Flashcards in Asphalt Deck (46)
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1
Asphalt
Petroleum Based cementitious material that is mixed with aggregate to form the pavement
2
Common names for Asphalt
Asphalt, asphalt pavement, asphalt concrete, bituminous Concrete
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Is Asphalt Flexible or Rigid?
Flexible
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ASTM
American Society for Testing and Materials
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AASHTO
American Association of State Highway and Transportation Officials
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Thermoplasticity
Deforms under loads
Liquefies with heat
Asphalt is a flexible type of pavement
7
Viscosity
a measure of a fluid's resistance to flow
directly influenced by the temperature
Temperature increase means a decrease in viscosity
8
Asphalt Grades
Degrees of Hardiness Grading for use-type
9
Asphalt Weathering
Oxidation and evaporation of hydrocarbons causes: Loss of plasticity
Become Brittle with Age
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How to avoid weathering in Asphalt?
Slope subbases and subgrades
Proper compaction of layers
Timely sealing
11
Asphalt Insolvency
Resistant: Water, Salts, Acids, Alkalis
Susceptible: Petroleum
Remedy: Tar Sealer
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Asphalt Color
Black
13
Selection Criteria for Asphalt Cements or Binder
Local Standards and practices
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Fine Aggregate (Flows through No. 8 Sieve)
Mineral Dust
Mineral Filler
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Coarse Aggregate (Retained by #8 Sieve)
Major Stabilizer
16
Macadam Aggregate
Coarse Aggregates of uniform size of 1.5-2.5”
Coarse wearing surface
Mixed with asphalt cement
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Fine-graded Aggregate
Finer texture
Less road noise
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Coarse-Graded Aggregate
Stable pavement
Coarser surface texture
More road noise
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Dense-Graded Aggregate
Durable
Watertight surface
Highly stable
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Open-Graded Aggregate
Little or no mineral filler
Larger aggregates
Good strength
Rough texture
High permeability
Used in regions free of frost/thaw conditions
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Recycled Glass as Aggregate
Works well in asphalt pavements of heavy use
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Aggregate Hardiness (Toughness)
Ability to withstand loads and wear
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Resistance to Stripping
Hydrophilic aggregates tend to strip away from the asphalt bond, reducing stability and skid resistance
Compounds (admixture?) added to asphalt mixtures
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Surface Texture
Rough surface aids in bonding, stability, resistance to skidding and abrasion
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Crushed Shape Aggregate
Interlock and give the pavement more strength
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Asphalt Paving Mixtures: Asphalt Concrete
Most Common asphalt paving mixture
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Asphalt Paving Mixtures: Surface Treatments
Color coating, sealing, improving skid resistance, or prolonging the service life of a fair to good pavement surface
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Asphalt Paving Mixtures: Paving Blocks
Pre-molded
Used for Pedestrian Paving
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Asphalt Paving Mixtures: Asphalt-treated Granular Base Courses
Less cost
Can be treated with asphalt cement to produce a stabilized base course
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Typical Pavement Sections
(1)Layered Asphalt-Aggregate mixtures over a subgrade/improved subgrade
(2)Layered Asphalt-Aggregate mixtures over an aggregate base over a subgrade
(3)Layered Asphalt-Aggregate mixtures over existing pavement
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Pavement Functions
Support loads
Smooth
Resistant to weathering
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Minimum total Thickness of the Combined Asphalt Concrete Layers
The minimum total thickness of the combined asphalt concrete layers is 3” - 4”
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Full-Depth Design
Asphalt aggregate mixture placed directly on a subgrade
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Aggregate Base Design
Asphalt concrete placed on an untreated aggregate base over the prepared subgrade
Used in locations with frost action
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Traffic Class I
Parking Lots, Driveways, Light Traffic, Residential Streets, Farm Roads
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Traffic Class II
Residential Streets, Rural Farm and Residential Roads
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Traffic Class III
Urban Minor Collector Streets
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Traffic Class IV
Urban Minor Arterial and Light industrial Streets, Rural Major Collector, Minor arterial Highway
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Traffic Class V
Urban Freeways, Expressways, Principal Arterial Highways, Urban interstate Highways, Some Industrial Roads
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Road Thickness Design Procedure
Classify the traffic
Classify the subgrade
Determine Optimum asphalt concrete specs
Determine the thickness
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Bike Paths and Walkway Width
3”-4” Wide
Use local codes and requirements
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Golf Cart Paths
Surface a sand-asphalt mixture
43
Tennis Courts
Asphalt-concrete base of 0.75” of nominal maximum size designation covered either with sand-asphalt for the surface course or with a proprietary surfacing
Base course 3”
Surface course 1”
44
Asphalt Curbs
Back-filled with a solid granular material or well-compacted soil
Install on top of a solid, impervious pavement
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Asphalt Gutters
Can be formed in a variety of cross-sections
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