asphalt Flashcards
Asphalt cement used in pavement is produced in three forms: ____
asphalt cement, asphalt cutback, asphalt emulsion
______ is a blend of hydrocarbons of different molecular weight.
asphalt cement
The characteristics of the asphalt depend on the ______ and the _______.
chemical composition, distribution of the molecular weight hydrocarbons
As the distribution shifts towards heavier molecular weight, the asphalt becomes ______.
harder and more viscous
At _____, asphalt cement is a semisolid material that cannot be applied readily as binder without being heated.
room temperature
_____ have been developed and can be used without heating (The Asphalt Institute, 2007)
liquid asphalt products, cutbacks, emulsion
______ has excellent adhesive characteristics, which make it a superior binder for pavement applications.
asphalt cement
A ____ is produced by dissolving asphalt cement in a lighter molecular weight hydrocarbon solvent.
cutback
In the past, cutbacks were widely used for _____. They were effective and could be applied easily in the field.
highway construction
What are the three disadvantages in the use of cutbacks? ____
- as petroleum costs have escalated, the used of these expensive solvents as a carrying agent for asphalt cement is no longer cost effective
- cutbacks are hazardous materials due to the volatility of the solvents
- application of the cutback releases environmentally unacceptable hydrocarbons into the atmosphere
An alternative to dissolving the asphalt in a solvent is _____.
dispersing the asphalt in water as emulsion
_____ typically consists of about 69% to 70% asphalt cement, 39% to 40% water, and a fraction of a percent of emulsifying agent.
emulsified asphalts
There are many types of emulsifying agents; basically they are a ____.
soap material
The emulsifying molecule has two distinct components: _____
the head portion, the tail portion
The _____, which has an electrostatic charge
head portion
The _____, which has a high affinity for asphalt.
tail portion
The charge can be either positive to produce a ____ emulsion or negative to produce an _____ emulsion.
cationic, anionic
When asphalt is introduced into the ______, the tail portion of the emulsifier attaches itself to the asphalt, leaving the head exposed.
water with the emulsifying agent
The _____ of the emulsifier causes a repulsive force between the asphalt globules, which maintains their separation in the water.
electric charge
Since the specific gravity of asphalt globules is very near that of water, the globules have a neutral buoyancy and, therefore, _____.
do not float or sink
When the ____ is sprayed on a pavement or mixed with aggregates, the solvent evaporates, leaving the asphalt residue as the binder.
cutback
When the ____ is mixed with aggregates or used on a pavement, the water evaporate, allowing the asphalt globs to come together, forming the binder.
emulsion
The phenomenon or separation between the asphalt residue and water is referred to as ______.
breaking or settling
The rate of emulsion settling can be controlled by ______.
varying the type and amount of emulsifying agent
The main use of asphalt is in ______.
pavement construction and maintenance
In addition, _____ is used in sealing and waterproofing various structural components, such as roofs and underground foundations.
asphalt
The selection of the type and grade of asphalt depends on the _______.
type of construction and the climate of the area
______, also called asphalt binders, are used typically to make hot-mix concrete and warm-mix concrete, HMA and WMA, respectively, for the surface and base layers of asphalt pavements.
asphalt cements
_______ is also used in patching and repairing both asphalt and portland cement concrete pavements.
asphalt concrete
______ (emulsions and cutbacks) are used for pavement maintenance and preservation applications, such as fog seals, chip seals, slurry seal, and microsurfacing.
liquid asphalts
The ______ of asphalt is greatly affected by temperature.
consistency
Asphalt gets ____ at low temperatures and ____ at high temperatures.
hard and brittle, soft
The _____ of the asphalt decreases when the temperature increases.
viscosity
Asphalt’s temperature susceptibility can be represented by the slope of the line; the steeper the the slope the _____ the temperature susceptibility of the asphalt.
higher
However, _____ can be added to reduce this susceptibility.
additives
When asphalt is mixed with aggregates, the mixture will perform properly only if the asphalt viscosity is within ______.
an optimum range
If the viscosity of asphalt is higher than the optimum range, the mixture will be ______.
too brittle and susceptible to low-temperature (thermal) cracking
If the viscosity is below the optimum range, the mixture will _______, resulting in permanent deformation (rutting).
flow readily
Due to temperature susceptibility, the _____ of the asphalt should be selected according to the climate of the area.
grade
______- grade asphalts are used for cold climates and ____- grade asphalts for hot climates.
soft, hard
There are four methods for classifying asphalt binders: ______
- performance grading
- penetration grading
- viscosity grading
- viscosity of aged residue grading
Names of grades start with PG (_______) followed by two numbers representing the maximum and minimum pavement design temperatures in Celsius.
performance graded
The temperatures are calculated ______ below the pavement surface.
20 mm (0.75 in)
The high and low pavement temperatures are related to the _____ as well as other factors.
air temperature
The performance-graded asphalt binder specifications AASHTO _____, ASTM _____.
M320, D6373
____, updated in 2010, includes a second specification table that replaces the creep stiffness and direct tension parameters with a critical temperature parameter.
AASHTO M320
One important difference between the Performance Grade specifications and the traditional specifications is _______.
in the way the specifications work
The _____ (criteria) remain constant for all grades, but the ____ at which these properties must be achieved vary, depending on the climate at which the binder is expected to be used.
physical properties, temperatures
The ____ is selected to satisfy the maximum and minimum design pavement temperature requirements.
binder
The ______ is used to determine the design maximum.
average seven-day maximum pavement temperature
Whereas, the design minimum pavement temperature is the ______.
lowest pavement temperature
Since the maximum and minimum pavement temperatures vary from one year to another, a ____ is considered.
reliability level
As use in the Performance Grade, _____ is the percent probability in a single year that the actual pavement temperature will not exceed the design high pavement temperature or be lower than the design low pavement temperature.
reliability
In addition to the pavement temperature, the ______ and the _____ should affect the selection of the binder.
amount of traffic loads, traffic speed
Adjustment to the binder selection needs to be made according to the Superpave mix design specification, AASHTO ______ using a binder “bump”.
M323
______ is a pavement design factor used in the design of pavement that considers both traffic volume and loads (Huang, 2004).
ESAL (equivalent single axle load)
AASHTO has introduced a provisional specification, _____, that will use a different protocol for the dynamic shear rheometer that measures and specifies material properties that are directly related to the binder’s properties to handle different traffic loads and speeds.
MP
Three types of cutbacks are produced, depending on the ______ and the _____.
hardness of the residue, type of solvent used
What are the three types of cutbacks? _____
- rapid-curing cutbacks
- medium-curing cutbacks
- slow-curing cutbacks
______ cutbacks are produced by dissolving hard residue in a highly volatile solvent, such as gasoline.
rapid-curing
_____ cutbacks use medium hardness residue and a less volatile solvent, such as kerosine.
medium-curing
_____ cutbacks are produced by either diluting soft residue in nonvolatile or low-volatility fuel oil or by simply stopping the refining process before all of the fuel oil is removed from the stock.
slow-curing
_____ refers to the evaporation of the solvent from the asphalt residue.
curing the cutbacks
______ cutbacks cure in about 5 to 10 minutes.
rapid-curing (RC)
______ cutbacks cure in a few days.
medium-curing (MC)
_____ cutbacks cure in a few months.
slow-curing (SC)
Grades ___, ___, __, ___, and ___ are manufactured, with higher grades indicating higher viscosities.
30, 70, 250, 800, 3000
Cutback asphalts are designated by letters (RC, MC, SC), representing the type, followed by a number that represents the _____.
grade
The specifications of cutbacks are standardized by ASTM ___, ____, and ____.
D2026, D2027, D2028
_____ are produced in a variety of combinations of the electric charge of the emulsifying agent, the rate of emulsion gets (breaks), the viscosity of the emulsion, and the hardness of the asphalt cement.
asphalt emulsions
Depending on the emulsion concentration, the set or break time is varied from ______ set.
rapid to medium to slow
The ____ of the emulsion is rated as normal flow or slow flow, based on the Saybolt-Furol viscosity (ASTM D244).
viscosity
The _____ of the asphalt in the emulsion is evaluated with the penetration test.
consistentcy
Asphalt residues with a penetration of _____ are typically used.
100-200
However, soft asphalts, with a penetration of greater than _____, or hard asphalts, with a penetration of ____, may be used.
200, 60-100
The _____ of the emulsion is designated next with a 1 or 2 for a normal or slow flow respectively.
flow rate
Other emulsion types are also produced, such as the _____ and the ______.
high float reside emulsion, quick-set emulsion
The specifications of various asphalt emulsions are standardized by ASTM _____.
D977
_____ consists of asphalt binder and aggregates mixed together at a high temperature and placed and compacted on the road while still hot.
asphalt concrete
Historically, asphalt concrete was called _____, HMA, as it was mixed at temperatures of 135 to 160 deg C (275 to 320 deg F).
hot mix asphalt
______, WMA, at temperatures of 110 to 130 deg C (230 to 265 deg F).
warm mix asphalt
______ pavements cover approximately 93% of the 2.2 million miles of paved roads in the United States.
asphalt (flexible)
The objective of the asphalt concrete mix design process is to provide the following properties (Robert et al., 2009): ____
- stability or resistance to permanent deformation under the action of traffic loads, especially at high temperatures
- fatigue resistance to prevent fatigue cracking under repeated loadings
- resistance to thermal cracking that might occur due to contraction at low temperatures
- resistance to hardening or aging during production in the mixing plant and in service
- resistance to moisture-induced damage that might result in stripping of asphalt from aggregate particles
- skid resistance, by providing enough texture st the pavement surface
- workability, to reduce the effort needed during mixing, placing, and compaction
The ____ is also used for determining moisture susceptibility.
indirect tensile strength test
In this test, a cylindrical specimen 102 or 150 mm (4 or 6 in.) in diameter is typically used.
indirect tensile strength test
The load is applied by using two curved loading strips moving with a typical rate of deformation of _______ (2 in./min).
51 mm/min
Tensile stresses are developed in the ____ direction, and when these stresses reach the tensile strength, the specimen fails in tension along the vertical diameter.
horizontal
