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1 COST EFFECTIVENESS OF ASPHALT RUBBER INTERLAYERS 18th Annual Complete Streets and Technology Conference April 19, 2017 Shakir Shatnawi, Ph.D., P.E. President, SHATEC ENGINEERING CONSULTANTS, LLC (Former Caltrans State Pavement Engineer) Presentation Outline California Experience Asphalt Rubber Interlayers Composite Layering Systems Cost Effectiveness Discussion Final Remarks 2 1

2 California Experience with AR Products 3 Chip Seal (SAM) Chip Seal Interlayers (SAMI) Open-Graded Hot Mix Dense-Graded Hot Mix Gap-Graded Hot Mix Reduced Thickness of AR 4 Conventional Asphalt Rubber 2

3 Thickness Equivalencies for Flexible Pavements 5 Thickness Equivalencies for Composite Pavements 6 3

4 Fatigue Model 7 Heavy Vehicle Simulator (HVS) 8 4

5 HVS Tests in South Africa ALF Experiment 10 5

6 Accelerated Pavement Testing Facility (ALF) 11 Asphalt Rubber Interlayers- Description 12 6

7 Chip Seals 13 Known as ARAM Asphalt Rubber Aggregate Membrane A quality AR Chip Seal has the ability to resist reflective cracking Can fill and bridge cracks 13 year old ARCS Asphalt Rubber Interlayers- Description 14 ARAM: Asphalt Rubber Aggregate Membrane SAM-R: Rubberized Stress Absorbing Membrane ARAM and SAM-R are the same descriptions for asphalt rubber chip seal. ARAMI and SAMI-R describe asphalt rubber chip seal interlayers. California Design: ARAMI is assumed equivalent to 45 mm of HMA. 7

8 Reflective Cracking Criteria Von Mises Strains 15 Interlayers (ARAMI/SAMI-R) 16 Increase reflective crack resistance Can fill and bridge cracks Provide thickness equivalencies 10 Year ARAMI 8

9 Composite Layering Systems 17 Cape Seals Two Layer System Three Layer System Composite Layering System- System I: Cape Seal (Slurry/ARAM) 18 9

10 Composite Layering System- System II: Cape Seal (Slurry/ARAM/Leveling Course) 19 AR Cape Seals 20 ARAM overlaid by slurry seal For residential streets NORWALK 1991 Have been used by local agencies since the mid 1980 s NORWALK 2010, 19 years after Cape Seal 10

11 Composite Layering System- System III: AR Overlay/ARAM/Leveling Course (3 Layers) 21 Three Layer System 22 ARAM overlaid by ARHM For arterial streets Costa Mesa, 1989 Have been used by local agencies since the mid 1980 s Costa Mesa 2009, 20 years after Three Layer System 11

12 Composite Layering System- System IV: AR Overlay/ARAM (2 Layer) 23 Two Layer System 24 ARAM overlaid by ARHM or conv. AC For arterial streets Azusa 2004 Have been used by local agencies since the mid 1980 s Azusa, After Two Layer System 12

13 Layering System Cost Effectiveness 25 Initial Cost Life Cycle Cost Example 1: Costa Mesa 26 Built in 1989 (Over 20 years ago) Alt1: Conventional: Full Reconstruction 125mm AC/125mm AB Cost:$135K Alt2: 3-Layer System 45mm RAC-G/ARAMI/25mm AC Cost:$83K Savings=$52K (40%) ARAMI allowed a reduction in thickness 13

14 Example 2: I-5 Orange County 27 CS & OL Caltrans Project Alt1:Conventional-Cold plane 120 mm 75mm AC/Fabric/30 mm AC/PCC Cost:$12Million Alt2: 3-Layer System-Cold plane 85 mm 30 mm RAC-O/ARAMI/45 mm RAC-G Cost:7.3Million Savings: $4.7 Million (40%) ARAMI allowed a reduction in thickness Life Cycle Cost Analysis (LCCA) Example Project 28 Project: 2-mile long segment, two lanes each direction AADT: 150,000 both directions. Existing Pavement: 150 mm distressed flexible pavement over an untreated aggregate base. Cracks over 3 mm Rehabilitation Design: 20-year service life based on reflective crack retardation. 14

15 Strategy Comparison 29 Strategy I: 105 mm Conventional HMA overlay. Strategy II: 60 mm Conventional HMA over ARAMI. Strategy III: 60 mm AR Overlay. Strategy IV: 30 mm AR Overlay over ARAMI. LCCA Analysis 30 FHWA RealCost Software and user s manual: gmt/lccasoft.cfm Caltrans Life-Cycle Cost Analysis Procedures Manual: ffices/pavement_engineering/pdf/lcca_man ual_masterfinal.pdf 15

16 LCCA Approach 31 Integrate all agency and user costs for initial and discounted future costs to account for all investments over the required service life. Identify the lowest and/or the best value for the investment outlays. Costs 32 Agency support costs: 31% Rehab and 19% CAPM of total project cost. User Costs: User delay, vehicle operation and crash costs. Per Caltrans Cal-B/C Model 2004: $10.46 per hour for passenger cars. $27.83 per hour for single unit trucks. $27.83 per hour for combination trucks. 16

17 LCCA Analysis 33 Net Present Value (NPV) Discount Rate (i): 4.0% IC=Initial Cost, FC: Future Cost Maintenance & Rehabilitation Sequence 34 17

18 Incorporating User and Agency Costs in All Activities 35 LCCA Results - Net Present Value (NPV) 36 18

19 Asphalt Rubber Usage Guide 37 ope/asphalt-rubber-usage-guide.pdf CA Pavement Preservation Center g/ Maintenance Technical Advisory Guide (MTAG) 38 A_GuideVolume1Flexible.html 19

20 Final Remarks 39 Strategies that use a combination of AR overlays and AR interlayers are the most cost-effective. Strategies that Use AR interlayers are more cost-effective than those without. Equivalencies of 30 mm to 45 mm for ARAMI seem to be conservative. Final Remarks 40 AR is a proven paving strategy and with a long history of successful performance. Composite layering systems have shown to provide superior performance over conventional strategies. 20

21 Thank You 41 Questions? 21