ASTM D7564/D7564M-09(2015)
(Practice)Standard Practice for Construction of Asphalt-Rubber Cape Seal
Standard Practice for Construction of Asphalt-Rubber Cape Seal
SIGNIFICANCE AND USE
3.1 The procedure described in this practice is used to design and construct an asphalt-rubber cape seal that will provide a wearing course when subjected to low to medium traffic volumes and where the pavement distress is due to block-type cracking resulting from pavement aging or reflective cracking only (not where there are clear indications of fatigue cracking due to repeated heavy axle loads).
Note 2: Block cracking is defined in Practice D6433. See Appendix X1 for an example of block cracking due to aging.
SCOPE
1.1 This practice covers asphalt-rubber cape seal, which is defined as the application of an asphalt-rubber seal coat placed onto an existing pavement surface, followed by the application of a conventional Type II or III slurry seal.
Note 1: An asphalt-rubber seal coat is also known as a stress absorbing membrane (SAM) which consists of an asphalt-rubber membrane seal followed by the application of precoated aggregate chips.
1.2 An asphalt-rubber cape seal is commonly used to extend the service life of low to medium trafficked and moderately distressed asphalt-surfaced pavements. The existing pavement condition can be used to determine the application rates for the asphalt-rubber binder and aggregate as well as the aggregate gradation. Pavements in relatively poor condition will require a coarser aggregate with a higher binder application rate.
1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
1.4 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.
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Designation: D7564/D7564M − 09(Reapproved 2015)
Standard Practice for
Construction of Asphalt-Rubber Cape Seal
This standard is issued under the fixed designation D7564/D7564M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope C127 Test Method for Relative Density (Specific Gravity)
and Absorption of Coarse Aggregate
1.1 This practice covers asphalt-rubber cape seal, which is
C128 Test Method for Relative Density (Specific Gravity)
defined as the application of an asphalt-rubber seal coat placed
and Absorption of Fine Aggregate
onto an existing pavement surface, followed by the application
C131 Test Method for Resistance to Degradation of Small-
of a conventional Type II or III slurry seal.
Size CoarseAggregate byAbrasion and Impact in the Los
NOTE 1—An asphalt-rubber seal coat is also known as a stress
Angeles Machine
absorbing membrane (SAM) which consists of an asphalt-rubber mem-
C136 Test Method for Sieve Analysis of Fine and Coarse
brane seal followed by the application of precoated aggregate chips.
Aggregates
1.2 Anasphalt-rubbercapesealiscommonlyusedtoextend
D946 Specification for Penetration-Graded Asphalt Cement
the service life of low to medium trafficked and moderately
for Use in Pavement Construction
distressed asphalt-surfaced pavements. The existing pavement
D1139 Specification for Aggregate for Single or Multiple
condition can be used to determine the application rates for the
Bituminous Surface Treatments
asphalt-rubber binder and aggregate as well as the aggregate
D2196 Test Methods for Rheological Properties of Non-
gradation. Pavements in relatively poor condition will require
Newtonian Materials by Rotational Viscometer
a coarser aggregate with a higher binder application rate.
D2419 Test Method for Sand Equivalent Value of Soils and
1.3 The values stated in either SI units or inch-pound units
Fine Aggregate
are to be regarded separately as standard. The values stated in
D3381 Specification for Viscosity-Graded Asphalt Cement
each system may not be exact equivalents; therefore, each
for Use in Pavement Construction
system shall be used independently of the other. Combining
D3910 Practices for Design, Testing, and Construction of
values from the two systems may result in non-conformance
Slurry Seal
with the standard.
D4791 Test Method for Flat Particles, Elongated Particles,
or Flat and Elongated Particles in Coarse Aggregate
1.4 This standard does not purport to address all of the
D5360 Practice for Design and Construction of Bituminous
safety concerns, if any, associated with its use. It is the
Surface Treatments
responsibility of the user of this standard to establish appro-
D5821 Test Method for Determining the Percentage of
priate safety and health practices and determine the applica-
Fractured Particles in Coarse Aggregate
bility of regulatory limitations prior to use.
D6114 Specification for Asphalt-Rubber Binder
2. Referenced Documents D6373 Specification for Performance Graded Asphalt
Binder
2.1 ASTM Standards:
D6433 Practice for Roads and Parking Lots Pavement Con-
C29/C29M Test Method for Bulk Density (“Unit Weight”)
dition Index Surveys
and Voids in Aggregate
C117 Test Method for Materials Finer than 75-µm (No. 200)
3. Significance and Use
Sieve in Mineral Aggregates by Washing
3.1 The procedure described in this practice is used to
design and construct an asphalt-rubber cape seal that will
This practice is under the jurisdiction of ASTM Committee D04 on Road and
provide a wearing course when subjected to low to medium
Paving Materials and is the direct responsibility of Subcommittee D04.24 on
Asphalt Surface Treatments.
traffic volumes and where the pavement distress is due to
Current edition approved Jan. 1, 2015. Published February 2015. Originally
block-type cracking resulting from pavement aging or reflec-
approved in 2009. Last previous edition approved in 2009 as D7564/D7564M – 09.
tive cracking only (not where there are clear indications of
DOI: 10.1520/D7564_D7564M-09R15.
fatigue cracking due to repeated heavy axle loads).
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on NOTE 2—Block cracking is defined in Practice D6433. See Appendix
the ASTM website. X1 for an example of block cracking due to aging.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7564/D7564M − 09 (2015)
see the Caltrans Maintenance Technical Advisory Guideline (MTAG).
4. Materials
Also shown in Appendix X2 is a suggested FHWAasphalt-rubber surface
4.1 Asphalt-Rubber Seal Coat (or Stress Absorbing
treatment design procedure.
Membrane—SAM):
4.2 Emulsified Asphalt Slurry Seal—The design and con-
4.1.1 Asphalt Cement—The asphalt cement for the asphalt-
struction of the slurry seal shall conform to Practice D3910.
rubber seal coat should comply with the requirements of
Specifications D946, D3381,or D6373. Asphalt cement grade
5. Construction of Asphalt-Rubber Cape Seal
selection is based on considerations of local climatic and traffic
5.1 Application of Asphalt-Rubber Binder:
conditions.The asphalt-rubber supplier should perform routine
5.1.1 The following construction recommendations are rep-
Q/C laboratory testing to ensure compatibility of the selected
resentative of the state-of-the-art practice and are not a
asphalt cement with the requirements of Specification D6114.
specification.
4.1.2 Asphalt-Rubber—The asphalt-rubber binder consists
5.1.2 It is recommended that the asphalt-rubber binder for
of an interacted blend of paving grade asphalt cement, ground
the asphalt rubber seal coat be applied at a rate of 2.0–3.0
recycled tire rubber, and other additives as needed to conform
2 2
L/m [0.50–0.75 gallons/yd ]. For pavement classified in fair
to the requirements of Specification D6114.
condition with a Pavement Condition Index (PCI) rating of 35
4.1.3 Aggregate—Aggregate consists of crushed materials
to 55 in accordance with Practice D6433, a lower application
conforming to the physical requirements of Specification
rate (generally with a finer aggregate gradation) is recom-
D1139 for degradation, soundness, and deleterious substances
mended and should generally range from 2.0–2.5
and, if the –4.75 mm [–No. 4] materials exceed 2 % of the total
3 2
L/m [0.50–0.65 gallons/yd ]. For pavement classified in poor
weight of aggregate, a minimum sand equivalent value of 50
condition with a PCI rating of 25 to 35 in accordance with
when tested in accordance with Test Method D2419 is re-
Practice D6433, a higher application rate (generally with a
quired. At least 90 percent by weight of the coarse aggregate
coarser aggregate gradation) is recommended, generally in the
shall consist of crushed particles with at least two fractured
3 2
range of 2.5–3.0 L/m [0.65–0.75 gallons/yd ].
faces as determined by Test Method D5821.
5.1.3 It is recommended that the Asphalt-rubber binder be
4.1.4 Aggregate Gradation—Aggregate size is often repre-
placed upon a clean, dry pavement surface. The pavement
sented by one of the following gradations and determined in
surface temperature is generally limited to a minimum of 13°C
accordance with Test Methods C136 and C117. Other similar
[55°F] and rising when the asphalt rubber binder is applied.
gradations may be used, as appropriate.
The recommended minimum atmospheric temperature should
Sieve Size Percent Passing Percent Passing
be 16°C [60°F] and rising.
19.5mm[ ⁄4 in.] 100 100
12.5mm[ ⁄2 in.] 95–100 95–100
NOTE 5—Placement of asphalt-rubber binder below the minimum
9.50 mm [ ⁄8 in.] 0–20 70–85
temperatures may cool the material to such a degree that the aggregate
4.75 mm [No. 4] 0–5 0–15
maynotembedandstick.Thismayleadtotheprematurelossofaggregate
2.36 mm [No. 8] 0–2 0–5
and bleeding or flushing of the surface.
0.075 mm [No. 200] 0–1 0–1
5.1.4 Distributorbarheight,distributionspeedandshielding
NOTE 3—The two examples shown in the table above are representative
materials can be utilized to reduce the effects of wind on the
of typical gradations from current state highway or transportation depart-
ments or other user agencies and from industry specifications for
spray distribution. Typically distributor bar height varies be-
asphalt-rubber seal coat. Either gradation may be used for pavements with
tween 200 and 350 mm [8–14 in.].
block cracking (see Appendix X1). The first (predominately 12.5 mm [ ⁄2
in.]) gradation is recommended for pavements with a high degree of block
NOTE 6—When high gusting winds or dusty conditions (or both)
cracking. The second (predominately 9.5 mm [ ⁄8 in.]) gradation is prevent or adversely affect binder or aggregate spreading application
recommended for pavements with a lesser degree of block cracking (see
operations, the work should be suspended and rescheduled.
Practice D6433, Figure X1.7 through X1.9).
5.1.5 All necessary equipment should be in position and
4.1.5 Selection of Coarse Aggregate—Coarse aggregate
ready to commence placement operations before starting the
shallhaveabrasionvaluesoflessthan30percentinaccordance
work.
with Test Method C131. Crushed gravel (if used) must have at
5.1.6 The asphalt rubber binder is applied to the pavement
least 90 percent particles with two faces and 95 percent
surface after mixing and reacting, consistent with the require-
particles with one face resulting from crushing in accordance
ments of Specification D6114. The binder should be applied at
with Test Method D5821. The percentage of flat and elongated
a material temperature not less than 195°C [385°F] or more
particles should not exceed 10 %, with a ratio of 5:1 in
than 215°C [415°F].
maximum to minimum dimension, respectively, in accordance
5.1.7 Following the asphalt-rubber binder application, the
with Test Method D4791.
binder should be promptly covered with the pre-coated aggre-
4.1.6 Design—Unlessprojectdocumentsindicateotherwise,
gate.
the seal coat shall be designed in accordance with Practice
NOTE 7—Experience has shown that if more than 2 minutes elapse
D5360 in general, modified for asphalt-rubber applications as
before the covering of the asphalt-rubber binder, the cover aggregate may
described in this practice. The asphalt-rubber binder is spray-
not properly embed into the binder. This could lead to premature raveling
applied using an application rate specified in Section 5.1.2,
followed by the application of aggregate chips using an
Caltrans, Maintenance Technical Advisory Guide (MTAG), State of California
application rate specified in 5.3.4.
Department of Transportation, Office of Pavement Preservation, Division of
NOTE 4—For more detailed asphalt-rubber seal coat design guidelines Maintenance, Sacramento, California, October, 2003.
D7564/D7564M − 09 (2015)
or unsuitable bleeding or flushing (or both) of the pavement surface. aging and weathering, not traffic loads and fatigue cracking. All underly-
Pre-coated aggregate as described in 5.3.1 is preferred in order to ensure ing subgrade or base failures (or both) should be corrected and any
a good bond to the asphalt-rubber binder and avoid aggregate chip loss. drainage problems should be rectified.
5.2 Workmanship, Finish and Appearance:
5.3.5 The spread rate is generally limited to any value
within 610 percent of the selected application rate during
5.2.1 When joining edges against areas with aggregate, the
joints should be swept clean of excess aggregate prior to the spreading to provide a uniform appearance.
adjacent application of asphalt rubber binder. Transverse joints
NOTE 10—The term “uniform appearance” refers to a surface that is
of this type are constructed by placing roofing paper or
generally free of gaps, ridges, depressions, or other irregularities caused
equivalent across and over the end of the previous asphalt
by the application of the asphalt rubber seal coat.
rubber seal coat application. Once spraying has progressed
5.4 Finishing of the Asphalt-Rubber Seal Coat:
beyond the paper, it should be removed immediately.
5.4.1 Thefirstpassoftherollersoverthenewasphaltrubber
5.2.2 The longitudinal joint between adjacent applications
seal coat consists of a minimum of one complete coverage
of aggregate should coincide with the line between designated
(covering the entire width of the seal, moving forward), using
traffic lanes. Longitudinal joints are overlapped for complete
the necessary number of pneumatic tired rollers. Rolling
coverage.
should be completed as soon as practical using three complete
NOTE 8—Overlapping of longitudinal joints is recommended to ensure
passes, which is defined as the first rolling pass moving
complete aggregate coverage. Lack of overlapping may result in exposed
forward, a second pass moving backward, and a final third pass
asphalt-rubber binder without aggregate, which may cause excessive
moving forward again to the next section thus covering each
tracking of the asphalt-rubber binder. Generally, overlapping is between
point on the pavement surface three times (up, back, and up).
100 mm and 200 mm [4–8 in.].
5.2.3 Atlongitudinaljointswithaggregate,theedgesshould NOTE 11—Rolling should occur immediately after the spreading of the
pre-coated aggregate and should be concluded as rapidly as practical to
be broomed back and blended to minimize differences in
ensure good aggregate embedment and bonding.The distance between the
elevation, in order to provide a uniform appearance consistent
rollers and the aggregate spreader generally should not exceed 60 m [200
with the adjacent sealed surface. Care should be taken to
feet] at any time during spreading operations. Rollers should be staggered
minimize ridges and depressions in order to enhance unifor-
in such a manner so full-width rolling coverage is ensured.
mity of appearance.
5.4.2 In addition to the pneumatic tired rolling described in
5.2.4 The application of asphalt rubber binder to areas not
Section 5.4.1, one additional roller coverage with one steel
accessible with the distributor bar on the distributor truck is
wheel roller may be needed to properly seat the aggregate.
generally accomplished by using pressurized hand wands or by
Steel wheel rolling coverage may be beneficial in reducing the
other appropriate means.
amount of loose aggregate during sweeping operations. If a
5.3 Spreading Pre-coated Aggregate: steel wheel roller is used, t
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7564/D7564M − 09 D7564/D7564M − 09 (Reapproved 2015)
Standard Practice for
Construction of Asphalt-Rubber Cape Seal
This standard is issued under the fixed designation D7564/D7564M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice covers asphalt-rubber cape seal, which is defined as the application of an asphalt-rubber seal coat placed onto
an existing pavement surface, followed by the application of a conventional Type II or III slurry seal.
NOTE 1—An asphalt-rubber seal coat is also known as a stress absorbing membrane (SAM) which consists of an asphalt-rubber membrane seal
followed by the application of precoated aggregate chips.
1.2 An asphalt-rubber cape seal is commonly used to extend the service life of low to medium trafficked and moderately
distressed asphalt-surfaced pavements. The existing pavement condition can be used to determine the application rates for the
asphalt-rubber binder and aggregate as well as the aggregate gradation. Pavements in relatively poor condition will require a
coarser aggregate with a higher binder application rate.
1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
C29/C29M Test Method for Bulk Density (“Unit Weight”) and Voids in Aggregate
C117 Test Method for Materials Finer than 75-μm (No. 200) Sieve in Mineral Aggregates by Washing
C127 Test Method for Density, Relative Density (Specific Gravity), and Absorption of Coarse Aggregate
C128 Test Method for Density, Relative Density (Specific Gravity), and Absorption of Fine Aggregate
C131 Test Method for Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles
Machine
C136 Test Method for Sieve Analysis of Fine and Coarse Aggregates
D946 Specification for Penetration-Graded Asphalt Cement for Use in Pavement Construction
D1139 Specification for Aggregate for Single or Multiple Bituminous Surface Treatments
D2196 Test Methods for Rheological Properties of Non-Newtonian Materials by Rotational (Brookfield type) Viscometer
D2419 Test Method for Sand Equivalent Value of Soils and Fine Aggregate
D3381 Specification for Viscosity-Graded Asphalt Cement for Use in Pavement Construction
D3910 Practices for Design, Testing, and Construction of Slurry Seal
D4791 Test Method for Flat Particles, Elongated Particles, or Flat and Elongated Particles in Coarse Aggregate
D5360 Practice for Design and Construction of Bituminous Surface Treatments
D5821 Test Method for Determining the Percentage of Fractured Particles in Coarse Aggregate
D6114 Specification for Asphalt-Rubber Binder
D6373 Specification for Performance Graded Asphalt Binder
D6433 Practice for Roads and Parking Lots Pavement Condition Index Surveys
This practice is under the jurisdiction of ASTM Committee D04 on Road and Paving Materials and is the direct responsibility of Subcommittee D04.24 on
BituminousAsphalt Surface Treatments.
Current edition approved Aug. 1, 2009Jan. 1, 2015. Published September 2009February 2015. Originally approved in 2009. Last previous edition approved in 2009 as
D7564/D7564M – 09. DOI: 10.1520/D7564_D7564M-09.10.1520/D7564_D7564M-09R15.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7564/D7564M − 09 (2015)
3. Significance and Use
3.1 The procedure described in this practice is used to design and construct an asphalt-rubber cape seal that will provide a
wearing course when subjected to low to medium traffic volumes and where the pavement distress is due to block-type cracking
resulting from pavement aging or reflective cracking only (not where there are clear indications of fatigue cracking due to repeated
heavy axle loads).
NOTE 2—Block cracking is defined in Practice D6433. See Appendix X1 for an example of block cracking due to aging.
4. Materials
4.1 Asphalt-Rubber Seal Coat (or Stress Absorbing Membrane—SAM):
4.1.1 Asphalt Cement—The asphalt cement for the asphalt-rubber seal coat should comply with the requirements of
Specifications D946, D3381, or D6373. Asphalt cement grade selection is based on considerations of local climatic and traffic
conditions. The asphalt-rubber supplier should perform routine Q/C laboratory testing to ensure compatibility of the selected
asphalt cement with the requirements of Specification D6114.
4.1.2 Asphalt-Rubber—The asphalt-rubber binder consists of an interacted blend of paving grade asphalt cement, ground
recycled tire rubber, and other additives as needed to conform to the requirements of Specification D6114.
4.1.3 Aggregate—Aggregate consists of crushed materials conforming to the physical requirements of Specification D1139 for
degradation, soundness, and deleterious substances and, if the –4.75 mm [–No. 4] materials exceed 2 % of the total weight of
aggregate, a minimum sand equivalent value of 50 when tested in accordance with Test Method D2419 is required. At least 90
percent by weight of the coarse aggregate shall consist of crushed particles with at least two fractured faces as determined by Test
Method D5821.
4.1.4 Aggregate Gradation—Aggregate size is often represented by one of the following gradations and determined in
accordance with Test Methods C136 and C117. Other similar gradations may be used, as appropriate.
Sieve Size Percent Passing Percent Passing
19.5 mm [ ⁄4 in.] 100 100
12.5 mm [ ⁄2 in.] 95–100 95–100
9.50 mm [ ⁄8 in.] 0–20 70–85
4.75 mm [No. 4] 0–5 0–15
2.36 mm [No. 8] 0–2 0–5
0.075 mm [No. 200] 0–1 0–1
NOTE 3—The two examples shown in the table above are representative of typical gradations from current state highway or transportation departments
or other user agencies and from industry specifications for asphalt-rubber seal coat. Either gradation may be used for pavements with block cracking (see
Appendix X1). The first (predominately 12.5 mm [ ⁄2 in.]) gradation is recommended for pavements with a high degree of block cracking. The second
(predominately 9.5 mm [ ⁄8 in.]) gradation is recommended for pavements with a lesser degree of block cracking (see Practice D6433, Figure X1.7 through
X1.9).
4.1.5 Selection of Coarse Aggregate—Coarse aggregate shall have abrasion values of less than 30 percent in accordance with
Test Method C131. Crushed gravel (if used) must have at least 90 percent particles with two faces and 95 percent particles with
one face resulting from crushing in accordance with Test Method D5821. The percentage of flat and elongated particles should not
exceed 10 %, with a ratio of 5:1 in maximum to minimum dimension, respectively, in accordance with Test Method D4791.
4.1.6 Design—Unless project documents indicate otherwise, the seal coat shall be designed in accordance with Practice D5360
in general, modified for asphalt-rubber applications as described in this practice. The asphalt-rubber binder is spray-applied using
an application rate specified in Section 5.1.2, followed by the application of aggregate chips using an application rate specified in
5.3.4.
NOTE 4—For more detailed asphalt-rubber seal coat design guidelines see the Caltrans Maintenance Technical Advisory Guideline (MTAG). Also
shown in Appendix X2 is a suggested FHWA asphalt-rubber surface treatment design procedure.
4.2 Emulsified Asphalt Slurry Seal—The design and construction of the slurry seal shall conform to Practice D3910.
5. Construction of Asphalt-Rubber Cape Seal
5.1 Application of Asphalt-Rubber Binder:
5.1.1 The following construction recommendations are representative of the state-of-the-art practice and are not a specification.
5.1.2 It is recommended that the asphalt-rubber binder for the asphalt rubber seal coat be applied at a rate of 2.0–3.0
2 2
L/m [0.50–0.75 gallons/yd ]. For pavement classified in fair condition with a Pavement Condition Index (PCI) rating of 35 to 55
in accordance with Practice D6433, a lower application rate (generally with a finer aggregate gradation) is recommended and
3 2
should generally range from 2.0–2.5 L/m [0.50–0.65 gallons/yd ]. For pavement classified in poor condition with a PCI rating of
25 to 35 in accordance with Practice D6433, a higher application rate (generally with a coarser aggregate gradation) is
3 2
recommended, generally in the range of 2.5–3.0 L/m [0.65–0.75 gallons/yd ].
Caltrans, Maintenance Technical Advisory Guide (MTAG), State of California Department of Transportation, Office of Pavement Preservation, Division of Maintenance,
Sacramento, California, October, 2003.
D7564/D7564M − 09 (2015)
5.1.3 It is recommended that the Asphalt-rubber binder be placed upon a clean, dry pavement surface. The pavement surface
temperature is generally limited to a minimum of 13°C [55°F] and rising when the asphalt rubber binder is applied. The
recommended minimum atmospheric temperature should be 16°C [60°F] and rising.
NOTE 5—Placement of asphalt-rubber binder below the minimum temperatures may cool the material to such a degree that the aggregate may not
embed and stick. This may lead to the premature loss of aggregate and bleeding or flushing of the surface.
5.1.4 Distributor bar height, distribution speed and shielding materials can be utilized to reduce the effects of wind on the spray
distribution. Typically distributor bar height varies between 200 and 350 mm [8–14 in.].
NOTE 6—When high gusting winds or dusty conditions (or both) prevent or adversely affect binder or aggregate spreading application operations, the
work should be suspended and rescheduled.
5.1.5 All necessary equipment should be in position and ready to commence placement operations before starting the work.
5.1.6 The asphalt rubber binder is applied to the pavement surface after mixing and reacting, consistent with the requirements
of Specification D6114. The binder should be applied at a material temperature not less than 195°C [385°F] or more than 215°C
[415°F].
5.1.7 Following the asphalt-rubber binder application, the binder should be promptly covered with the pre-coated aggregate.
NOTE 7—Experience has shown that if more than 2 minutes elapse before the covering of the asphalt-rubber binder, the cover aggregate may not
properly embed into the binder. This could lead to premature raveling or unsuitable bleeding or flushing (or both) of the pavement surface. Pre-coated
aggregate as described in 5.3.1 is preferred in order to ensure a good bond to the asphalt-rubber binder and avoid aggregate chip loss.
5.2 Workmanship, Finish and Appearance:
5.2.1 When joining edges against areas with aggregate, the joints should be swept clean of excess aggregate prior to the adjacent
application of asphalt rubber binder. Transverse joints of this type are constructed by placing roofing paper or equivalent across
and over the end of the previous asphalt rubber seal coat application. Once spraying has progressed beyond the paper, it should
be removed immediately.
5.2.2 The longitudinal joint between adjacent applications of aggregate should coincide with the line between designated traffic
lanes. Longitudinal joints are overlapped for complete coverage.
NOTE 8—Overlapping of longitudinal joints is recommended to ensure complete aggregate coverage. Lack of overlapping may result in exposed
asphalt-rubber binder without aggregate, which may cause excessive tracking of the asphalt-rubber binder. Generally, overlapping is between 100 mm
and 200 mm [4–8 in.].
5.2.3 At longitudinal joints with aggregate, the edges should be broomed back and blended to minimize differences in elevation,
in order to provide a uniform appearance consistent with the adjacent sealed surface. Care should be taken to minimize ridges and
depressions in order to enhance uniformity of appearance.
5.2.4 The application of asphalt rubber binder to areas not accessible with the distributor bar on the distributor truck is generally
accomplished by using pressurized hand wands or by other appropriate means.
5.3 Spreading Pre-coated Aggregate:
5.3.1 Following the application of the asphalt rubber binder, the pre-coated aggregate is placed over areas receiving asphalt
rubber binder. The aggregate should be pre-coated using 0.5–1.0 % asphalt cement by weight of aggregate, conforming to
Specifications D946, D3381, or D6373.
5.3.2 Aggregate for the asphalt rubber seal coat should be pre-coated at the hot plant at a temperature between 135°C and 165°C
[275–325°F] and then applied at a temperature not less than 105°C (225°F) after applying the asphalt rubber binder.
5.3.3 No vehicle, including construction equipment, should be driven over the asphalt rubber binder prior to the application of
the pre-coated aggregate.
2 2
5.3.4 The precoated aggregate is generally applied at a rate of 10.5–16.0 kg/m [23–34 lbs/yd ] depending on the pavement
condition. For pavement in fair condition with a PCI rating of 40 to 55 in accordance with Practice D6433, the finer 9.5 mm [ ⁄8
2 2
in.] aggregate gradation (or a similar gradation) is recommended, with a spread rate of 10.5–13.5 kg/m [23–30 lbs/ydlbs ⁄yd ]. For
pavement in poor condition with a PCI rating of 25 to 40 in accordance with Practice D6433, the coarser 12.5 mm [ ⁄2 in.] aggregate
2 2
gradation (or a similar gradation) is recommended with an spread rate of 12.0–16.0 kg/m [27–34 lbs/yd ].
NOTE 9—Although an asphalt-rubber cape seal has been used on pavements in poor condition, the designer should consider many factor
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