AGGREGATE

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AGGREGATE
Aggregates may be NATURAL or MANUFACTURED Natural
aggregates sand, gravel, crushed
rock Manufactured aggregates blast furnage slag
Aggregates may also be COARSE or FINE or
FILLER Coarse aggregates gt 4.76mm Fine
aggregates 0.075mm 4.76mm Filler lt 0.075mm
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COARSE AGGREGATEproperties
Strength (kekuatan) and toughness
(kekerasan) Particle shape Porosity Surface
texture Surface coatings Specific
gravity Gradation
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FINE AGGREGATEproperties
Hard Non-plastic (clean free from organik
materials) Gradation Salt content
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Strength and toughness

• - to prevent breakdown under traffic and
  subsequent loss of stability
• no truly satisfactory test to measure the
  effective strength and toughness
• Measured by abrasion test using the Los Angeles
  Machine

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Particle shape

• - to provide aggregate interlock and stability of
  mixture
• Crushed aggregates give a better interlocking
  than rounded gravels
• Rounded gravels produce a more highly stable
  surface mixture than crushed aggregates. (adhesi
  antara agregat dan aspal agregat bulat lebih baik
  daripada batu pecah)
• Thin and elongated aggregates are being subject
  to size segregation in the mixing process and
  tend to be of low strength.

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Porosity

• - Porosity gives a proper adhesion between
  aggregate and bitumen
• Porosity affects the economic of mixture
• High porosities cause more bitumen will be
  absorbed into the aggregate (desired around 0.5
  of bitumen is absorbed into aggregate)
• High porosities generally do not affect the
  quality of mixture. It could be noted that if
  more bitumen is absorbed into aggregate this will
  leave a hard residue on the surface of aggregate
  particle and then lead to raveling and stripping.

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Surface texture

• The rougher the surface texture of aggregate
  gives the higher the stability and durability
• A rough aggregate surface reduces the
  displacement under pavement loading and then
  increases the stability of mixture
• Is important to adhesion between aggregate and
  bitumen. This will increase the durability of
  mixture

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Surface coatings

• Aggregate may be coated by clay, silt, calcium
  carbonat, iron oxides, gypsum and other subtances
  in varying thiskness and hardness.
• Surface coatings has responsible for aggregate
  stripping due to disturb the bitumen to seal the
  aggregate

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Specific gravity
Specific gravity is importand for mixture
calculation such as to determine the void content
of the compacted bituminous mixture

• 3 (Three) types of aggregate specific gravity
• Bulk specific gravity (Graviti spesifik bulk)
• SSD (Saturated Surface Dry) specific gravity
  (Graviti spesifik kering permukaan jenuh)
• Apparent specific gravity ( Graviti spesifik
  semu)
• There is also known effective specific gravity.
  It is used to estimate the amount of bitumen
  absorbed by aggregate

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Specific gravity
Bulk specific gravity perbandingan antara berat
kering agregat dan volume total agregat
SSD specific gravity perbandingan antara berat
agregat kondisi permukaan jenuh dan volume total
agregat
Apparent specific gravity perbandingan antara
berat kering agregat dan volume kedap air agregat
Effective specific gravity perbandingan antara
berat kering agregat dan volume kedap aspal
agregat
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Volume of aggregate to calculate Specific gravity
Volume agregat tanpa pori/ solid (Vs)
Volume agregat kedap air/ impermeable (Vi)
Volume agregat rembes air/ permeable (Vp)
Volume total agregat (V)
Volume agregat rembes aspal (V-Vs-Vi-Vp)
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Measuring Specific gravity
Diukur Ws berat kering partikel agregat ?w
berat volume air Bk berat agregat kering Ba
berat agregat di dalam air Bj berat agregat
jenuh air (SSD)
Vi
Vp
Vs
Ws
Bk
Bulk SG

(VsViVp)/?w
Bj - Ba
Ws
Bj
Vs
SSD SG

(VsViVp)/?w
Bj - Ba
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Measuring Specific gravity
Diukur Ws berat kering partikel agregat ?w
berat volume air Bk berat agregat kering Ba
berat agregat di dalam air Bj berat agregat
jenuh air (SSD)
Vi
Vp
Ws
Bk
Vs
Apparent SG

(VsVi)/?w
Bk - Ba
Bulk SG App SG
Estimasi Effective SG
2
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Gradation
Gradation is size distribution of aggregate
particles Gradation can be assessed by sieve
analysis
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Aggregate specification
Specification for aggregate is some requirements
that to be fulfilled by aggregate properties to
ensure the performance of bituminous mixture For
examples Item
Requirement Apparent Specific gravity
min 2.50 Absorption
max 3.0 Abrasion loss
max 35 Elongated and flat particles
max 25 Soundness loss max
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Sieving analysis
2 1/2 inch (63 mm)
2 inch (50 mm)
1 1/2 inch (37.5 mm)
1 inch (25 mm)
3/4 inch (19 mm)
1/2 inch (12.5 mm)
3/8 inch (9.5 mm)
No.4 (4.75 mm)
No.8 (2.36 mm)
No.16 (1.18 mm)
No.30 (0.6 mm)
No.50 (0.3 mm)
No.100 (0.015 mm)
No.200 (0.0075 mm)
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Making gradation curve
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Type of gradation
GAP GRADED
UNIFORMLY GRADED
WELL GRADED
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Finer or coarser aggregate
Agregat semakin halus (finer)
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Blending two aggregates (1)
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Blending two aggregates metode grafis (2)
B 63
Hasil blending A B 37 63
1.5 in
3/4 in
No 4
No 10
No 200
A 37