View
93
Download
2
Category
Preview:
DESCRIPTION
FLEXIBLE OVERLAYS FOR RIGID PAVEMENTS. Camille Crichton- Sumners Manager, Bureau of Research NJ Department of Transportation http://www.state.nj.us/transportation/refdata/research 609-530-5966 - PowerPoint PPT Presentation
Citation preview
FLEXIBLE OVERLAYS FOR RIGID PAVEMENTS
Camille Crichton-SumnersManager, Bureau of ResearchNJ Department of Transportationhttp://www.state.nj.us/transportation/refdata/research609-530-5966
Principal Investigator: Tom Bennert, Ph.D. Rutgers University, Center for Advanced Infrastructure and Transportation
Project Number:FHWA-NJ-2009-014
Problem Statement
• PCC reconstruction costly and timely– Rubblization is option, but require minimum of 6 inches hot mix
asphalt cover– HMA cover requirements restricts area with overhead clearance
and/or guide rail issues• PCC rehabilitation generally not successful• Most simple rehabilitation technique – Hot Mix Asphalt
(HMA) Overlay– Unfortunately, high deflections at PCC joints/cracks creates
excessive straining in HMA overlay– Most cases, cracking initiated in HMA above crack/joint in PCC
(called Reflective Cracking)
Problem Statement - continued• When reflective crack reaches pavement
surface– Affects overall integrity of pavement
• Smoothness – intermittent cracking also affects safety
• Pathway for water intrusion• Area for immediate raveling
• Little guidance on how to design HMA overlays for PCC pavements– HMA material/mixture selection
• Immediate need to develop a rational methodology of HMA mixture selection/design methodology for overlaying PCC pavements
Research Approach• Literature Review• National Survey (Distributed to all 50 states – state
pavement designers and materials engineers)• Develop Methodology
– Based on information collected• Develop Test Sites (PA, Mass, NJ)
– Field Evaluation– Laboratory Evaluation
• Analyze collected data and evaluate prediction methodology
• Develop a Decision Tree Methodology for HMA Overlay Design for PCC Pavements
• Conclusions/Recommendations
Major Conclusions from Literature Review• Major mechanism generating reflective cracking is tensile strain at
bottom of PCC– Shearing at joint/crack an accelerator not initiator (if cracking can be mitigated,
shearing should not result in cracking)• All PCC pavements respond differently in both vertical and
horizontal mode – need methods to test/identify potential magnitude of movements (Load and Climate related)
• Best mechanical laboratory tests for simulation– Vertical Bending: Flexural Beam Fatigue– Horizontal Deflection: Overlay Tester (HMA) and Coefficient of Thermal
Expansion (PCC)• Critical cracking condition
– Air temperatures already low and climate under-going a cooling cycle• HMA brittle – more crack prone to vertical and horizontal movements• PCC slabs contracting
Major Conclusions from Literature Review - continued
• No consensus exists on successful mitigation methods– Did indicate geotextiles/fabrics poor in colder climates
• Strain-tolerant interlayers (asphalt mixtures) excellent fracture resistance compared to conventional dense graded mixtures– Help to reduce strain magnitudes– Residual strain still may be too high for conventional
mixes• When field deformations at PCC joint/crack are accurately
measured, these deformations can be used in laboratory to simulate field movements– Provides reasonable estimates on reflective cracking life
MT
WY
ID
WA
OR
NV
UT
CA
AZ
ND
SD
NE
CO
NM
TX
OK
KS
AR
LA
MO
IA
MN
WI
IL IN
KY
TN
MS AL GA
FL
SC
NC
VAWV
OH
MI
NY
PA
MD
DE
NJ
CTRI
MA
ME
VT
NH
AK
HI RespondedNo Response
28 Responding StatesNational Survey on Reflective Cracking
Reflective Cracking Mitigation Methods
9 97
10
3
59
7
4
6
10
21
0
5
10
15
20
25
30
PFG GEO SAMI's RCRI CAL EOT
Num
ber o
f Sta
te H
ighw
ay A
genc
ies
(SH
A)
SuccessfulUnsuccessful
Summary of Survey Responses Reflective cracking appeared to occur equally at different
traffic levels and base types General trends to greater reflective cracking life at
stronger base materials (PCC and Bit-treated) Shorter joint spacing generally had longer life HMA overlay material (asphalt binder type) had large
impact on reflective cracking HMA overlay needs to be resistant to cracking at low
temperatures (different than thermal-induced cracking) Using one grade or more less than LTPPbind was more
successful
Summary of Survey Responses PCC Treatments
Variety of treatments have been used but with varying success – based on responses, joint/slab replacement most effective
Reflective Cracking Mitigation Methods Better performing mitigation methods were asphalt based
(SAMI’s and RCRI mixes) Both commonly use low temperature, crack-resistant
binders Performance influenced by RCRI overlay material
States in warmer/milder climates had better success with paving fabrics, geosynthetics, and geogrids (similar conclusions by Lytton and Button, 2007)
Excessive Overlay thickness successful 33% of time
Proposed Analysis Methods
• Since shear mode mainly a crack accelerator, to mitigate reflective cracking, methodology to concentrate on bending (vertical) and expansion/contraction (horizontal)
• Bending – Vertical Mode– Utilize Falling Weight Deflectometer to model PCC joint/crack vertical
deflections– Model movements in Flexural Beam Fatigue
• Expansion/Contraction – Horizontal Mode– Utilize pavement characteristics, Coefficient of Thermal Expansion, and
climate conditions to determine horizontal movements– Model movements in Overlay Tester– Overlay Tester used to assess cracking limits of hot mix asphalt in
horizontal mode
Test Sections in Research Study
• Rt 34N – New Jersey– 3 Test Sections (1 Control; 2 Reflective Crack Relief Interlayers)
• Rt 202S – New Jersey– 4 Test Sections (1 Control; 3 Various Materials)
• Interstate 495 – Massachusetts– 2 Test Sections
• Interstate 476 – Pennsylvania– 1 Test Section
• Each pavement had traffic information, Falling Weight Deflectometer testing, material sampling and climatic conditions
Total of Eleven (11) Test Sections
Rt 34N, New Jersey – Extracted Core
9.5H76
RCRI
12.5M76
Rt 34N, New Jersey (Section #3)
0
10
20
30
40
50
60
0 1 2 3 4 5 6 7 8 9 10Time After Construction (Years)
Perc
ent o
f Tra
nsve
rse
Join
ts C
rack
ed (%
) 9.5H7612.5M76RCRI (Strata)Measured
RCRI
12.5M76 9.5H76
Measured
I495, Massachusetts – Extracted Core
RCRI
LevelingCourse
IntermediateCourse
I476, Pennsylvania (75 Gyration Surface Mix)
0
10
20
30
40
50
60
70
80
90
100
0 6 12 18 24 30 36Time After Construction (Months)
% o
f Tra
nsve
rse
Join
ts C
rack
ed (%
)
100 Gyr - Leveling CourseRCRI75 Gyr - Surface CourseMeasured
RCRI
Leveling Course
Measured
Surface Course
I476, Pennsylvania (100 Gyration Surface Mix)
0
10
20
30
40
50
60
70
80
90
100
0 6 12 18 24 30 36Time After Construction (Months)
% o
f Tra
nsve
rse
Join
ts C
rack
ed (%
)
100 Gyr - Leveling CourseRCRI100 Gyr - Surface CourseMeasured
RCRI
Leveling Course
Surface Course
Measured
Decision Tree ProcedureHMA Overlay Design
AndMix Type Selection
Determine h(Equation 6.4 and
Figure 7.23)
h < 0.01inches h > 0.01inches
Select Conventional
HMASelect
RCRI/SAMI
Check Vertical Mode(Deflection Spectra Approach,
Section 7.1)
Pass
Fail
Evaluate Intermediateand/or Wearing Course Materials (Section 7.1)
Pass
Final Design Passes
Select NewMixture
Fail
Decision Tree Procedure
FLEXIBLE OVERLAYS FOR RIGID PAVEMENTS
Camille Crichton-SumnersManager, Bureau of ResearchNJ Department of Transportationhttp://www.state.nj.us/transportation/refdata/research609-530-5966
Principal Investigator: Tom Bennert, Ph.D. Rutgers University, Center for Advanced Infrastructure and Transportation
Project Number:FHWA-NJ-2009-014
Recommended