Term
| Components of Asphalt Concrete (3) |
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Definition
1. Mineral Aggregate
-Stone Framework
2. Binder
-Asphalt Cement
-Modified Asphalt Cement
3. Air |
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Term
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Definition
1. Permanent Deformation
- Subgrade
- Asphalt Concrete surface
2. Fatigue Cracking
3. Thermal Cracking |
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Term
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Definition
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Term
| Asphalt Binder - Bitumen: (4) |
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Definition
1. High molecular weight hydrocarbons
2. Asphalt
-Natural or from petroleum processing
-soluble in petroleum products
3. Tar
-condensates in the destruction distillation of coal, wood, sugar, coal, etc
-insoluble in petroleum products
4. Pitch
-fractional distillation of tar |
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Term
| Sources of Asphalt Cement (2) |
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Definition
1. Natural:
-Natural Deposit
-Impregnated Rock Deposits
2. Refining: started in 1890s
-in 1907 its use exceeds that of natural asphalt |
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Term
Petroleum Based Asphalt:
-Asphalt is a waste product from refining of ____________
-Properties depend on: |
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Definition
Crude Oil
Refinery Operations
Composition crude-source dependent |
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Term
| Types of Asphalt Products (3) |
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Definition
1. Asphalt cements
-generally refinery produced
-air-blown asphalt cements
2. Cut-back
-rapid/medium/slow curing
3. Emulsion (anionic or cationic)
-rapid/medium/slow setting |
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Term
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Definition
Asphalt cements "cut" with petroleum solvents
Rapid cure - Naphtha or Gasoline
Medium cure - Kerosene
Slow cure - Low viscosity oil |
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Term
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Definition
High volatility of solvent
Tack coats, surface treatments |
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Term
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Definition
Moderate volatility
Stockpile patching mix |
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Term
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Definition
Low volatility
Prime coat, dust coat |
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Term
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Definition
| Mixture of asphalt cement, water, and emulsifying agent |
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Term
| ___________ gives surface charge to asphalt droplets suspended in water medium |
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Definition
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Term
Anionic emulsifier -
- ___________ charge
- alkaline/acid
- good with __________ (_________ charge) |
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Definition
| Negative; alkaline; limestone (positive) |
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Term
Cationic emulsifier
- ___________ charge
- alkaline/acid
- good with ________________ (___________ charge) |
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Definition
| positive; acid; silica gravels (negative) |
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Term
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Definition
- Fundamental properties related to pavement performance
-Environmental factors
-In-service and construction temperatures
-Short and long term aging |
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Term
| PG specifications are based on _____________ testing. |
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Definition
| Rheological - study of flow and deformation |
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Term
| Asphalt cement is a _______________ material. |
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Definition
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Term
PG Superpave
Behavior depends on: (3) |
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Definition
Temperature
Time of loading
Aging |
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Term
| SUPERPAVE high temperature behavior |
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Definition
- High in-service temp
-desert climates
-summer temps
- sustained loads
-slow moving trucks
-intersections
Binder acts as a viscous liquid
Permanent deformation (rutting)
Mixture is plastic
Depends on asphalt source, additives, and aggregate properties |
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Term
| SUPERPAVE low temp behavior |
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Definition
-cold climates and winter temps
Rapid slows - fast moving trucks
Binder acts as an elastic solid
Thermal cracks:
-stress generated by contraction due to drop in temperature
-crack forms when thermal stresses exceed ability of material to relieve stress through deformation
-material is brittle
- Depends on source of asphalt and aggregate properties |
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Term
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Definition
-asphalt reacts with oxygen
-oxidative or age hardening
-Short term
-volatization of specific components
-during construction process
- Long term
-over life of pavement (in-service) |
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Term
| Asphalt binder specification is based on _________. |
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Definition
Climate.
PG (performance grade) 64-22
64 - average 7-day maximum pavement temp
-22 = minimum pavement temp
High temp is 20mm below surface
Low temp is at surface |
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Term
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Definition
rolling thin film oven
- Provides simulated short term aged asphalt binder for physical property testing
- Asphalt binder is exposed to elevated temperatures to simulate manufacturing and placement aging
- Provides quantitative measure of volatiles lost during the aging process |
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Term
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Definition
pressure aging vessel
- Provides simulated long term aged asphalt binder for physical property testing
- Takes RTFO sample and ages in a stainless steel pan for 20 hours in a heated vessel pressurized to 305 psi |
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Term
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Definition
rotational viscometer
- Used to determine the viscosity of asphalt binder in high temperature range of manufacturing and construction
- Conducted at 275 °F |
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Term
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Definition
dynamic shear rheometer
- Used to characterize the viscous and elastic behavior of asphalt binders at medium and high temperatures |
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Term
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Definition
Bending Beam rheometer
- Provides measure of the low temperature stiffness and relaxation properties of asphalt binders
- Gives an indication of the asphalt binders ability to resist low temperature cracking |
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Term
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Definition
Direct Tension Tester
- Provides measure of the low temperature stiffness and relaxation properties of asphalt binders
- Gives an indication of the asphalt binders ability to resist low temperature cracking |
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Term
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Definition
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Term
| Asphalt pavements are subjected to fatigue loading measured in _____. |
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Definition
| ESAL (equivalent single axle loading: 18 kips) |
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Term
| Asphalt pavement are designed as _________________. |
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Definition
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Term
| Asphalt cement will __________, lose _________________ and become __________ with age |
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Definition
| oxidize, light weight volatiles, brittle |
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Term
| Surface mixtures contain more _________________ and smaller _______________________. |
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Definition
| asphalt cement; max agg size |
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Term
| Maximum density curve is a ______________________. |
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Definition
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Term
| Maximum density gradation does not have sufficient _____________ between aggregate particles to produce an asphalt concrete mixture with sufficient asphalt cement to produce a durable pavement. |
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Definition
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Term
Dense or Well-Graded
Refers to a gradation that is near the: |
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Definition
| FHWA’s 0.45 power curve for maximum density |
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Term
| . The most common HMA and PCC mix designs in the U.S. tend to use: |
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Definition
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Term
| Generally, a true maximum density gradation (exactly on the 0.45 power curve) would result in: |
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Definition
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Term
Gap Graded
Refers to a gradation that contains: |
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Definition
| only a small percentage of aggregate particles in the mid-size range |
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Term
| Some PCC mix designs use gap graded aggregate to provide a more economical mix because: |
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Definition
| less sand can be used for a given workability |
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Term
| HMA gap graded mixes can be prone to ____________ during placement |
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Definition
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Term
Open Graded
Refers to a gradation that contains only a small percentage of aggregate particles in the _______ range |
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Definition
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Term
| Why does open graded result in more air voids? |
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Definition
| because there are not enough small particles to fill in the voids between the larger particles |
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Term
Uniformly Graded
Refers to a gradation that contains most of the particles in a _________________ size range |
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Definition
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Term
Restricted Zone
Gradations that pass through the restricted zone are ______________ mixtures. |
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Definition
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Term
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Definition
- Compact poorly
- less resistant to permanent deformation
- may have insufficient air voids which results in flushing and skin resistance problems |
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Term
| Crushed aggregate faces increase the ______________ of the mixture and thus increase the ________________. |
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Definition
| internal friction; mixture stability |
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Term
| Are flat and elongated particles of coarse aggregate strong or weak? |
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Definition
| Weak because they don't compact well and reduce density |
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Term
| Angularity: angular particles increase the ______________ of the mixture, thus increase ______________________. |
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Definition
| internal friction; mixture stability |
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Term
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Definition
| Percent VOIDS IN TOTAL MIXTURE |
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Term
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Definition
| percentage of Voids Filled with Asphalt |
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Term
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Definition
| Voids in Mineral Aggregate |
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Term
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Definition
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