PAVEMENT SECTION CONSTRUCTION AND MATERIALS

Transcription

1 PAVEMENT SECTION CONSTRUCTION AND MATERIALS ME DESIGN MANUAL March

2 ME DESIGN MANUAL CONTENTS SECTION 1.0 INTRODUCTION SECTION 2.0 GENERAL RECOMMENDATION 2.1 Uncalibrated ME Design Guide Justification SECTION 3.0 DESIGN LIFE SECTION 4.0 DISTRESS THRESHOLDS 4.1 Jointed Plain Concrete Pavement Slab Cracking Faulting Roughness 4.2 Hot Mix Asphalt Rutting Bottom-up Cracking Roughness SECTION 5.0 RELIABILITY SECTION 6.0 INPUTS 6.1 General Information 6.2 Site/Project Identification 6.3 Analysis Parameters 6.4 Traffic Traffic Volume Adjustment Factors Monthly Adjustment Vehicle Class Distribution Hourly Truck Distribution Traffic Growth Factor Axle Load Distribution Factors General Traffic Inputs Number Axles/Truck Axle Configuration Wheelbase 6.5 Climate 6.6 Structure Design Features (PC only) Drainage and Surface Properties Layers 2

3 ME DESIGN MANUAL Thermal Cracking (AC only) 6.7 Distress Potential (AC only) APPENDIX 3

4 INTRODUCTION SECTION 1.0 Introduction 4

5 INTRODUCTION 1.0 INTRODUCTION Missouri Department of Transportation (MoDOT) is in the process of implementing the Mechanistic-Empirical (M-E) Design Guide for pavements. The current and major step for implementation is local calibration of the model. Local calibration will not be completed till the late summer of 2005 at the earliest. Upon completion of this task the Design Guide predictions will approximate actual pavement field performance as close as conceivably possible. Prior to this completion; however, MoDOT faces the dilemma of using an older empirical model that has long been suspected of producing overconservative designs, particularly for higher truck volumes, versus using a technologically appropriate method that has not been fine tuned for Missouri conditions. 5

6 GENERAL RECOMMENDATION SECTION 2.0 General Recommendation 6

7 GENERAL RECOMMENDATION 2.0 GENERAL RECOMMENDATION The Pavement Group will use the uncalibrated Design Guide program effective immediately. The highest level program inputs available will be used. Initially, these inputs, out of necessity, will be primarily Level 3 (lowest level). As higher level inputs are made available, such as for truck traffic distributions or mechanistic material properties, they will be substituted for the previous ones. 2.1 UNCALIBRATED ME DESIGN GUIDE JUSTICATION 1. The current empirical-based AASHTO Guide for Design of Pavement Structures produces over conservative thickness designs. The original pavement tests, from which these designs are derived, experienced only a fraction of the loads anticipated for present and future Missouri medium- and heavy-duty roads. Also, materials, mix designs, and pavement structures have changed from the ones in the old Road Test. This method is no longer contemporary. 2. MoDOT has a responsibility to provide the most economical long-term pavement designs that meet the minimum performance criteria. 3. M-E Design Guide performance predictions from the uncalibrated model meet most of the general expectations of engineers within MoDOT that have had access to the results. 4. Using the M-E program now will eliminate the future user learning curve during the transition to the fully calibrated version. 7

8 DESIGN LIFE SECTION 3.0 Design Life 8

9 DESIGN LIFE 3.0 DESIGN LIFE Life cycle costs analyses (LCCA) for Portland cement concrete (PCC) and hot mix asphalt (HMA) pavements are based on 45-year design lives. Contained within the design lives are assumed milestones for rehabilitation. Distress thresholds will be checked at these milestones to ensure acceptable performance levels. 9

10 DISTRESS THRESHOLDS SECTION 4.0 Distress Thresholds 10

11 DISTRESS THRESHOLDS 4.0 DISTRESS THRESHOLDS The following criteria for distress thresholds will be used to determine whether a particular pavement design meets minimum performance standards during its design life: Jointed plain concrete pavement (new full-depth and unbonded overlay) Slab cracking 1.5 percent maximum at 25 years Faulting 0.15 inches maximum at 25 years Hot mix asphalt (new full-strength and overlay on rubblized concrete) Rutting 0.5 inches maximum at 20 years Bottom-up fatigue cracking 2.0 percent maximum at 30 years 4.1 JOINTED PLAIN CONCRETE PAVEMENT (JPCP) Slab Cracking 1.5 is the anticipated percentage of JPCP slabs that must be replaced at 25 years according to current LCCA assumptions. Limiting the Design Guide predictions to this amount will allow the design to meet LCCA expectations Faulting 0.15 inches is the approximate maximum faulting depth a transverse joint can attain prior to causing discomfort to motorists. The entire driving surface will be diamond ground at 25 years according to current LCCA assumptions, thus removing all joint faulting. Limiting the Design Guide predictions to this amount will allow the design to meet LCCA expectations Roughness Roughness or IRI will not be used for the interim until further notice. Additional analysis of predicted IRI values at the end of the design life, as well as the appropriate initial IRI at the time of construction, is necessary before using these models to supplement pavement selection. 11

12 4.2 HOT MIX ASPHALT (HMA) Rutting 0.5 inches signifies the onset of moderate rutting. This distress level is greater than what would normally be considered acceptable, however; it appears to be offset by some uncertainty regarding subgrade and base rutting predictions. The entire 1 ¾-inch wearing course in the driving lanes will be coldmilled and resurfaced at 20 years according to current LCCA assumptions, thus removing all surface rutting Bottom-up Cracking 2.0 percent at 30 years is the acceptable damage limit based on a combination of factors. Since the design life is 45 years, all structural damage that cannot be corrected with milling and filling must be curtailed. Whereas surface rutting and top-down fatigue or thermal cracking can be eliminated with a new wearing course, bottom-up or alligator cracking would still be present, although hidden for a short time, and compromise the integrity of the pavement. The Design Guide program has a computational ceiling of 30 years for HMA pavements, because of internal memory limitations. This problem will probably be resolved in the future so that longer HMA design lives can be run; however, this will not likely occur this year, so the fatigue limit must be applied to 30 years for the interim. Limiting deep-seated structural damage to zero percent is not practical or possible, so 2.0 percent provides a reasonable threshold, recognizing that damage at 45 years would be at least 50 percent higher Roughness Roughness or IRI will not be used for the interim until further notice. Additional analysis of predicted IRI values at the end of the design life, as well as the appropriate initial IRI at the time of construction, is necessary before using these models to supplement pavement selection. 12

13 RELIABILITY SECTION 5.0 Reliability 13

14 RELIABILITY 5.0 RELIABILITY All distress predictions are at the 50 percent reliability level or in plainer terms, average values. The predictions match the average performance data obtained from like pavements across the country. Using higher reliability for roadways, where lane closures for repairs must be minimized, is common practice in other methods, such as the old AASHTO design. Higher reliability results in more conservative pavement design thickness. The M-E Design Guide can apply reliability factors to distress predictions, but this feature will not be used before local calibration is complete for two reasons. The reliability in the Design Guide is derived directly from the standard deviations of measured national pavement distresses. It is not derived from the variance of individual material and design properties. Therefore, a State with tight quality control standards at the time of construction, such as Missouri, cannot apply small standard deviations to individual inputs other than by simply using a lower reliability factor close to the average value. The primary source of the distress standard deviations are apparently construction-related, because the performance gap between a 90 percent and 50 percent reliability pavement is apparent at day one and remains largely unchanged for the design life duration. 14

15 INPUTS SECTION 6.0 Inputs 15

16 INPUTS 6.0 INPUTS The following sections provide current guidance for the values and level of accuracy that should be applied to individual inputs. Create New Project: Project Name Folder Measurement System Route_Project Number_Type_Thickness J:\AA ME Design US Customary 6.1 GENERAL INFORMATION Design Life Base/subgrade Construction Pavement Construction Description Type of Design 45 years for new JPCP and unbonded PCC overlay 30 years for full-depth HMA and HMA overlay on rubblized PCC Expected Date Expected Date Route, County, Project Number, and Location Actual New Pavement, Restoration, or Overlay 6.2 SITE/PROJECT IDENTIFICATION Location Project ID Section ID Date Station/milepost format Station/milepost begin Station/milepost end Traffic Direction Route and Location Project Number Blank Date when design is ran Blank Blank Blank NB, EB, SB, or WB 16

17 INPUTS 6.3 ANALYSIS PARAMETERS Initial IRI (in/mi) Terminal IRI (in/mi) Transverse Cracking (% slabs cracked) (JPCP) Mean Joint Faulting (in) (JPCP) CRCP Punchouts (per mi) (CRCP) AC Surface Down Cracking Long. Cracking (ft/mi) (HMA) AC Bottom Up Cracking Alligator Cracking (%) (HMA) AC Thermal Fracture (ft/mi) (HMA) Chemically Stabilized Layer Fatigue Fracture (%) (HMA) Permanent Deformation AC Only (in) (HMA) Permanent Deformation Total Pavement (in) (HMA) Reliabilities Default Default 1.5 percent at 25 years 0.15 inches at 25 years Default Default 2.0 percent at 30 years Default Default Default 0.5 inches at 20 years Default 6.4 TRAFFIC Initial two-way AADTT Actual Number of lanes in design direction Actual Percent of trucks in design direction (%) Actual, otherwise 50 Actual, otherwise Percent of trucks in design lane (%) 100 for 1 lane, 85 for 2 lanes, 75 for 3 or more lanes Operational speed (mph) Posted or Design Speed TRAFFIC VOLUME ADJUSTMENT FACTORS MONTHLY ADJUSTMENT Load Monthly Adjustment Factors Actual, otherwise use Level 3 defaults (1.00) 17

18 INPUTS VEHICLE CLASS DISTRIBUTION AADTT distribution by vehicle class Actual, otherwise use one of the recommended Level 3 default distributions for functional class type See Appendix for low volume routes distribution HOURLY TRUCK DISTRIBUTION Hourly truck traffic distribution by period beginning Actual, otherwise use Level 3 defaults TRAFFIC GROWTH FACTOR Vehicle class specific traffic growth Default Growth Function Default growth rate Blank Actual Planning estimate, usually Compound Growth Actual Planning estimate AXLE LOAD DISTRIBUTION Axle Load Distribution Factors Actual, otherwise use Level 3 defaults GENERAL TRAFFIC INPUTS Mean wheel location (in) 18 Traffic wander standard deviation (in) 10 Design lane width Actual NUMBER AXLES/TRUCK Number of axles per truck Level 3 defaults 18

19 INPUTS AXLE CONFIGURATION Average axle width (ft) 8.5 Dual tire spacing (in) 12 Single Tire Pressure (psi) 120 Dual Tire Pressure (psi) 120 Tandem Axle Spacing (in) 51.6 Tridem Axle Spacing (in) 49.2 Quad Axle Spacing (in) WHEELBASE Short Medium Long Average Axle Spacing (ft) Percent of trucks (%) CLIMATE Single site weather station data should be used when the project is in very close proximity (five miles or less). Interpolated multiple (three or more) weather station data should be used when the project is not in close proximity to a particular weather station. 5 miles Import previously generated climatic data file > 5 miles Generate new climatic data file with three or more weather stations Depth of water table (ft) Actual or assume 3 19

20 INPUTS 6.6 STRUCTURE DESIGN FEATURES (PC ONLY) Permanent curl/warp effective temperature difference ( F) -10 Joint spacing (ft) 15 Sealant type Liquid Doweled transverse joints Yes Dowel diameter (in) 1.25 for for >10 Dowel bar spacing (in) 12 Edge Support, Tied PCC shoulder, Longterm LTE (%) 40, for tied shoulders Edge Support, Widened slab, Slab width (ft) 14, 12 for AADT 1700 Base type Actual, from Layers Base inputs PCC-Base Interface Unbonded PTB very erosion resistant Erodibility index Rock Base erosion resistant Type 1 or 5 fairly erodable Loss of bond age (months) N/A DRAINAGE AND SURFACE PROPERTIES Surface shortwave absorptivity 0.85 Infiltration (JPCP) Minor (10%) Drainage path length (ft) 2 ft more than lane width Pavement cross slope (%) 2 20

21 INPUTS LAYERS JPCP PCC material JPCP Layer thickness (in) Actual Unit weight (pcf) Actual or 145 Poisson s ratio 0.2 Coefficient of thermal expansion (per F x 10-6) 5.5 Thermal conductivity (BTU/hr-ft-F ) 1.25 Heat capacity (BTU/lb-F ) 0.28 Cement type Type I Cementitious material content (lb/yd 3 ) 564 Water/cement ratio 0.42 Aggregate type Actual or Limestone Reversible shrinkage (% of ultimate shrinkage) 50 Time to develop 50% of ultimate shrinkage (days) 35 Curing method Curing compound Strength property input level Level 3 defaults 28-day PCC modulus of rupture (psi) N/A 28-day PCC compressive strength (psi) 4500 HMA Asphalt material type Asphalt concrete Layer thickness (in), first layer 1.75 Layer thickness (in), second layer Remaining thickness, or 3.00 for SP250, or remaining thickness for BP Layer thickness (in), third layer Remaining thickness, if needed Aggregate Gradation Actual Asphalt Binder Options Superpave binder grading High/Low Temperature ( C) Actual per PDM Reference temperature (F ) 70 Effective binder content (%) Actual Air voids (%) 7.0 Total unit weight (pcf) Actual Poisson s ratio 0.35 Thermal conductivity asphalt (BTU/hr-ft-F ) 0.67 Heat capacity asphalt (BTU/lb-F ) 0.23 See Appendix for average gradations, effective binder contents, total unit weights, and high/low temperatures. 21

22 INPUTS BASE Unbound Material Crushed stone Actual Thickness (in) 18 (Rock Base) 4 (Type 1 or 5) Strength Properties Input Level Level 3 Poisson s ratio 0.35 Coefficient of lateral pressure 0.5 Modulus (psi) (Rock Base) (Type 1 or 5) Plasticity Index, PI 3 (Rock Base) Actual (Type 1 or 5) Passing #200 sieve (%) 10 Passing #4 sieve (%) 20 (Rock Base) 47 (Type 1 or 5) D60 (mm) 25 (Rock Base) 8 (Type 1 or 5) See Appendix for average PI for Type 1 or 5 Aggregate Base. SUBGRADE Unbound Material Actual, from soil report Thickness (in) Semi-infinite (Last layer) Strength Properties Input Level Level 2 Poisson s ratio 0.4 Coefficient of lateral pressure (A-4 soil) (A-5 soil) Modulus (psi) 8000 (A-6 soil) 5000 (A-7-5 soil) 3000(A-7-6 soil) Plasticity Index, PI Actual or default for soil classification Passing #200 sieve (%) Actual or default for soil classification Passing #4 sieve (%) Actual or default for soil classification D60 (mm) Actual or default for soil classification 22

23 INPUTS THERMAL CRACKING (AC ONLY) Thermal Cracking Level 3 defaults 6.7 DISTRESS POTENTIAL (AC ONLY) Block cracking (L/M/H) ((% of total lane area) Sealed longitudinal cracks outside of wheel path (M/H) (ft/mile) None None 23

24 APPENDIX Appendix 24

25 APPENDIX Low Volume Routes Vehicle Class Distribution Vehicle Percent Class

26 APPENDIX 2004 Average Gradations for Asphalt Mixes SP125 BB UBAWS 3/4 " 0 3/4 " 5.6 3/4 " 0 3/8 " /8 " /8 " 25.3 # # # 4 68 # # # SP190 BP1 SL 3/4 " 1.7 3/4 " 0 3/4 " 0 3/8 " /8 " 3.8 3/8 " 20.1 # # # # # # SP250 BP2 3/4 " /4 " 0 3/8 " /8 " 20.9 # # # # All SP All BP 3/4 " 2.5 3/4 " 0 3/8 " /8 " 25.3 # # 4 38 # # State Average Effective Binder Content and Total Unit Weight SP125BSM BB Eff. AC Content Eff. AC Content 8.43 Spec Unit Wt Spec Unit Wt SP125B BP1 Eff. AC Content Eff. AC Content 9.96 Spec Unit Wt Spec Unit Wt SP125C Eff. AC Content Spec Unit Wt SP250 Eff. AC Content 8.16 Spec Unit Wt

27 APPENDIX High/Low Temperatures TYPE OF CORRIDOR LOCATION Heavy Duty All Districts TYPE OF CONSTRUCTION Full Depth Asphalt TYPE OF MIX Surface mixture (SP125 or SMA) and first underlying lift Remaining Underlying Lifts ASPHALT BINDER PG PG All Districts Asphalt Overlays Surface mixture (SP125 or SMA) and first underlying lift PG Remaining Underlying Lifts PG All Districts Full Depth Asphalt Surface mixture (SP125) and first underlying lift PG Medium Duty All Districts Asphalt Overlays Remaining Underlying Lifts Surface mixture (SP125) and first underlying lift PG PG Remaining Underlying Lifts PG Light Duty All Districts All Districts Full Depth Asphalt Asphalt Overlays All Mixtures All Mixtures PG PG

28 APPENDIX Average Plasticity Index for Type 1 or 5 Aggregate Base District PI