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Concrete PavementOverlay DesignJeffery Roesler, Ph.D., P.E. ProfessorDepartment of Civil & Env. Eng.University of Illinois Urbana-Champaign
25 June 2015ISCP Concrete Pavement SeminarIDOT District 1 (Schaumburg, IL)
Concrete Overlay Overview Overlay Design Objectives Overlay Design Guides Inputs & critical variables Bonded Concrete Overlays
Concrete-Asphalt
Unbonded Concrete Overlays Whitetopping & Composites
Performance of Illinois O/L References for O/L design Summary of Overlay Design
Concrete Overlay Design: Objectives Achieve desired concrete pavement overlay
service life given: Existing pavement condition Expected traffic Layer and material properties Interface condition Slab geometry Climatic conditions
SCinitial SCOverlay
SCeffective
SCfuture traffic
Load Applications
- 76
Guide on Existing Overlay Design Methods
Not a design procedure Background on
recommended overlay design methods 18 pages
Detailed design examples 35 pages
StreetPave12 released after this guide
http://www.cptechcenter.org/technical-library/documents/Overlays_Design_Guide_508.pdf
How to start design of concrete O/L? Roadway site evaluation Existing pavement structure New pavement performance objectives Select candidate Overlay Options Collect input data & choose design features
Support layers, Slab size, etc.
Use appropriate overlay design methods Optimize design Write construction specs to reflect design objectives
Concrete Overlays: General Types
Whitetopping (unbonded) Bonded Concrete Overlay Asphalt (BCOA)
Bonded Concrete to Concrete Unbonded Concrete w/ Separation Layer
Concrete Overlay Guide, Third EditionContents
Overview of Overlays Overlay types and uses Evaluations & Selections Six Overlay Summaries Design Section Misc. Design Details Overlay Materials Section Work Zones under Traffic Overlay Construction Accelerated Construction Specification
Considerations Repairs of Overlays
http://www.cptechcenter.org/technical-library/documents/Overlays_3rd_edition.pdf
Concrete Overlays Categories
Concrete Overlays
Bonded Concrete Resurfacing of Concrete Pavements
Bonded Concrete Resurfacing of Asphalt Pavements
Bonded Concrete Resurfacing of Composite Pavements
Bonded Overlay Group
UnbondedConcrete Resurfacing of Concrete Pavements
Unbonded Concrete Resurfacing of Asphalt Pavements
Unbonded Concrete Resurfacing of Composite Pavements
Unbonded Overlay Group
Thinner Thicker
Bond is integral to design Old pavement is base layer
Thinner Concrete Pavement Options
Bonded Concrete Resurfacing of Asphalt Pavements
Bonded Concrete Resurfacing of Composite Pavements
Bonded Overlay Systems
Unbonded Concrete Resurfacing of Concrete Pavements
Unbonded Concrete Resurfacing of Asphalt Pavements
Thinner Concrete Pavement or Short Slabs
Unbonded Systems
ACPA BCOA or BCOA MEh=3 to 6 in.L=4 to 6 ft
Thin Concrete
Inlay -Preservation
h=2 to 3.5 inchL=4 to 6 ftEmerging
Colorado Method6in. x 6ft x 6ft
Opti-Paveh=2.5 to 9 in.L=4 to 9 ft
Which Overlay Design Method(s)?Concrete Overlay Type Design MethodsUnbonded on Asphalt, Composite, or Concrete
AASHTO ME, ACPA StreetPave 12, AASHTO 93, OptiPave 2.0
Bonded on Asphalt or Composite
ACPA BCOA, ACPA StreetPave 12,BCOA ME, CO 6x6x6, IDOT Chpt 53
Bonded on Concrete AASHTO ME, ACPA StreetPave 12, AASHTO 93
• Slab thickness• Concrete Strength, CTE, Modulus, fibers (?)• Concrete-Asphalt Interface• Support layers (surface, base/subbase, soil) • Joint Spacing• Edge Support• Load Transfer• Subgrade Support • Traffic & Design Life• Climate
What are main Concrete Overlays Design Inputs?
Hamilton County, IL
Pre-overlay Repair & Reflective Crack Control Sub-drainage Structural vs Functional Overlays Recycling Existing Pavement (PCC & AC) Existing PCC Slab Durability PCC Overlay Reinforcement PCC Overlays Bonding / Separation Layers Overlay Design Reliability Level Pavement Widening Traffic Disruptions and User Delay Costs
Other Important Considerations in Overlay Design
BCOA vs. “Whitetopping” Whitetopping (h > 6 in.)
More conventional slab sizes (6ft to 15ft)
30+ years experience
Ignores interface bond (unbonded)
Bonded Concrete Overlay Asphalt (h ≤ 6 in.) 20+ years experience (1991)
Smaller slab sizes (≤ 6ft)
Concrete/AC bond is essential
Ultra-Thin Whitetopping (UTW)
Composite Behavior Mechanics
Unbonded“Whitetopping”
Neutral AxisPCC
Bit.
BondedBonded Concrete Overlay Asphalt
PCC
Bit.
Riley
Concrete Overlay Solutions:Rehabilitation and Maintenance
Site Visit: Existing Pavement Condition
Why use smaller slab sizes?
1.2m 1.2m1.2m>2m
•Interface bond assumption (BCOA)-Reduce de-bonding of concrete and asphalt at early ages
•Short slab sizes reduce bending and curling stresses
Thickness Design for Concrete Overlays Highways/Roads AASHTO Pavement ME (2011) or MEPDG StreetPave 12 (ACPA) ACPA (Whitetopping/UTW) – 1998
Illinois DOT (2009) – new fatigue eqn. & fibers Chapter 53-4.08
BCOA Calculator (2012) – add climate database
BCOA ME (2012) – Univ. of Pittsburg AASHTO (1993)
Airports: Federal Aviation Administration (FAARFIELD)
AASHTO Pavement MEor formerly known as MEPDG
AASHTO Pavement ME - INPUTS!
Many OUTPUTS to Synthesize
Bonded Concrete Overlay Options
Thinner overlays (3 to 6 in) Constructed over concrete,
asphalt, and composite sections.
Existing pavement condition fair to good
Interface Bond is Critical!
Bonded Concrete
Resurfacing of
Concrete Pavements
Bonded Concrete
Resurfacing of
Asphalt Pavements
Bonded Concrete
Resurfacing of
Composite Pavements
Bonded Overlay Options
Bonded Concrete Overlay of AsphaltAASHTO 1993 Not applicableAASHTO Pavement ME (2011) Thickness 6 in. Slab length 10ftACPA (2012);IDOT (2009);Pitt BCOA ME (2013)Ultra-Thin Whitetopping Thickness 6 in. Slab length 6ft
Unbonded ConcreteOverlay of HMA
http://apps.acpa.org/apps/bcoa.aspx
HMA
PCC
Base
40kN 40kN
EAC, AC
EPCCt
AC
Subgrade k-value
Bonded
hPCC
hAC
BCOA Critical Locations (Concrete and AC Layers)
t
Fibers Structural vs. non-structural (plastic shrinkage)
Structural Macro-Fibers
Micro-Fibers (non-structural)
012345
0 10 20 30 40CMOD (mm)
Load
(kN
)
IDOT Concrete Thickness Calculation
Variable
Design Traffic Factor (BDE Manual, Figure 54-4C) TF 2.50
Modulus of Rupture (3-point bending, 14-day average) MOR 750 psi MORFRC Residual Strength Ratio 20%
Remaining Thickness of Asphalt h ac 3.0 in.Joint Spacing L 72 in. L
Elastic Modulus of Concrete E c 3,600,000 psi E c
Coefficient of Thermal Expansion CTE 5.50E-06 in./in./°F CTEElastic Modulus of Asphalt E AC 350,000 psi
Modulus of Subgrade Reaction k 100 pci
k
Thickness of Concrete h c 5.48in.
Solved
Note 1: The design MOR is the mean design strength, not the minimum 550 psi flexural strength (center-point loading) specified for opening to traffic. Also note that as MOR increases the risk of debonding increases and the effectiveness of synthetic fibers decreases.
PCC Inlay / Overlay Design Sheet, Required Thickness of PCC
5.50 x 10-6 in./in./°F
E AC
100,000 psi (poor)
350,000 psi (moderate)
3,600,000 psi
0% (w/o fiber reinforcement)
20% (w/ fiber reinforcement)
600,000 psi (good)
100 pci
Default InputsDefault Value
750 psi (Note 1)
48 in. or 72 in.
150150R
Compute Concrete Thickness
Help
150150R
http://www.dot.state.il.us/desenv/pdp.html
IDOT Chapter 53-4.08 Tables
Asphalt Modulus (Eac)
0
1
2
3
4
5
6
1E+04 1E+05 1E+06 1E+07
ESALs
Conc
rete
Thi
ckne
ss h
c (in
)
Eac = 100,000psiEac = 350,000psiEac = 600,000psi
k = 100 pci
MOR = 650 psi
R150 = 0%
hac = 3 in
L = 4 ft
ΔT/h = -0.65 °F/in
35 % time
Effect of Asphalt thickness
0
1
2
3
4
5
6
1E+04 1E+05 1E+06 1E+07
ESALs
Conc
rete
Thi
ckne
ss h
c (in
)
hac = 3 inhac = 4 inhac = 5 inhac = 6in
k = 100 pci
MOR = 650 psi
R150 = 0%
Eac = 350,000 psi
L = 4 ft
ΔT/h = -0.65 °F/in
35 % time
R150= Residual Strength Ratio Concept
0
1
2
3
4
5
6
1E+04 1E+05 1E+06 1E+07
ESALs
Conc
rete
Thi
ckne
ss h
c (in
)
R150,3 = 0%R150,3 = 15%R150,3 = 20%R150,3 = 25%
k = 100 pci
MOR = 650 psi
Eac = 350,000 psi
hac = 3 in
L = 4 ft
ΔT/h = -0.65 °F/in
35 % time
Effect of Slab Size (L)
0
1
2
3
4
5
6
7
8
1E+04 1E+05 1E+06 1E+07
ESALs
Conc
rete
Thi
ckne
ss h
c (in
)
L = 12 ftL = 6 ftL = 4 ft
k = 100 pci
MOR = 650 psi
R150 = 0%
Eac = 350,000 psi
hac = 3 in
ΔT/h = -0.65 °F/in
35 % time
ACPA Bonded O/L of Asphalt
http://apps.acpa.org/applibrary/BCOA/ (2012)
BCOA ME failure modes5 to 7 ft
Long. & DiagCrack
Positive ΔT Negative ΔT
< 4.5 ftCorner Break
Positive ΔT
10 x 12 ft12 x 12 ft12 x 15 ft
Trans. Crack
Vandenbossche (2013)
Surface Preparation Milling AC surface.
Remove rutting Restore profile Enhance bond
Minimum AC thickness remaining after milling: 6.5 cm
Surface cleaning Waterblast - preferred Sweeping
Guide to Concrete Overlays of Asphalt Parking Lots (2012)
www.rmc-foundation.org/images/Concrete_Overlay_Guide_11-14-12.pdf
Contents: Parking Lot Features Existing Pavement
Condition Concrete Overlay
Design Jointing Parking lot details Materials Construction Fibers
PERFORMANCE OF UTW SECTIONS
Illinois Projects Visited (20)
UTW Projects in Illinois (USA)
Intersection
Farm / Rural Road
State Highway
Parking Lot
Decatur, IL: Intersection of US 36 and Oakland Avenue (1998)
Major distresses Longitudinal, transverse or corner cracking in
33.8% of slabs Faulting throughout the project in joints and
cracks Three to five instances of partial slab blowups
due to slab migration
Slab migration Inside five rows of slabs had migrated into the
intersection from 2.5 to almost 15cm at the end of the project
Use of structural fibers likely could have locked the panels in and prevented this movement
2012
Kane County, IL: North Lorang Road (2004) 11cm thick concrete overlay of 7.5-9cm of HMA over
aggregate base 2.4 kg/m3 synthetic macro-fibers Square 1.5m x 1.5m panels Project built to serve a quarry: average of 30 trucks/day (peak
of 280/day)
2012
Mundelein, IL: Schank Avenue (2005) 10cm. concrete overlay of a composite pavement (5.7-16.5cm
HMA over 12-23.5cm PCC) Square 1.2m x 1.2m panels 2.4 kg/m3 synthetic macro-fibers High truck traffic volume (no data available, but comparable
to Lorang Road and more general traffic)
2012
Hamilton County, IL (Sept. 16, 2014)FRC UTW (4 in.)
Existing Asphalt Concrete (3 in.)
Cement Treated Soil (8 in)Natural Soil
Built in 2013
Built in 9/2014
Built in 9/2014
Overall Summary for BCOA Parking lots = 4ft x 4ft panels are fine w/ fibers Maintain 5.5 ft or 6 ft panel sizes w/ fibers More cracking/faulting on skewed joints Thinner saw blades No sealing except when joint in wheel path
No faulting or cracking on 4x4 ft or 6x6ft slab sizes with macrofibers (>2006)
FRC needs minimum revolutions at high torque in mixer
Bonded Concrete Overlay
Concrete Overlay hol
Existing Concrete Pavement
he
Excellent Interface Bond
Bonded Concrete O/L Design Methods
AASHTO Pavement ME (2011) Slab thickness based on following: Slab geometry, climate, structure, concrete
material and layer properties Complete interface bond hol = hf - heff
AASHTO 1993 Dol = Df - Deff
Unbonded Concrete Overlay Options Thicker concrete overlays
than bonded.
Constructed on existing concrete, asphalt, or composite pavements.
Bond is NOT considered in the design.
Slab sizes vary depending on type of design
Unbonded Concrete Resurfacing of Concrete Pavements
Unbonded Concrete Resurfacing of Asphalt Pavements
Unbonded Concrete Resurfacing of Composite Pavements
Unbonded Overlay Option
“Whitetopping”
Pavement evaluation establishes whether existing concrete and subbase can provide uniform support and, if not, what actions are necessary to obtain that uniformity.
Look for movement in the slab. Profile is a good check.
Unbonded Concrete Overlays of Existing Concrete Pavements
Unbonded Concrete O/L Design Methods
AASHTO Pavement ME (2011) or MEPDG Slab geometry, climatic factors, concrete
material and layer Assumes unbonded interface without friction
AASHTO (1993) D2
0L = D2f - (Deff)2
StreetPave 12
Separation Layer Good Performance.
Isolate overlay from existing pavement: Prevent reflection cracking. Prevent bonding/mechanical
interlocking. Provide level surface for overlay
construction. Interlayer material:
2.5 to 5cm dense-graded HMA. GEOTEXTILE (Missouri 2008)
I-57/I-64 Alternatives (2010-2013)
HMA overlay of existing CRCP Rubblization with HMA JPCP and CRCP options
MEPDG & IDOT designs Milling options vs. rubblization Interlayer type Thickness options
Poor Section I-57/I-64 NB
MEPDG CRCP Overlay: Inputs 20-year design life Mattoon-Charleston, IL Climate
ESALs 80x106
A-7-6 soil type k=200 psi/in
Tied concrete shoulder 40 to 80% LTE
CRCP Steel properties 3.5 inch depth; #6 bar; 0.7% steel content
MEPDG CRCP Design: Results New CRCP = 11 inches HMA base unbonded = 4inches
Unbonded CRCP = 9 inches AC base interlayer = 2 inches CRCP (existing) = 8 inches
Unbonded CRCP = 10.5 inches HMA interlayer = 1 to 2 inches CRCP (rubblized) = 8 inches
I-57 / I-64 Mt. Vernon (2011-2013) Mill existing HMA overlay Rubblize existing 8-inch CRCP Place 3-inch HMA interlayer 10.5-in. CRCP overlay w/ 0.7% steel
2012 Unbonded CRCP Overlay (I-57)
Unbonded Concrete O/L of Asphalt Concrete
Dol = Df
Df = new concrete slab thickness
Existing Asphalt
Dol = Df
Subgrade
Base
Unbonded Bonded Concrete O/L of Asphalt
AASHTO Pavement ME (2011)-whitetopping Thickness > 6 inches Slab length > 10ftOptiPave 2.0 (2012) - TCPavements Short jointed slab systems Slab sizes < 10ft & thickness 2 in.AASHTO 1993 Existing asphalt treated as base layer
(Thin) Unbonded Concrete O/L
Interlayer or thicker slab required relative to BCOA
Empirical designs to date in U.S.
TCPavements, Inc. (2007) – Chile, S.A. OptiPave 2.0 (2012) Only current design method for short jointed
unbonded concrete overlay
Final Day PavingOak Park, July 2001
• 10 cm “Fast-Track” Unbonded, Steel-Fiber Reinforced Concrete Inlay
• Mirafi 500N Woven Geotextile
Pavement Depth
Oak Park, IL: Marion Street (2001)
10 cm concrete over original concrete layer UNBONDED- woven geotextile placed between the layers at the time
of casting
2.0m x 1.5m panels 24 kg/m3 crimped steel fibers
2012
I-72 Unbonded Overlay (2015)
6-inch PCC Asphalt
interlayer 8” CRCP 6ft x 6ft
panel sizes Fibers
What is Flowable Fibrous Concrete (FFC)?
187
Flowable Fibrous Concrete
Ultra-Thin Whitetopping
Fiber-Reinforced
Concrete
Self-Consolidated Concrete
High Toughness/ Reduced Cracking
Ease of Placement
Cost-Effective Thin Pavement
HPFRSCC(ECC)
ConventionalPavingMixture
Flowable Fibrous Concrete (FFC) for Thin Pavement Preservation Inlays
Lower speed applications Slab thickness < 8 cm 10-year service life Concrete wearing surface (Preservation) Asphalt-concrete bond essential Loads transmitted to substrate layers
Other sustainability enhancements: Reflectivity, skid, air pollutant reducer
Bordelon & Roesler (2010)
FFC Field Project (ATREL) Ensure Good Bond with Underlying HMA
Milled and cleaned surface Measured the FFC inlay bond with 10 cm diameter core, sheared off at greater
than 500 Nm torque (HMA overlays typically ~400 Nm)
Check Workability & Constructability of FFC Placed 5 cm thick inlay directly from truck Vibrated with screed and bull float finish
Joint Cracking Monitored Slabs sawcut at spacing 1.1 to 3.4 m (4 to 11 ft) Crack widths average from 0.4 to 1 mm wide after 20 days
Field Demonstration 2in (5 cm)
Concrete Overlay: Summary Existing pavement condition assessment Select new concrete pavement type Define interface assumption
Available structural design methods AASHTO Pavement ME (2011) IDOT BCOA (Chapter 53-4.08) ACPA (BCOA Calculator & StreetPave12) Pitt BCOA ME FAARFIELD- airfield
Construction details essential!!
Questions?
141 fibers 131 fibersBordelon (2011)
Acknowledgements Illinois Department of Transportation
Illinois Center for Transportation www.ict.illinois.edu
Randell RileyIL-ACPA
Amanda Bordelon Asst. Prof. @ University of Utah
National Concrete Pavement Technology Center Dale Harrington
American Concrete Pavement Association (ACPA) Rob Rodden
Daniel King (2012-2015) Research Assistant, UIUC
Dr. Julie Vandenbossche University of Pittsburg
Annotated Bibliography Harrington, D. et al. (2012), Guidance for the Design of Concrete Overlays
Using Existing Methodologies, National Concrete Pavement Technology Center, Iowa State University, Ames, IA.
Roesler, J. R., Bordelon, A., Ioannides, A. M., Beyer, M., and Wang, D. (2008), Design and Concrete Material Requirements for Ultra-Thin Whitetopping, Final Report, Illinois Center for Transportation Series No. 08-016, University of Illinois, Urbana, IL, 181 pp.
Rasmussen, R., Rogers, R., Ferragut, T. (2009), Continuously Reinforced Concrete Pavements Design and Construction Guidelines, FHWA-CRSI.
Harrington, D. et al. (2014), Guide to Concrete Overlays Sustainable Solutions for Resurfacing and Rehabilitating Existing Pavements, National Concrete Pavement Technology Center, Iowa State University, Ames, IA.
Smith, K.D., H. Yu, D. Peshkin, (2002), Portland Cement Concrete Overlays: State of the Technology Synthesis, Federal Highway Administration, Washington, DC.
Vandenbossche (2011) Development of a Design Guide for Thin and Ultrathin Concrete Overlays of Existing Asphalt Pavements, TPF-5(165)