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