Aggregates 2.0 (grading)

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Aggregates 2.0 (grading)
2014-04-07 18:53:01
Aggregates grading
Aggregates 2.0 (grading)
Aggregates 2.0 (grading)
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  1. Types of gradations
    • Uniformly graded
    •   Few points of contact
    •   Poor interlock 
    •   High Permeability 

    • Well graded 
    •   Good interlock 
    •   Low permeability

    • Gap graded
    •   Only limited sizes  
    •   Good interlock
    •   Low Permeability
  2. Angular shape with rough texture
    Improved inter particle friction, stability and bond with binder - better for case course and asphalt concrete - but harder to work into place (i.e consolidate)
  3. Round shape with smooth surfaces
    Easier to work into shape and require less water in PC concrete
  4. Aggregate particle sizes ranges typically from
    <150 microns to >20 mm
  5. Single sized aggregate results in
    Large voids
  6. gap graded
    Smaller particles reduce void size
  7. Reducing past content of concrete leads to :
    • Reduced cost
    • Reduced temperature rise
    • Reduced shrinkage
    • Reduced permeability
  8. Gradation affects properties such as
    • Stiffness
    • Durability
    • Workability
    • resistance to moisture damage
    • Permeability
    • Fatigue resistance
  9. Sieve maximum size
    Is the smallest sieve through which the entire sample passes
  10. Nominal maximum size
    • is the standard sieve opening immediately smaller than the smallest through which all aggregate passes
    • must retain less than 10% of the sample