Civ Mat Final

Describe the correct and the incorrect direction of travel of rollers for proper compaction of asphalt mixtures.

Correct: travel with its larger wheel (drive wheel) in front, small wheel (tiller wheel) in back

Differences b/w asphalt and tar (3)

(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.

What are the three commonly used methods for grading of asphalt cements? Describe (A) the tests used (B) the nomenclature used to denote the different grades for each grading method. Give an example for each method.

(1) grading by penetration at 25 C A) penetration test B) AC-20 would have an absolute viscosity of around 2,000 poises at 60 C (2) grading by absolute viscosity at 60 C A) flash point, ductility, TFOT B) (3) grading by absolute viscosity of aged asphalt residue after the rolling thin film oven test (RTFOT) procedure A) RTFOT B) AR-6000 would have an aged residue with an absolute viscosity of around 6000 poise

What are the most suitable grades of asphalt cements and/or asphalt emulsions for the surface treatments listed above? Explain the reasons for choosing them.

(A) Single-pass surface treatment (B) Multiple-pass surface treatment (C) Fog seal coat (D) Slurry seal (E) Sand seal

Describe the basic procedure and function of the following surface treatments: (A) Single-pass surface treatment (B) Multiple-pass surface treatment (C) Fog seal coat (D) Slurry seal (E) Sand seal

(A) Single-pass surface treatment thin asphalt agg applied to existing surface/base (B) Multiple-pass surface treatment >= 2 applications of binder-agg (C) Fog seal coat diluted asphalt w no cover agg, used for maintaining, sealing, and rejuvenating existing pavement (D) Slurry seal emulsified asphalt and fine agg, seals cracks (E) Sand seal asphalt coverd w fine agg, improve skid resistance, air seal

What is the range of penetration index of a normal paving asphalt cement? What is the meaning of a high ora low penetration index?

-2 to 2 high PI indicates low temperature susceptibility. those with a PI of less than -2 are of excessively high temperature susceptibility.

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?

1 first agg application 2 first rolling 3 first binder application 4 second agg application 5 second rolling 6 second binder application 7 third agg application 8 final rolling RS 1 and RS 2

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 (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)

Describe the basic functions of a pavement structure. (3)

1. Provide smooth and safe driving surface 2. Protect subgrade from frost action 3. protect subgrade from permanent deformation

What is an emulsified asphalt?

A colloidal mixture of asphalt cement, water and emulsifying agent.

Describe the characteristics and usages of the following natural asphalts: (A)Lake asphalt (B)Rock asphalt (C)Gilsonite

A) B) found in sandstone or limestone -used as a surfacing material for highway. - It has good skid resistance. C) hard and brittle, from 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 mixtures

Describe (A) the purpose of the test (B) how the test results are reported (C) the meaning or significance of the test results for each of the following tests on asphalt cement: (G) Absolute viscosity (H) Kinematic viscosity (I) Saybolt Furol viscosity (J) Ring and ball softening point

Abs Visc a) viscosity of an asphalt at std 60 deg C b) units of Poise c) viscosity of the asphalt at the maximum temperature a pavement is likely to experience in most parts of the United States. Kinematic visc a) high temp visc b) Stokes or centi-Stokes c) represents the viscosity of the asphalt during mixing and placement of a hot mix. Saybolt Furol a) visc at 50 C b) seconds c) used mainly in measuring viscosity of emulsified asphalt. Ring and ball softening point a) temperature at which an asphalt reaches a certain softness. (pen = 800) b) celsius c) can be used along with the penetration to determine the temperature susceptibility of an asphalt

An AR-6000 grade asphalt cement has the following property:

Absolute viscosity of 6000 poises at 60 C

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 (C) emulsifying agent?

Anionic a) - b) + charged (calcareous) c) fatty acids Cationic a) + b) - charged (siliceous) c) fatty amines

Describe the water sensitivity test used in the Superpave Volumetric design procedure.What criteria must the mix design meet in order to be accepted.

Average tensile strengths of the conditioned specimens divided by that of the control specimen should be greater than 80%.

What are the main differences between an asphalt batch plant and a drum mixplant? What are the possible advantages and disadvantages of each type of plant? (3)

Batch Advantages highest level of flexibility in production. high-quality finished product due to accurate of measurement can easily switch back and forth between different mix recipes if necessary. Drum advantages There is no interruption in the production process, which creates a homogeneous mixture that can be manufactured at a high rate (sometimes as high as 600-800 tons per hour). Batch plants make small accurate "batches" of asphalt mixture until the total tonnage has been manufactured.Drum plants prep the asphalt through a continuous process use silos for temporary storage prior to the mix being trucked to the paving location. In batch plants, the aggregate is dried first and then weighted into the pugmill. In drum plants the drying and mixing are done in conjunction in the drum plant In batch plants, the pugmill uses arms with paddles attached to them, thus creating a forced or physical mixing of the components. Also, the batch times can be adjusted to facilitate more mixing of the materials when necessary. In a drum plant, the material is rotated and moved which creates a falling curtain of material. The only practical way to lengthen this process is to slow down the production rate of the plant.

What are the main differences between an asphalt batch plant and a drum mixplant? What are the possible advantages and disadvantages of each type of plant? (3)

Batch plants make small accurate "batches" of asphalt mixture until the total tonnage has been manufactured.Drum plants prep the asphalt through a continuous process use silos for temporary storage prior to the mix being trucked to the paving location. In batch plants, the aggregate is dried first and then weighted into the pugmill. In drum plants the drying and mixing are done in conjunction in the drum plant In batch plants, the pugmill uses arms with paddles attached to them, thus creating a forced or physical mixing of the components. Also, the batch times can be adjusted to facilitate more mixing of the materials when necessary. In a drum plant, the material is rotated and moved which creates a falling curtain of material. The only practical way to lengthen this process is to slow down the production rate of the plant.

An SS asphalt emulsion should pass what test?

Cement Mixing Test

What is the main difference between the Cleveland Open Cup and the Tag Open Cup flash point tests?

Cleveland used on asphalts w higher flashpoints Tag used on asphalts w flashpoints below 79 C

Describe the four consensus aggregate properties specified in the Superpave Volumetric mix design method.For each of the consensus properties, describe (A) the test used (B) the test results reported (C) the meaning of the test results (D) the Superpave requirements for these test results.

Coarse Aggregate Angularity A) % particles with 1 or more crushed faces &% particles with 2 or more crushed faces B) % C) D) Fine Aggregate Angularity A) Uncompacted void content test B) C) D) Flat and Elongated Particles A) minimum dimension ratio of 5 to 1. B) C) D) Clay Content A) B) C) D)

The main purpose of the Solubility Test on asphalt is

Determines amount of bitumen (as a %) in asphalt. Should be close 100%

What does G*sin(δ) of an asphalt at intermediate service temperature measure? What should this value be in order to have satisfactory performance?

Fatigue cracking value of less than 5000 kPa at a specified intermediate pavement temperature.

Which solvent is usually used in producing a RC cutback asphalt?

Gasoline

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

High resistance to low temp cracking

Which one of the following is a component of a hot-mix batch plant but not in a drum mix plant?

Hot mix bins

The most appropriate type of asphalt to be used for an open-graded cold asphalt mixture is

MS

Which asphalt material can be mixed with and coat a coarse aggregate easily without heating, and will also be resistant to washing after mixing?

MS emulsion

In Superpave binder specification testing, at what aged condition would an asphalt be tested in the Bending Beam Rheometer Test?

PAV-aged residue

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.

PI = - 2 to +2 normal asphalt PI > 2 low temp. susceptibility PI < -2 high temp. susceptibility

Describe (A) the purpose of the test (B) how the test results are reported (C) the meaning or significance of the test results for each of the following tests on asphalt cement: (A) Penetration (B) Flash point (C) Ductility

Penetration a) measures the consistency (hardness) of an asphalt at a specified test condition b) units of 0.1 mm (or penetration unit) c) softer asphalt will have a higher penetration, while a harder asphalt will have a lower penetration. used to designate grades of asphalt cement, and to measure changes in hardness due to age hardening or changes in temperature. Flash Point a) determines the temperature to which an asphalt can be safely heated in the presence of an open flame b) temperature (celsius) c) test results have been related to the hardening potential of asphalt. An asphalt with a high flash point is more likely to have a lower hardening potential in the field. Ductility a) Distance a standard asphalt sample will stretch without breaking under a standard testing condition b) cm c) very low ductility will have poor adhesive properties and thus poor performance in service

What is the advantage of using a hot plant mix as compared with a penetration macadam construction?

Plant mix: Pros: more uniform and stable Cons: equipment and construction cost Pen. Macadam mix: Pros: low equipment and construction cost Cons: less uniform and stable

What are the advantages and disadvantages of using a road mix as compared with using a plant mix in asphalt paving?

Plant mix: Pros: more uniform and stable Cons: equipment and construction cost Road mix: Pros: low equipment and construction cost Cons: less uniform and stable

Describe the major functions of the power unit and the screed unit in an asphalt paver.

Power: Provides moving power to the paver Screed: Strikes off the mix to the specified thickness and smoothness and provides initial compaction

Describe the two primary dust control systems and two secondary dust control systems for hot-mix plants.

Primary: knockout box cyclone Secondary: wet scrubber baghouse dust collector

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.

RS Test: demulsibility little to no ability to mix w agg fast setting, spray application MS Test: Stone coating good for mixing w coarse agg SS Test: Cement mixing good w fine agg

What are the typical usages of RS, MS and SS asphalt emulsions in pavement construction?

RS: Penetration Macadam, tack coat, single/multi pass surface treatment, sand seal MS: Cold plant open graded mix, road mix open graded SS: cold plant dense graded mix, road mix dense graded, slurry seal, fog seal

What are the desirable properties of an asphalt cement to be used in asphalt pavement? (8)

Resistance to permanent deformation Fatigue resistance Resistance to low temperature cracking. Durability Resistance to moisture-induced damage. Skid resistance. Workability Low noise and good drainage properties

The PI of an asphalt can be determined by running the following two tests

Ring and Ball Softening Point Test Penetration Test

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 = creep stiffness at time t, should be less than 300 MPa to control low-temperature cracking high m value = asphalt creep at a faster rate to reduce the thermal stress => more desirable to reduce low-temperature cracking.

The most appropriate type of asphalt to be used for a prime coat

SS

Describe the (A) typical materials used, (B) relative position in the pavement structure (C) main functions of the following layers in a conventional asphalt pavement structure: (A) Seal coat (B) Surface (C) Binder (D) Tack coat (E) Prime coat (F) Base (G) Subbase

Seal: improve texture, waterproof, SS or RS surface: asphalt mix tack: bond two asphalt layers, RS or SS binder: asphalt mix prime: penetrates into base to plug voids and help bonding, SS base: granular material (limestone) or asphalt mix subbase: granular material, treating subgrade soil w cement, lime or asphalt emulsion

What other source aggregate properties may be required for a Superpave mix?

Soundness, Toughness and Deleterious Materials

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 (C) usages.

Steel tired tandem roller a) two axle steel b) c) pneumatic tired roller a) 3 to 4 tires on front axle, 4 to 5 tires on rear axle b) c) vibratory roller a) b) compaction by vibration c)

How is the Superpave binder specification different from the conventional asphalt specifications, such those for the AC grade and AR grade asphalts? (5)

Superpave spec. specify min and max temp. Conventional spec. does not. •Superpave requires the same properties, but at different testing temperatures. Conventional requires different properties, but at the same testing temperatures. •Superpave specifies properties after long-term aging in service. Conventional does not. •Superpave binder tests are more costly to run. •Superpave spec. is still not well established and is still being modified.

Describe (A) the purpose of the test (B) how the test results are reported (C) the meaning or significance of the test results for each of the following tests on asphalt cement: (D) Thin film oven (E) Rolling thin film oven (F) Solubility

TFOT a) simulate the effects of heating in a hot-mix plant operation on an asphalt cement. b) changes in physical properties c) properties of the hardened asphalt in service RTFOT same as TFOT but a larger number of samples can be tested at the same time, and less time is required to perform the test. Solubility a) Bitumen content of a bituminous material is measured by means of its solubility in carbon disulfide. b) bitumen content as a percentage of the weight of the original asphalt. c) contamination in asphalt cement.

Which of the following is the correct rolling sequence for compacting a thin hot-mix asphalt layer?

TRANSVERSE JOINTS LONGITUDINAL JOINTS OUTSIDE EDGE INITIAL ROLLING INTERMEDIATE ROLLING FINISH ROLLING

Describe how a test specimen is loaded in the Bending Beam Rheometer test, and what properties are measured in this test.

The test specimen is to be submerged in a temperature-controlled fluid bath and to be simply supported between supports Beam deflection is measured after a vertical load is applied to the middle of the beam

Describe the proper rolling sequence in compaction of thick and thin lifts of asphalt mats.

Thick (1) TRANSVERSE JOINTSRolling transversely with static steel-wheel roller (2) LONGITUDINAL JOINTS (3) INITIAL ROLLING (4) OUTSIDE EDGE (5) INTERMEDIATE ROLLING (6) FINISH ROLLING Thin (1) TRANSVERSE JOINTSRolling transversely with static steel-wheel roller (2) LONGITUDINAL JOINTS (4) OUTSIDE EDGE (3) INITIAL ROLLING (5) INTERMEDIATE ROLLING (6) FINISH ROLLING

In the U.S., "bitumen" is defined as

a substance composed principally of high-molecular-weight hydrocarbons soluble in Carbon disulfide

What results are reported by the Direct Tension test? What should the result be in order to have satisfactory performance?

amount of elongation at failure (distance measurement) the failure strain at this condition should not be less than 1% in order to control low temperature cracking.

Describe the PAV test apparatus and procedure.

asphalt samples that have gone thru RTFOT are heated in PAV apparatus, aged for 20 hrs

Describe how the results of the ring and ball softening point test and penetration test can be used to measure the penetration index of an asphalt?

both used to calculate penetration index PI

The results of the standard Ductility Test on asphalt are reported in units of

cm

Describe the two common methods of manufacturing of tar.

coke production and watergas

Describe the meaning of G* and δ as measured by the Dynamic Shear Rheometer.

complex shear modulus, G*, and the phase angle, δ.

The Tag Open Cup flash point test can be used on which asphalts?

cutback asphalts or asphalts with flash points of less than 79 C.

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?

flexible pavements distribute wheel load over a wider surface through grain to grain contact

Describe the aggregate gradation requirements for a Superpave mix.

gradation must pass through certain control points at nominal maximum, 2.36 mm (#8) and 75 μm(#200).

What is a cutback asphalt?

liquid asphalt which is a blend of asphalt and petroleum solvents can be mixed and placed with little or no application of heat.

What is the purpose of the Bending Beam Rheometer test?

measure the stiffness of asphalts at low service temperatures.

What is the purpose of the Direct Tension test?

measures the stress-strain characteristics of an asphalt binder in direct tension at low temperature.

What is the purpose of the Dynamic Shear Rheometer test?

measures the viscoelastic properties of an asphalt binder by testing it in an oscillatory mode.

What does G*/sin(δ) of an asphalt at high service temperature measure? What should G*/sin(delta) be in order to have satisfactory performance at high service temperature?

permanent deformation greater than 1.0 kPa before aging and 2.2 kPa after the RTFOT process

Describe how the design asphalt content is selected in the Superpave Volumetric design method.Describe all the mix criteria that a Superpave mix must satisfy in order to be accepted.

prep diff asphalt contents, age them, compact them in a gyratory compactor % asphalt at 4% air void. This is the design asphalt content.

Which one of the following is nota dust control system in a hot-mix plant?

pugmill

What are the three main types of cutback asphalts?

rapid curing medium curing slow curing

What are the differences among the three types of cutback asphalt in terms of (A) the solvent, and (B) the base asphalt used?

rapid curing dissolved in gasoline hard asphalt medium curing kerosine solvent intermed. asphalt slow curing low volatility oil soft asphalt

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?

resulting in a more stable and durable mix.

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? (6)

resulting in a more stable and durable mix. decreased stiffness, reduced fatigue life, accelerated aging/decreased durability, rutting, raveling, and moisture susceptibility

The results of Saybolt Furol Viscosity Test are reported in units of

seconds

The Thin Film Oven Test (TFOT) is used to

simulate the effects of heating in a hot-mix plant operation on an asphalt cement.

What is the purpose of the Pressure Aging Vessel (PAV) procedure?

simulation of long-term aging of asphalt binders in service.

the main purpose of the PAV test is

simulation of long-term aging of asphalt binders in service.

At what temperature is the Bending Beam Rheometer test run, and why?

stiffness of an asphalt after 60 seconds at Tmin+ 10 C is approximately equal to its stiffness at Tmin after 2 hours loading time, which is related to low-temperature cracking potential.

The function of the screed unit in a paver is

strikes off the mix to the specified thickness and smoothness and provides initial compaction

what bituminous material does not occur in natural form?

tar, petroleum asphalt