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VOLUMETRIC ANALYSIS OF HMA MIXTURES

VOLUMETRIC ANALYSIS OF HMA MIXTURES. Volumetrics. All matter has mass and occupies space Volumetrics are the relationships between mass and volume. Specific Gravity, G. Mass. Volume *  w. Basic Terms. Specific Gravity (G): G xy x: b = b inder s = s tone (i.e., aggregate)

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VOLUMETRIC ANALYSIS OF HMA MIXTURES

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  1. VOLUMETRIC ANALYSIS OF HMA MIXTURES Volumetric Analysis of HMA Mixtures

  2. Volumetrics • All matter has mass and occupies space • Volumetrics are the relationships between mass and volume Volumetric Analysis of HMA Mixtures

  3. Specific Gravity, G Mass Volume * w Volumetric Analysis of HMA Mixtures

  4. Basic Terms • Specific Gravity (G): Gxy • x: b = binder s = stone (i.e., aggregate) m = mixture • y: b = bulk e = effective a = apparent m = maximum • Example: • Gmm = gravity, mixture, maximum (i.e., maximum gravity of the mixture) Volumetric Analysis of HMA Mixtures

  5. Basic Terms (cont.) • Mass (P) or Volume (V) Concentration: Pxy or Vxy • x: b = binder s = stone (i.e., aggregate) a = air • y: e = effective a = absorbed • Example: • Pb = percent binder Volumetric Analysis of HMA Mixtures

  6. Va VMA Vb Vba Vse Vmm Vmb Vsb Volumetric Relationships Volumetric Analysis of HMA Mixtures

  7. HMA Volumetric Terms • Bulk specific gravity (Gmb) of compacted HMA • Maximum specific gravity (Gmm) • Air voids or voids total mix (Va) • Effective specific gravity of aggregate (Gse) • Voids in mineral aggregate, VMA • Voids filled with asphalt, VFA Volumetric Analysis of HMA Mixtures

  8. Gmb of Compacted HMA • AC mixed with agg. and compacted into sample Mass agg. and AC Vol. agg., AC, air voids Gmb = Vmb Volumetric Analysis of HMA Mixtures

  9. Testing • Mixing of asphalt and aggregate • Compaction of sample • Mass of dry sample • Mass under water • Mass saturated surface dry (SSD) Volumetric Analysis of HMA Mixtures

  10. Testing Obtain mass of dry compacted sample Volumetric Analysis of HMA Mixtures

  11. Soak in water for 3 – 5 minutes Volumetric Analysis of HMA Mixtures

  12. Testing Obtain mass of specimen at SSD Volumetric Analysis of HMA Mixtures

  13. Calculations • Gmb = A / ( B - C ) Where: A = mass of dry sample B = mass of SSD sample C = mass of sample under water Volumetric Analysis of HMA Mixtures

  14. Maximum Specific Gravity Loose (uncompacted) mixture Mass agg. and AC Vol. agg. and AC Gmm = Vmm Volumetric Analysis of HMA Mixtures

  15. Testing • Mixing of asphalt and aggregate • Mass in air • Mass under water Volumetric Analysis of HMA Mixtures

  16. Testing Loose Mix at Room Temperature Volumetric Analysis of HMA Mixtures

  17. Testing Residual Manometer Metal Bowl with Lid Vacuum Pump Shaker Table Volumetric Analysis of HMA Mixtures

  18. Calculations • Gmm = A / ( A - C ) Where: A = mass of dry sample C = mass of sample under water Volumetric Analysis of HMA Mixtures

  19. Air Voids Calculated using bulk and maximum specific gravities Gmm – Gmb Gmm Air voids (Va) = 100 * Va Vmb Volumetric Analysis of HMA Mixtures

  20. Why Are Air Voids Important? • Related to Rut Resistance • Related to Durability (aging and fatigue) Volumetric Analysis of HMA Mixtures

  21. Surface Voids Solid Agg. Particle Effective Specific Gravity Mass, dry Gse = Effective Volume Vol. of water-perm. voids not filled with asphalt Absorbed asphalt Effective volume = volume of solid aggregate particle + volume of surface voids not filled with asphalt Volumetric Analysis of HMA Mixtures

  22. Effective Specific Gravity 100 - Pb Gse = 100 - Pb Gmm Gb Gse is an aggregate property Determined from a mix test Volumetric Analysis of HMA Mixtures

  23. Voids in Mineral Aggregate Gmb Ps Gsb VMA = 100 - VMA VMA is an indication of film thickness on the surface of the aggregate Vmb Volumetric Analysis of HMA Mixtures

  24. Voids Filled with Asphalt VMA - Va VMA VFA = 100 x VFA is the percent of VMA that is filled with asphalt cement Volumetric Analysis of HMA Mixtures

  25. Percent Binder Absorbed Gse - Gsb Gse Gsb Pba = 100 ( ) Gb Pba is the percent of absorbed asphalt by wt. of aggregate Volumetric Analysis of HMA Mixtures

  26. Effective Asphalt Content Pba 100 Pbe = Pb - Ps The effective asphalt content is the total asphalt content minus the percent lost to absorption? Volumetric Analysis of HMA Mixtures

  27. Dust /Asphalt Ratio F % passing No. 200 = A % Pbe Volumetric Analysis of HMA Mixtures

  28. Factors That Influence Volumetric of HMA • Asphalt viscosity • Mix temperature • Time held at elevated temperature Volumetric Analysis of HMA Mixtures

  29. Important Considerations • Consistent laboratory procedures • Equiviscous mixing temperatures • Mixing times • Curing time to simulate field conditions Volumetric Analysis of HMA Mixtures

  30. Example Problem Volumetric Analysis of HMA Mixtures

  31. - Example Problem - • Let’s assume we have a compacted HMA mixture with the following properties. Bulk Specific Gravity of the Mixture - Gmb = 2.425 Theoretical Maximum Specific Gravity - Gmm = 2.521 Asphalt Binder Specific Gravity - Gb = 1.015 Asphalt Content - Pb = 5.0 % (by mass of total mix) Percent passing No. 200 = 5.3% Volumetric Analysis of HMA Mixtures

  32. - Example Problem - • Let’s also assume that three stockpiled aggregates were used to manufacture this HMA mixture. The percent of each aggregate and the Bulk Specific Gravity (Gsb) for each is as follows: Aggregate % of Total Aggregate G sb A B C 50 % 25 % 25 % 2.695 2.711 2.721 Volumetric Analysis of HMA Mixtures

  33. Example Problem – • Based on the information given for this problem, the following steps should be followed: • Calculate the bulk specific gravity of the combined aggregate • Calculate the effective specific gravity of the aggregate • Calculate the percent absorbed asphalt for the mixture • Calculate the percent effective asphalt for the mixture • Calculate the percent voids in total mix for the mixture • Calculate the percent voids in mineral aggregate for the mixture • Calculate the percent voids filled with asphalt for the mixture • Calculate the dust to asphalt ratio

  34. Example Problem – • Bulk Specific Gravity of the Combined Aggregate - Gsb ( PA + PB + PC ) Where: PA, PB & PC = Percent by Mass of Each Aggregate in Blend GA, GB & GC = Bulk Specific Gravity of Each Aggregate Gsb = PA PB PC + + GA GB GC Based on the information given: PA = 50% PB = 25% PC = 25% GA = 2.695 GB = 2.711 GC = 2.721 ( 50+ 25 + 25 ) Gsb = = 2.705 50 25 25 + + 2.695 2.711 2.721

  35. Example Problem – • Effective Specific Gravity of Aggregate - Gse 100 - Pb Where: Pb = Percent Asphalt Binder by Total Mass of Mixture Gmm = Theoretical Maximum Specific Gravity of Mixture Gb = Specific Gravity of Asphalt Binder Gse = 100 Pb - Gmm Gb Based on the information given: Pb = 5.0 % Gmm = 2.521 Gb = 1.015 100- 5.0 Gse = = 2.735 100 5.0 - 2.521 1.015 Volumetric Analysis of HMA Mixtures

  36. Example Problem – • Percent Absorbed Asphalt Binder - Pba (100 * Gb) (Gse - Gsb) Where: Gb = Specific Gravity of Asphalt Binder Gse = Effective Specific Gravity of Aggregate Gsb = Bulk Specific Gravity of Aggregate Pba = Gse * Gsb Based on the information given: Gb = 1.015 Gse = 2.735 Gsb = 2.705 ( 100 * 1.015 ) (2.735 - 2.705 ) Pba = = 0.4 % ( 2.735 * 2.705 ) Volumetric Analysis of HMA Mixtures

  37. Example Problem – • Percent Effective Asphalt Binder - Pbe ( Pba * Ps ) Where: Pb = Percent Asphalt Binder in Total Mix Pba = Percent Absorbed Asphalt Binder in Total Mix Ps = Percent Aggregate in Total Mix Pbe = Pb - 100 Based on the information given: Pb = 5.0 % Pba = 0.4 % Ps = 95.0 % ( 0.4 * 95.0) 5.0 - Pbe = = 4.6 % 100 Volumetric Analysis of HMA Mixtures

  38. Example Problem – • Percent Voids in Total Mix - Va ( Gmm - Gmb ) Where: Gmm = Theoretical Maximum Specific Gravity of Mix Gmb = Bulk Specific Gravity of Mix Va, % = 100 * Gmm Based on the information given: Gmm = 2.521 Gmb = 2.329 (2.521 - 2.425 ) Va = 100 * = 3. 8 % 2.521 Volumetric Analysis of HMA Mixtures

  39. Example Problem – • Percent Voids in Mineral Aggregate - VMA ( Gmb * Ps ) Where: Gmb = Bulk Specific Gravity of Mix Ps = Percent Aggregate in Total Mix Gsb = Bulk Specific Gravity of Aggregate VMA, % = 100 - Gsb Based on the information given: Gmb = 2.329 Ps = 95.0 % Gsb = 2.705 ( 2.425 * 95.0 ) VMA = 100 - = 14.8 2.705 Volumetric Analysis of HMA Mixtures

  40. Example Problem – • Percent Voids Filled with Asphalt - VFA ( VMA - Va) Where: VMA = percent Voids in Mineral Aggregate Va = percent Voids in Total Mix VFA, % = 100 * VMA Based on the information given: VMA = 14.8 % Va = 3.8 % ( 14.8 - 3.8 ) VFA = 100 * = 74 % 14.8 Volumetric Analysis of HMA Mixtures

  41. Dust /Asphalt Ratio F % passing No. 200 = A Pbe Given: P-200 = 5.3% F 5.3 A 4.60 = = 1.15 Volumetric Analysis of HMA Mixtures

  42. Example Problem - Volumetric Equations • Summary Gsb = 2.705 Gse = 2.732 Pbe , % = 4.6 % Pba , % = 0.4 % Va, % = 3.8 % VMA , % = 14.8 % VFA, % = 74 % F/A = 1.15 Volumetric Analysis of HMA Mixtures

  43. Classroom Exercise Volumetric Analysis of HMA Mixtures

  44. - Classroom Exercise 1 - • Let’s assume we have a compacted HMA mixture with the following properties at 25o C. Bulk Specific Gravity of the Mixture - Gmb = 2.413 Theoretical Maximum Specific Gravity - Gmm = 2.501 Asphalt Binder Specific Gravity - Gb = 1.025 Asphalt Content - Pb = 4.3 % (by mass of total mix) Percent Passing No. 200 = 4.8% Volumetric Analysis of HMA Mixtures

  45. - Classroom Exercise 1 - • Let’s also assume that four stockpiled aggregates were used to manufacture this HMA mixture. The percent of each aggregate and the Bulk Specific Gravity (Gsb) for each is as follows: Aggregate % of Total Aggregate Gsb A B C D 45 % 15 % 25 % 15 % 2.650 2.661 2.675 2.697 Volumetric Analysis of HMA Mixtures

  46. - Classroom Exercise 1 - • Based on the information given for this problem, the following steps should be followed: • Calculate the Bulk Specific Gravity of the combined aggregate • Calculate the Effective Specific Gravity of the aggregate • Calculate the Percent Absorbed Asphalt for the Mixture • Calculate the Percent Effective Asphalt For the Mixture • Calculate the Percent Voids in Total Mix for the Mixture • Calculate the Percent Voids in Mineral Aggregate for the Mixture • Calculate the Percent Voids Filled with Asphalt for the Mixture • Calculate the Dust/AC Ratio Volumetric Analysis of HMA Mixtures

  47. - Classroom Exercise 1 - • Bulk Specific Gravity of the Combined Aggregate - Gsb Where: PA , PB , PC & PD = percent by mass of each aggregate in blend GA , GB , GC & GD= Bulk Specific Gravity of each aggregate ( PA + PB + PC + PD ) Gsb = PA PB PC PD + + + GA GB GC GD Based on the information given: PA = % PB = % PC = % PD = % GA = GB = GC = GD = Gsb = Volumetric Analysis of HMA Mixtures

  48. - Classroom Exercise 1 - • Effective Specific Gravity of Aggregate - Gse 100-Pb Where: Pb = percent asphalt binder by total mass of mixture Gmm = Theoretical Maximum Specific Gravity of mixture Gb = Specific Gravity of asphalt binder Gse = 100 Pb - Gmm Gb Based on the information given: Pb = % Gmm = Gb = Gse = Volumetric Analysis of HMA Mixtures

  49. - Classroom Exercise 1 - • Percent Absorbed Asphalt Binder - Pba (100 * Gb) (Gse - Gsb) Where: Gb = Specific Gravity of asphalt binder Gse = Effective Specific Gravity of aggregate Gsb = Bulk Specific Gravity of aggregate Pba = Gse * Gsb Based on the information known: Gb = Gse = Gsb = Pba = Volumetric Analysis of HMA Mixtures

  50. - Classroom Exercise 1 - • Percent Effective Asphalt Binder - Pbe ( Pba * Ps ) Where: Pb = percent asphalt binder in total mix Pba = percent Absorbed Asphalt Binder into aggregate Ps = percent aggregate in total mix Pbe = Pb - 100 Based on the information known: Pb = % Pba = % Ps = % Pbe = Volumetric Analysis of HMA Mixtures

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