Longer Lasting Roads...

Transcription

1 Polymer Modified Asphalt... Longer Lasting Roads

2 Why Polymer? Improve pavement performance Lower life cycle costs For perpetual pavements Longer Lasting Roads...

3 Definition of a Polymer The term polymer refers to a large molecule formed by chemically reacting many ( poly ) smaller molecules l (monomers) to one another in long chains or clusters. Physical properties of a specific polymer are determined by the sequence and chemical structure of the monomers from which it is made.

4 Types of Polymer ELASTOMERS Able to stretch under load then recover to original shape when the load is removed. Provide benefit when deformed. Used in asphalt binders in HMA mixtures to resist: Permanent deformation and Cohesive failure.

5 ELASTOMER SB/SBS block co-polymer SBR Reduces temperature susceptibility Increases strain recovery Tensile strength at high strains Increases cohesion Increases adhesion

6 Why Modify? Increase serviceable temperature range Stiff at high temperature Flexible at low temperature Improve durability at all temperatures Reduce moisture damage Address construction issues: Reduce draindown for SMA/OGFC More forgiving i binder: reduce secondary damage at cracks/joints less raveling/stripping in segregated areas

7 Polymer Modified Asphalts Polymer network structure determines PMAC s physical properties The network structure depends on: chemistry of both asphalt and polymer their compatibility PERFORMANCE OF A PMA DEPENDS ON THE COMPATIBILITY BETWEEN ASPHALT AND POLYMER

8 Examples of asphalts (all AC-20s with 6% of the same SBS polymer) Asphalt A Asphalt B Asphalt C Asphalt D Reflective florescence photomicrographs Reflective florescence photomicrographs. White is polymer, black is asphalt Ideal microstructure: finely networked polymer in asphalt

9 Performance Tests Binder testing

10 Superpave PG binder grading Polymer is less temperature susceptible SHRP Low Temp p, C SHRP High Temperature, C Increased resistance to thermal cracking -40 Unmodified AC PMAC Increased resistance to rutting

11 PG+ SPECIFICATION Toughness and Tenacity Ductility at 4 C Elastic Recovery

12 Toughness & Tenacity

13 Elastic Recovery & Force Ductility Elastic polymer recovers AC doesn t

14 Force Ductility Unmodified AC Stress PMAC (same base AC) Strength at elongation given by the polymer Elongation, cm

15 Performance of Modified d Mix

16 Rut tr Resistance SST Shear Creep Test, 40 C % Strain, Shear Time, Seconds Decreasin ng Resist tance to Rutting PG (unmod) PG PMA Response to Applied Load of 35 kpa for 10 seconds

17 Durability - Fatigue Resistance Withstands many loading cycles Has greater strain tolerance Flexural Beam Fatigue 20 C PG HMA (PMA) 5,950 PG HMA 1, Cycles to Failure *AASHTO TP-8

18 Rut & Moisture Resistance Same PG unmodified & modified 0 Hamburg Wheeltracking Deforma ation, mm m PMA Unmodified PG Number of Cycles

19 Resistance to Thermal Cracking - Indirect Tensile Test (IDT) 1000 Tensile 800 Strength 600 and Pavement 400 Thermal Stress (psi) 200 PG PMA (~PG 70-28) Cracking temperatures Temperature ( C)

20 Why Modify? Field Performance PMAC 20 years proven performance Formulated locally

21 Life Cycle Cost Analysis: Polymer HMA Saves average of $3844 Canadian per Lane- KM on 4 Projects Costs -km Worth of C 1,000/lane- al Present anadian $1 Tota Ca $50 $45 $40 $35 $30 $25 $20 $15 $10 $5 $0 PMA Conventional Savings $/lane-km $2,685 $1,612 $7,564 $3,516 Highway 401 Coldwater Road Larch Street Durham Region CSHRP Test Site Carrick, Fraser, Hein & Emery, CTAA, 1996

22 Comparative Field Trials & Life Cycle Cost Comparisons Texas: Jones, Kennedy & Torshizi, TRB, 1993 Michigan: Hawley & Baldi, MDOT, 1996 California: Reese & Goodrich, AAPT, 1993 Maryland: Roads & Bridges, Fall, 1996 Kentucky: Blankenship, et. al., AAPT, 1998 Canada: Carrick & Fraser, CTAA, 1996 Pennsylvania: Anderson & Maurer, TRB, 1999 N.D.O.T. Many others

23 Binder Selection In a Superpave World

24 Choosing the right liquid AC binder LTTPBind software Pavement Temperature Reliability factor Traffic speed & load grade bumping for prolonged stresses Application i Performance Testing SHRP Plus for desired modification method Asphalts that give customers the desired performance Goal: perpetual pavements

25 Are modified dbi binders effective? Enhanced Pavement Performance Life-cycle cost - Ride quality - Safety Physical properties of modified mixture Constructibility Stability/Compatibility of AC & modifier QA/QC Environmentally i t friendly Manufacturing variables Consistent product

26 Mnf Manufacture tr & Houston Hobby Airport Construction ti

27 PMAC is easy to use Preblended, pre-reacted reacted, ready-to to-use Doesn t separate No special mixing / agitation required No special equipment needed Optimum AC content varies less than 0.1% from unmodified AC Mix Temperatures may be slightly higher Check with local rep for product you re using

28 Normal good practice gives good results Preheat screed with screed heater Keep continuous flow of mix to paver Keeps screed plate hot Cold screed may cause tearing Prevents premature cooling of the mix Correct temperature give best results Climate, distance of haul, etc. should be considered Prevents mix from getting too sticky

29 Thank You Questions?