Civil Engineering Reference
In-Depth Information
tests to evaluate the mixture characteristics relative to expected field per-
formance. This method will continue to be refined by highway agencies.
With the support of the Federal Highway Administration, there is a con-
certed effort being placed on replacing the traditional Marshall and Hveem
mix design methods with the Superpave procedures.
QUESTIONS
AND
PROBLEMS
9.1 What is the difference between tar and asphalt cement?
9.2 Discuss the main uses of asphalt.
9.3 Define what is meant by temperature susceptibility of asphalt. Dis-
cuss the effect on the performance of asphalt concrete pavements.
Are soft asphalts used in hot or cold climates?
9.4 Temperature has a large effect on the asphalt viscosity. On one
graph, plot the relationship between asphalt viscosity (logarithmic)
and temperature for two cases: (a) a low-temperature susceptible as-
phalt and (b) a high-temperature susceptible asphalt. Label all axes
and relations.
9.5 Briefly discuss the chemical composition of asphalt.
9.6 What is the significance of each one of these tests:
a. flash point test
b. RTFO procedure
c. rotational viscometer test
d. dynamic shear rheometer test
e. penetration test.
9.7 Discuss the aging that occurs in asphalt cement during mixing with
aggregates and in service. How can the different types of aging of as-
phalt cement be simulated in the laboratory?
9.8 Show how various Superpave tests used to characterize the asphalt
binder are related to pavement performance.
9.9 Define the four methods used to grade asphalt binders. Which
method is used in your state?
9.10 To select an asphalt binder for a specific location, the mean seven-
day maximum pavement temperature is estimated at 61°C with a
standard deviation of 1.5°C. The mean minimum pavement temper-
ature is with standard deviation of 3.2°C. What grade asphalt
(PG) is needed at 98% reliability.
- 8°C
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