The document discusses bituminous mix design and the Marshall mix design method. It describes the objectives of mix design as developing an economical blend of aggregates and asphalt that meets design requirements such as sufficient asphalt, stability, air voids, and workability. The Marshall mix design procedure involves selecting and testing aggregates and asphalt, developing trial blends, compacting specimens, and evaluating properties according to criteria like stability, flow, air voids, and tensile strength ratio. Calculations are also required to determine properties like theoretical maximum density and voids in the mix.

1. Bituminous Mix Design
Archana M R
Assistant Professor, Department of Civil
Engineering, RV College of Engineering, Bangalore
28th January 2016

2. Bituminous Mix Design
• Objective:
– Develop an economical blend of aggregates and asphalt
that meet design requirements
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

3. Marshall mix design
• Developed by Bruce
Marshall for the Mississippi
Highway Department
Steps involved:
• Select and test aggregate
• Select and test asphalt
cement
– Establish mixing and
compaction temperatures
• Develop trial blends
– Heat and mix asphalt
cement and aggregates
– Compact specimen (100
mm diameter)

4. Marshall mix design - Procedure
Video

5. Marshall mix design criteria
Sl.
No.
Parameter Test Method Specifications as per
MoRT&H – V Revision
1 Compaction Level 75 Blows on each side of the sample
2 Marshall stability at
600C, kN
AASHTO T 245 9, 12*, 10**
3 Marshall flow, mm AASHTO T 245 2-4, 2.5-4*, 3.5-5**
4 % Air voids 3-5
5 % Voids filled with
Asphalt
65-75
Tensile strength ratio AASHTO T 283 80% minimum
*Modified Asphalt under hot climate
** Modified asphalt under cold climate
Source: Table 500.11, MoRT&H – V Revision

6. Mix design - Calculations
1. Theoretical Maximum Density
2. Bulk Specific Gravity of the mix
3. Percent Air voids
4. Voids in Mineral aggregate
5. Voids filled with bitumen

7. Marshall Properties – for OBC

8. Marshall properties – at OBC
Marshall Stability
•Laboratory and field results – cannot be
matched
•If stability is a problem, it necessitates
comprehensive study
•Helps in determining the consistency of
plant produced HMA
Flow value
•High flow value – Indicates plastic mix
•Low Flow value – Indicates mix with
higher than normal voids/ insufficient
asphalt

9. Marshall properties
Unit weight
•Magnitude of density achieved in lab –
not very important
•Field density requirement – expressed
as a percent of theoretical density – so
that the density is achieved by increased
compaction, asphalt content, filler
content or any other methods
•Satisfactory compaction effort on
properly designed mixture – produces
high shear strength and reduces
permanent deformation
Percent Air voids
•Higher air voids – must ensure air and
water permeability are quite low
•Air voids – isolated and not inter-
connected
•Low air voids – minimize aging of
asphalt
•Ultimate density in situ – should be 3-
5% air voids

10. Marshall properties
Voids filled with
bitumen
•Maximum aggregate size increases – VMA
reduces
•Large VFB – Permanent deformation
•Low VFB – Inadequate film thickness –
oxidation faster, tensile strength greatly
affected

11. Thank you