aggregates - aapa q€¦ · average range average range granite 299 190-460 244 144-440 diorite 255...
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Aggregates
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AAPA training
Aggregates
Topics
Aggregate sources and rock types Aggregate Production Aggregate Properties Coarse and fine aggregates in Asphalt Mixes Aggregates in Sprayed Seals Filler in asphalt mixes
Australian Continent Aggregate (Rock) Types Igneous rocks
– Basalt – Granite / rhyolite / diorite
Metamorphic rocks – Hornfels / Greywacke/ Greenstone – Quartzite / Argillite
Sedimentary rocks – Limestone – Sandstone
Aggregate Types
Aggregate Sources
Crushed and screened quarry products
Naturally occurring sands and gravels
Manufactured aggregates (e.g. Blast furnace slag)
Recycled material - RAP
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Aggregate Production Aggregate Production
Primary Crushing
Secondary Crushing
Screening
Washing / dust extraction systems
Stockpiling
Crusher Types
Jaw Crusher Cone Crusher
Impact Crusher / Hammer Mill Vertical Shaft Impactor
Typical crushing and screening plant
Bins
Primary Crushing
A Jaw Crusher is one of the main types of primary crushers A fixed jaw is the stationary breaking surface, while the movable jaw exerts force on the rock by forcing it against the stationary plate (impact) The rock remains in the jaws until it is small enough to pass through the gap at the bottom of the jaws
Aggregates
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Secondary Crusher
Gyratory cone crushers can be used for primary or secondary crushing The crushing action is caused by the closing of the gap between the mantle line (movable) mounted on the central vertical spindle and the concave liners (fixed) mounted on the main frame of the crusher
Aggregate Properties
Properties dependent on type (source) of material (acidic / intermediate/ basic)
Properties controlled by processing suitability of bituminous activities
Mechanical Sieve
Stack in Mechanical
Shaker
Properties controlled by processing
Shape Particle size distribution (grading) Cleanliness (silt, clay and organic matter)
Face sampling – shielding ( AS 1141.3.1)
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Sampling
Sampling Rock Spalls AS 1141.3.2
Sampling Product AS 1141.3.1
The sample needs to be representative of the material!
Evaluation – General
Aggregates for use in asphalt mixes or sprayed seals should be: – sound and durable – well shaped – cubical, not elongated – clean and consistently graded – resistant to polishing – resistance depends
on the particular application e.g. lower resistance can be tolerated on lightly trafficked roads subjected to slow moving traffic
Properties Dependant on Source
Toughness (strength, hardness and resistance to wear) Soundness Density Porosity (water absorption) Resistance to polishing Affinity for bitumen
Toughness
Aggregate Crushing Value (Wet-Dry Strength Variation) Los Angeles Test
Typical Wet & Dry Strengths AS 1141.22 – 1996 Table 2
ROCK TYPE DRY STRENGTH (kN)
WET STRENGTH (kN)
AVERAGE RANGE AVERAGE RANGE
GRANITE 299 190-460 244 144-440
DIORITE 255 230-280 225 210-240
BASALT 340 210-520 280 150-470
DOLERITE 233 170-350 145 80-300
LIMESTONE 145 130-150 97 85-110
SANDSTONE – 150 – 45
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LA Abrasion Test
- Approx. 10% loss for extremely hard igneous rocks - Approx. 60% loss for soft limestones and sandstones
Typical Los Angeles Abrasion Loss Values
LA (% max)Rock typeClass A Class B
Granite 25 35Basalt 20 25Hornfels 20 25River gravel 25 30Sedimentary 25 25Blast furnace slag 20 25
Evaluation – Coarse Aggregate Evaluation – Coarse Aggregate
Test methods in AS 1141 – Particle density – Particle size distribution – Particle shape – Flakiness Index – Aggregate Crushing Value – Wet-dry Strength Variation – Los Angeles Abrasion Loss – Sodium Sulphate Soundness – Polished Aggregate Friction Value
Adhesion with bitumen – Plate stripping test for sealing aggregate – Modified-Lottman Test for asphalt – loss of Marshall Stability or
stiffness after soaking
Classification
Applies only to aggregate for use in asphalt mixes
Coarse > 4.75mm Fine < 4.75mm Filler < 75µm, i.e. 0.075mm
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AGGREGATE SPECIFICATIONS Functions in Asphalt Mixes Coarse aggregate
– Major contribution to the stability and strength of the mix – Macro- and micro-texture which determine skid resistance – Abrasion resistance
Fine aggregate – Stability – Reduction of voids in the coarse aggregate structure – Contribution to the micro-texture and hence skid resistance – Improves mix durability – increases surface area and binder
effectiveness
Filler – Reduction in air voids – Increase the stiffness of the binder – depends on the fineness of the
filler – Improves mix durability – increases surface area and binder
effectiveness
Evaluation – Fine Aggregate
Quality controlled by – the selection of the source – particle size distribution – particularly the
percentage passing 75µm – Plasticity Index (LL/PL)
For crushed fines acceptance also based on testing of the coarse aggregate
Evaluation – Fillers Depends on the type of filler Types of filler
Baghouse dust – Hydrated lime Cement – Cement works flue dust Fly Ash – Ground Limestone
Tests applied to all fillers Particle size distribution Dry compacted voids – measure of fineness Moisture Content
Tests applied to some fillers Loss on Ignition – applied to fly ash Clay Index (rock source / baghouse) Water soluble fraction – applied to cement works flue dust
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Functions of Aggregates in Asphalt Surfacing
Provides a safe road surface for the public to use.
Provides surface texture and skid resistance
Provides the increased resistance to the traffic loads and tyre pressures
Spreads wheel loads to lower pavement layers
Wheel Tracking
wheel tracking device as per TRL design test at 60 C 42 passes per
minute load with 700 N terminate at 15 mm
rut or 10,000 passes
Sand Patch Test
SCRIM
Sideway-force Coefficient Routine Investigation Machine
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Functions of Aggregates in Sprayed Seals
Provides a safe road surface for the public to use.
Provides the resistance to the traffic loads and tyre pressures
Provides surface texture and skid resistance
Aggregates in asphalt
Fine Aggregate50%
Coarse Aggregate
34%
Air Voids 5%
Binder6%
Filler5%
Coarse Aggregate
34 %
Fine Aggregate
50 %
Air Voids 5 % Binder
6 % Filler 5 %
Aggregate Sizes Used in Sprayed Seals
5 & 7 mm – Lightly trafficked pavements, second application in
multiple application seals, temporary treatments, corrective treatments
10 & 14 mm – Common sizes for single/single seals
16 & 20 mm – Generally only as first application in double/double
seals, e.g 16/7, 20/7 or 20/10
Australian Standards The following Australian Standards apply to aggregate and fillers
AS 2758 Aggregates and rock for engineering purposes Part 2: Aggregate for sprayed bituminous surfacing
Part 5: Asphalt aggregates
AS 1141 Methods for sampling and testing aggregates
AS1289 Methods of testing soils for engineering purposes
AS 2357 Mineral filler for asphalt has been withdrawn and requirements incorporated in AS 2150 Hot Mix Asphalt
Other Reference Material
AUSTROADS Asphalt Guide AAPA National Asphalt Specification State Road Authority Specifications Queensland TMR Technical Standards
MRTS11 – Spray (Bituminous) Surfacing MRTS22 – Aggregate Coverings MRTS30 – Dense & Open Graded Asphalt
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