification shall be equipped with
a SBR polymer flow meter and monitoring system. The system shall be approved
by the Department prior to use. It shall consist of a magnetic flow meter
capable of measuring the SBR polymer within 2.0% and a totalizer interfaced
with a data logging computer. The computer shall produce printouts of the
logged data every 5 minutes for drum plants or for every batch when a batch
plant is utilized. The logged data shall include time, date, flow rate
and flow total. For drum plant production, the SBR polymer shall be introduced
directly into the asphalt cement line through means of an in-line motionless
blender capable of providing a homogenous blend for sampling. A sampling
valve shall be located between the in-line blender and the drum. For batch
plant production the SBR polymer shall be added into the pug mill after
the aggregate has been completely coated with bitumen. Mixing shall be
continued for a minimum of 20 seconds after the SBR polymer is added and
as long as required to provide a uniform mixture.
For each project, the PGM
Binder supplier shall give the Contractor a handling guide specifying temperature,
circulation, shelf life, and other requirements for assuring the PGM Binder
will perform as desired. This handling guide will be given to the Monitoring
Team and be available in the plant control room and plant laboratory. If
PGM Binder is retained at the asphalt concrete mixing plant for more than
two weeks before use or beyond the supplier recommended shelf life, whichever
is less, a top and bottom sample test (material property difference between
samples taken from the top and bottom of the storage tank) shall be performed
by the Laboratory on samples retrieved by the Contractor at the Department's
direction and material on hand shall not be used until approved.
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XXX.051 Sampling of PGM
Binder. The
Contractor shall take two 1-quart (1 liter) binder samples from the first
transport truck load, before incorporation into the storage tank. The Contractor
will label the samples with binder type, supplier, project number and date
and retain them in the plant laboratory for future reference by the Department.
In addition to the above
sampling requirements, twice during each project (once if project has less
than 3000 tons (3000 metric tons) of mix), the Monitoring Team will direct
the Contractor to take two 1 quart (1 liter) samples of a PGM Binder, except
when SBR polymer is incorporated into batch plants. In this case the base
binder and SBR polymer shall be sampled and stored independently. Samples
shall be taken from the binder line between the last piping ‘tee’ and inlet
into the plant. They shall be labeled and handled as above. All samples
shall be held after project completion until the Department's Engineer
of Tests collects or releases them.
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XXX.052 Mix Design for
PGM Binder. The
PGM Binder supplier, as well as the polymer type, shall be identified on
the Job Mix Formula (JMF) submittal. A change in binder or polymer source
will require a redesign. The PGM Binder shall be graded, except for Direct
Tension, and provide the actual pass temperatures confirming the grade
requirement. All dated data shall be reported with the JMF submittal. In
addition to the PG Binder grading, the dated test results for the requirements
of Table A shall be reported. All data shall be neatly summarized on one
page. No data shall be more than three months old. If SBR polymer is added
at the asphalt concrete mixing plant, the JMF shall contain data from the
SBR polymer supplier for total solids (percent) and ash (percent). As well,
the submittal shall contain the target amount of SBR polymer greater than
or equal to 3.0 for 70-22M or 4.0 percent for 76-22M to achieve the properties
specified. A letter of certification from the polymer supplier verifying
percent butadiene in the SBS or SBR polymer shall be included in the JMF
submittal.
Each JMF submittal shall
report supplier recommended temperatures for mixing and compaction. A maximum
of 10 percent reclaimed asphalt concrete pavement or reclaimed bituminous
aggregate base may be used. If used it shall be included in the JMF. At
no time shall the amount of reclaimed asphalt concrete pavement or reclaimed
bituminous aggregate base in production exceed 10 percent of the mix by
dry weight.
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XXX.053 Quality Control
for PGM Binder. The
Contractor's Plant Operation Quality Control Plan shall include plans for
meeting this specification and any handling requirements of the PGM Binder
supplier. If the Contractor does additional testing or plant modifications,
this shall be explained in the plan.
A pre-approved asphalt ignition
oven is required to obtain an aggregate sample from an asphalt concrete
sample. The asphalt ignition oven may be used in place of hot bin or belt
samples.
Some solvent testing may
be performed early in a project as information in helping to verify plant
operation and determining an Asphalt Content Nuclear Gauge (AC Gauge) or
asphalt ignition oven calibration. However, any solvent testing shall be
accompanied by an asphalt ignition oven test.
For SBR polymers added at
the asphalt concrete mixing plant, the flow meter printouts shall be totaled
for each day's production. The percent of polymer versus neat binder in
the mix shall be calculated each day and recorded. Calculation worksheets
and printouts shall be available in the plant laboratory for review by
the Monitoring Team. A +/- 0.2 percent tolerance from the target amount
of SBR polymer shall be used as a guide for an acceptable amount of SBR
polymer use, but shall not be consistently low. To clarify, if the target
amount of SBR polymer is 3.5% of the asphalt content, then the latex shall
be added as 3.3% to 3.7% of the asphalt content. Disposition of all data
records shall be at the direction of the Department's Engineer of Test.
Table A Material Requirements
for PGM Binder
|
Test/Requirement
Final PG Binder Grade
Actual Pass Temperature
RTFO Mass Loss, percent
Phase Angle, max
Elastic Recovery, min
Toughness, in lb
Tenacity, in lb
Ductility, in, min
Separation, F max
Homogeneity |
SBR Polymer
70-22M (a)
Report
<0.5
80
100
60
28
|
SBR Polymer
76-22M (b)
Report
<0.5
76
125
72
28
|
SBS Polymer
70-22M (c)
Report
<0.5
80
65
10
None Visible |
SBS Polymer
76-22M (c)
Report
<0.5
76
75
10
None Visible |
Notes
d
j
e
e
f
g,e
g,e
k,e
h
i,e |
|
|
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|
a. Post blended PGM Binder made from neat certified or pre-approved
standard PG Binder grade and rubber solids amount equal to or above 3.0
percent by weight of total binder to achieve the PG Binder grade.
b. Post blended PGM Binder made from neat certified or pre-approved
standard PG Binder grade and rubber solids amount equal to or above 4.0
percent by weight of total binder to achieve the PG Binder grade.
c. Preblended PGM Binder with a base binder of at least -22 grade or
stiffer.
d. As required by Section XXX.052.
e. PGM Binder
f. ASTM D 6084, 10cm @ 25C, hold 5 min. before cutting, on RTFO material
g. ASTM D 5801, 50cm/min @ 25C
h. Softening point difference of top and bottom of frozen sealed aluminum
tube conditioned at 340F for 48 hours. Compatibility of polymer and neat
binder is sole responsibility of supplier. PGM Binder shall be formulated
to retain dispersion for 3 days minimum. Failure in the field to retain
dispersion for this time will mean automatic removal from certification
list.
i. Heat a minimum 400 gram sample at 177C for 2.5-3 hours. Pour entire
sample over a hot No 50 (300 µm) sieve at 340F. Look for retained
polymer lumps.
j. Actual high and low temperature achieved by PGM Binder beyond required
grade, but shall not grade out to the next standard PG Binder grade for
low temperature.
k. ASTM D 113, @ 4C, 1 cm/min |
IMPORTANT NOTICE TO THE ENGINEER. The foregoing is for engineers
only for the purpose of assisting them in preparing job specifications.
Suggested specifications are for use under what may be termed “average
conditions”. No single standard specifications, however, will cover satisfactorily
all variations in local conditions relevant to individual jobs. Before
adopting suggested specifications, the owner's engineer should give particular
consideration to any special problems and make such changes as are necessary.
Nothing contained herein shall be construed as recommendations or inducements
to practice any invention covered by patent without permission of the patent
owner.
