Quality Pavement from Design through Construction. Dave Newcomb Texas A&M Transportation Institute Minnesota AAPT

Transcription

1 Quality Pavement from Design through Construction Dave Newcomb Texas A&M Transportation Institute Minnesota AAPT

2 Issues Pavement Design Material Quality Mix Type Selection Production and Paving Life Cycle Costs 5-minute Construction Screw Ups

3 For many engineers, contractors, and consultants Sophistication Understanding Time

4 (a) Year (b) Year 2040.

5

6 What Can We Do? Have a discussion about it and come up with solutions! Possibilities: Design catalogs for low-volume roads Simplified specifications (4 pages, not 40) Reach out to engineers about common problems and solutions Promote best practices We all have a common goal, we need to act!

7 PAVEMENT DESIGN

8 Pavement Design Low Volume Developers given choice of sections Example: equivalent sections 2 Asphalt 6 Limestone Base 6 Stabililzed Subgrade 6 Asphalt 6 Stabililzed Subgrade 6 JPCP 6 Stabililzed Subgrade Clayey Subgrade Clayey Subgrade Clayey Subgrade

9 Next Steps Build the Cheapest Pavement with Little or No Inspection Allow Construction Traffic (Not Accounted for in Design) 90 to 200 concrete trucks 180 brick trucks 300 lumber trucks??? heavy equipment deliveries Pavement Starts Failing

10

11 Proposed Pavement Standards TABLE VIII MINIMUM PAVEMENT THICKNESS CRITERIA FLEXIBLE PAVEMENTS STREET CLASSIFICATION RESIDENTIAL MINOR COLLECTOR SUBGRADE TREATMENT 6-in Lime-Stab. 6-in Lime-Stab. BASE MATERIAL 6-in. Limestone, 6-in. Cement Stabilized Base or 4-in. HMAC 8-in. Limestone, 8-in. Cement Stabilized Base or 5-in. HMAC SURFACE TREATMENT 2-in. HMAC 2-in. HMAC COLLECTOR & ARTERIAL Design based upon Geotechnical Report, but not less than pavement structure shown for a minor collector. RIGID PAVEMENTS STREET CLASSIFICATION RESIDENTIAL (includes alleys) COLLECTOR AND PRIVATE LOCAL STREETS ARTERIAL SUBGRADE TREATMENT 6-in Lime-Stab. 6-in Lime-Stab. CONCRETE PAVEMENT 6-in. 8-in. Design based upon Geotechnical Report, but not less than pavement structure shown for a collector. NOTE: Lime stabilization is the most commonly used for local clay soils. If other types of stabilization are desired, please submit information.

12 Pavement Design High Volume Lots of Practice in Backing Up the Paver Mix Type Selection and Density Each Added Step Leaves Room for More Problems 10 Full Depth Pavement in 5 2-inch lifts 12.5 mm 12.5 mm 19 mm 19 mm 19 mm Stabilized Subgrade

13 Design from Bottom-Up

14 Perpetual Pavement } Zone of High Compression mm (1.5-3 ) SMA, OGFC or Superpave Rut Resistant Intermediate Course mm (3 4 ) Max Tensile Strain Durable Base mm (4 10 ) Pavement Foundation

15 Design for Best Performance/Application Start at the bottom subgrade While designing layers consider: Construction tolerance Material availability/quality Construction (lifts and density) (3-5X NMAS) Where lift will be placed (surface/base) Type of traffic during development Surface Long. joints Permeability

16 Rehabilitation Pre-construction Investigation Subsurface moisture Deflection Testing Cores DCP Rehabilitation Design 90% of construction What we teach worst

17 Construction Considerations Layer thickness Aggregate Base ± ½ 2 Asphalt Surface ± ¼? Maybe ± ½? 6 Asphalt Surface ± ¼ Density at Curbs

18 Finnish Design Philosophy Subgrade Design for 100 years Everything Below 4 Design for 60 years From 4 Up Design for 30 years

19 SPECIFICATIONS

20 Bad Specifications Use combination ASTM and AASHTO specs pick and choose but have no way to verify. Use spec no. without source designation. Require mix design for OAC and asphalt content range (e.g., 5 to 7%) but have allowance of +0.3%. Conflicting mix types in specs and on plans. Density requirements tighter than the agency they came from. Different definitions of lot as one day s production, 1000 tons and 2000 tons in the same spec.

21 Simple Appropriate Clear Consistent Good Specifications Provide an asphalt mixture according to MnDOT Specification 2360 with a nominal maximum aggregate size of 12.5 mm and a PG58-28 asphalt binder.

22 PRODUCTION AND PLACEMENT

23 Construction Foundation requirements for construction Interlayer friction Density especially in asphalt base layer Overly stiff mixtures Segregation Joint density Asphalt layer bonding QC/QA

24 Production Best Practices! Checklist Condition of Plant Aggregate Stockpiles Handling RAP Stockpiles Asphalt Storage Operation of Drum/Burner Loadout Balance Production with Paving

25 Paving Best Practices! Checklist Personnel: Safety, Toolbox Talk, Day s Work Safety: Barricades, Signs in Place Paver: Condition, Settings, Operations Rollers: Condition, Settings, Number, Operations Site: Clean, Safe, WZ Traffic Controlled Keep Up with, Not Ahead of Production

26 Traffic Control Advantages of long lane closures (FHWA, 2003) - Full lane closures, weekend, week-long Faster project delivery Reduced motorist inconvenience Larger work area/more productivity Reduced congestion Reduced hazard exposure for workers/motorists Reduced traffic accidents Smoother pavement Better public image

27 Traffic Control

28 Inspection & QC We don t have enough inspectors for all the jobs. The inspector might come by for about 5 minutes. These young people just don t get it! Higher quality means higher cost!

29 5-minute Screw Up

30 The Rest of the Street

31 Job Site is not Driver s Ed Class

32 Joint Density Use fine-graded surface mix Construct and compact joint properly

33 Four Years Prior

34 Making Up for Sunny Days

35 Inspection and Quality Control Integrity Doing the right thing even when no one is watching. Inspection Focuses your crews on best practices and high quality One inspector, but everyone should be trained to inspec Quality Control Should be part of contract public and private Corrective action should be part of contract

36 Proposed Pavement Standards TABLE VIII MINIMUM PAVEMENT THICKNESS CRITERIA FLEXIBLE PAVEMENTS STREET CLASSIFICATION RESIDENTIAL MINOR COLLECTOR SUBGRADE TREATMENT 6-in Lime-Stab. 6-in Lime-Stab. BASE MATERIAL 6-in. Limestone, 6-in. Cement Stabilized Base or 4-in. HMAC 8-in. Limestone, 8-in. Cement Stabilized Base or 5-in. HMAC SURFACE TREATMENT 2-in. HMAC 2-in. HMAC COLLECTOR & ARTERIAL Design based upon Geotechnical Report, but not less than pavement structure shown for a minor collector. RIGID PAVEMENTS STREET CLASSIFICATION RESIDENTIAL (includes alleys) COLLECTOR AND PRIVATE LOCAL STREETS ARTERIAL SUBGRADE TREATMENT 6-in Lime-Stab. 6-in Lime-Stab. CONCRETE PAVEMENT 6-in. 8-in. Design based upon Geotechnical Report, but not less than pavement structure shown for a collector. NOTE: Lime stabilization is the most commonly used for local clay soils. If other types of stabilization are desired, please submit information.

37 Attention to Detail!

38 Materials Foundation Soils Granular Materials Stabilization Asphalt Materials and Mix Design Base Layer Intermediate Layer Wearing Course

39 Interlayer Bonding Ensure complete tack coverage Use trackless or polymer modified or hot tack Keep traffic to a minimum

40 Economics Asphalt is NOT the cheap option anymore 1990s: ~$20/ton 2017: ~$75/ton People want better performance if they pay more money. They want fewer traffic disruptions.

41 CA Crack & Seat I Life-Cycle Cost Analysis (Lee et al., 2011)

42 The Public s Perception

43 WE Know How to do This!

44 OWN the ROAD WE agencies, contractors, material suppliers, consultants, supervisors, QC inspectors, resident engineers, mix designers, QA inspectors, paving crews, plant operators, researchers, pavement designers, maintenance engineers, maintenance crews, administrators, and everyone else MUST make the ROAD the PRIORITY!

45 The Future is Bright!