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CE 4650 LECT. 4
Terms in this set (60)
___ relates to any material relating to flow, and it's used to influence pavement performance.
what is rheology?
the study of deformation and flow of matter
what is a rheometer?
an instrument for measuring the deformation of materials with flow characteristics
what are the seven rheological properties?
what are the quantifications of temperature susceptibility?
what is asphalt aging?
oxidation of asphalt mixture in flexible pavements (stiffer with age) because asphalt is a hydrocarbon
how does aging influence pavement performance?
rutting and cracking
three phases of age hardening:
- mixing in the ___
- storage, transportation, and laydown
- short term: ___ rate for first 2-3 years in service
- long term: ___ rate after 2-3 years in service
construction & installation
- very slow
the slower the rate of age hardening, the more ___ the AC is.
what are the age harding contributing factors?
what is oxidation?
reaction of AC to oxygen due to the rate of temperature
- [define it]
- function of ___
- ___ to long term aging
- evaporation of lighter constituents from AC
- not significant
___ is the combining like molecules to form larger molecules, and it causes progressive ___.
thixotropy (steric/reversible) is:
- ___ of structure within the AC overtime
- causes ___ hardening
- destroyed by ___ and ___ the material
- associated with pavements that have ___ traffic
- reheating & working
- little or no
syneresis is an exudation reaction, which is the act or an instance of ___.
describe the exudation reaction in AC.
the thin oily liquids are exuded to the surface of the AC film, and then the AC becomes hard.
___ is like forming a skin protecting the material, so there is no damage done.
___ is the removal of oily constituents or resins from the AC, and it absorbs by ___.
what is the percent retained penetration formula?
% retained pen. = (pen. of aged asphalt/pen. of orig. asphalt)×100
what is the aging index formula for viscosity?
aging index = (visc. of aged asphalt/visc. of orig. asphalt)
what are the three phases asphalt goes through?
(hard) solid --> maltene --> oil (soft)
age hardening is useful for evaluating aging among different ___ and sources, but it's not a good predictor for ___ aging.
Age hardening includes the ___ and ___ tests, and it allows hardening during ___ only.
TFO & RTFO
___ is measured at high stresses and short loading times, and it have a variable shear rate. (*there's a vast storehouse of data on ___ of aged asphalts)
penetration (for both)
penetration influences overall HMA performances, especially ___, at an avg. yearly service temperature of ___.
the objective of penetration on pavement is to use as ___ penetration as possible without reducing ___.
___ refers to the distance in ___ that a standard asphalt cement will stretch before breaking when the two ends of the specimen are pulled apart at a specified __ and ___.
what is ductility an indicator of?
physiochemical state of asphalt colloid system
in pavement performance, good and poor service are from ___ Pen. good service has ___ ductility, and bad service has vice versa.
an extensive crack is less than ___.
___ can discriminate between different AC. tests are conducted on highly ___ asphalt at ___ temperatures after further aging of ___ test.
what is viscosity? (include formula)
it is used to describe resistance of liquid to flow
viscosity = shear stress/rate of shear strain
at high temperatures, viscosity is a ___ liquid and ___, meaning they're ___ of shear rates.
at low temperatures, viscosity is a ___ liquid and the ___ affects viscosity.
shear strain rate
___ asphalt is an example of newtonian fluid, and ___ is an example of a shear thinning fluid.
why are viscous fluids sometimes called plastic?
once they start flowing, they do not return to its original position (ex. rutting)
in a shear thinning fluid, viscosity ___ as shear strain rate ___, also known as ___. (ex. ketchuo, whipped cream, blood, paint)
in shear thickening fluid, viscosity ___ as shear strain rate ___, also known as ____.
what type of pavement distress does low viscosity induce at 60°C? & why?
permanent deformation (rutting) because of the selection of viscosity grade
what type of pavement performance does high viscosity induce at low temperatures?
low temperature cracking
what is temperature susceptibility?
rate at which the consistency of asphalt changes with a change in temperature
___ temperature susceptibility is not desirable.
viscosity at 135°C is ___, and what problem does this cause?
tender mixing problem during compaction
viscosity at low temperatures is ___, and what problem does this cause?
low temperature shrinkage cracking
___ is based on penetration values at 2 or 3 temperatures.
what is the PI range of most asphalts and high temperature susceptibility?
+1 to -1
PI can be estimated from penetration at the ___ test at __.
what problem is associated with PI and the softening point test?
variation in the penetration at softening point
what is the formula for PI?
PI = (20-500A)/(1+50A)
what is the formula for the slope, A?
A = (log Pen (T₁)-log Pen (T₂))/(T₁-T₂)
the lower the __ or ___, the higher temperature susceptibility.
PI or PVN
what temperatures is PVN based on? and where are they obtained?
penetration at 25°C
viscosity at 135°C or 60°C
obtained from existing specification data
what is the range of PVN?
0.5 to -2.0
how does PVN change with aging?
stays about the same
what is the formula for PVN at 135°C? include units.
PVN = [(L-X)/(L-M)]×-1.50
L = log visc. (V) (cSt) at 0.0 PVN
M = log V (cSt) at -1.5 PVN
X = log V (cSt) at x PVN
what number of temperatures is VTS based on? and what is the VTS range?
2 or more
3.36 to. 3.98
what is the formula for VTS? include units.
VTS = [log (log V, T₂)-log (log V, T₁)]/(log T₁-log T₂)
**temperature is in Kelvins (K = C+273), and V is in cP**
the ___ VTS, the higher the temperature susceptibility.
what is stiffness?
it is temperature and time dependent.
stiffness = stress/strain
for high temperatures, ___ stiffness is desirable. vice versa for low temperatures.
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