Lecture 31 Flashcards
(22 cards)
4 Steps of the Mix Design Flowchart
Materials Selection
Design aggregate structural trial blend design
Conduct in-depth volumetric mix design
Test for stripping/moisture dmg/ performance testing
What’s the objective of hot mix design
To develop an economic blend of aggregates and asphalt that meets design requirements
Requirements of Asphalt Mixes
Designed to withstand heavy traffic loads under adverse climatic conditions and to provide adequate structural and functional character to the pavement
What are the components of asphalt
Asphalt Binder
Minerals Aggregate
(coarse, fine, mineral filler)
Additives
typical % of air in asphalt
2-20%
typical binder % in asphalt
3-8%
typical absorbed asphalt binder % in asphalt
<1%
typical mineral aggregate % in asphalt
85-95%
What are the 3 mix design methods
Marshall
Hveem
Superpave
Marshall Mix Design steps
aggregate selection
asphalt binder evaluation
sample preparation
density and voids calculations
stability and flow determination
optimum asphalt binder selection
Marshall Mix aggregate type
Strong and Tough
Angular and Equi-dimensional
Low Porosity
Clean
Rough
Hydrophobic
Most common asphalt binder evaluation
superpave PG binder system
How many blows/side for Light traffic with the marshall hammer compaction test
35
Voids in the Mineral Aggregate Definition
The space occupied by the asphalt cement and air voids (not including the
asphalt cement absorbed)
How many blows/side for medium traffic with the marshall hammer compaction test
50
How many blows/side for heavy traffic with the marshall hammer compaction test
75
what are the 2 things you must determine in the lab for the marshall Density and Voids Analysis?
Bulk specific gravity of compacted HMA
Maximum SG of loose mix (TMD)
what are the 4 things you must calculate for the marshall Density and Voids Analysis?
air voids
effective SG of aggregate
voids in mineral aggregate
voids filled with asphalt
what is the Marshall Stability and Flow Test
Provides the performance
prediction measure for the Marshall mix design method.
how do you Select the Optimum Asphalt Content
The optimum asphalt binder content is selected based on
the combined results of Marshall stability and flow, density
analysis and void analysis
what are the advantages of the Marshall design method
Inexpensive equipment
Portable compaction hammer
Widely used
what are the disadvantages of the Marshall design method
Impact method of compaction
Does not consider shear strength
