Roadway Base Stabilization Current Practice

Transcription

1 Roadway Base Stabilization Current Practice AGC MNDOT TRANSPORTATION CONSTRUCTION AND GRADING INNOVATIONS FORUM December 6, 2016

2 OVERVIEW ROAD TYPES BASE STRENGTHENING APPLIES TO ALL KEY CONSIDERATIONS for SUCCESS PROCESS OVERVIEW PAVEMENT ASSESSMENT REHAB PROCESS SELECTION ASSURE PERFORMANCE 2

3 GRAVEL What are my current costs? What are my future needs? RURAL HMA Staged construction/perpetual pavements URBAN HMA ROAD TYPES Adding strength to existing design INTERSTATE HMA Mn/Road 3

4 Road Type - Old Hwy 3 (S Robert Trail) Concrete 4

5 Traffic s Effect on Maintenance Costs/Mile An increase in traffic should lead to an increase in maintenance costs, particularly for gravel roads More gravel needed More blading and smoothing of road Paved low volume roads may not have adequate structure to handle loads. Up front pavement evaluations can address this issue MAINTENANCE COST/MILE ( $ ) $3,000 $2,500 $2,000 $1,500 $1,000 $500 $ up ADT RANGE BITUMINOUS GRAVEL 5

6 FHWA Recycled Materials Policy Recycled materials should get first consideration in materials selection Recycling engineering, economic and environmental benefits Remove restrictions prohibiting use of recycled materials without technical basis 6

7 Identifying Roads for Rehabilitation Adequate base strength/stability Root cause of distress Sufficient base depth Can existing pavement address base deficiency 7

8 Wearing Surface Layers HMA, Surface Treatment, Whitetopping? Overlay Wearing Surface Layers Base Subbase Subgrade Fill or Natural Soil 8

9 Definitions Mechanical stabilization - 1st step in reclamation; also used to describe FDR without addition of binder (Pulverization) Chemical stabilization - FDR with chemical additive ( Base One, Calcium or Magnesium Chloride, Lime, Fly Ash, Kiln Dust, Portland Cement, etc.) Bituminous stabilization - FDR with asphalt emulsion, emulsified recycling agent, or foamed / expanded asphalt additive Combination stabilization - Any 2 or more of above 9

10 Full Depth Reclamation (FDR) Keys to Success Stabilization Considerations Pulverization Mill to 3 - material No stabilization required Shape, compact Granular Equivalent of 1 inch per inch 10

11 Stabilized Full Depth Reclamation (SFDR) 11

12 Base Stabilization vs. HMA Overlay Stabilized Base Flexible Overlay Over Poor Existing Base Base Stabilization Strengthens base Reduces Overlay Thickness Flexible Better Fatigue Resistance Ready for Staged construction Future growth 4-6 HMA Overlay Over existing base Poor base = overlay failure Requires widening, slope corrections 12

13 Stabilized Full Depth Reclamation (SFDR) - Keys to Success Stabilization Considerations Fly Ash or Cement Stabilization Mill to 3 - material Can incorporate some plastic subgrade soils Cement addition rate of 2-4% by weight, fly ash addition rate of 6-10% by weight Short working time due to hydration Specific design for each project Higher stiffness, lower flexibility 13

14 Stabilization Agent Options Cutbacks/Roadmix Proprietary Products Engineered Emulsion Lime/Chlorides Foamed Asphalt Flyash/Cement Combinations of above 14

15 Surfacing Options Chip Seal Slurry/Micro Bonded Wearing Course (BWC) Thin Lift HMA Overlay Single Lift HMA Overlay Multi Lift HMA Overlay Combinations of above 15

16 Base Stabilization Cells 2, 3, 4 CELL 50% 6 inch 4% 2 RAP Stab. EE CELL 75% 6 inch 3% 3 RAP Stab. EE CELL 100% 8 inch.075% 4 RAP Stab. EE SHLD 50% RAP 4 inch Stab. 4.5% EE 16

17 Perpetual Pavement Concept MnRoad 2 1 UTBWC Zone of High Compression Flexible Fatigue Resistant Bound Material 6-8 High Modulus Rut Resistant Material Max Tensile Strain Pavement Foundation 17

18 Full Depth Reclamation (SFDR) Keys to Success Flexible Granular Stiff Stiff Organic Plastic Clay 18

19 Cold In-Place Recycling (CIR) The Train Machine Concept 19

20 ADDROCK Barnes County, ND 2009 Scenic Byway 20

21 CIR Crack Elimination

22 Conventional No mix design 2% Emulsion QC requirements Two gradations per day 100% passing 1-1/ % passing 1 Control strip Cold In-place Recycling (CIR) Fundamentals of CIR Comparison of Conventional and Engineered CIR Engineered Defined sampling protocol Engineered design Performancerelated specs Early strength & long term durability 22

23 Hot-in-Place Recycling 23

24 Grids/Fabrics Pre-overlay Treatments Acts as localized reinforcement over cracks Delays reflective cracking Reduces the number and severity of reflective cracks 24

25 Pavement Assessment Pavement assessment is the first step in making good decisions. The condition of the existing pavement is assessed through: Pavement History Pavement Condition/Distress Survey Pavement Strength Evaluation Surface, Base and Subgrade Analysis Drainage Review 25

26 Pavement Assessment Pavement History Historic or existing information for the pavement should be gathered and assessed, including: Original design information As-built/constructed data Quality Control/Quality Assurance construction data Pavement Management System (PMS) data Maintenance activity records 26

27 Pavement Assessment Pavement Condition/Distress Survey What is a pavement condition survey? A detailed visual inspection which rates all of the surface irregularities, flaws and imperfections found in a given area A link to key insights into the causes of deterioration Project level versus network level 27

28 Pavement Assessment Keys to Success Determine the Root Cause Springtime (preferred) structural evaluation Structure; layer evaluations Drainage Distresses Road needs Dynamic Cone Penetrometer (DCP)

29 Pavement Coring Confirm inplace materials and review conditions Coring performed in non-cracked (sound) pavement areas, as well as on cracks to assess extent of cracking. 29

30 Pavement Coring 30

31 Pavement Assessment Pavement Strength Evaluation Pavement Structural Capacity Non-destructive testing methods include Falling Weight Deflectometer (FWD), Ground Penetrating Radar (GPR) and Dynamic Cone Penetrometer (DCP) Destructive testing methods include soil borings, probe holes, test pits and coring 31

32 Ground Penetrating Radar Ground-coupled GPR Air-coupled GPR 32

33 GPR for Pavements 33

34 Typical GPR Output File Pavement Surface Bitumino us Aggregate Base 34

35 Primary Uses for Roadway GPR Determining inplace thicknesses o Pre mill-and-overlay or cold in-place recycling (CIR) thickness determination o Bituminous and base thickness if considering full-depth reclamation (FDR) Layer thicknesses for FWD Estimation of construction removal quantities QA testing following project completion 35

36 Pavement Strength Evaluation Evaluation of the structural capacity of an existing pavement can be determined by Falling Weight Deflectometer testing: Identify spring load capacity Identify potential pavement failures In-site R-value for use in pavement design Design overlay thickness 36

37 Repair Recommendations Does the roadway meet structural needs? Review Distresses and What are the inplace materials? Perform FWD Testing Recommendations - Provides R-value for design - Tells us road is structurally sound; 10- tons overall with 200 feet of weak area Coring and GPR - Detect severe stripping at bottom of bituminous (eliminates M&OL) - Approx 8 inches of bituminous over 6 inches of aggregate base - GE requirements are 20 - Premill 4-8 FDR & 5 Overlay - Correct 200 feet of weak area - No reflective cracking - Less costly than full recon - Longer life than M&OL 37

38 Project Level Site specific data used to evaluate the in place materials and make economic decisions on the best rehabilitation Sufficient information to develop a construction plan and specifications Network Level Pavement Inventory Looking for sufficient data to manage your system Making macro/long-term decisions based on more general information 38

39 Pavement Management Options 100 Fog Seal / Chip Seals Micro-surfacing Pavement Condition Curve shape determined by quality, traffic, climate, etc. Bonded wearing course / Crack seal Overlay (ideally) Reflective crack relief Overlay (typically) In-place recycling Engineered SFDR stabilization 0 Years 39

40 QUESTIONS? 40