No
4. What is the form of the tools you use for design:
a. Paper design guide / nomographs
b. Pavement
catalogue
42
c. Pavement
analysis
software
d. Pavement
design
software
5. Specify the year in which the current design method was implemented within your
organization _______
6. Give an estimated percentage of new roads constructed using:
a. Flexible pavements
____%
b. Composite
pavements*
____%
c. Rigid pavements
____%
* How much percentage are a result of HMA overlay over existing PCC**
____%
** If the percentage of composite pavements is 0%, please skip to the SECTION 5
SECTION 3
: COMPOSITE PAVEMENT DESIGN INPUTS
7. Which environmental factors are taken into consideration in the design method used:
a. Climatic zone(s)
b. Air
temperatures
c. Pavement
Temperatures
d. Detailed daily temperature data
e. Mean monthly/seasonal/annual
temperatures
f. Maximum and minimum monthly/seasonal/annual temperatures
g. Equivalent monthly/seasonal/annual temperatures
h. Precipitation
i. Frost index
j. Frost
penetration
depth
k. Other(s):_______________________________________________________
8. What kind of traffic input do you use for the design of composite pavements?
a. Equivalent Single Axle Load (ESAL)
b. Load spectra
c. Maximum
axle
or
wheel
load
9. What is the design life (in years) that composite pavements are typically designed for in
your agency?
<20
20
25
30
40
50
>50
10. During the Pavement Type Selection (PTS) process for composite pavements, which of
the following factors are considered?
a. Construction costs
b. Preventive
maintenance
costs
c. Rehabilitation
costs
43
d. User-related costs (e.g., user delay)
e. Environmental impact
f. Other(s):_______________________________________________________
11. Do you use Reliability as a part of the pavement design process? If so, what level of
reliability do you normally consider for designing composite pavements?
a. No Reliability is used
b. 85%
c. 90%
d. 95%
e. 99%
f. Other: ________________________________________________________
12. Do you use any other inputs for the design procedure (besides the material properties)
not listed above? If so, please describe.
________________________________________________________________________
SECTION 4
: COMPOSITE PAVEMENT DESIGN CRITERIA
13. What method or design procedure do you use to design composite pavements?
a. AASHTO
modified
method
b. US Navy and Military composite pavement design procedure
c. NCHRP 1-37 – Mechanistic-Empirical Pavement Design Method
d. Illinois Department of Transportation (IDOT) method
e. United Kingdom composite pavement procedure
f. Other: ________________________________________________________
14. What types of layers comprise your typical composite pavement structure?
a. Surface (flexible) layer
i. Dense Graded / Hot-Mix Asphalt (HMA)
ii. Stone Matrix Asphalt (SMA)
iii. Open-Graded Friction Course (OGFC)
b. Base (rigid) layer
i. Jointed Plain Concrete (JPC) pavement
ii. Continuously Reinforced Concrete (CRC) pavement
iii. Roller-Compacted Concrete (RCC)
1
pavement
iv. Lean Mix Concrete
2
v. Cement-Treated Base (CTB)
3
vi. Soil Cement
4
vii. Other: _______________________________________________
1
Dry concrete consistency; zero slump; vibratory compaction; compressive strength 4,000 to 10,000 psi; flexural strength 500 to 1,000 psi; modulus of elasticity
3,000,000 to 5,500,000 psi; cement content 9 to 18%.
2
Low strength concrete (low cement content); slump 1 to 3 in.; air content 4 to 8%; compressive strength at 7 days 500 psi (minimum), at 28 days 750 to 1,200
psi; cement-aggregate ratio 1:20 to 1:24 in volume.
3
Cement content 3 to 6% (weight); compressive strength at 7 days 650 psi, at 28 days 1,160 psi; modulus of elasticity 250,000 to 1,000,000 psi
4
Natural soil modified with 3 to 7% cement content; modulus of elasticity 50,000 to 100,000 psi.
44
c. Subbase
i. Granular
material
ii. Cement Modified material/soil
iii. No subbase is used for the design
iv. Other: ________________________________________________
d. Subgrade
i. Cement Modified material/soil
ii. Natural
subgrade
compacted
iii. Other: ________________________________________________
15. Are there any minimum thickness requirements for some or all of the layers of the
composite structure?
a. Surface course
______ in.
b. Base layer
______ in.
c. Subbase
______ in.
d. Subgrade
______ in.
e. No minimum thickness is required
16. For each of the layers described below, what characteristics are used in the design
procedure (please check all that apply):
a. Subgrade
i. California Bearing Ratio (CBR)
ii. Resilient Modulus (elastic stiffness)
iii. Frost
susceptibility
iv. Soil
type/classification
v. Gradation
vi. Other(s): _______________________________________________
b. Subbase
i. California Bearing Ratio (CBR)
ii. Resilient Modulus (elastic stiffness)
iii. Permeability
iv. Frost
susceptibility
v. Soil
type/classification
vi. Material strength (unconfined comp. strength)
vii. Other(s): _______________________________________________
c. Base (rigid layer)
i. Cement content
ii. Flexural strength @ 7
th
day
iii. Compressive strength @ 7
th
day
iv. Coefficient of thermal expansion
v. Other(s): _______________________________________________
d. Surface course (flexible layer)
i. Elastic
Modulus
ii. Dynamic
Modulus
iii. Rheological
properties
45
iv. Coefficient of thermal expansion
v. Fatigue
resistance
vi. Rutting
performance
vii. Other(s): _______________________________________________
17. Please specify the typical properties of the following layers in your composite pavement
system.
a. Surface course (flexible layer)
i. Asphalt content
____%
ii. Air voids (target)
____%
iii. Other(s): _______________________________________________
b. Base (rigid layer)
i. Typical cement content
____%
ii. Typical flexural strength @ 7
th
day
____psi
iii. Typical compressive strength @ 7
th
day
____psi
iv. Other(s): _______________________________________________
18. Is there a design consideration/criteria regarding the mitigation or control of reflective
cracking? If so, please describe.
a. Yes
__________________________________________________________________
b. No
SECTION 5
: CONSTRUCTABILITY
19. Have you used/placed any reflective cracking mitigation technique/method such as
Stress Absorbing Membrane Interlayer (SAMI), Microcracking, Pre-Cracking,
Geotextiles, etc.? If so, which ones and what has been your experience?
a. Yes
__________________________________________________________________
b. No
20. If you have used CTB or Soil Cement, where have you prepared this mix:
a. In the field
b. In a plant
21. Please describe any issues or challenges that composite pavements brought in your
construction.
_________________________________________________________________________
_________________________________________________________________________
SECTION 6
: COMMENTS
46
22. Please comment on any additional information that you believe could help to better the
understanding, design, and construction of composite pavements.
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
47
APPENDIX B
SURVEY RESULTS
The survey created during this study was sent to state DOT pavement design engineers.
Responses were received from 34 state DOT’s. From these responses, 11 agencies responded as
having experience designing composite pavements. Eight responses indicated the experience
came from the rehabilitation of existing rigid pavements and 3 of the 11 indicated experience
designing new composite pavements. The survey results presented in this appendix are based on
the response of all 11 states that have the experience with composite pavement design.
48
Table B.1. Summarized Survey Results
Transportation Agency
SCDOT
OhioDOT TxDOT MDOT MDSHA NJDOT
Design method for
composite pavements
AASHTO 1993
AASHTO Modified
FPS-19W
AASHTO 1993
AASHTO 1993
AASHTO 1993
New Composite pavements
in road network
2 0 4 0 0 0
Typical design life for
composite pavements
20 20 20 20 20 20
Reliability used in the
design process
No Yes Yes Yes Yes Yes
Flexible layer for CPS
HMA
HMA
HMA
HMA
HMA, SMA
HMA, SMA, OGFC
Rigid layer for CPS
CTB
JPCP CTB JRCP JPCP,
CRCP
JPCP
Subbase for CPS
Cement modified
material/soil, or no
subbase
Granular material
No subbase is used
Granular material
No subbase is used Granular
material
Subgrade for CPS
Natural subgrade
compacted
Cement modified
material/soil, and/or
natural subgrade
compacted
Lime modified
material/soil
Natural subgrade
compacted
Natural subgrade
compacted
Natural subgrade
compacted
Min. thickness for flexible
layer (inches)
4 3 2 3.5
Min. thickness for rigid
layer ( inches)
6 8 8
Typical asphalt content
4 to 6%
7%
5%
5 to 6%
5%
Typical air voids (target)
4 to 4.5%
3.5%
4%
4%
4%
4%
Typical cement content
2 to 5%
600 lb
3 to 4%
Typical compressive
strength
600 psi @ 14 days
350 psi @ 7 days
Design criteria or
consideration for reflective
cracking
Yes Yes Yes Yes Yes Yes
Comments
Their philosophy is
to use a low strength
cement-treated base
material to control
shrinkage cracking
and place that layer
at a relatively high
thickness to avoid
fatigue cracking.
Their design
procedure for
composite pavements
consists of designing
a rigid pavement and
then reducing the
thickness of the
concrete by one inch
and add a three inch
asphalt surface.
Microcracking of the
CTB has been used
as a method to retard
reflective cracking
on the surface
course.
Ongoing research has
shown Strata and
other interlayer
mixtures to be
effective, binder rich
surfaces such as
SMA and OGFC
perform better that
SUPERPAVE, geo-
textiles have not been
very effective.
49
Transportation Agency
GaDOT
CODOT TnDOT ConnDOT
IowaDOT
Design method for
composite pavements
AASHTO 1972
AASHTO 1993
AASHTO 1993
AASHTO Modified
AASHTO 1993
Composite pavements in
road network
0 0 2 0 0
Typical design life for
composite pavements
20 20 20 20 20
Reliability used in the
design process
No Yes Yes Yes Yes
Flexible layer for CPS
HMA, SMA, OGFC
HMA, SMA
HMA
HMA
HMA
Rigid layer for CPS
JPCP, CRCP
JPCP, CTB, Soil Cement
CTB, Lime Fly-ash
JPCP, JRCP JPCP,
CRCP
Subbase for CPS
Granular material
Granular material,
Cement modified
material/soil, or no
subbase is used.
No subbase design unless
soil conditions (CBR less
than 3) warrant cement
modified soil.
Granular material
Granular material
Subgrade for CPS
Cement modified
material/soil, natural
subgrade compacted
Cement modified
material/soil, natural
subgrade compacted
Natural subgrade
compacted
Natural subgrade
compacted
Natural subgrade
compacted
Min. thickness for flexible
layer (inches)
5.5
9.25 3 3
Min. thickness for rigid
layer (inches)
5
Typical asphalt content
5%
5.5%
3 to 8%
5%
6%
Typical
air
voids
(target)
7% 4% 4% 4%
Typical cement content
4%
Typical compressive
strength
Design criteria or
consideration for reflective
cracking
Yes No No Yes No
Comments
A drainage layer is used
on top of the rigid base
layer.
Requirement: PCC
Modulus of Rupture (700
psi), also PCC Elastic
modulus (typically
3,500,000 psi)
Modulus of Rupture
(MOR) of 650 psi @ 28
days
50
Detailed Survey Results
The following are plots and pie charts that represent the 11 responses from the DOTs that
had some degree of experience with composite pavements.
Figure B.1. Survey participants (in red [dark]).
51
Figure B.2. Survey participants indicating experience with composite pavement design (in green [dark]).
52
Figure B.3. Response to Question 1, What is the name (or acronym) of the design method used by your
agency/company for flexible pavement design?
Figure B.4. Response to Question 2, What is the name (or acronym) of the design method used by your
agency/company for rigid pavement design?
53
Figure B.5. Response to Question 3, What is the name (or acronym) of the design method used by your
agency/company for composite pavement design?
Figure B.6. Response to Question 10, During the Pavement Type Selection (PTS) process for composite
pavements, which of the following factors are considered?
Figure B.7. Response to Question 14, What types of layers comprise your typical composite pavement structure?
54
Figure B.8. Response to Question 15, Are there any minimum thickness requirements for some or all of the
layers of the composite structure?
55
Survey Comments
The following lists the comments from the survey responses from the 11 states that have
some degree of experience with composite pavements:
• All DOTs use ESALs as the preferred traffic input parameters for designing
composite pavements.
• TxDOT, SCDOT, and TnDOT construct new composite pavements (i.e., composite
pavements that are not the result of a HMA overlay of an already in-service rigid
pavement).
• MDSHA is the only transportation agency that recommends the use of a permeable
drainage layer on top of the rigid base layer. They state that this permeable drainage
layer works well enough, especially when compared to some cases where no drainage
layer exists.
• Most DOTs—with the exception of CODOT, TnDOT, and IowaDOT—have a design
consideration or criteria regarding the mitigation or control of reflective cracking.
• SCDOT: Uses a low-strength CTB to control shrinkage cracking and places that layer
at a relatively high thickness to avoid fatigue cracking. This results in pavements
with very low surface deflections (2-5 mils at 9-kips).
• Ohio DOT: Design procedure for composite pavements consists of designing a rigid
pavement and then reducing the concrete thickness by one inch and add a three inch
asphalt surface course.
• ConnDOT:
— Sawing and sealing performance has been observed to depend on very accurate
placement of saw cut (within 2 in. in many cases), and its beneficial effects are
higher the thinner the AC layer over PCC.
— Milling to expose the PCC slab and full-depth repair of PCC joints that are
deteriorated in the existing PCC slab is essential to achieving performance in their
experience.
— Have not considered building brand-new composite pavements as the benefits are
unclear (beyond perhaps noise reduction).
20>
Chia sẻ với bạn bè của bạn: |