NCHRP Project 9-33 A Mix Design Manual for Hot Mix Asphalt

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					NCHRP Project 9-33:
A Mix Design Manual for Hot
Mix Asphalt


NEAUPG Fall Meeting
October 18, 2007
Mystic, Connecticut
                 Advanced Asphalt Technologies, LLC


                  “Engineering Services for the Asphalt Industry”
HMA Mix Design Manual

No.          Topic   Pp.   Figs. Tbls.
1     Introduction   ---    ---   ---
2     Background     17     9     ---
3     Binders        19     9      1
4     Aggregates     11     5      4
5     Rap            58     11    25
6     Volumetrics    28     9      4
HMA Mix Design Manual
No.        Topic        Pp.   Figs. Tbls.
7     Performance       41     10     9
8     Dense Graded      70     18    23
      HMA Design
9     SMA Design        29     5     15
10 OGFC Design          29     5      7
11 Mix Type Selection   15     2      3
12 Field Production     29     7      6
Remaining Work
 Review by panel
 Revisions
 Photos, references
 Cross-editing by co-authors
 Editing by subcontractor (LazerPro)
 Complete spreadsheet HMA Tools
 Interactive CD-ROM (LazerPro)
 Planned completion by June 2008
What’s New—Content/Chapters
 SMA
 OGFC
 HMA performance
 RAP
 Mix type selections
 Field adjustments/QC
Recycled Asphalt Pavement

 Complete chapter on RAP
 Extensive and detailed
 Sampling
 Blending and variability
 RAP aggregate properties
 RAP binder properties
 Handling RAP in the laboratory
RAP Mineral Filler Variability
                                               4.0
Standard Deviation of RAP % Passing 0.075 mm



                                                                                                0%
                                               3.5
                                                                                                5%
                                                                                                10 %
                                               3.0
                                                                                                15 %

                                               2.5
                    Sieve




                                               2.0


                                               1.5


                                               1.0


                                               0.5


                                               0.0
                                                     0%   10%   20%   30%   40%   50%   60%   70%    80%   90%
                                                                      Allowable RAP Content
What’s New—Specifications

 Fatigue resistant mixes: higher VMA,
 dust/binder ratio
 Maximum VMA
 No VFA requirements
 N-design as per NCAT
 recommendations
 Some changes in consensus properties
VMA Requirements: Standard
Mixtures
  Aggregate   Minimum Maximum   Target
   NMAS        VMA     VMA      VMA
    (mm)        (%)     (%)      (%)
     4.75       16.0    18.0     17.0
      9.5       15.0    17.0     16.0
     12.5       14.0    16.0     15.0
     19.0       13.0    15.0     14.0
     25.0       12.0    14.0     13.0
     37.5       11.0    13.0     12.0
VMA Requirements: Fatigue
Resistant Mixtures
  Aggregate   Minimum Maximum   Target
   NMAS        VMA     VMA      VMA
    (mm)        (%)     (%)      (%)
     4.75       17.0    19.0     18.0
      9.5       16.0    18.0     17.0
     12.5       15.0    17.0     16.0
     19.0       14.0    16.0     15.0
     25.0       13.0    15.0     14.0
     37.5       12.0    14.0     13.0
Dust/Binder Ratio

                                 Dust/binder ratio level*:
         Mixture Type              High            Low
 Standard (Table 8-5)            0.8 to 1.6     0.6 to 1.2
 Fatigue resistant (Table 8-6)   1.0 to 1.8     0.8 to 1.6
 All 4.75-mm mixtures                     0.9 to 2.0
Consensus Properties: CAA
  Design       Depth of Pavement Layer from Surface, mm
  ESALs
                      0 to 100                  Below 100
 (million)
   < 0.30                 40                        ---
 0.3 to < 3               40                        ---
 3 to < 10                45                        40
 10 to < 30               45                        45
30 or more                45                        45
Criteria are presented as percent air voids in loosely
compacted coarse aggregate.
What’s new—HMA Performance
 Entire chapter on HMA performance
 – Factors affecting performance
 – Tests for evaluating performance
 – Tests and data for MEDG
 Performance tests in HMA mix design
 – Moisture resistance
 – Rutting tests: SPT/flow number,
   SST/RSCH, high-temperature IDT strength
SPT: Flow Number Test

                      Minimum Flow
      Traffic Level      Number
      Million ESALs
            <3             ---
        3 to < 10         200
       10 to < 30         320
          ≥ 30            580
What’s New-Mix Design

 Select and maintain design binder
 content throughout process
 Control points are guidelines
 Aggregate blending and evaluation
 through trial-and-error, graphical tools
 Technicians should feel free to use any
 design method that works
 Volumetric Mix Design
                 air        Design binder content
        VMA    binder     is target VMA minus
                          design air void content.
                            Aggregate content is
                          100% minus target
total
              aggregate   VMA.
                            Binder content is kept
                          constant while
                          aggregate blend is
                          varied.
Overview of Design of Dense-
Graded HMA Mixes
1.   Gather information
2.   Select asphalt binder
3.   Determine compaction level
4.   Select aggregate size
5.   Determine target VMA
6.   Calculate target binder content
7.   Calculate aggregate volume
Overview of Design of Dense-
Graded HMA Mixes
8. Proportion aggregate blends for trial
    mixtures
9. Calculate trial mix proportions by
    weight and check dust/binder ratio
10. Evaluate and refine trial mixtures
11. Compile report
Conclusions
 Draft manual is complete
 Work remaining
 – Revise & edit manual
 – HMA Tools, commentary & CD-ROM
 – Training course
 – Final report
 Planned completion by June 2008
Acknowledgments

 NCHRP and panel members
 Associates at AAT
 Allen Cooley
 LazerPro Digital Media Group