Overlay Design Workshop for Flexible Pavements James A. Crovetti Marquette University

WHRP Project Background Project : Implementation of Flexible Pavement Overlay Design Procedures Project : Implementation of Flexible Pavement Overlay Design Procedures Project : Development of Rational Overlay Design Procedures for Flexible Pavements (WHRP 05-12) Project : Development of Rational Overlay Design Procedures for Flexible Pavements (WHRP 05-12) Project : Development of Modulus-to-Temperature Relations for HMA Mixtures in Wisconsin (WHRP 05-11) Project : Development of Modulus-to-Temperature Relations for HMA Mixtures in Wisconsin (WHRP 05-11)

Implementation of Flexible Pavement Overlay Design Procedures Development of Overlay Design Software Development of Overlay Design Software Revisions to FDM Revisions to FDM Knowledge Transfer Knowledge Transfer Follow-Up Follow-Up

FDM Structural Number Approach – New Structural Number Approach – New –Design Traffic, Soil Support Structural Deficiency Approach – Overlay Structural Deficiency Approach – Overlay –SN ol = SN new – SN eff Design Reliability Design Reliability –Traffic, Materials

Structural Deficiency Approach New pavement designed using WisPAVE (SN new ) New pavement designed using WisPAVE (SN new ) Existing pavement analyzed to determine structural adequacy (SN eff ) Existing pavement analyzed to determine structural adequacy (SN eff ) –FWD data –Component analysis Overlay thickness developed to overcome SN shortage Overlay thickness developed to overcome SN shortage –h OL = (SN new -SN eff )/0.44

Traffic Analysis Analyzed 2006 WIM data from 17 sites across the State Analyzed 2006 WIM data from 17 sites across the State ESALs per truck computed based on AASHTO principles ESALs per truck computed based on AASHTO principles Cumulative frequency of EALFs developed to select appropriate factors for variable levels of design reliability Cumulative frequency of EALFs developed to select appropriate factors for variable levels of design reliability

EALF = 0.3 (WisDOT FDM ) 85.6% Design Reliability

Traffic-Based Design Reliability TruckFDM Design% of Total DesignationEALFReliabilityTrucks 2D % 3SU % 2S-1, 2S % 3S % 2-S % Overall Design Reliability = 71.9%

67% Design Reliability EALF= % Design Reliability 1.84

Reliability-Based EALFs Design Truck Designation Reliability 2D (0.3) 3SU (0.8) 2S-1,2S-2 (0.5) 3S-2 (0.9) 2-S1-2 (2.0)

Recommended EALFs Design Truck Designation Reliability 2D (0.3) 3SU (0.8) 2S-1,2S-2 (0.5) 3S-2 (0.9) 2-S1-2 (2.0)

Overlay Design Software Eri and/or SN eff variations determined based on FWD test results or component analysis Eri and/or SN eff variations determined based on FWD test results or component analysis –FWD provides SN eff and SSV without pavement coring New pavement (SN new ) and overlay (SN OL ) requirements determined based on current WisDOT procedures with varying levels of design reliability New pavement (SN new ) and overlay (SN OL ) requirements determined based on current WisDOT procedures with varying levels of design reliability

Component Analysis Material Type Surface Condition Layer Coefficient AC Surface Little or no alligator cracking and/or only low severity transverse cracking <10% low severity alligator cracking and/or <5% medium and high severity transverse cracking >10% low severity alligator cracking and/or <10% medium and high severity alligator cracking and/or >5-10% medium and high severity transverse cracking >10% medium severity alligator cracking and/or <10% high severity alligator cracking and/or >10% medium and high severity transverse cracking >10% high severity alligator cracking and/or >10% high severity transverse cracking

Component Analysis Material Type Surface Condition Layer Coefficient Stabilized Base Little or no alligator cracking and/or only low severity transverse cracking <10% low severity alligator cracking and/or <5% medium and high severity transverse cracking >10% low severity alligator cracking and/or <10% medium and high severity alligator cracking and/or >5-10% medium and high severity transverse cracking >10% medium severity alligator cracking and/or <10% high severity alligator cracking and/or >10% medium and high severity transverse cracking >10% high severity alligator cracking and/or >10% high severity transverse cracking

Component Analysis Material Type Surface Condition Layer Coefficient Granular Base or Subbase No evidence of pumping, degradation, or contamination by fines Some evidence of pumping, degradation, or contamination by fines

Overlay Design Equations Based on FWD Data - No Milling Before Overlay - Eri = D D 36 2 Eri = D D 36 2 AUPP = ½ (5D 0 – 2D 12 – 2D 24 – D 36 ) AUPP = ½ (5D 0 – 2D 12 – 2D 24 – D 36 ) E 1/3 T = 10 ( Log AUPP Log Eri) E 1/3 T = 10 ( Log AUPP Log Eri) SN eff = (E 1/3 T) Eri SN eff = (E 1/3 T) Eri

Subgrade Effects Eri = D D 36 2

Seasonal Subgrade Stiffness Variations

Subgrade Estimations

Correction Factors for Subgrade Strength FWD Testing during: FWD Testing during: –Critical Spring Period: 2.48 –Late Spring: 0.83 –Summer/Fall: 0.50

Constructed Pavement Layer Variations Strong Weak F W D

“Strong” Pavement AUPP

“Weak” Pavement AUPP

Pavement Strength, SN eff Eri = D D 36 2 Eri = D D 36 2 AUPP = ½ (5D 0 – 2D 12 – 2D 24 – D 36 ) AUPP = ½ (5D 0 – 2D 12 – 2D 24 – D 36 ) E 1/3 T = 10 ( Log AUPP Log Eri) E 1/3 T = 10 ( Log AUPP Log Eri) SN eff = (E 1/3 T) Eri SN eff = (E 1/3 T) Eri

Log Mr = P 200 – V v – t p 1.45 P b.5 Modulus-to-Temperature Effects for HMA

Example Pavement 2” HMA E varies 3” HMA E=450ksi 12” CABC Stress Hardening 240” Subgrade Stress Softening Bedrock

FWD Deflection Basins

Temperature Corrected Deflections

Overlay Design Equations Based on FWD Data - With Milling Before Overlay - AUPP 2 = 8D 0 – 6D 8 – 2D 12 AUPP 2 = 8D 0 – 6D 8 – 2D 12 SN HMA = (AUPP 2 ) SN HMA = (AUPP 2 ) a 1 = SN HMA / T HMA a 1 = SN HMA / T HMA SN post-mill = SNeff – a 1 T mill SN post-mill = SNeff – a 1 T mill

Overlay Design Example 4-Lane State Trunk Highway 4-Lane State Trunk Highway 20 year overlay design 20 year overlay design CYADT=12,000; DYADT=17,000 CYADT=12,000; DYADT=17,000 7% Heavy Trucks 7% Heavy Trucks Existing pavement contains 10% alligator cracking and slight rutting Existing pavement contains 10% alligator cracking and slight rutting Thickness information from coring not available (8” HMA from plans) Thickness information from coring not available (8” HMA from plans) FWD test data provided from September testing FWD test data provided from September testing

Let’s Explore Importing FWD Data Importing FWD Data Adjusting Traffic Adjusting Traffic Computing SN values and Overlay Thicknesses Computing SN values and Overlay Thicknesses