Bitumen and Asphalt Mixes Flashcards
What are Cutbacks?
Asphalt cement cut with petroleum solvents.
What is Emulsion?
Mix of asphalt cement, water, and emulsifying agents.
What is the process of Rapid Curing (Cutbacks)?
Dissolving hard residue in highly volatile solvents (gasoline or naphtha)
What is the use of Rapid Curing (Cutbacks)?
Tack coats or surface treatments.
What is the process of Medium Curing (Cutbacks)?
Dissolving medium residue in less volatile solvents (kerosene)
What is the use of Medium Curing (Cutbacks)?
Stockpile patching mix and prime coat.
What is the process of Slow Curing (Cutbacks)?
Diluting soft residue in nonvolatile/low volatile fuel oil or by stopping refining process before all fuel is removed from stock.
What is the use of Slow Curing (Cutbacks)?
Prime coat, stock piling and road mixing.
What is the process of Emulsion?
Surface charge to asphalt droplets suspended in water medium. Both anionic and cationic.
What is anionic?
Negative
Alkaline
Good with limestone (+charge)
What is cationic?
Positive
Acid
Good with silica gravels (-charge)
What does emulsion do?
Sets viscosity of emulsions and hardness of asphalt cement.
What is Slow Setting for (Emulsion)?
Tack coats, fog seals.
Dense graded cold mixes.
What is Medium Setting for (Emulsion)?
Open graded cold asphalt agg mixtures.
What is Fast Setting for (Emulsion)?
Surface treatments.
What do higher grades (Cutbacks) mean in terms of viscosity?
Higher viscosity.
What is curing the Cutback?
Evaporating the solvent from the asphalt residue.
What are 7 different problems with asphalt pavements?
1) Fatigue
2) Thermal Cracks
3) Transverse Cracks
4) Shoring
5) Pothole and Ravelling
6) Bleeding
7) Rutting
What does Bitumen consistency testing involve?
Penetration
Viscosity
Ductility
What does Bitumen durability testing involve?
Short term ageing
Long term ageing
What does Bitumen safety testing involve?
Flash point clevland open cup
What does Bitumen purity testing involve?
Solubility test
What does consistency describe?
Fluidity or plasticity of bitumen.
What is penetration testing?
Penetrating a needle into substance with specific load, temperature and time.
What are the advantages of the penetration test?
Fast
Precision established
Grades asphalt
Temp susceptibility can be determined
What are the disadvantages of the penetration test?
Empirical test
Does not reflect differences in asphalt.
What are the grades of the penetration test (5)?
40-50 60-70 80-100 130-150 180-200
What climates are soft (low viscosity) asphalts used in?
Cold climates to avoid thermal cracking.
What climates are hard (high viscosity) asphalts used in?
Hot climates to avoid rutting.
How is short term binder ageing tested?
Using a rolling thin film oven
- Simulates ageing from hot mixing and construction.
How is long term binder ageing tested?
In a pressure ageing vessel.
- 7 to 10 years simulation.
- 50 grams for 20 hours
- Pressure of 2070 kPa
- At a temp of either 90, 100 or 110.
Advantages of viscosity testing?
Fundamental property
Based on max pave surface temp
Test method precision established
Temperature susceptibility is controlled
Disadvantages of viscosity testing?
Not applicable to non-newtonian materials
Wide range of properties for the same grade
What is viscosity in physical terms?
It is the ratio between applied shear stress and the rate of shear.
How is viscosity tested?
Using viscosity tubes of rotational viscometers.
List the Viscosity grading based on the viscosity of the original asphalt (AC).
AC-2.5 AC-5 AC-10 AC-20 AC-30 AC-40
List the Viscosity grading based on the viscosity of the asphalt residue (AR). This is from rolling film oven testing.
AR-1000 AR-2000 AR-4000 AR-8000 AR-16000 This is at 60 degrees
How does the ductility test work?
- By measuring the distance that a standard briquette of asphalt cement will stretch before breaking.
- Done at temp of 25 degrees (achieved by water bath)
- Two ends separated at 5cm/min
- Salt added to water to prevent sample from floating in water bath.
How does the softening point test work?
- Measures temperature at which bitumen will flow under own weight.
- Bitumen poured in two copper rings on a copper plate and cooled
- Put into water bath of 4 degrees, leave for 15mins
- Apply temp at 5 degrees/min.
- Bit will soften as temp increases.
What is the solubility test for?
Measuring purity of bitumen and quantify amount of impurities.
How pure is refined bitumen?
Usually more than 99.5%.
What is temperature susceptibility of bitumen?
Rate of which the consistency of bitumen changes with change in temperature.
How is the penetration index determined?
Measuring penetration at two different temperatures an drawing log (pen) versus temperature.
Slope is susceptibility.
(rise over run in calculation)
What does higher penetration index mean in terms of temperature susceptibility?
Higher penetration index means lower susceptibility.
Vice versa.
How is the viscosity temperature susceptibility (VTS) defined?
The slope of the log log (viscosity at 135 degrees) and the log (temperature in K)
What does higher temperature susceptibility mean in regards to VTS?
Higher temperature susceptibility means higher VTS.
