AF2903 Road Construction and Maintenance. Volumetric Analysis of Asphalt Mixtures

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Francis Harrell
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Technology Stockholm, April 8 th 2014 Dr.

1 AF2903 Road Construction and Maintenance Volumetric Analysis of Asphalt Mixtures Royal Institute of Technology Stockholm, April 8 th 2014 Dr. Alvaro Guarin Highway and Railway Engineering Department of Transportation Science

2 Volumetrics All matter has mass and occupies space. Volumetrics are the relationships between mass and volume Specific Gravity, G Mass Volume

3 Volumetric Relationships V a VMA Air V b V ba V be Binder V mb V se V sb Solids

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)

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

6 HMA Volumetric Terms Bulk specific gravity (BSG) 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 Bulk Specific Gravity AC mixed with agg. and compacted into sample G mb = Mass agg. and AC Vol. agg., AC, air voids

8 Gmb Procedure Mixing of asphalt and aggregate Compaction of sample Mass of dry sample Mass under water Mass saturated surface dry (SSD)

9 Gmb Procedure Obtain mass of dry compacted sample Then, measure mass of specimen at SSD condition

10 Gmb Calculation G mb = A / ( B - C ) Where: A = mass of dry sample B = mass of SSD sample C = mass of sample under water

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

12 Gmm Procedure Mixing asphalt and aggregates Mass in air Mass under water

13 Gmm Calculation G mm = A / ( A - C ) Where: A = mass of dry sample C = mass of sample under water

14 Air voids Air voids (Va) = 100 * Gmm Gmb Gmm Example: G mb = G mm = Air voids (Va) = 100 * Air voids (Va) = 4.7 %

15 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

16 Effective Specific Gravity G se = P b P b G mm G b G se is an aggregate property Example: Mix with 5.5 % asphalt cement G mm = G b = G se = =

17 Voids in Mineral Aggregate VMA is an indication of film thickness on the surface of the aggregate VMA = G mb P s G sb Given that G mb = 2.401, P s = 94.5%, and G sb = VMA = (2.401) (94.5) = 14.6

18 Voids Filled with Asphalt VFA is the percent of VMA that is filled with asphalt cement VFA = 100 x VMA - V a VMA Given that Va = 4.7, VMA = 14.6 VFA = 100 X = 68 %

19 Percent Binder Absorbed P ba is the percent of absorbed asphalt by wt. of aggregate P ba = 100 ( G se - G sb G sb G se ) G b P ba = 100 ( *2.657 ) 1.03 P ba = 1.32 %

20 Effective Asphalt Content The effective asphalt content is the total asphalt content minus the percent lost to absorption. P be = P b - P ba 100 P s P be = x 95 P be = = 4.26 %

21 Factors That affect Volumetrics of HMA Asphalt viscosity Mix temperature Time held at elevated temperature When V mm decreases, G mm increases Affects calculations: G se Percent binder absorbed Calculated maximum specific gravity Air voids

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

23 Example Problem

24 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 = 1.03 Asphalt Content - P b = 5.0 % (by mass of total mix)

25 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 %

26 Example Problem Based on the information given for this problem, the following parameters should be calculated: Bulk Specific Gravity of the combined aggregate Effective Specific Gravity of the aggregate Percent Absorbed Asphalt for the Mixture Percent Effective Asphalt For the Mixture Percent Voids in Total Mix for the Mixture Percent Voids in Mineral Aggregate for the Mixture Percent Voids Filled with Asphalt for the Mixture

27 Example Problem - Answers Bulk Specific Gravity of the Combined Aggregate - G sb 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 = G sb = ( ) 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 = 2.663

28 Example Problem - Answers Effective Specific Gravity of Aggregate - G se G se = P b P b G mm G b Based on the information given: P b = 5.0 % G mm = G b = 1.03 Where: P b = Percent asphalt binder by total mass of mixture G mm = Theoretical Maximum Specific Gravity of mixture G b = Specific Gravity of asphalt binder G se = = 2.729

29 Example Problem - Answers Percent Absorbed Asphalt Binder - P ba P ba = (100 * G b ) (G se - G sb ) Gsb * Gse Where: G b = Specific Gravity of asphalt binder G se = Effective Specific Gravity of aggregate G sb = Bulk Specific Gravity of aggregate Based on the information known: G b = G se = G sb = P ba = ( 100 * 1.03 ) ( ) ( * ) = 0.95 %

30 Example Problem - Answers Percent Effective Asphalt Binder - P be P be = P b - ( P ba * P s ) 100 Where: P b = Percent asphalt binder in total mix P ba = Percent Absorbed Asphalt Binder in total mix = Percent aggregate in total mix P s Based on the information known: P b = 5.0 % P ba = 0.4 % P s = 95.0 % P be = ( 0.93 * 95.0 ) 100 = 4.1 %

31 Example Problem - Answers Percent Voids in Total Mix - Va Va, % = 100 * ( G mm - G mb ) G mm Where: G mm = Theoretical Maximum Specific Gravity of mix G mb = Bulk Specific Gravity of mix Based on the information known: G mm = G mb = Va = 100 * ( ) = 4.0 %

32 Example Problem - Answers Percent Voids in Mineral Aggregate - VMA VMA, % = ( G mb * P s ) G sb Where: G mb = Bulk Specific Gravity of mix P s = percent aggregate in total mix G sb = Bulk Specific Gravity of aggregate Based on the information known: G mb = P s = 95.0 % G sb = VMA = ( * 95.0 ) = 13.4

33 Example Problem - Answers 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 = 14.8 % Va = 3.8 % VFA = 100 * ( ) 13.7 = 71 %

34 Example Problem - Summary Summary: G sb = G se = P ba, % = 0.93 % P be, % = 4.2 % Va, % = 4.0 % VMA, % = 13.7 % VFA, % = 71 %

35 Questions

Commonwealth of Pennsylvania PA Test Method No. 709 Department of Transportation October Pages LABORATORY TESTING SECTION. Method of Test for

Commonwealth of Pennsylvania PA Test Method No. 709 Department of Transportation 15 Pages LABORATORY TESTING SECTION Method of Test for EFFECTIVE ASPHALT CONTENT OF BITUMINOUS PAVING MIXTURES 1. SCOPE