Quality Pavement from Design through Construction Dave Newcomb Texas A&M Transportation Institute Minnesota AAPT
Issues Pavement Design Material Quality Mix Type Selection Production and Paving Life Cycle Costs 5-minute Construction Screw Ups
For many engineers, contractors, and consultants Sophistication Understanding Time
(a) Year 2011. (b) Year 2040.
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!
PAVEMENT DESIGN
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
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
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.
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
Design from Bottom-Up
Perpetual Pavement } Zone of High Compression 38 75 mm (1.5-3 ) SMA, OGFC or Superpave Rut Resistant Intermediate Course 75 100 mm (3 4 ) Max Tensile Strain Durable Base 100 250 mm (4 10 ) Pavement Foundation
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
Rehabilitation Pre-construction Investigation Subsurface moisture Deflection Testing Cores DCP Rehabilitation Design 90% of construction What we teach worst
Construction Considerations Layer thickness Aggregate Base ± ½ 2 Asphalt Surface ± ¼? Maybe ± ½? 6 Asphalt Surface ± ¼ Density at Curbs
Finnish Design Philosophy Subgrade Design for 100 years Everything Below 4 Design for 60 years From 4 Up Design for 30 years
SPECIFICATIONS
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.
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.
PRODUCTION AND PLACEMENT
Construction Foundation requirements for construction Interlayer friction Density especially in asphalt base layer Overly stiff mixtures Segregation Joint density Asphalt layer bonding QC/QA
Production Best Practices! Checklist Condition of Plant Aggregate Stockpiles Handling RAP Stockpiles Asphalt Storage Operation of Drum/Burner Loadout Balance Production with Paving
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
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
Traffic Control
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!
5-minute Screw Up
The Rest of the Street
Job Site is not Driver s Ed Class
Joint Density Use fine-graded surface mix Construct and compact joint properly
Four Years Prior
Making Up for Sunny Days
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
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.
Attention to Detail!
Materials Foundation Soils Granular Materials Stabilization Asphalt Materials and Mix Design Base Layer Intermediate Layer Wearing Course
Interlayer Bonding Ensure complete tack coverage Use trackless or polymer modified or hot tack Keep traffic to a minimum
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.
CA Crack & Seat I-710 2003 Life-Cycle Cost Analysis (Lee et al., 2011)
The Public s Perception
WE Know How to do This!
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!
The Future is Bright!