Presentation on theme: "Benefits of Modified Asphalts John Duval, P.E. Oregon Asphalt Conference March 8, 2006."— Presentation transcript:
Benefits of Modified Asphalts John Duval, P.E. Oregon Asphalt Conference March 8, 2006
Modified Binder Use to Increase It is likely that modified binders represent as much as 15% of the total annual tonnage of asphalt binder used in the United States; this percentage is expected to increase in the coming decade NCHRP Report 9-10 (2001)
Overview Commonly used asphalt modifiers? What is the benefit of asphalt modifiers? PG PLUS Specifications The Path to PG PLUS Specifications –How did other states arrive there? Finally—A way to Quantify the Benefit of Modified Asphalt Binders Summary/Recommendations
Extenders Sulfur Lignin Extenders are typically cheaper than asphalt and replace asphalt binder Sulfur Extended Asphalt?
Fibers Natural –Rock Wool –Cellulose Man-Made –Polypropylene –Polyester –Fiberglass Fibers can be used to increase asphalt stiffness, but are primarily used to control “drain-down” in open-graded mixtures
Plastomers Polyethylene Polypropylene Ethyl-vinyl-acetate (EVA) Polyvinyl-chloride (PVC) EVA is a plastic that is used to create stiffer insoles for your shoes PVC Pipe Image courtesy slpipe.com Image courtesy cyclingfitness.com
Polyphoshoric Acid (PPA) PPA is a liquid mineral polymer PPA be used alone or in conjunction with polymers PPA can improve high temperature stiffness PPA modification does not oxidize the asphalt binder Care should be taken to avoid neutralization of amine-based liquid antistrip chemicals IS-220
Many Highway Agencies have developed PG PLUS specifications The intent is to ensure that the preferred modifier is used Agency Perspective
Industry Perspective Encourage Agencies to use performance specifications This allows suppliers to innovate and compete in the marketplace to earn a profit
ER-Elastic Recovery FD-Force Ductility TT-Toughness & Tenacity PA-Phase Angle States with PG PLUS Specs PG + modifier PG ER SB/SBS Required ER & PA PA ER SB/SBS Required ER & TT ER ER & FD FD & ER ER Ductility Ductility, TT & ER ER & PA ER FD ER TT & DT PA ER & TT ER Source: Asphalt Institute ER 215 (2005)
Research on Modified Binders NCHRP 9-10 (Prof. H. Bahia) FHWA Accelerated Loading Facility European Studies Industry Research State DOT research –Nevada DOT I-80 Study (Prof. P. Sebaaly) –Nevada DOT Construction Variability Study (Prof. P. Sebaaly)
Nevada DOT (2003) Source:Sebaaly et al. RR 1393-5, (2003)
The Path to PG PLUS (Its shorter than you might think)
Mississippi DOT “PG 76-22 or PG82-22 and shall be made by adding a polymer modifier to a PG 67-22 or lower grade asphalt. Polymer shall be SBS, SBR, or equal approved by Engineer.” Mississippi DOT Std Spec Section 702.02 “We make the suppliers start with the PG 67-22, then modify that to get the PG 76-22.” Jimmy Brumfield, Mississippi DOT Polymer adds between $3 to $5 per ton of mix, which increases the cost of mix to about $38 to $42 per ton. “Working with Polymers,“ Better Roads, 2004
Finally—A way to Quantify the Benefit of Modified Asphalt Binders
Quantifying the Effects of PMA for Reducing Pavement Distress This study (published in Feb 2005) uses national field data to determine enhanced service life of pavements containing polymer modified binders versus conventional binders. The data is from a variety of climates and traffic volumes within North America. ER 215 IS 215
Study Objectives Quantify the effect of using PMA as compared to conventional-unmodified HMA mixtures in terms of: –Increasing pavement life –Reducing occurrence of distresses Identify conditions that maximize effect of PMA to increase HMA pavement & overlay life.
Field Test Sections FHWA’s LTPP –SPS-1; SPS-5; SPS-6; SPS-9 –GPS-1; GPS-2; GPS-6; GPS-7 M.T.Ontario Modifier Study Accelerated Pavement Tests –FHWA ALF –NCAT Test Track –California HVS Studies –Ohio Test Road –Corp of Engineers
Locations of Test Sections - PMA and Unmodified Companion Not all sites located on map.
Companion Sections—Montana HMA Overlay (w/ PMA) HMA Soil-Aggregrate Base Soil-Aggregate Base HMA Overlay HMA Soil-Aggregate Base
Companion Sections—Montana HMA Overlay (w/PMA) HMA Soil-Aggregrate Base Soil-Aggregate Base HMA Overlay HMA Soil-Aggregate Base
Direct Comparisons – Rutting 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 00.20.40.60.811.2 Rut Depths on PMA Sections, inches Rut Depths on Companion Sections, inches
Mechanistic-Empirical Analysis Use M-E distress prediction models from new 200x Pavement Design Guide for: –Fatigue Cracking –Rutting Damage indices computed using factorial cell specific calibration Compare damage indices to actual distress measurements for both PMA and unmodified sections
Summary of Expected Increase in Service Life, Years, Based on M-E Damage Based Analysis Site FactorCondition Description Added Life Foundation Non-expansive, coarse soils 5-10 Expansive and plastic soils (PI>35) 2-5 Frost Susceptible in cold climate 2-5 Water Table & Drainage Deep 5-10 Shallow; adequate 5-8 Shallow; inadequate 0-2 Existing Pavement Condition HMA Good 5-10 Poor-extensive cracking 1-3 PCC Good 3-6 Poor-faulting & cracking 0-2
Summary of Expected Increase in Service Life, Years, Based on M-E Damage Based Analysis Site Factor Condition DescriptionAdded Life Climate; Temp. Fluctuations Hot Hot Extremes 5-10 Mild 2-5 ColdCold Extremes 3-6 Traffic, Truck Volumes Low Intersections 5-10 Thoroughfares 3-6 Heavy Loads 5-10 Moderate 5-10 High 5-10
Generic LCCA Strategy/ Timeline and Revised PMA Timelines Based on Results PMA Surface 2-4 in. RM HMA OL Years510152025303540 Conv. Struct. RM Mill- Fill HMA OL Mill- Fill HMA OL PMA Full Depth RM Mill- Fill
Life Cycle Cost Analysis Time Net Present Value Initial Construction Rehabilitation Maintenance Salvage 0
EXAMPLE 1, Unmodified All Layers Yr.ActivityCost,$NPW,$ 0 10” Base668K668K 2.5” Binder 2” Wearing 102” mill/fill 87K58K 1% patching (not on shoulders) 182” mill285K141K 3% patching scratch 2.5” Binder 2” Wearing (incl. shoulders) 28 Same as yr.1087K29K 34Same as yr.18 285K75K AnnualMaint ($1.8K/yr)73K33K Total NPW:1,005K
EXAMPLE 2, Modified Wearing Course (top 2”, including shoulders) Yr.ActivityCost,$NPW,$ 0 10” Base682K682K 2.5” Binder 2” Wearing 182” mill298K147K 3% patching scratch 2.5” Binder 2” Wearing (incl. shoulders) 34Same as yr.18 298K79K AnnualMaint ($1.8K/yr)73K33K Total NPW:941K
EXAMPLE 3, Perpetual Pavement: Modified Wearing Course (top 2”) and Bottom 4” of Base (incl. shoulders) Yr.ActivityCost,$NPW,$ 0 10” Base709K709K 2.5” Binder 2” Wearing 182” mill/fill141K70K (incl. shoulders) 34Same as yr.18 141K37K AnnualMaint ($1.8K/yr)73K33K Total NPW:849K
Quantifying the Benefit Pavement Type Initial CostChange # NPV Savings 1) Unmodified669K - 1,005K - (resurface yr.10 and 28, structural overlay yr.18 and 34) 2) Modified Wearing682K+ 2.0% 941K 6.5% (structural overlay yr.18 and 34) 3) Modified Wearing & Base709K+ 6.0% 849K 15.5% (Perpetual Pavement: resurface yr. 18 and 34) Cost to use PMA equates to approx. 1% of initial cost per inch modified
Summary/Recommendations Modifiers can improve high and low temperature properties of asphalt binders We are still waiting for a PG PLUS test that is “blind” to the modifier AI ER 215 provides a sound method to measure the benefit of modified asphalts in order to make decisions based on lowest lifecycle cost.
Summary/Recommendations ODOT should study the cost and benefit of modified asphalt mixes in Oregon –Laboratory assessment of rut susceptibility using Asphalt Pavement Analyzer –Field studies of full-scale modified asphalt sections subjected to actual traffic
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