2. HMA MATERIALS

3. Background l Asphalt – Soluble in petroleum products – Generally a by- product of petroleum distillation process –Can be naturally occurring l Tar –Resistant to petroleum products –Generally by-product of coke (from coal) production

4. Background l First US hot mix asphalt (HMA) constructed in 1870’s –Pennsylvania Ave. –Used naturally occurring asphalt from surface of lake on Island of Trinidad l Two sources –Island of Trinadad –Bermudez, Venezuela

5. Background l Each lake asphalt source very consistent –Used solubility test to determine source » Insolubles differed substantially between sources l Demand for paved roads exceeded the supply of lake asphalts in late 1800’s –Led to use of petroleum asphalts

6. Petroleum-Based Asphalts l Asphalt is waste product from refinery processing of crude oil –Sometimes called the “bottom of the barrel” l Properties depend on: –Refinery operations –Composition crude source-dependent Gasoline Kerosene Lt. Gas Oil Diesel Motor Oils Asphalt Barrel of Crude Oil

7. Asphalt Cement Components l Asphaltenes –Large, discrete solid inclusions (black) –High viscosity component l Resins –Semi-solid or solid at room temperature »Fluid when heated »Brittle when cold l Oils –Colorless liquid –Soluble in most solvents –Allows asphalt to flow

8. Refinery Operation FIELD STORAGE PUMPING STATION LIGHT DISTILLATE HEAVY DISTILLATE PROCESS UNIT ASPHALT CEMENTS FOR PROCESSING INTO EMULSIFIED AND CUTBACK ASPHALTS STILL AIR BLOWN ASPHALT STORAGE TOWER DISTILLATION REFINERY RESIDUUM OR GAS PETROLEUM SAND AND WATER CONDENSERS AND COOLERS TUBE HEATER MEDIUM DISTILLATE

9. Types l Asphalt cements –Generally refinery produced material –Air blown asphalt cements l Cutbacks –Asphalt cements “cut” with petroleum solvents l Emulsions –Mixture of asphalt cement, water, and emulsifying agent

10. Cutbacks l Rapid cure (RC) (Naphtha or Gasoline) –High volatility of solvent –Tack coats, surface treatments l Medium cure (MC) (Kerosene) –Moderate volatility –Stockpile patching mix l Slow cure (SC) (Low viscosity oil) –Low volatility –Prime coat, dust control

11. Emulsions l Emulsifier gives surface charge to asphalt droplets suspended in water medium –Anionic »Negative charge »Alkaline »Good with limestones (positive charge) –Cationic »Positive charge »Acid »Good with silica gravels (negative charge)

12. Purchasing of Asphalt Cements l Need to be able to specify desirable characteristics l “Desirable characteristics” have evolved over time and with increasing technological advances l Purchasing requires specifications

13. Early Specifications l Lake Asphalts –Appearance –Solubility in carbon disulfide l Petroleum asphalts (early 1900’s) –Consistency »Chewing »Penetration machine l Measure consistency

14. Penetration Testing l Sewing machine needle l Specified load, time, temperature 100 g Initial Penetration in 0.1 mm After 5 seconds

15. Penetration Specification l Five Grades 40 - 50 60 - 70 85 - 100 120 - 150 200 - 300

16. Viscosity Graded Specifications

17. Viscosity: the ratio between the applied shear stress and the rate of shear.  Definition

18. Types of Viscosity Tubes Asphalt Institute Tube Zietfuchs Cross-Arm Tube

19. Testing Absolute viscosity –U-shaped tube with timing marks & filled with asphalt –Placed in 60C bath –Vacuum used to pull asphalt through tube –Time to pass marks –Viscosity in Pa s (Poise)

20. Table 1 Example AC 2.5AC 40 AC 2.5AC 40 Visc, 60C 250 + 50 4,000 + 800 Visc, 135C 80+ 300+ Penetration 200+ 20+ Visc, 60C<1,250 <20,000 Ductility 100+ 10+

21. 40 50 60 70 85 100 120 150 200 300 Penetration Grades AC 40 AC 20 AC 10 AC 5 AC 2.5 100 50 10 5 Viscosity, 60C (140F) AR 16000 AR 8000 AR 4000 AR 2000 AR 1000

22. Aggregates Usually refers to a soil that has in some way been processed or sorted.

23. Excavation

24. Crushing

25. Transportation

26. Sizing Stockpiling

27. Desired Aggregate Properties Toughness Soundness Deleterious Materials Gradation

28. Soundness Before After

29. l Aggregate Gradation –The distribution of particle sizes expressed as a percent of total weight. –Determined by sieve analysis Gradations

30. Mechanical Sieve Individual Sieve Stack of Sieves

31. Mechanical Sieve Stack in Mechanical Shaker

32. * Uniformly graded - Few points of contact - Poor interlock (shape dependent) - High permeability * Well graded - Good interlock - Low permeability * Gap graded - Only limited sizes - Good interlock - Low permeability Types of Gradations

33. Aggregate Size Definitions l Nominal Maximum Aggregate Size –one size larger than the first sieve to retain more than 10% l Maximum Aggregate Size –one size larger than nominal maximum size 1001009072654836221594100998972654836221594

34. 100 0.075.3 2.36 4.759.512.5 19.0.075.3 2.36 4.759.512.5 19.0 Percent Passing control point restricted zone max density line maxsizenommaxsize Sieve Size (mm) Raised to 0.45 Power

35. Questions - ?