Asphalt mixtures are made up of aggregates, binder and air voids. In order to make a economic and satisfactory performing asphalt mixture the quantity of these individual constituent is required. Mixture design is a tool to determine these optimum quantities.

1. for Hot Bituminous Mix
By Priyansh Singh
Indian Institute of Technology Guwahati
Mix Design

2. Introduction
• Asphalt Mix design is first traced in 1860s, using
Tar as binder in Washington, D.C.
• Richardson used ‘Pat Test’ for optimum test to
determine optimum mix design.
• Hubbard-Field Method.
• Mix design is the method to determine that
whether a suitable mixture can be prepared with
the available materials and to determine the best
combination of these materials for optimum
performance.

3. Requirements
• Sufficient asphalt to ensure a durable
pavement
• Sufficient stability under traffic loads
• Sufficient air voids
– Upper limit to prevent excessive environmental
damage
– Lower limit to allow room for initial densification
due to traffic
• Sufficient workability

4. Elements of Mix Design
Items must be evaluated during the mix design
to ensure that optimum performance is
obtained.
• Resistance to Permanent Deformation
• Fatigue Resistance.
• Resistance to Low Temperature Cracking
• Durability.
• Resistance to Moisture Induced Damage

5. Elements of Mix Design
• Skid Resistance.
• Workability.
• Gradation and Maximum Density Curves.

6. Methods of Mix Design
• Haveems Method of mix design.
• Marshall Method of mix design.
• Superpave Method of mix design.

7. Marshall Method
• The method is developed by Bruce Marshall
around 1939 for design of Air Field
Pavements.

8. Steps for Marshall Method
1. Aggregate Evaluation.
2. Asphalt Cement Evaluation
3. Preparation Of Marshall Specimens
4. Density And Voids Analysis
5. Marshall Stability And Flow Test
6. Tabulating And Plotting Test Results
7. Optimum Asphalt Content Determination

9. Preparation of Marshall Specimens
ASTM D6926–10 Standard Practice for Preparation of Bituminous Specimens
Using Marshall Apparatus
• Equipment required
– Specimen Mold
Assembly

10. Equipment required
– Specimen Extractor
– Compaction Hammers

11. Equipment required
– Specimen Mold-Holder
– Ovens, Heating Pots or Hot Plates
– Mixing Apparatus, etc.

12. Preparation of test Specimens
• Preparation of Aggregates: Dry aggregates to
constant weight. Oven drying should be done
at 105 to 110°C (221 to 230°F). After cooling,
separate the aggregates by dry-sieving into
the desired size fractions.
• Determination of Mixing and Compacting
Temperatures

13. Determination of Mixing and
Compacting Temperatures
• The asphalt cement used in preparing the
samples must be heated to produce viscosities
of 170 ± 20 cP (0.17 ± 0.02 Pa·s) and
0.28 ± 0.03 Pa·s (280 ± 30 cP) for mixing and
compacting, respectively. An example of a
viscosity temperature chart is given in Fig. 2 of
D2493

15. Determination of Mixing and
Compacting Temperatures
Determination of mixing and compaction by use of
equation.
• the chart coordinates are logarithm of the
logarithm of the viscosity in centipoise as the
ordinate, and logarithm of the absolute
temperature in degrees Rankine (degrees F +
459.7) as the abscissa. However, viscosity in
poise, and the temperature in degrees Fahrenheit
is shown in the chart for convenience.

16. Determination of Mixing and
Compacting Temperatures
.1
.2
.3
.5
1
10
5
100 110 120 130 140 150 160 170 180 190 200
Temperature, C
Viscosity,Pas
Compaction Range
Mixing Range

17. Determination of Mixing and
Compacting Temperatures
• If we have two point data
• 𝑦 − 𝑦1 =
𝑦1
−𝑦2
𝑥1
−𝑥2
(𝑥 − 𝑥1)
• 𝑦 = −2.318𝑥 + 7.0849
• For this equation for Viscosity 150 cp the
temperature is 373 °F (189 °C).
Viscosity Temperature
367 cP 302 °F
2245 cP 221 °F

18. Preparation of test Specimens
– Preparation of mold and hammer.
– Preparation of mixture.
– Placing in mold and compaction.

19. Density and Void Analysis

20. Density and Void Analysis
• Bulk specific gravity of compacted sample.
• Maximum specific gravity of loose mix.

21. Stability and flow
• 60oC water bath (30 to 40 minutes)
• 50 mm/min loading rate.
• Max. load = uncorrected stability
• Corresponding vertical deformation = flow

22. Stability and flow

23. Stability and flow

24. Stability and flow
ASTM D6927 – 06 Standard Test Method For Standard Test Method for Marshall Stability
and Flow of Bituminous Mixtures

25. Use of Data
Asphalt Institute Procedure
Air Voids, %
Asphalt Content, %
Stability
Asphalt Content, %
Unit Wt.
Asphalt Content, %
Target optimum asphalt content = average
4%

26. Use of Data
Asphalt Institute Procedure
Flow
Asphalt Content, %
VMA, %
Asphalt Content, %
Use target optimum asphalt content to
check if these criteria are met
Lower Limit
Upper limit
Minimum
OK
OK

27. Use of Data
NAPA Procedure
Air Voids, %
Asphalt Content, %
Target optimum asphalt content =
the asphalt content at 4% air voids
4%

28. Use of Data
NAPA Procedure
Stability
Asphalt Content, %
The target stability is checked
OK

29. Use of Data
NAPA Procedure
Flow
Asphalt Content, %
VMA, %
Asphalt Content, %
Use target optimum asphalt content to
check if these criteria are met
Lower Limit
Upper limit
Minimum
OK
OK

30. Marshall Design Criteria
Light Traffic Medium Traffic Heavy Traffic
ESAL < 104 10 4 < ESAL< 10 ESAL > 106
Compaction 35 50 75
Stability N (lb.) 3336 (750) 5338 (1200) 8006 (1800)
Flow, 0.25 mm (0.1 in) 8 to 18 8 to 16 8 to 14
Air Voids, % 3 to 5 3 to 5 3 to 5
Voids in Mineral Agg.
(VMA) Varies with aggregate size

31. Marshall Design Criteria
Table 500-19 Requirements for Bituminous Pavement Layers (MoRTH Section 500)
Minimum Stability 9.0
Minimum Flow 2
Maximum Flow 4
Compaction Level 75 blows each face
Per cent air voids 3-6
VMA Table 500-12
VFB 65-75
Loss of Stability on immersion in water Min. 75% retained strength

32. Marshall Design Method
• Advantages
– Attention on voids, strength, durability.
– Inexpensive equipment.
– Easy to use in process control/acceptance .
• Disadvantages
– Impact method of compaction.
– Does not consider shear strength.
– Load perpendicular to compaction axis.

33. Thanks
Prentation By Priyansh Singh