Hot Mix Asphalt 101 - Cornell Local Roads Program...Job Mix Formula In the laboratory Aggregate...
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Transcript of Hot Mix Asphalt 101 - Cornell Local Roads Program...Job Mix Formula In the laboratory Aggregate...
Objectives
Describe mix types
Define ingredients
Discuss mix design procedures
Discuss mix production
Discuss mix placement
Defining Mix Types
Dense gradedWell gradedMixes used in NY
Open gradedPorous mixesCoarse stones only
Gap gradedStone Mastic Asphalt (SMA) mixesMostly coarse stones, little fines, and high mineral fillerCellulose fiber may be added to reduce drain down
Primary Ingredients
PG Binder
Aggregates
Aggregate Quality
Particle shapeRoundedAngular
ToughnessResistance to abrasion and impact
PG Binder
Superpave grading systemStandard grades in NY are:
PG 64-22, 70-22Polymer modified grades are:
PG 58-34P, PG 64-28P, PG 64-22P, PG 76-22P 0° C
64° C
-22° C
What do these numbers mean?
Mix Design Procedures
Superpave DesignAll 402 items
DOT standard items
Marshall DesignAll 403 items
Used by municipalities
Job Mix Formula
In the laboratoryAggregate (coarse, fine, mineral filler) and PG binder is combined in proportionsExample: 57% 1A’s, 41% Sand, 2% Filler, and 6.0% AC
Must meet the design volumetricsAir voids, VMA, VFA
Batch or Drum Plant?
Both make quality mix
Choice based on business decision
Batch Plant
Batch Tower
StorageSilos
Cold Feed Bins
Dryer
AsphaltStorageTanks
SecondaryCollector
PrimaryCollector
Drum Mix Plant
Storage Silos
RAP Bin
Slat Conveyor
Dryer/Mixer
Cold Feed Bins
AsphaltStorageTanks
SecondaryCollectors
Job Mix Formula
At the plantJMF aggregate proportions and PG binder are usedQC tests performed for complianceAdjustments are made to meet the volumetric targets
Transporting HMA
3 or 5 drops at plantReduce segregation
Trucks must be covered with tarp
Reduce heat lossMust use release soap-based release agents
Not fuel oil
This could happen…
Placing HMAGeneral good paving practice must be followed
Paver must travel at constant speedTrucks should not bump the paver
Will affect smoothness
Avoid this mess
Placing HMA
Check mix tempsHelps in achieving the required density
Compaction
It very critical that HMA layer is properly compactedOtherwise,
RuttingMoistureRavelingOxidize
Density Measurements
CoresDensity gauges
NuclearNon-nuclear
If all Goes Well…
You will have a long lasting HMA pavementLess maintenanceLess disruption to traveling publicNow that’s a winning combination for the tax payers
If not….
Job Mix Formula
Questions?????
