CGN 3501 Exam 4
What is a tack coat?
- An application of asphalt to ensure bond between two asphalt layers.
Which one of the following bituminous materials does not occur in natural form? (A) Petroleum asphalt. (B) Lake asphalt. (C) Rock asphalt. (D) Gilsonite.
A) Petroleum Asphalt
TRUE or FALSE: rock asphalt has good skid resistance
true
What are the two types of lake asphalt?
(A) Bermudez Asphalt-comes from Bermudez 'Pitch' Lake, Northern Coast of Venezuela-asphalt crude is dug out from the lake (B) Trinidad Asphalt -from Trinidad Asphalt Lake
Describe drum mix plant
(A) Produces mixes in a continuous process. (B) Dries the aggregate and blends it with asphalt in the same piece of equipment.
Describe a batch plant
(A) Produces one batch at a time (3,000 to 10,000 lbs/batch) (B) Dries and heats the aggregate in a dryer, and mixes the aggregate and asphalt in a separate mixer
Describe PAV apparatus and procedure
- 50 g samples placed in pans and placed in the PAV - Up to 10 pans can be placed in the PAV - PAV temperatures: 90, 100 or 110 °C - PAV pressure: 2.1 MPa (300 psi) - PAV time duration: 20 hours
Describe anionic emulsified agents
- Asphalt droplets are negatively charged - More compatible with aggregate with positive surface charges (such as Limestone) - Typical emulsifying agent: fatty acids.
Describe cationic emulsified agents
- Asphalt droplets are positively charged. - More compatible with agg. with negative surface charges (such as siliceous agg.) - Typical emulsifying agent: fatty amines.
What is a friction course?
- For high-speed road, such as Interstate highway, the surface is usually covered with a friction course (1/2 to ¾ inch thick) to improve the skid resistance of the pavement surface.
Describe medium setting (MS) and the test associated with it
- Good mixing characteristics with coarse agg. - Can be demulsified by a relatively large amount of Calcium Chloride. - Passes the Stone Coating Test.
What is the demulsibility test?
- Run on RS Emulsions to ensure that the emulsions will break (or DEMULSIFY) easily (upon contact with aggregates) - uses diluted calcium chloride; Dioctyl Sodium Sulfosuccinate if cationic - minimum of 60% of emulsion must be retained on sieve to pass
What is the Cement Mixing Test?
- Run on SS Emulsions to ensure its stability. - Add SS and Portland Cement and distilled water, stir - pour over #14 sieve to determine the amount of coagulated asphalt, should be <2%
What is the Stone Coating Test?
- Run on a MS Emulsion to ensure (1) good coating of aggregate, (2) ability to be mixed, & (3) resistance to washing action after mixing. - report coating as good, fair, or poor for washed and unwashed
What values are required of the bending beam rheometer test and why?
- S of the binder after PAV should be less than 300 MPa, and the m-value should be greater than 0.3 at 60 seconds at the test temperature (Tmin+ 10 °C) - in order to reduce low-temperature cracking at Tmin.
Describe rapid setting (RS) and the test associated with it
- Sets rapidly - High demulsibility - It can be demulsified by adding a small amount of Calcium Chloride, (for cationic emulsions, Dioctyl Sodium Sulfosuccine.) -Passes the demulsibility test
Describe slow setting (SS) and the test associated with it
- Sets slowly - Very stable (it does not demulsify easily) - Passes the Cement Mixing Test.
What is a prime coat?
- an application of low viscosity liquid asphalt on an untreated base. - It penetrates into the base, plugs the voids and helps to bond it to the overlaying asphalt layer.
What is a seal coat?
- thin surface treatment used to improve the texture of and waterproof an asphalt surface. - Seal coats may or may not be covered with aggregate. - Examples: Fog Seal, Slurry Seal, Sand Seal.
What is the range of penetration index of a normal paving asphalt cement?
-2 to 2
What are the testing conditions for the Thin Film Oven Test (TFOT)?
-325 deg F (163 deg C) for 5 hours. -Asphalt placed in pans on rotating shelf. -Asphalt film thickness 1/8-inch (3 mm).
What are the testing conditions for the Rolling Thin Film Oven Test (RTFOT)?
-325 deg F (163 deg C) for 75 minutes -35 g of asphalt placed in each glass bottle, which is placed on its side and rolled continuously.
What are the three commonly used dust control systems for hot-mix plants?
-Cyclone Dust Collector -Wet Scrubber Dust Collector -Baghouse Dust Collector
What does low ductility indicate?
-low ductility is related to poor adhesive property
What are the two components of SUPERPAVE?
1. Asphalt Binder Specification. 2. Mixture Design and Analysis System.
What are the two ways to manufacture tar?
1. By-product of Coke production 2. By-product of water gas production
What are the main components of a drum mix plant? (10)
1. Cold Feed Bins 2. Cold Feed Conveyor 3. Automatic Weighing System 4. Drum Mixer 5. Asphalt Pump 6. Asphalt Storage Tank 7. Dust Collector 8. Hot-Mix Conveyor 9. Mix Surge Silo 10. Control Van
What are the main components of a batch mix plant? (14)
1. Cold bins 2. Cold feed gate 3. Cold elevator 4. Dryer 5. Dust collector- may also have baghouse 6. Exhaust stack 7. Hot elevator 8. Screening unit 9. Hot bins 10. Weigh box 11. Mixing unit -or pugmill 12. Mineral filter storage 13. Hot asphalt cement storage 14. Asphalt weigh bucket
How are asphalt and tar similar? (4)
1. Composed principally of Bitumen 2. Black or dark brown in color. 3. Cementitious 4. Water repellent.
Describe the procedure for Penetration Macadam Construction (8 steps)
1. First application of aggregate 2. First rolling 3. First Binder application 4. Second application of aggregate 5. Second Rolling 6. Second binder application 7. Third application of aggregate 8. Third rolling
How are asphalt and tar different? (8)
1. Odor- tar has a smell 2. The insoluble portion in natural asphalt is mineral matter and in tar is free carbon 3. Tar molecules tend to be aromatic (ring or cyclic), while asphalt molecules tend to be aliphatic (straight chain) 4. Tar is more temperature susceptible 5.Tar can coat aggregates better and is more water resistant 6. Asphalt is more weather resistant 7. Asphalt can occur in natural form or come as a by-product of petroleum refinery, but tar does not occur in natural form, but comes as a by-product in the manufacture of coke or water-gas. 8. Fumes from heated tar cause health hazards such as severe eye and skin irritation.
Describe how a finished pavement mat is to be inspected to ensure that it is of acceptable quality.
1. Surface Texture- by visual inspection 2. Surface Tolerance- Florida DOT :with a rolling straightedge (deviation should be less than 3/16 inch) 3. Density Requirment- Florida DOT (for Superpave mixes):94.5 ± 1.3 % Gmm for Coarse Mixes(5.5 ± 1.3 % air voids)93.0 +2.0, -1.0 % of Gmm for Fine Mixes(7.0 -2.0, +1.0 % air voids)
Describe the flow of material in a batch plant
1. The gates of the weigh box are opened, and the aggregates empty into pugmill. 2. The asphalt is discharged into the pugmill by a spraybar. 3. The aggregates and the asphalt are mixed. 4. The pugmill gate opens, and the finished mix is discharged. 5. The pugmill gate closes to receive the next batch.
What are the 3 functions of a pavement?
1. To provide a smooth and safe driving surface. 2. To protect the subgrade from frost action. 3. To protect the subgrade from permanent deformation.
How is a sample loaded for the bending beam rheometer test?
100 g force applied to the middle of the beam for a total of 240 seconds.
Describe what the following grades indicate: 40/50 pen, 120/150 pen, 200/300 pen
40/50 pen asphalt- Penetration at 25 C: 40 -50 120/150 pen asphalt- Penetration at 25 C: 120 -150 200/300 pen asphalt- Penetration at 25 C: 200 -300
What is cutback asphalt?
A liquid asphalt made by dissolving an asphalt in a petroleum solvent.
Describe slurry seal
A mixture of emulsified asphalt and fine aggregate in the form of a slurry, used to seal cracks on an asphalt surface.
Describe single pass surface treatment/ chip seal
A thin asphalt aggregate application applied to an existing surface or base.
Describe friction course
A thin wearing course, usually a hot asphalt mixture, used to improve skid resistance of an asphalt surface.
The Tag Open Cup flash point test can be used on which of the following asphalts? (A) MC cutback asphalt. (B) 60/70 pen asphalt. (C) AR-4000 asphalt. (D) PG 70-22 asphalt.
A) MC cutback asphalt- uses a water bath so can only go up to 100 deg C; all the other examples have flashpoint temperatures above 100 deg C - petroleum solvent of cutback asphalt allows it to dissolve easy
Describe (A) the purpose of the test, (B) how the test results are reported, of the penetration test
A) a consistency test used to identify an asphalt as to its hardness or grades; other uses: to measure changes in hardness due to heating or changes in temperature. B) reported in mm
The results of the standard Ductility Test on asphalt are reported in units of (A) cm, (B) strain in %, (C) psi, or (D) seconds.
A) cm
Which solvent is usually used in producing a RC cutback asphalt? (A) Gasoline. (B) Kerosene. (C) Diesel Oil. (D) Benzene.
A) gasoline
According to the Superpave asphalt binder specification, an asphalt with a low G*sin(delta) value as measured in the Superpave specification testing is expected to have a (A) high resistance to fatigue cracking, (B) high resistance to rutting, (C) low resistance to rutting, or (D) high resistance to low-temperature cracking.
A) high resistance to fatigue cracking
The main purpose of the Solubility Test on asphalt is (A) to determine the bitumen content, (B) to determine the flexibility, (C) to determine the flammability, (D) to assess the hardening rate.
A) to determine the bitumen content
The main purpose of the PAV test is (A) to simulate long-term aging of asphalts in service, (B) to evaluate the resistance of asphalts to pressure and vacuum, (C) to measure the low temperature characteristics of asphalts, or (D) to measure the rutting resistance of asphalts at high temperature.
A) to simulate long-term aging of asphalts in service
Describe what the following grades indicate: AC-30, AC-40, AC-5
AC-30 asphalt- Absolute Viscosity at 60 C: 3000 ±600 Poises AC-40 asphalt- Absolute Viscosity at 60 C: 4000 ±800 Poises AC-5 asphalt- Absolute Viscosity at 60 C: 500 ±100 Poises
Describe sand seal
An application of asphalt covered with fine aggregate. It may be used to improve skid resistance and/or to seal against air and water infiltration.
Describe fog seal
An application of diluted asphalt emulsion with no cover aggregate. A remedial or maintenance treatment for deteriorating surfaces, sealing and rejuvenating existing pavement surfaces.
What is road mix?
An asphalt course produced by mixing aggregate and asphalt at the road site by means of travel plants, motor graders, drags or special road-mixing equipment.
What is plant mix?
Asphalt mixture produced in an asphalt mixing plant. This can be done either hot or cold.
Describe medium curing (MC) cutback asphalt
Asphalt of intermediate hardness (300 -1200 P at 60 C or 120-250 Pen) dissolved in kerosene
Which asphalt material can be mixed with and coat a coarse aggregate easily without heating, and will also be resistant to washing after mixing? (A) RS asphalt emulsion. (B) MS asphalt emulsion. (C) SS asphalt emulsion. (D) AC-10.
B) MS asphalt emulsion - even if you wash with water will not be able to wash away because it has already set
he PI of an asphalt can be determined by running the following two tests: (A) Flash Point and Penetration. (B) Ring and Ball and Penetration. (C) Flash Point and Ductility. (D) Ductility and Absolute Viscosity.
B) Ring and Ball and Penetration
An AR-6000 grade asphalt cement has the following property: (A) The absolute viscosity of the original asphalt at 60 deg C is 6000 +- 1200 poises. (B) The absolute viscosity of the RTFOT residue at 60 deg C is 6000 +- 1500 poises. (C) The absolute viscosity of the original asphalt at 25 deg C is 6000 +- 1200 poises. (D) The absolute viscosity of the RTFOT residue at 25 deg C is 60,000 +-15,000 poises.
B) The absolute viscosity of the RTFOT residue at 60 deg C is 6000 +- 1500 poises. - AR grade is based on rolling thin film oven (RTFOT) residue - based on absolute viscosity which is measured at 60 deg - then +- 25%
Which of the following is the correct rolling sequence for compacting a thin hot-mix asphalt layer? (A) Transverse joint, longitudinal joint, initial rolling, outside edge, intermediate rolling, final rolling. (B) Transverse joint, longitudinal joint, outside edge, initial rolling, intermediate rolling, final rolling. (C) Initial rolling, transverse joint, longitudinal joint, outside edge, intermediate rolling, final rolling. (D) Initial rolling, intermediate rolling, transverse joint, longitudinal joint, outside edge, final rolling.
B) Transverse joint, longitudinal joint, outside edge, initial rolling, intermediate rolling, final rolling. - if thick layer to initial before edge - for thin edge comes first because worried about cooling too quickly
The most appropriate type of asphalt to be used for an open-graded cold asphalt mixture is (A) a RS emulsion, (B) a MS emulsion, (C) a SS emulsion, or (D) a soft asphalt cement.
B) a MS emulsion
Which one of the following is a component of a hot-mix batch plant but not in a drum mix plant? (A) Cold aggregate bins, (B) hot aggregate bins,(C) dust collector, or (D) asphalt cement storage tank.
B) hot aggregate bins
The Thin Film Oven Test (TFOT) is used to (A) measure the flexibility of an asphalt film, (B) to simulate the effects of heating during mixing and placement of a hot asphalt mixture, (C) to measure the temperature at which a asphalt becomes combustible, or (D) to measure the creep behavior of an asphalt.
B) to simulate the effects of heating during mixing and placement of a hot asphalt mixture
Define bitumen
Black or dark brown sticky substance composed principally of high-molecular-weight hydrocarbons soluble in Carbon Disulfide (CS2). Carbon Disulfide is now replaced by Trichloroethylene (CHCl:Cl2) in the solubility test (because carbon disulfide is known as a carcinogen.).
Describe the production of water gas
C + H20 ->(cracking) H2 + CO residue is tar
If an asphalt is graded as PG70-22, at what temperature would the Bending Beam Rheometer Test be run in specification testing of this asphalt? (A) 70 deg C. (B) 22 deg C. (C) -12 deg C. (D) -22 deg C.
C) -12 deg C
The most appropriate type of asphalt to be used for a prime coat is (A) a RS emulsion, (B) a MS emulsion, (C) a SS emulsion, or (D) a soft asphalt cement.
C) a SS emulsion- we want it to penetrate
In the U.S., "bitumen" is defined as a substance composed principally of high-molecular-weight hydrocarbons soluble in (A) gasoline, (B) benzene, (C) carbon disulfide, or (D) kerosene.
C) carbon disulfide
What are the two flash point tests?
Cleveland Open Cup and Tag Open Cup
Four different asphalts have four different Penetration Indexes as follows. Which one would you choose for use in paving applications? (A) -1.5. (B) 0. (C) +1.5. (D) +2.5.
D) +2.5- the higher the number the less temperature sensitive
An SS asphalt emulsion should pass which one of the following tests? (A) Demulsibility Test. (B) Stone Coating Test. (C) Flash Point Test. (D) Cement Mixing Test.
D) Cement Mixing Test.
In Superpave binder specification testing, at what aged condition would an asphalt be tested in the Bending Beam Rheometer Test? (A) Original asphalt. (B) RTFOT-aged residue. (C) TFOT-aged residue. (D) PAV-aged residue.
D) PAV-aged residue
Which one of the following statements is not true concerning the differences between asphalt and tar? (A) Tar does not occur in natural form. (B) Tar has a stronger odor than asphalt. (C) Tar is more hazardous to work with than asphalt. (D) Tar is more weather resistant than asphalt.
D) Tar is more weather resistant than asphalt.
According to the Superpave asphalt binder specification, an asphalt with a low S value as measured in the Superpave specification testing is expected to have a (A) high resistance to fatigue cracking, (B) high resistance to rutting, (C) low resistance to rutting, or (D) high resistance to low-temperature cracking
D) high resistance to low-temperature cracking
Which one of the following is not a dust control system in a hot-mix plant? (A) Cyclone, (B) wet scrubber, (C) baghouse, or (D) pugmill.
D) pugmill
The results of Saybolt Furol Viscosity Test are reported in units of (A) poises, (B) stokes, (C) pascal-seconds, or (D) seconds.
D) seconds
The function of the screed unit in a paver is (A) to provide moving power to the paver, (B) to strike off asphalt mix to specified thickness and smoothness, (C) to provide initial compaction to the asphalt mix, or (D) to strike off asphalt mix to specified thickness and smoothness, and to provide initial compaction to the asphalt mix,
D) to strike off asphalt mix to specified thickness and smoothness, and to provide initial compaction to the asphalt mix
How is delta measured?
Difference is shear stress and strain phases, the one further ahead is lagging (takes more time / cycle)
What properties are measured by the dynamic shear rheometer?
G* & delta
How is G* measured
G* = (tau max-tau min) / (gamma max-gamma min) tau- shear stress gamma- shear strain
What temperature does the dynamic shear rheometer use?
High and intermediate pavement temperatures.
What is the purpose of the Bending Beam Rheometer Test?
Measures stiffness of binders at low service temperatures.
What is the purpose of the direct tension test?
Measures the failure stress and failure strain of a binder after PAV at low service temperature.
What is the purpose of dynamic shear rheometer test?
Measures the viscoelastic properties of a binder by testing it in an oscillatory mode.
What is penetration macadam?
Pavement layer using coarse open-graded aggregate. It is made up of alternating layers of aggregate and binder.
Describe rapid curing (RC) cutback asphalt
Relatively hard asphalt (600 -2400 P at 60 C or 80-120 Pen) dissolved in gasoline
What is the purpose of the pavement aging vessel (PAV)?
Simulates long term (3-5 years) aging of binders in service
Describe slow curing (SC) cutback asphalt
Soft asphalt dissolved in diesel oil
What properties are measured by the Bending Beam Rheometer test?
Stiffness (S) & m (slope of log S versus log time)
How do you convert kinematic viscosity to absolute viscosity?
Stoke x (spec. gravity) = Poise
What are the required results of the direct tension test?
The failure strain in the direct tension test must be at least 1.0% at the test temperature (Tmin+ 10 °C) to meet the specification. The m-value requirement must be satisfied in both cases.
Describe the correct and the incorrect direction of travel of rollers for proper compaction of asphalt mixtures.
The proper direction of travel would be to have the dry wheel in the front. Improper direction would be doing the opposite of this.
What temperature is used for the Bending Beam Rheometer test?
Tmin+10 in Celsius
Describe multiple-pass surface treatment/ chip seal
Two or more applications of binder-aggregate.
What are the two main uses for gilsonite?
Used mainly in varnishes and paper where hard solid asphalt is required. Used also as an asphalt additive to improve rutting resistance of asphalt mixtures
What is the base made out of?
Usually of a granular material, such as crushed limestone. It can also be an asphalt mixture (i.e. an asphaltic base.)
What is the subbase made out of?
Usually of a granular material. In Florida, the subbase is called "stabilized subgrade", and is usually made by treating a subgrade soil with cement, lime or asphalt emulsion.
What are the three types of velocity tests?
absolute (poise), kinematic (stokes), and saybolt furol velocity tests
What are the two types of hot mix plants?
batch and drum mix
What is the advantage of using a hot plant mix as compared with a penetration macadam construction or road mix?
better uniformity and more stable mixtures; it is also more expensive
Describe the production of coke
bituminous coal->destructive distillation-> coke, gas, and tar
What is an emulsified agent?
colloidal mixture of asphalt cement, water and emulsifying agent.
What is the purpose of the solubility test?
determines the amount of Bitumen (in %) in an asphalt. Bitumen content should be close to 100%.
TRUE or FALSE conventional asphalt specifies properties after long-term aging in service?
false; superpave does
How is rock asphalt found and give and example
found impregnated in Sandstone or Limestone. e.g. Kentucky Rock Asphalt -occurs in Sandstone impregnated with asphalt.
Describe gilsonite and where it is mined
hard and brittle; mined in Utah
Does asphalt get harder or softer with time?
harder/ more brittle
What does a PI<-2 indicate?
high temperature susceptibility
Does asphalt cement need to be used hot or room temp?
hot
What does a PI>2 indicate?
low temperature susceptibility
What is the purpose of the ring and ball softening point test?
measures temperature at which asphalt reaches a certain softness ( Pen =800 )
What is is the purpose of the ductility test?
measures the distance a standard asphalt sample will stretch without breaking under a standard testing condition ( 5 cm/min at 25 C ).
3 main uses of bituminous materials?
road construction, roofing, waterproofing material
Which type of asphalt is used to surface highways?
rock asphalt
What is the order of pavement structure, from the top?
seal coal-> surface-> tack coat-> binder-> prime coat-> base-> subbase-> compacted subgrade-> natural subgrade
What should G*/sin(delta) be at the highest pavement temp?
should be greater than 1.0 kPa before aging and 2.2 kPa after RTFOT to control rutting.
What should G*/sin(delta) be at intermediate pavement temps?
should be less than 5000 kPa after PAV to control fatigue cracking.
Which are more expensive: superpave or conventional asphalt binder tests?
superpave
Which asphalt specifies low temperature properties superpave or conventional?
superpave
Which specifications specify the highest and lowest service temperatures superpave or conventional asphalt?
superpave
TRUE or FALSE Superpave requires the same properties, but at different testing temperatures. Conventional requires different properties, but at the same testing temperatures.
true
What are the surface and binder made of?
typically made of an asphalt mixture
