Exam 4
5. Describe the two common methods of manufacturing of tar.
(1) By-product of coke production: bituminous coal goes through destructive distillation process (Decomposition of a solid by heating it in a closed container in the absence of oxygen) that creates coke and gas and therefor tar. (2) By-product of water gas production
ACCEPTANCE OF FINISHED PAVEMENT MAT 10. 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 REQUIREMENT 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)
4. Describe the basic procedure and function of the following surface treatments: MULTIPLE-PASS SURFACE TREATMENT
(Chip Seal) Two or more applications of binder-aggregate.
4. Describe the basic procedure and function of the following surface treatments: SINGLE-PASS SURFACE TREATMENT
(Chip Seal) a thin asphalt aggregate application applied to an existing surface or base.
ASPHALT CEMENTS 1. Describe (A) the purpose of the test, (B) how the test results are reported, and (C) the meaning or significance of the test results for each of the following tests on asphalt cement: (i) Penetration
(i) Penetration A. A consistency test used to identify an asphalt as to its hardness or grades. B. Results are reported in "pen." (i.e. 10 pen = 1 mm; 85 pen = 8.5 mm) C. Less pen means that it is a harder asphalt. More pen means softer asphalt.
ASPHALT CEMENTS 1. Describe (A) the purpose of the test, (B) how the test results are reported, and (C) the meaning or significance of the test results for each of the following tests on asphalt cement SOLUBILITY
(vi) Solubility A. Determines the amount of Bitumen (in %) in an asphalt. Bitumen content should be close to 100% B. Results are reported in percentage of Bitumen. C. The greater the amount of Bitumen, the stronger it is
ASPHALT CEMENTS 1. Describe (A) the purpose of the test, (B) how the test results are reported, and (C) the meaning or significance of the test results for each of the following tests on asphalt cement ABSOLUTE VISCOSITY
(vii) Absolute viscosity A. Used to test viscosity B. Measures in units of Poises (P) [ Poise = dyne-sec / cm2 = 0.1 Pa-s ]
ASPHALT CEMENTS 1. Describe (A) the purpose of the test, (B) how the test results are reported, and (C) the meaning or significance of the test results for each of the following tests on asphalt cement KINEMATIC VISCOSITY
(viii) Kinematic viscosity A. Used to test viscosity B. Measures in units of Stokes (St) [ Stoke = cm2 ]
ASPHALT CEMENTS 1. Describe (A) the purpose of the test, (B) how the test results are reported, and (C) the meaning or significance of the test results for each of the following tests on asphalt cement RING AND BALL SOFTENING POINT
(x) Ring and ball softening point A. Measures temperature at which an asphalt reaches a certain softness (Pen = 800) B. Results are reported in temperature susceptibility C.
4. Describe the three commonly used dust control systems for hot-mix plants.
-Cyclone Dust Collector -Wet Scrubber Dust Collector -Baghouse Dust Collector
3. Describe the flow of materials in a drum mix plant operation. Describe also the main components of a drum mix plant and their functions.
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
2. Describe the flow of materials in the production of a hot asphalt mixture in a batch plant. Describe also the main components of a batch plant and their functions.
1. Cold Process 2. Drying, Dust Collecting 3. Exhaust Stack 4. Hot elevator 5. Screening Unit 6. Hot Bins 7. Weigh Box 8. Mixing Unit 9. Mineral filter storage 10. Hot asphalt cement storage 11. Asphalt weigh bucket
Describe the characteristics and usages of the following natural asphalts LAKE ASPHALT
1. LAKE ASPHALT - occurs in form of a lake (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
2. What are the three main types of cutback asphalts
1. Rapid Curing (RC) 2. Medium Curing (MC) 3. Slow Curing (SC)
3. What are the differences among the three types of cutback asphalt in terms of (A) the solvent, and (B) the base asphalt used?
1. Rapid Curing (RC) a. Dissolved in gasoline b. Relatively hard asphalt (600-2400P @ 60 °C or 80-120 Pen) 2. Medium Curing (MC) a. Dissolved in Kerosene b. Asphalt of intermediate hardness (300-1200P @ 60 °C or 120-250 Pen) 3. Slow Curing (SC) a. Dissolved in diesel oil b. Soft asphalt (Kinematic viscosity of asphalt residue from SC - 70 = 4 - 70 St at 60 °C)
7. Describe 3 major types of roller for compaction of asphalt mixtures in terms of their (A) wheel or roller configurations, (B) applied loads and compaction mechanism, and (C) usages.
1. STEEL-TIRED TANDEM ROLLER (A) Two-axle steel rollers (B) 3 to 14 tons (2.7 to 13 Mg) or more (C) 250 lb/in (4470 kgf/m) (D) Proper direction of travel drive wheel ahead of the tiller wheel 2. PNEUMATIC TIRED ROLLER (A) 3 to 4 tires on front axle 4 to 5 tires on rear axle For compaction rolling (B) 10 to 35 tons (9 to 32 Mg) weight per wheel: 3,000 to 3,500 lbs. (680 to 910 kg) (C) 20 in. (51 cm) minimum wheel diameter (D) Tire pressure 70 to 75 psi when cold 90 psi when hot 3. VIBRATORY ROLLER (A) Compaction by weight and vibration (B) 7 to 17 tons (6 to 15 Mg) (C) 2,000 to 3,000 vibrations per minute
3. Describe the (A) typical materials used, (B) relative position in the pavement structure, and (C) Main functions of the following layers in a conventional asphalt pavement structure: SEAL COAT
1. Seal coat A. Fog Seal, Slurry Seal, Sand Seal. B. Top of the pavement structure. C. A thin surface treatment used to improve the texture of and waterproof an asphalt surface. Seal coats may or may not be covered with aggregate.
Describe the characteristics and usages of the following natural asphalts ROCK ASPHALT
2. ROCK ASPHALT - found impregnated in Sandstone or Limestone. E.g. Kentucky Rock Asphalt - occurs in Sandstone impregnated with asphalt. - It is blended to 7% asphalt and crushed to sand grain sizes and used as a surfacing material for highway. - It has good skid resistance.
3. Describe the (A) typical materials used, (B) relative position in the pavement structure, and (C) Main functions of the following layers in a conventional asphalt pavement structure: SURFACE
2. Surface A. Asphalt mixture B. Under the Seal Coat in the pavement structure C. Holds the most amount of stress
3. Describe the (A) typical materials used, (B) relative position in the pavement structure, and (C) Main functions of the following layers in a conventional asphalt pavement structure: TACK COAT
3. Tack coat A. Asphalt B. Between the Surface and Binder C. An application of asphalt to ensure bond between two asphalt layers.
3. Describe the (A) typical materials used, (B) relative position in the pavement structure, and (C) Main functions of the following layers in a conventional asphalt pavement structure: BINDER
4. Binder A. Asphalt mixture B. Under the Tack Coat in the pavement structure
3. Describe the (A) typical materials used, (B) relative position in the pavement structure, and (C) Main functions of the following layers in a conventional asphalt pavement structure: PRIME COAT
5. Prime coat A. Low viscosity liquid asphalt B. Under Binder and above the Base layer C. 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.
3. Describe the (A) typical materials used, (B) relative position in the pavement structure, and (C) Main functions of the following layers in a conventional asphalt pavement structure: BASE
6. Base A. Granular material or asphalt mixture (i.e. Crushed limestone or Asphaltic base) B. Under the Prime Coat
3. Describe the (A) typical materials used, (B) relative position in the pavement structure, and (C) Main functions of the following layers in a conventional asphalt pavement structure: SUBBASE
7. Subbase A. Granular material B. Under the Base layer C. In Florida, the subbase is called "stabilized subgrade", and is usually made by treating a subgrade soil with cement, lime or asphalt emulsion.
CUTBACK ASPHALTS 1. What is a cutback asphalt?
A liquid asphalt made by dissolving an asphalt in a petroleum solvent.
4. Describe the basic procedure and function of the following surface treatments: SLURRY SEAL
A mixture of emulsified asphalt and fine aggregate in the form of a slurry, used to seal cracks on an asphalt surface.
2. What are the differences between an anionic and a cationic emulsified asphalt in terms of (A) electric charges of asphalt droplets, (B) compatibility with aggregate, and (C) emulsifying agent?
A. Anionic emulsified asphalts are negatively charged while cationic emulsified asphalts are positively charged. B. Anionic emulsified asphalts are more compatible with aggregates with positive surface charges (such as limestone). Cationic emulsified asphalts are more compatible with aggregates with negative surface charges (such as siliceous aggregates). C. Typical emulsifying agents for anionic emulsified asphalts are fatty acids. Typical emulsifying agents for cationic emulsified asphalts are fatty amines.
ASPHALT CEMENTS 1. Describe (A) the purpose of the test, (B) how the test results are reported, and (C) the meaning or significance of the test results for each of the following tests on asphalt cement FLASH POINT
A. Determines temperature to which an asphalt can be safely heated in the presence of an open flame. B. Results are reported in temperature
ASPHALT CEMENTS 1. Describe (A) the purpose of the test, (B) how the test results are reported, and (C) the meaning or significance of the test results for each of the following tests on asphalt cement SOLUBILITY
A. Determines the amount of Bitumen (in %) in an asphalt. Bitumen content should be close to 100% B. Results are reported in percentage of Bitumen. C. The greater the amount of Bitumen, the stronger it is
ASPHALT CEMENTS 1. Describe (A) the purpose of the test, (B) how the test results are reported, and (C) the meaning or significance of the test results for each of the following tests on asphalt cement ROLLING THIN FILM OVEN
A. Laboratory procedure to stimulate the effects of heating during mixing and placement of hot mix. B. Results are not reported C. To determine how hard the asphalt
ASPHALT CEMENTS 1. Describe (A) the purpose of the test, (B) how the test results are reported, and (C) the meaning or significance of the test results for each of the following tests on asphalt cement THIN FILM OVEN
A. Laboratory procedure to stimulate the effects of heating during mixing and placement of hot mix. B. Results are not reported C. To determine how hard the asphalt is
ASPHALT CEMENTS 1. Describe (A) the purpose of the test, (B) how the test results are reported, and (C) the meaning or significance of the test results for each of the following tests on asphalt cement SAYBOLT FUROL VISCOSITY
A. Mainly in measuring viscosity of emulsified asphalt B. Report results in seconds C.
ASPHALT CEMENTS 1. Describe (A) the purpose of the test, (B) how the test results are reported, and (C) the meaning or significance of the test results for each of the following tests on asphalt cement DUCTILITY
A. Measures the distance a standard asphalt sample will stretch without breaking under a standard testing condition ( 5 cm/min at 25 C ) B. Report specimen in distance (cm or in) at which it breaks C. The higher the distance at which it breaks, the more ductile it
FUNDAMENTALS OF ASPHALT PAVEMENT STRUCTURE 1. Describe the basic functions of a pavement structure
A. To provide a smooth and safe driving surface B. To protect the subgrade from frost action. C. To protect the subgrade from permanent deformation
3. What are the advantages and disadvantages of using a road mix as compared with using a plant mix in asphalt paving?
Advantages: Lower equipment and construction cost Disadvantages: Less uniform and stable mixtures are produced.
4. Describe the basic procedure and function of the following surface treatments: 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.
4. Describe the basic procedure and function of the following surface treatments: FOG SEAL COAT
An application of diluted asphalt emulsion with no cover aggregate. A remedial or maintenance treatment for deteriorating surfaces, sealing and rejuvenating existing pavement surfaces.
1. What is an emulsified asphalt?
An emulsified asphalt is a colloidal mixture of asphalt cement, water, and emulsifying agent.
HOT-MIX PLANTS 1. What are the main differences between an asphalt batch plant and a drum mix plant? What are the possible advantages and disadvantages of each type of plant?
Batch Plant -Produces one Batch at a time -Dries and heats the aggregate in a dryer, and mixes the aggregate and asphalt in a separate mixer DRUM MIX PLANT -Produces mixes in a continuous process -Dries the aggregate and blends it with asphalt in the same piece of equipment
2. What is the advantage of using a hot plant mix as compared with a penetration macadam construction?
Better uniformity and more stable mixtures.
Describe the differences between asphalt and tar
Differences: (1) Distinguished by odor (tar has an aromatic odor). (2) The insoluble portion in natural asphalt is mineral matter, while the insoluble 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. 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.
9. Describe the proper rolling sequence in compaction of thick and thin lifts of asphalt mats.
FOR THICK LIFTS (1) TRANSVERSE JOINTS Rolling transversely with static steel-wheel roller (2) LONGITUDINAL JOINTS (3) INITIAL ROLLING (4) OUTSIDE EDGE (5) INTERMEDIATE ROLLING (6) FINISH ROLLING FOR THIN LIFTS, DO STEP (4) BEFORE (3)
4. What is the range of penetration index of a normal paving asphalt cement? What is the meaning of a high or a low penetration index?
For normal paving asphalt cement, the penetration index = -2 - 2. A high penetration index means the asphalt is low temperature sensitive and a low penetration index means the asphalt is high temperature sensitive.
4. Describe the meaning of G* and δ as measured by the Dynamic Shear Rheometer.
G* measures the stiffness. It is run at high temperature it measures asphalt's resistance to rutting (We want a high stiffness, therefore we want a high G*). δ is the phase shift/angle at which it is out of phase. We want δ = 0.
5. What does G*/sin(δ) of an asphalt at high service temperature measure? What should G*/sin(δ) be in order to have satisfactory performance at high service temperature?
G*/sin(δ) of an asphalt at high service temperature measures the ability of the asphalt to rut. We want to make sure the asphalt WON'T rut. G*/sin(δ) should be greater than 1.0 kPa before aging and 2.2 kPa after RTFOT to control rutting.
6. What does G*sin(δ) of an asphalt at intermediate service temperature measure? What should this value be in order to have satisfactory performance?
G*sin(δ) measures the ability to crack due to fatigue. We want to make sure the asphalt WON'T crack due to fatigue at intermediate temperatures. G*sin(δ) should be less than 5000 kPa after PAV to control fatigue cracking.
Describe the characteristics and usages of the following natural asphalts GILSONITE
GILSONITE - Hard and brittle Asphalt mined in Utah. - Used mainly in varnishes and paper where hard solid asphalt is required. - Used also as an asphalt additive to improve rutting resistance of asphalt
7. What is the purpose of the Bending Beam Rheometer test?
Measures stiffness of binders at low service temperatures.
11. What is the purpose of the Direct Tension test?
Measures the failure stress and failure strain of a binder at low service temperature
3. What is the purpose of the Dynamic Shear Rheometer test?
Measures the viscoelastic properties of a binder by testing it in an oscillatory mode. Tests high and intermediate pavement temperatures.
3. Describe the differences in the setting and mixing characteristics of Rapid-Setting (RS), Medium-Setting (MS) and Slow-Setting (SS) asphalt emulsions. Describe also the three tests that can be used to differentiate among these three types of asphalt emulsion based on their setting and mixing characteristics. Medium Setting
Medium Setting (MS) A. Good mixing characteristic with coarse aggregate. B. Can be demulsified by a relatively large amount of Calcium Chloride. C. Stone Coating Test - Run on a MS Emulsion to ensure (1) good coating of aggregate, (2) ability to be mixed, and (3) resistance to washing action after mixing.
13. How is the Superpave binder specification different from the conventional asphalt specifications, such those for the AC grade and AR grade asphalts?
PG-64-22 PG = Performance Grade 64 = Maximum Pavement Temperature @ 64 ºC 22 = Minimum Pavement Temperature @ -22 ºC
ASPHALT PAVEMENT CONSTRUCTION 1. Describe the basic procedure in a Penetration Macadam construction. If an asphalt emulsion is to be used, which type would be the most appropriate to be used?
Pavement layer using coarse open-graded aggregate, it is made up of alternating layers of aggregate and binder. 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. Final rolling **Medium Setting
5. What are the three commonly used methods for grading of asphalt cements? Describe (A) the tests used, and (B) the nomenclature used to denote the different grades for each grading 2 method. Give an example for each method.
Penetration Grading -Five penetration grades specified: 40-50 60-70 85-100 120-150 200-300 -Example: Thin film oven AC Grading - Viscosity grading - AC-2.5 - AC-5 - AC-10 - AC-20 - AC-40 AR Grading - for properties after mixing - AR 1000 - AR 2000 - AR 4000 - AR 8000 - AR 16000
3. Describe the differences in the setting and mixing characteristics of Rapid-Setting (RS), Medium-Setting (MS) and Slow-Setting (SS) asphalt emulsions. Describe also the three tests that can be used to differentiate among these three types of asphalt emulsion based on their setting and mixing characteristics. RAPID SETTING
Rapid-Setting (RS) A. Sets rapidly B. High demulsibility - It can be demulsified by adding a small amount of calcium chloride, (for cationic emulsions, Dioctyl sodium sulfosuccine) C. Demulsibility Test - Run on RS Emulsions to ensure that the emulsions will break (or DEMULSIFY) easily (upon contact with aggregates
10. Describe the meaning of S and m values as measured by the Bending Beam Rheometer test. What should these two values be in order to have satisfactory performance?
S is the creep stiffness at a given time. M is the slope of log S versus log time plot. We want to have a LOW value for S and a HIGH value for m. In order to have satisfactory performance it is required that S should be less than 300 MPa, and m-value should be greater than 0.3 at 60 seconds at the test temperature (T_min+10 C), in order to reduce low-temperature cracking at T_min.
Describe the similarities between asphalt and tar
Similarities: (1) Composed principally of Bitumen. (2) Black or dark brown in color. (3) Cementitious. (4) Water repellent
3. Describe the differences in the setting and mixing characteristics of Rapid-Setting (RS), Medium-Setting (MS) and Slow-Setting (SS) asphalt emulsions. Describe also the three tests that can be used to differentiate among these three types of asphalt emulsion based on their setting and mixing characteristics. SLOW SETTING
Slow Setting (SS) A. Sets slowly B. Very stable (it does not demulsify easily) C. Cement Mixing Test - Run on SS Emulsions to ensure its stability.
9. At what temperature is the Bending Beam Rheometer test run, and why?
The Bending Beam Rheometer is run at a test temperature of: T_min+10 C. The reason for this being, is because at low temperatures, cracking occurs. In order to avoid cracking, we add an addition ten degrees.
8. Describe how a test specimen is loaded in the Bending Beam Rheometer test, and what properties are measured in this test.
The asphalt is put onto a rectangular prism of measurements: 12.5mm x 6.25mm x 125mm with a distance between supports of 102mm. Then, a 100g force is applied to the middle of the beam for a total of 240 seconds. The properties measured are the stiffness (S) and the slope of log S versus log time (m).
2. What is the main difference between the Cleveland Open Cup and the Tag Open Cup flash point tests?
The main difference between the Cleveland Open Cup and the Tag Open Cup flash point tests is that the Tag Open Cup is heated by water and the maximum temperature is 100 ºC.
6. What is the main purpose of compaction of asphalt mixtures in pavement construction? What are the possible consequences of improper compaction of an asphalt mixture during construction?
The main purpose of compaction of asphalt mixtures in pavement construction is to compress a given volume of asphalt mix into a smaller volume, resulting in a more stable and durable mix. If this is done improperly, there will be gaps causing holes and cracks.
ASPHALT PAVING 5. Describe the major functions of the power unit and the screed unit in an asphalt paver.
The power unit provides moving power to the paver. The screed unit strikes off the mix to the specified thickness and smoothness and provides initial compaction.
8. 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.
SUPERPAVE ASPHALT BINDER TESTS AND SPECIFICATIONS 1. What is the purpose of the Pressure Aging Vessel (PAV) procedure?
The purpose of the Pressure Aging Vessel is to stimulate long term (3-5 years) aging of binders in service.
12. What results are reported by the Direct Tension test? What should the result be in order to have satisfactory performance?
The results reported by the Direct Tension test are strain and stress. The failure strain in the direct tension test must be at least 1.0% at the test temperature (T_min+10 C) to meet the specification. The m-value requirement must be satisfied in both cases.
2. What is a typical vertical stress distribution in a pavement structure due to a wheel load? How is it considered in the design of a conventional asphalt pavement structure?
The strongest parts go on the top. From top to bottom: 1. Seal Coat 2. Surface 3. Tack Coat 4. Binder 5. Prime Coat 6. Base 7. Subbase 8. Compacted Subgrade 9. Natural Subgrade
4. What are the typical usages of RS, MS and SS asphalt emulsions in pavement construction?
We want RS for fixing roads, we want SS for making foundations, and we want MS for things that won't take too much time.
2. Describe the PAV test apparatus and procedure.
a cylinder with 8 pans for the asphalt to sit in. It subjects the asphalt to high heat and pressure for 20 hrs to simulate aging in the asphalt.
4. Describe how asphalts are manufactured from petroleum crude oils.
everything is extracted from crude oil. Left over materials is partly asphalts.
6. What are the desirable properties of an asphalt cement to be used in asphalt pavement?
high viscosity=does not flow low viscosity=it does flow