VOLUMETRIC ANALYSIS OF HMA MIXTURES. Volumetric Analysis of HMA Mixtures

Transcription

1 VOLUMETRIC ANALYSIS OF HMA MIXTURES 1

2 Volumetrics All matter has mass and occupies space Volumetrics are the relationships between mass and volume 2

3 Specific Gravity, G Mass Volume * w 3

4 Basic Terms Specific Gravity (G): G xy x: b = binder s = stone (i.e., aggregate) m = mixture y: b = bulk e = effective a = apparent m = maximum Example: G mm = gravity, mixture, maximum (i.e., maximum gravity of the mixture) 4

5 Basic Terms (cont.) Mass (P) or Volume (V) Concentration: P xy or V xy x: b = binder s = stone (i.e., aggregate) a = air y: e = effective a = absorbed Example: P b = percent binder 5

6 Volumetric Relationships V a VMA V b V ba V mb V se V mm V sb 6

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 7

8 G mb of Compacted HMA AC mixed with agg. and compacted into sample Mass agg. and AC G mb = Vol. agg., AC, air voids V mb 8

9 Testing Mixing of asphalt and aggregate Compaction of sample Mass of dry sample Mass under water Mass saturated surface dry (SSD) 9

10 Testing Obtain mass of dry compacted sample 10

11 Soak in water for 3 5 minutes 11

12 Testing Obtain mass of specimen at SSD 12

13 Calculations G mb = A / ( B - C ) Where: A = mass of dry sample B = mass of SSD sample C = mass of sample under water 13

14 Maximum Specific Gravity Loose (uncompacted) mixture Mass agg. and AC G mm = Vol. agg. and AC V mm 14

15 Testing Mixing of asphalt and aggregate Mass in air Mass under water 15

16 Testing Loose Mix at Room Temperature 16

17 Residual Manometer Testing Metal Bowl with Lid Vacuum Pump Shaker Table 17

18 Calculations G mm = A / ( A - C ) Where: A = mass of dry sample C = mass of sample under water 18

19 Air Voids Calculated using bulk and maximum specific gravities Air voids (Va) = 100 * V a Gmm Gmb Gmm V mb 19

20 Why Are Air Voids Important? Related to Rut Resistance Related to Durability (aging and fatigue) 20

21 Effective Specific Gravity Surface Voids G se = Mass, dry Effective Volume Solid Agg. Particle 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 21

22 Effective Specific Gravity G se = P b P b G mm G b G se is an aggregate property Determined from a mix test 22

23 Voids in Mineral Aggregate VMA = G mb P s G sb VMA VMA is an indication of film thickness on the surface of the aggregate V mb 23

24 Voids Filled with Asphalt VFA = 100 x VMA - V a VMA VFA is the percent of VMA that is filled with asphalt cement 24

25 Percent Binder Absorbed P ba = 100 ( G se -G sb G se G sb ) G b P ba is the percent of absorbed asphalt by wt. of aggregate 25

26 Effective Asphalt Content P be = P b - P ba 100 P s The effective asphalt content is the total asphalt content minus the percent lost to absorption? 26

27 Dust /Asphalt Ratio F % passing No. 200 = A % Pbe 27

28 Factors That Influence Volumetric of HMA Asphalt viscosity Mix temperature Time held at elevated temperature 28

29 Important Considerations Consistent laboratory procedures Equiviscous mixing temperatures Mixing times Curing time to simulate field conditions 29

30 Example Problem 30

31 - Example Problem - Let s assume we have a compacted HMA mixture with the following properties. Bulk Specific Gravity of the Mixture - G mb = Theoretical Maximum Specific Gravity - G mm = Asphalt Binder Specific Gravity - G b = Asphalt Content - P b = 5.0 % (by mass of total mix) Percent passing No. 200 = 5.3% 31

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 (G sb ) for each is as follows: Aggregate % of Total Aggregate G sb A B C 50 % 25 % 25 %

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 G sb = Aggregate -G sb ( P A + P B + P C ) P A P B P C G A G B G C Based on the information given: P A = 50% P B = 25% P C = 25% + + G A = G B = G C = Where: P A, P B & P C = Percent by Mass of Each Aggregate in Blend G A, G B & G C = Bulk Specific Gravity of Each Aggregate G sb = ( ) = 2.705

35 -Example Problem Effective Specific Gravity of Aggregate -G se P b Where: P b = Percent Asphalt Binder by Total G se = 100 P b Mass of Mixture - G G mm G mm = Theoretical Maximum Specific b Gravity of Mixture G b = Specific Gravity of Asphalt Based on the information given: Binder P b = 5.0 % G mm = G b = G se = =

36 -Example Problem Percent Absorbed Asphalt Binder -P ba P ba = (100 * G b ) (G se -G sb ) G se * G sb Where: G b G se G sb = Specific Gravity of Asphalt Binder = Effective Specific Gravity of Aggregate = Bulk Specific Gravity of Aggregate Based on the information given: G b = G se = G sb = P ba = ( 100 * ) ( ) ( * ) = 0.4 % 36

37 -Example Problem Percent Effective Asphalt Binder -P be P be = P b - ( P ba * P s ) 100 Where: P b P ba P s = Percent Asphalt Binder in Total Mix = Percent Absorbed Asphalt Binder in Total Mix = Percent Aggregate in Total Mix Based on the information given: P b = 5.0 % P ba = 0.4 % P s = 95.0 % P be = ( 0.4 * 95.0 ) 100 = 4.6 % 37

38 -Example Problem Percent Voids in Total Mix -Va Va, % = 100 * ( G mm -G mb ) G mm Where: G mm = Theoretical Maximum Specific Gravity of Mix = Bulk Specific Gravity of Mix G mb Based on the information given: G mm = G mb = Va = 100 * ( ) = 3. 8 % 38

39 -Example Problem Percent Voids in Mineral Aggregate -VMA ( G mb * P s ) Where: G mb = Bulk Specific Gravity of Mix VMA, % = G P sb s = Percent Aggregate in Total Mix G sb = Bulk Specific Gravity of Aggregate Based on the information given: G mb = P s = 95.0 % G sb = VMA = ( * 95.0 ) =

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

41 Dust /Asphalt Ratio F % passing No. 200 = A Pbe Given: P-200P = 5.3% F 5.3 = = 1.15 A

42 Example Problem - Volumetric Equations Summary G sb = G se = P be, % = 4.6 % P ba, % = 0.4 % Va, % = 3.8 % VMA, % = 14.8 % VFA, % = 74 % F/A =

43 Classroom Exercise Volumetric Analysis of HMA Mixtures 43

44 - Classroom Exercise 1 - Let s assume we have a compacted HMA mixture with the following properties at 25 o C. Bulk Specific Gravity of the Mixture - G mb = Theoretical Maximum Specific Gravity - G mm = Asphalt Binder Specific Gravity - G b = Asphalt Content - P b = 4.3 % (by mass of total mix) Percent Passing No. 200 = 4.8% 44

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 (G sb ) for each is as follows: Aggregate % of Total Aggregate G sb A B C D 45 % 15 % 25 % 15 %

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 46

47 - Classroom Exercise 1 - Bulk Specific Gravity of the Combined Aggregate -G sb G sb = ( P A + P B + P C + P D ) P A P B P C P D G A G B G C G D Where: P A, P B, P C & P D = percent by mass of each aggregate in blend G A, G B, G C & G D = Bulk Specific Gravity of each aggregate Based on the information given: P A = % P B = % P C = % P D = % G sb = G A = G B = G C = G D = 47

48 - Classroom Exercise 1 - Effective Specific Gravity of Aggregate -G se G se = 100-P b Where: P b = percent asphalt binder by total mass of mixture 100 P b G mm - G b G mm = Theoretical Maximum Specific Gravity of mixture = Specific Gravity of asphalt binder G b Based on the information given: P b = % G mm = G b = G se = 48

49 - Classroom Exercise 1 - Percent Absorbed Asphalt Binder -P ba P ba = (100 * G b ) (G se -G sb ) G se * G sb Where: G b = Specific Gravity of asphalt binder G se = Effective Specific Gravity of aggregate = Bulk Specific Gravity of aggregate G sb Based on the information known: G b = G se = G sb = P ba = 49

50 - Classroom Exercise 1 - Percent Effective Asphalt Binder -P be P be = P b - ( P ba * P s ) 100 Where: P b P ba P s = percent asphalt binder in total mix = percent Absorbed Asphalt Binder into aggregate = percent aggregate in total mix Based on the information known: P b = % P ba = % P s = % P be = 50

51 - Classroom Exercise 1 - Percent Voids in Total Mix -VTM Va, % = 100 * ( G mm -G mb ) G mm Where: G mm G mb = Theoretical Maximum Specific Gravity of mix = Bulk Specific Gravity of mix Based on the information known: G mm = G mb = Va = 51

52 - Classroom Exercise 1 - Percent Voids in Mineral Aggregate -VMA VMA, % = ( G mb * P s ) Where: G mb P G s se G se = Bulk Specific Gravity of mix = percent aggregate in total mix = Effective Specific Gravity of aggregate Based on the information known: G mb = P s = % G se = VMA = 52

53 - Classroom Exercise 1 - Percent Voids Filled with Asphalt -VFA VFA, % = 100 * ( VMA - Va) VMA Where: VMA = percent Voids in Mineral Aggregate Va = percent Voids in Total Mix Based on the information known: VMA = % Va = % VFA = 53

54 Dust /Asphalt Ratio F % passing No. 200 = Pbe A Based on the information known: P-200 = Pbe = F Α = 54

55 - Classroom Problem 1 - Summary G sb = G se = P ba, % = P be, % = Va, % = VMA, % = VFA, % = F/A = 55

56 Classroom Exercise 2 Volumetric Analysis of HMA Mixtures 56

57 Classroom Exercise 3 Given Gmm = Asphalt Content = 4.5 % Bulk Sp. Gravity of Aggregate = Bulk Sp. Gravity of Asphalt = Determine Gmm at 5.0, 5.5 & 6.0 % 57

58 Asphalt Content 4.5% 5.0% 5.5% 6.0% Gmm 58

59 Questions does it all make sense? 59