A Few Words About Asphalt Quality

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2 A Few Words About Asphalt Quality Modified Asphalt in a RAP World Asphalt Pavement Association of New Mexico and Asphalt Institute June 16, 2016 Albuquerque, NM

3 Workshop Goals Asphalt Quality a civil engineering perspective on asphalt quality very basic introduction to polymer modification set the stage for Mike RAP Issues grade dumping and bumping characterization of RAP binders blending charts effect of RAP on binder properties effect of RAP on mix properties modified asphalt in a RAP world

4 Quality = Consistency Asphalt Quality (Two Definitions) same results: day after day after day Quality = How good is it? good stuff better stuff best stuff

5 Asphalt Quality (PG 64-22) Original DSR, kpa DSR m-value /9/2012 1/23/2012 2/6/2012 2/20/2012 3/5/2012 3/19/2012 4/2/2012 4/16/2012 4/30/2012 5/14/2012 5/28/2012 6/11/2012 6/25/2012 7/9/2012 7/23/2012 8/6/2012 8/20/2012 9/3/2012 9/17/ /1/ /15/ m-value Avg DSR = 1.29 kpa Std Dev = 0.08 kpa

6 Asphalt Quality Good Best! Let s discuss asphalt quality in these terms Better

7 Performance Graded Asphalt Binders PG spec involves running binder tests at anticipated pavement temperatures PG high temp grade (deg C) low temp grade (deg C)

8 Another Way to Look at It Test asphalt binder at temps this layer feels (high, intermediate, low) Testing binder to get good performance for this layer at expected pavement temps.

9 PG Physical Property Tests Dynamic Shear Rheometer (high temp grade) Bending Beam Rheometer (low temp grade)

10 Concept of Temperature Spread Numerical difference between high and low temperature grade e.g., PG = 64-(-22) = 86 deg spread sometimes called Useful Temperature Interval (UTI) Supply versus Demand roadway environmental conditions demand an 86 degree spread binder PG supplies at least 86 degrees Temperature spread is gross indicator of binder quality

11 Nominal versus Theoretical Temperature Spread Nominal: PG = 86 deg Theoretical: PG = 89.3 deg DSR Value m-value 1.00 spec spec

12 Effect of Test Precision on Asphalt Quality Laboratory Acceptable Test Parameter HAC Glendale HAC Albuquerque Range 1 Original Binder G*/sin 58º C, kpa Absolute 60º C, P RTFO Binder G*/sin 58º C, kpa Mass Loss, % PAV Binder (100º C) G*sin 19º C, kpa Creep -18º C, MPa Creep Slope -18º C Based on AASHTO multilab precision statements

13 Asphalt Quality PG Good PG Better PG Best! Main takeaway asphalt binder quality is indicated by PG temperature spread

14 How Do We Increase the Temp Spread to Improve Asphalt Quality? Modify the asphalt! Use soft asphalt to provide better low temp properties (cracking) Use modifier to maintain high temperature properties (rutting)

15 So you want to use modified asphalt binders Will it have the intended performance effect? effect as stand along modifier effect as co-modifier How can it be specified? recipe vs performance vs both How much does it cost? price volatility, availability How must it be handled and incorporated? Does it stay homogeneous? Is it heat stable? Does it affect constructability? Are there testing considerations? Compatibility concerns with other additives? for example, RAP, RAS, etc.

16 Types of Modifiers Inorganic acids (e.g., PPA) Polymers and attendant stuff Construction Enhancers (e.g., WMA additives) Waste Post Consumer Products (e.g., crumb rubber) Fillers and Fibers Antistripping agents Hydrocarbons Antioxidants Extenders Rejuvenators

17 Log Log Stiffness, Viscosity, etc. Modification via polymer polymer modified Unmodified Log Temperature

18 Types of Polymers Elastic Type - SB diblock (Dynasol 1205) - SBS (LCY 3501, Kraton D1118) - SBR latex (Ultrapave 1156) - Waste rubber (CRM WRF-14) Plastic Type - EVA (Exxon Polybilt 103) - polyethylene (Novaphalt)

19 How to Test Polymer Modified Binders PG tests Elastic Recovery Force Ductility MSCR % Recovery

20 Polymer Modified Asphalt (Elastic) Advantages Significant performance history Elastic effect Improved cohesion τ = σ tan (φ) + c Many specs designed around stretchy polymers (no mysteries) Favorable co-modifier with others (e.g., PPA) Disadvangates Can be challenging to manufacture Compatibility can be a problem Tougher to handle Not heat stable Challenge to emulsify Sometimes supply/price not stable Relatively expensive

21 Engineering Management Question How is modified asphalt strategy affected by incorporation of Reclaimed Asphalt Pavement?

22 Take it Away Mike!