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ANALYSIS OF OKLAHOMA MIX DESIGNS FOR THE NCAT TEST TRACK USING THE BAILEY METHOD TRB 85 TH ANNUAL MEETING WORKSHOP PRACTICAL APPROACHES TO DESIGN OF HOTMIX.

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Presentation on theme: "ANALYSIS OF OKLAHOMA MIX DESIGNS FOR THE NCAT TEST TRACK USING THE BAILEY METHOD TRB 85 TH ANNUAL MEETING WORKSHOP PRACTICAL APPROACHES TO DESIGN OF HOTMIX."— Presentation transcript:

1 ANALYSIS OF OKLAHOMA MIX DESIGNS FOR THE NCAT TEST TRACK USING THE BAILEY METHOD TRB 85 TH ANNUAL MEETING WORKSHOP PRACTICAL APPROACHES TO DESIGN OF HOTMIX ASPHALT DANNY GIERHART, P.E. ODOT BITUMINOUS ENGINEER

2 PRESENTATION TOPICS BAILEY METHOD OVERVIEW CASE STUDY – ODOTs NCAT TEST TRACK MIX DESIGNS ODOT OPINION OF THE METHOD AT THIS POINT

3 THE BAILEY METHOD ACHIEVING VOLUMETRICS AND HMA COMPACTABILITY

4 TRANSPORTATION RESEARCH CIRCULAR Number E-C044 Bailey Method for Gradation Selection in Hot- Mix Asphalt Mixture Design Vavrick, Huber, Pine, Carpenter, Bailey October 2002

5 How Can the Bailey Method Help? In Developing New Blends: –Field Compactibility –Segregation Susceptibility In Evaluating Existing Blends: –Whats worked and what hasnt? –More clearly define ranges referenced in the method In Estimating VMA/Void changes between: –Design trials –QC samples –Potentially Saves Time and Reduces Risk!

6 Originally developed in the 1980s by Robert D. Bailey, a civil engineer now retired from Illinois DOT The method focuses on how aggregate particles fit together

7 Aggregate Packing What Influences the Results? GRADATION - continuously-graded, gap-graded, etc. SHAPE - flat & elongated, cubical, round - smooth, rough SURFACE TEXTURE STRENGTH - resistance to breaking, abrasion, etc. TYPE & AMOUNT OF COMPACTIVE EFFORT - static pressure, impact, or shearing

8 REQUIRED LABORATORY TESTING

9 Sieve Size (mm) Raised to 0.45 Power % Passing Illustration of the Four Principles – Predominantly Coarse Aggregate Mix CoarseFine

10 PRINCIPLE # 1 – CATEGORIZE MIX AS PREDOMINANTLY COARSE OR FINE Coarse particles create voids Fine particles fill voids Designation of coarse and fine particles is based on the Nominal Maximum Particle Size (NMPS).

11 Diameter = NMPS Average Void Size = 0.22 x NMPS Primary Control Sieve 0.22 x NMPS

12 Primary Control Sieve PCS determines the break between Coarse and Fine in the combined blend and if a given aggregate is a CA or FA

13 Chosen Unit Weight - CA(s) LUWRUW Coarse-GradedSMAFine-Graded < LUW < 90%95-105% %

14 Coarse-Graded Mix Some particle-to- particle contact of CA Coarse and Fine fractions carry load Reduced FA strength acceptable

15 Fine-Graded Mix Little to No particle- to-particle contact of CA Fine fraction carries most of the load Increased amount of FA support needed

16 Sieve Size (mm) Raised to 0.45 Power % Passing Combined Blend Gradation – Predominantly Fine Aggregate Mix CoarseFine PCS New PCS = 0.22 x PCS 1 PCS New NMPS

17 PRINCIPLE # 2 – ANALYSIS OF THE COARSE FRACTION OF THE BLEND Smaller particles in the coarse fraction are still too large to fit into the voids created by the larger particles The coarse fraction is the portion retained above the Primary Control Sieve (PCS)

18 PCS NMPS Half Sieve Half sieve = half of NMPS CA Ratio = Where: % Half sieve = % passing the Half sieve % PCS = % passing the PCS Adjusting CA Ratio –Alter volume blend of CAs –Change CA source/gradation % Half sieve - % PCS 100% - % Half sieve PRINCIPLE # 2 is evaluated using the Coarse Aggregate Ratio pluggers interceptors

19 interceptor particles increase voids because they are large enough to prevent plugger particles both from packing together and from packing the fine fraction

20 CA Ratio Effects FINE IN CONTROLCOARSE IN CONTROL Portion evaluated as new coarse fraction is smaller – less sensitive to changes Portion evaluated as coarse fraction is larger – more sensitive to changes Low New CA Ratio – Lower VMA & air voids Low CA Ratio – Lower VMA & air voids Coarse particles floating in fine particles – New CA Ratio does not relate to segregation, Old still does Low CA Ratio – too many pluggers, mix prone to segregation High New CA Ratio – too many interceptors, mix can be difficult to compact High CA Ratio – too many interceptors, mix can be difficult to compact

21 CA Ratio Guidelines COARSE IN CONTROL NMPS 25.0mm19.0mm12.5mm9.5mm4.75mm CA Ratio – – – – 0.45 FINE IN CONTROL NMPS All Sizes New CA Ratio

22 PRINCIPLE # 3 – ANALYSIS OF THE FINE FRACTION OF THE BLEND (COARSE PORTION) The coarser fine particles also create voids which finer particles fill The fine fraction is the portion passing the Primary Control Sieve (PCS)

23 PRINCIPLE #3 is evaluated using the FA c ratio Secondary Control Sieve (SCS) –View fine fraction as a blend –New coarse and fine break –SCS = 0.22 x PCS PCS generally serves as the maximum and NMPS of overall fine fraction FA c Ratio = PCS Fine Fraction % SCS % PCS SCS

24 FA c Ratio Effects COARSE IN CONTROLFINE IN CONTROL 0.05 increase in New FA c Ratio up to 0.50 results in an approximate 1% decrease in VMA and Air Voids Once New FA c Ratio increases beyond 0.50 VMA begins to increase As New FA c Ratio increases toward 0.50, compactability of fine fraction increases 0.05 increase in FA c Ratio up to 0.55 results in an approximate 1% decrease in VMA and Air Voids Once FA c Ratio increases beyond 0.55 VMA begins to increase As FA c Ratio increases toward 0.50, compactability of fine fraction increases

25 PRINCIPLE # 4 – ANALYSIS OF THE FINE FRACTION OF THE BLEND (FINE PORTION) Again, the larger fine particles of this portion also create voids which the finest particles fill Now looking at the finer portion of the fine fraction passing the Secondary Control Sieve (SCS)

26 PRINCIPLE #4 is evaluated using the FA f ratio Tertiary Control Sieve (TCS) –View fine part of fine fraction as a blend –New coarse and fine break –TCS = 0.22 x SCS SCS generally serves as the maximum and NMPS of fine part of fine fraction FA f Ratio = PCS Fine FractionFine Fraction % TCS % SCS SCS TCS

27 FA f Ratio Effects COARSE IN CONTROLFINE IN CONTROL Once New FA f Ratio increases beyond 0.50 VMA begins to increase As New FA f Ratio increases toward 0.50, VMA begins to decrease Once FA f Ratio increases beyond 0.55 VMA begins to increase As FA f Ratio increases toward 0.55, VMA begins to decrease

28 FA c & FA f Ratio Guidelines COARSE IN CONTROL NMPS All Sizes FA c & FA f Ratio 0.35 – 0.50 FINE IN CONTROL NMPS All Sizes New FA c & FA f Ratio 0.35 – 0.50

29 Combined Blend Evaluation Coarse-Graded Mixes 1.CA CUW increase = VMA increase –4% change in PCS 1% change in VMA or Voids 2.CA Ratio increase = VMA increase –0.20 change 1% change in VMA or Voids 3.FA c Ratio increase = VMA decrease –0.05 change 1% change in VMA or Voids 4.FA f Ratio increase = VMA decrease –0.05 change 1% change in VMA or Voids Has the most influence on VMA or Voids

30 Estimating VMA or Voids Coarse-Graded Mix Example Trial #1 –PCS = 38.2% 100% CA LUW –CA ratio = –FA c ratio = –FA f ratio = –AC = 4.6% –Air Voids = 3.4% –VMA = 12.6% Trial #2 –PCS = 37.2% 102.5% CA LUW –CA ratio = –FA c ratio = –FA f ratio = –AC = 4.6% –Expected VMA? –Expected Air Voids?

31 Estimating VMA or Voids Trial #2 vs. Trial #1 PCS 37.2% % = - 1.0% CA ratio – = FA c ratio – = FA f ratio – = Increases VMA or Voids –1.0/4.0 = % Increases VMA or Voids –0.032/0.2 = +.16% Increases VMA or Voids –0.048/0.05 = +.96% Decreases VMA or Voids –0.018/0.05 = % Total Estimated Change: –Plus ~ 1.0% VMA

32 ODOTS PERPETUAL PAVEMENT STRUCTURAL SECTIONS AT NCAT TEST TRACK PLAN VIEW SECTION 1 – 150 SECTION 2 – TRANSITION 50 TRANSITION 25 TRANSITION

33 PLAN VIEW SECTION 1 – 150 SECTION 2 – TRANSITION 50 TRANSITION 25 TRANSITION PROFILE VIEW 2 SMA w/PG SuperPave 19.0mm w/PG SuperPave 19.0mm w/PG RBL w/PG RBL w/PG *RBL = RICH BOTTOM LAYER ODOTS PERPETUAL PAVEMENT STRUCTURAL SECTIONS AT NCAT TEST TRACK

34 AGGREGATE SUMMARY Hanson Martin Marietta 2.0 GMI Sand Aggregate Type Aggregate Shape L.A. Abrasion Micro Deval Screenings P 200 RhyoliteLimestone River Sand Very Angular Angular Dolese Limestone AngularRounded n/a

35 RBL MIX DESIGN INFORMATION Hanson Dolese 5/8 Chips Screenings 35%20%45% PbPb 6.0 % Air Voids 2.0 % VMA14.6

36 RBL MIX – EVALUATED AS A FINE-GRADED MIX OLD CA RATIO – NEW CA RATIO – NEW FA c RATIO – NEW FA f RATIO – N/A For fine-graded mixes, the volume of the fine fraction exceeds the CA LUW voids. This value is less than 90% of CA LUW, and ensures that the fine aggregate is in control. CHOSEN UNIT WT. = 78.9%

37 RBL MIX – EVALUATED AS A FINE-GRADED MIX OLD CA RATIO – NEW CA RATIO – NEW FA c RATIO – NEW FA f RATIO – N/A For coarse- graded mixes, the preferred range is 0.50 – For this fine-graded mix, the high CA Ratio indicates a low susceptibility to segregation. CHOSEN UNIT WT. = 78.9%

38 RBL MIX – EVALUATED AS A FINE-GRADED MIX OLD CA RATIO – NEW CA RATIO – NEW FA c RATIO – NEW FA f RATIO – N/A The preferred range is 0.60 – The New CA Ratio is primarily controlled by the FAs rather than the CAs and its affect on the entire blend is therefore mitigated. CHOSEN UNIT WT. = 78.9%

39 RBL MIX – EVALUATED AS A FINE-GRADED MIX OLD CA RATIO – NEW CA RATIO – NEW FA c RATIO – NEW FA f RATIO – N/A The preferred range is 0.35 – The value of indicates a high dust/binder ratio (1.4 for this design) and a high mortar stiffness. Higher values lower VMA. CHOSEN UNIT WT. = 78.9%

40 RBL MIX – EVALUATED AS A FINE-GRADED MIX OLD CA RATIO – NEW CA RATIO – NEW FA c RATIO – NEW FA f RATIO – N/A The tertiary sieve for 12.5mm fine- graded mixes would fall below the 0.075mm, therefore the FA f Ratio cannot be calculated. CHOSEN UNIT WT. = 78.9%

41 AIR 6.0% BINDER – ACTUAL vs. ESTIMATED RBL MIX ACTUAL EST. % AIR VOIDS TRIAL #

42 mm SUPERPAVE MIX DESIGN INFORMATION Hanson DoleseMMGMI 1 ChipsScreenings Stone SandSand 30%25%15%20%10% PbPb 4.3 % Air Voids 4.0 % VMA13.6

43 19.0mm MIX – EVALUATED AS FINE-GRADED OLD CA RATIO – NEW CA RATIO – NEW FA c RATIO – NEW FA f RATIO – This value is far less than 90% of CA LUW, and ensures that the fine aggregate is in control. However, such a low value indicates that the mix may be difficult to compact. CHOSEN UNIT WT. = 50.7%

44 19.0mm MIX – EVALUATED AS FINE-GRADED OLD CA RATIO – NEW CA RATIO – NEW FA c RATIO – NEW FA f RATIO – Even though this is a fine- graded mix, the low CA Ratio means that in the CA there is a higher % of pluggers than interceptors, indicating a potential problem with segregation. CHOSEN UNIT WT. = 50.7%

45 OLD CA RATIO – NEW CA RATIO – NEW FA c RATIO – NEW FA f RATIO – The preferred range is 0.60 – This mix falls within the preferred range, which means any compaction issues would likely not be attributed to this fraction. CHOSEN UNIT WT. = 50.7% 19.0mm MIX – EVALUATED AS FINE-GRADED

46 OLD CA RATIO – NEW CA RATIO – NEW FA c RATIO – NEW FA f RATIO – The preferred range is 0.35 – The value of might indicate a tenderness problem if the mix contained a high % sand. However, this mix contains only 10% natural sand. CHOSEN UNIT WT. = 50.7% 19.0mm MIX – EVALUATED AS FINE-GRADED

47 OLD CA RATIO – NEW CA RATIO – NEW FA c RATIO – NEW FA f RATIO – The preferred range is 0.35 – However, the FA ratios are generally a problem only if both are high or both are low. CHOSEN UNIT WT. = 50.7% 19.0mm MIX – EVALUATED AS FINE-GRADED

48 AIR 4.3% BINDER – ACTUAL vs. ESTIMATED 19.0mm SUPERPAVE MIX % AIR VOIDS TRIAL # ACTUAL EST.

49 SMA MIX DESIGN INFORMATION Hanson DoleseBoral 5/8 Chips Screenings Mineral Filler 67%13%10% PbPb 6.8 % Air Voids 4.0 % VMA17.9

50 SMA MIX CA RATIO – FA c RATIO – FA f RATIO – This value barely falls within the preferred range of % of CA RUW. This indicates that the %CA, although acceptable, is on the low side for a SMA mix. CHOSEN UNIT WT. = 110.0%

51 SMA MIX CA RATIO – FA c RATIO – FA f RATIO – This value falls within the preferred range of 0.25 – Be careful interpolating the value for the half sieve on a 12.5mm SMA. It would be best to insert a ¼ sieve into the nest. CHOSEN UNIT WT. = 110.0%

52 SMA MIX CA RATIO – FA c RATIO – FA f RATIO – This value falls within the preferred range of 0.60 – 0.85, indicating a good balance in the relative fractions of the fine aggregate. CHOSEN UNIT WT. = 110.0%

53 SMA MIX CA RATIO – FA c RATIO – FA f RATIO – This value falls within the preferred range of 0.65 – Typically, the higher the ratio, the greater P 200. This mix was designed on the high side to decrease permeability potential. CHOSEN UNIT WT. = 110.0%

54 AIR 7.0% BINDER – ACTUAL vs. ESTIMATED 12.5mm SMA MIX % AIR VOIDS TRIAL # ACTUAL EST.

55 EXAMPLE OF ACTUAL ODOT QC/QA PROJECT DATA AIR VOIDS – ACTUAL vs. ESTIMATED 19.0mm SuperPave Mix ACTUAL EST. % AIR VOIDS SAMPLE #

56 OUR THOUGHTS SO FAR: The Bailey Method principles make sense when reviewed in the context of previous mix design experience The Method provides a way to quantify changes that we have only made educated guesses at before Based on previous experience, the Method gives a reasonable indication of aggregate combinations which are susceptible to segregation and field compactability problems

57 OUR THOUGHTS SO FAR: Based on previous experience, the mixes that fall into the Coarse-Graded category are often too permeable The voids estimation process looks at gradation only, and is therefore blind to changes in aggregate shape and texture The voids estimation process performs better when working with aggregates of similar properties

58 OUR THOUGHTS SO FAR: Although the Bailey Method is a good tool, users must not forget the things they already know about the materials they are using The default values used in the void estimation process should vary depending on the types of aggregate used Each user should analyze historical data and interview field personnel to calibrate the method to their own materials

59 SOME TOOLS REQUIRE MORE PRACTICE AND EXPERIENCE THAN OTHERS…

60 THANK YOU!


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