Pavement research presentation vandenbossche

Infrastructure Renewal Assessment Tools: Pavement Assessment using the Falling Weight Deflectometer Pittsburgh Transportation Forum -April 5, 2017-

Julie M. Vandenbossche, PE, PhD Kevin Alland Nate Bech

University of Pittsburgh Department of Civil and Environmental Engineering

Infrastructure Renewal

Transportation Infrastructure

Nationally: • 20% of highways are in poor condition, (32% of urban roads) • 9% of bridges are structurally deficient • 40% of busses are in marginal or poor condition • 20% of airline flights are delayed • $2 Trillion needed over 10 years to restore/maintain surface transportation system (Data from 2017 ASCE Infrastructure Report Card)

University of Pittsburgh Department of Civil and Environmental Engineering

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Infrastructure Renewal

mljom[l ’ Transportation Infrastructure

Nationally: • 20% of highways are in poor condition, (32% of urban roads) • 9% of bridges are structurally deficient • 40% of busses are in marginal or poor condition • 20% of airline flights are delayed • $2 Trillion needed over 10 years to restore/maintain surface transportation system (Data from 2017 ASCE Infrastructure Report Card)

University of Pittsburgh Department of Civil and Environmental Engineering

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Timely Interventions

(adapted from Federal Highway Administration) University of Pittsburgh Department of Civil and Environmental Engineering

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Timely Interventions

(adapted from Federal Highway Administration) University of Pittsburgh Department of Civil and Environmental Engineering

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Timely Interventions

(adapted from Federal Highway Administration) University of Pittsburgh Department of Civil and Environmental Engineering

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Pavement Evaluation Early/unneeded preservation/rehabilitation results in unnecessary‌.

& Solution: Non Destructive Testing (NDT) University of Pittsburgh Department of Civil and Environmental Engineering

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Pavement Evaluation Performing the right fix at the right time is essential for maintaining pavements in an efficient and cost effective manner.

Solution: Non Destructive Testing (NDT)

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Pavement NDT

Load Plate

Falling Weight Deflectometer (FWD) University of Pittsburgh Department of Civil and Environmental Engineering

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Pavement NDT

Load Plate

Falling Weight Deflectometer (FWD) University of Pittsburgh Department of Civil and Environmental Engineering

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Pavement Evaluation • Establish structural condition • Identify needed repairs • Define design inputs (PavementInteractive.org)

University of Pittsburgh Department of Civil and Environmental Engineering

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Structural Condition Life Cycle Costs ($)

Optimum Under Design

Over Design

Total Lifecycle Cost

Maint./Rehab Cost Overlay Cost Overlay Capacity (Federal Highway Administration)

FWD can help determine optimum design of overlays University of Pittsburgh Department of Civil and Environmental Engineering

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Pavement Evaluation Rigid Pavements • Establish structural condition • Identify needed repairs • Define design inputs (PavementInteractive.org)

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FWD Test Locations

• Joint Performance • Void Detection • k-value

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Joint Performance Poor load transfer • Faulting • Voids • Corner breaks

(PavementInteractive.org) University of Pittsburgh Department of Civil and Environmental Engineering

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Joint Performance

• Joint Performance • Void Detection • k-value

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Joint Performance ΔL = x ΔU = 0

LTE = 0% (Poor) High Diff. Defl

ΔL = x

Load transfer efficiency (LTE LTE = ΔU / ΔL *100% Differential Deflection Diff. Defl = ΔL - ΔU

ΔU = x

LTE = 100% (Good) Diff. Defl. = 0

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Joint Performance Assess need for dowel bar retrofits: • Poor load transfer (< 50–60%) • Differential deflections > 0.01 in • Faulting: 0.12–0.5 in

(PavementInteractive.org) University of Pittsburgh Department of Civil and Environmental Engineering

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Joint Performance - Pitt

University of Pittsburgh Department of Civil and Environmental Engineering

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Joint Performance- Pitt

Negative Temp. & Moist. Gradient

Positive Temp.

Gradient

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Joint Performance- Pitt Socketing

Flat Slab

Negative Gradient

Positive Gradient

Negative and positive curvature â&#x20AC;&#x153;lockâ&#x20AC;? in dowel increasing LTE

Negative Gradient Positive Gradient University of Pittsburgh Department of Civil and Environmental Engineering

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Void Detection

• Joint Performance • Void Detection • k-value

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Void Detection Corner Break

Direction of Travel

Approach slab

Saturated support layer

Leave slab Joint or crack Void

Movement of water and fines

Wedge of â&#x20AC;&#x153;injected â&#x20AC;&#x153; fines

University of Pittsburgh Department of Civil and Environmental Engineering

(infopave.com)

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Void Detection

Fill with grout or polyurethane All overlay designs in Pavement ME assume the slab is fully supported.

University of Pittsburgh Department of Civil and Environmental Engineering

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Current Methods Peak Deflection

Normalized 9kip Deflection

Normalized 9kip Deflection

Compare Deflections

Joint Along Project

FWD Load (kips)

ELTG

Void Parameter (VP)

(oF/in)

Corner Deflection (mils) University of Pittsburgh Department of Civil and Environmental Engineering

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Void Detection 35

Max Deflect. (mils)

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11/2/2010 Night, Avg Air Temp 56 ยบF

25 20

Void Cutoff

4/14/2011 Day, Avg. Air Temp 68 ยบF

15 10 5

4/19/2011 Night, Avg. Air Temp 51 ยบF

0 0

500

1000 Offset (ft)

1500

2000

I-79 FWD Testing 2010-2011 (Ramirez 2011) University of Pittsburgh Department of Civil and Environmental Engineering

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Joint Performance- Pitt Potential for False Positive

Negative Temp. & Moist. Gradient

Potential for False Negative

Positive Temp.

Gradient

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Void Detection-Pitt I-79, Bridgeville, PA

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Void Detection - Pitt Void Prediction Tool â&#x20AC;˘ TempCurv: CTE*ELTG â&#x20AC;˘ LTE: in the wheelpath, from NDT

â&#x20AC;˘ Total Deflection: normalized deflection at 9,000 lbs â&#x20AC;˘ Void Parameter: intercept of regression line â&#x20AC;˘ Deflection Ratio (DR) đ??ˇđ?&#x2018;&#x2026; = đ??ˇđ??šđ?&#x2018;&#x160;đ??ˇ,9đ?&#x2018;&#x2DC; /đ??ˇđ?&#x2018;&#x2021;â&#x201E;&#x17D;đ?&#x2018;&#x2019;đ?&#x2018;&#x153;,9đ?&#x2018;&#x2DC; DFWD,9k = Measured deflection for 9 kip FWD load DTheo,9k = Calculated deflection for 9 kip load

University of Pittsburgh Department of Civil and Environmental Engineering

Void Detection - Pitt

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Pavement Evaluation Rigid Pavements • Establish structural condition • Identify needed repairs • Define design inputs Bonded Concrete Overlay

Concrete Pavement Restoration Existing Pavement Existing Stabilized Base

Unbonded Concrete Overlay Overlay Existing Pavement Existing Stabilized Base

Epcc and k-value

University of Pittsburgh Department of Civil and Environmental Engineering

Overlay Existing Pavement Existing Stabilized Base

Asphalt Overlay Overlay Existing Pavement Existing Stabilized Base

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Design Inputs PCC stiffness (Epcc) and modulus of subgrade reaction (k-value): • Concrete pavement restoration k-value • Bonded concrete overlays • Unbonded concrete overlays • Asphalt overlays

Epcc, Unbonded overlay

Epcc, Bonded & AC overlay & Restoration

University of Pittsburgh Department of Civil and Environmental Engineering

Backcalculate Design Inputs Stiffness = f (materials and shape) P

h b

δ PL3 δ= 48EI

L/2

I=

bh3 12

L University of Pittsburgh Department of Civil and Environmental Engineering

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Design Inputs

• Joint Performance • Void Detection • Epcc and k-value

University of Pittsburgh Department of Civil and Environmental Engineering

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Design Inputs -Pitt

Positive gradient Positive gradient

PCC Elastic Modulus (I-79)

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k-Value (I-79)

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Design Inputs-Pitt

Positive Gradient

Reduced support

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Pavement Evaluation Flexible Pavements â&#x20AC;˘ Define design inputs

(PavementInteractive.org)

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Design Inputs Overlay: • Layer thicknesses • Stiffness • Asphalt concrete • Base • Subgrade • Overlay mixture design Asphalt concrete overlay (Texas A&M Transportation Institute)

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FWD Test Location

Outside Wheelpath

â&#x20AC;˘ Backcalculate layer stiffnesses

University of Pittsburgh Department of Civil and Environmental Engineering

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Design Inputs Overlay: • Layer thicknesses • Stiffness • Asphalt concrete • Base • Subgrade • Overlay mixture design Asphalt concrete overlay (Texas A&M Transportation Institute)

University of Pittsburgh Department of Civil and Environmental Engineering

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Factors Influencing Asphalt Stiffness • Load Frequency

Increase Stiffness

Mastercurve

• Temperature

Increase Stiffness

• Aging –Increase stiffness • Fatigue- Decreases stiffness University of Pittsburgh Department of Civil and Environmental Engineering

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Dynamic Modulus (E*) Master Curve 3500 3000

14 F

2500

40 F

2000 70 F

1500 Log(a(40)) = 2.10

1000 Log(a(130)) = -3.57

100 F

Shift = log(a(T))

Dynamic Modulus (E*) (ksi)

Log(a(14)) = 4.14

Log(a(100)) = -1.88

130 F

500 0 0.00001

5 4 3 2 1 0 -1 -2 -3 -4 -5

Shift Factors

0 0.01

10

10000

Load Frequency (Hz)

University of Pittsburgh Department of Civil and Environmental Engineering

50

100

Temperature (F)

42

150

Determining E* 1. Measure E* on cores

2. Witzcak equation â&#x20AC;˘ Mixture parameters (use cores)

3. FWD testing

(Pavement Interactive)

Dynamic Modulus (E*) (ksi)

3000 2500 2000 1500 1000 500 0 (American Engineering Testing)

20

Asphalt core sample

University of Pittsburgh Department of Civil and Environmental Engineering

70 Temperature (oF)

43

120

Laboratory E* Testing Perform E* testing on cores

Dynamic Modulus (E*) (ksi)

3000 2500 2000 1500 1000 500 0

Laboratory dynamic modulus test Asphalt core sample

20

40

60

80

100

Temperature (oF)

(American Engineering Testing)

University of Pittsburgh Department of Civil and Environmental Engineering

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120

Witczak Equations Estimate E* from mix parameters of sample

â&#x20AC;˘ â&#x20AC;˘ Mix parameters from core sample

Determine mixture parameters from cores Use mixture parameters to estimate variables in Witcak equation

Dynamic Modulus (ksi)

3000

University of Pittsburgh Department of Civil and Environmental Engineering

2500 2000 1500

1000 500 0 20

40

60

80

Temperature

100

(oF)

45

120

FWD Testing â&#x20AC;˘ Perform FWD testing â&#x20AC;˘ Backcalculate stiffness of existing asphalt 3000

FWD Testing (Cornell Local Roads Program)

FWD Load

Deflection Sensors

Modulus (ksi)

2500 2000 1500 1000

500 0

Calculated Deflection Basin

20

70

120

Temperature (oF)

Measured Deflection Basin

Backcalculation (Pavement Interactive)

University of Pittsburgh Department of Civil and Environmental Engineering

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Comparison of E* Estimates -Pitt 3000 Dynamic Modulus (E*) from Coring and Lab Testing

Modulus (ksi)

2500 2000

Dynamic Modulus (E*) from Coring and Predictive Equation

1500 1000 500

Elastic Modulus (E ) from Backcalculation

0 20

40

60

80

100

120

Temperature (oF) University of Pittsburgh Department of Civil and Environmental Engineering

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Challenges â&#x20AC;˘ Do all methods provide the same mastercurve? â&#x20AC;˘ If not, what E* provides the best estimate of performance in PA? â&#x20AC;˘ Best approach for using FWD testing to establish E* 3000

Modulus (ksi)

2500 2000 1500

1000 500 0 20

70

120

Temperature (oF) University of Pittsburgh Department of Civil and Environmental Engineering

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Predicted Performance - Pitt MnROAD Cell 21 Asphalt Thickness = 8 in

Design Life = 20 years AADTT = 750

Distress Predicted using Pavement ME

Maximum Allowable

Dynamic Modulus from Coring & Testing E* in Lab

Dynamic Modulus from Coring and Predictive Equation

Modulus from FWD Testing

Total Rutting (in)

0.75

0.87

0.75

0.91

AC Rutting (in)

0.25

0.32

0.22

0.35

1000

2029

1034

2029

25.00

1.98

1.99

2.02

2000

1011

456

1159

AC Thermal Cracking (ft/mi) AC Bottom-up cracking (%) AC Top-down Cracking (ft/mi)

Which best reflects actual performance??

University of Pittsburgh Department of Civil and Environmental Engineering

Conclusions • FWD testing can enhance infrastructure renewal by: • Aiding in selecting pavement restoration/preservation techniques • Developing more accurate design inputs

• FWD testing on rigid pavements is affected by curling and warping • Methods to minimize errors due to curling and warping are being developed

• E* for asphalt can be determined using FWD, E* lab testing, and predictive models • Effect of using each method on overlay design is being evaluated • Approach for establishing design inputs using FWD testing being developed University of Pittsburgh Department of Civil and Environmental Engineering

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Acknowledgements PennDOT • Project funding • Providing FWD testing and traffic control Bill Dipner, Tom Adams, Theresa Thompson, Steve Nixon, Lydia Peddicord and Josh Freeman

MnDOT • Providing extensive MnROAD FWD and instrumentation data Ben Worel, Tom Burnham, and Dave Van Deusen

University of Pittsburgh Department of Civil and Environmental Engineering

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Thank You

Any Questions?

University of Pittsburgh Department of Civil and Environmental Engineering