Aggregates. AAPA training

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Randall Riley
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1 Aggregates AAPA training

2 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

3 Australian Continent

4 Aggregate (Rock) Types Igneous rocks Basalt Granite / rhyolite / diorite Metamorphic rocks Hornfels / Greywacke/ Greenstone Quartzite / Argillite Sedimentary rocks Limestone Sandstone

5 Aggregate Types

6 Aggregate Sources Crushed and screened quarry products Naturally occurring sands and gravels Manufactured aggregates (e.g. Blast furnace slag) Recycled material - RAP

7 Aggregate Production

8 Aggregate Production Primary Crushing Secondary Crushing Screening Washing / dust extraction systems Stockpiling

9 Crusher Types Jaw Crusher Cone Crusher Impact Crusher / Hammer Mill Vertical Shaft Impactor

10 Bins Typical crushing and screening plant

11 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

13 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

15 Aggregate Properties Properties dependent on type (source) of material (acidic / intermediate/ basic) Properties controlled by processing suitability of bituminous activities

16 Stack in Mechanical Shaker Mechanical Sieve

17 Properties controlled by processing Shape Particle size distribution (grading) Cleanliness (silt, clay and organic matter)

18 Face sampling shielding ( AS )

19 Sampling Sampling Rock Spalls AS Sampling Product AS The sample needs to be representative of the material!

20 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

21 Properties Dependant on Source Toughness (strength, hardness and resistance to wear) Soundness Density Porosity (water absorption) Resistance to polishing Affinity for bitumen

22 Toughness Aggregate Crushing Value (Wet-Dry Strength Variation) Los Angeles Test

24 Typical Wet & Dry Strengths AS Table 2 ROCK TYPE DRY STRENGTH (kn) AVERAGE RANGE WET STRENGTH (kn) AVERAGE RANGE GRANITE DIORITE BASALT DOLERITE LIMESTONE SANDSTONE

25 LA Abrasion Test - Approx. 10% loss for extremely hard igneous rocks - Approx. 60% loss for soft limestones and sandstones

26 Typical Los Angeles Abrasion Loss Values Rock type LA (% max) Class A Class B Granite Basalt Hornfels River gravel Sedimentary Blast furnace slag 20 25

27 Evaluation Coarse Aggregate

28 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

30 Classification Applies only to aggregate for use in asphalt mixes Coarse > 4.75mm Fine < 4.75mm Filler < 75µm, i.e mm

31 AGGREGATE SPECIFICATIONS

32 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

33 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

36 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

38 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

39 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

41 Sand Patch Test

42 SCRIM Sideway-force Coefficient Routine Investigation Machine

43 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

44 Aggregates in asphalt Binder 6 % Filler 5% 5 % Binder 6% Air Voids 5 % Air Voids 5% Coarse Aggregate 34 % Coarse Aggregate 34% Fine Aggregate Fine 50% Aggregate 50 %

45 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

46 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

47 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

Chapter 2. The Ideal Aggregate. Aggregates

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