and modified as necessary to improve their reliability ...spave/old/mcdaniel/shrp/tra1_46-53.pdf ·...

Strain in the asphalt concrete is calculated using analyticalprocedures for structural analysis of the pavements. The repetitions tofailure is based on the cumulative damage hypothesis which is the mechanismwhich results in fatigue cracking.

Both strain and modulus are a function of asphalt and asphalt-aggregate properties in the above illustration; hence, the model would be acandidate for predicting fatigue cracking.

A limited number of models have been develop.ed to predictdeformation. The permanent deformation model selected will include provisionfor asphalt properties and mixture properties for both short (0.01 seconds)and long periods of loading (1 hour) as required to simulate field loadingconditions under moving loads and standing loads.

The permanent deformation model will also include provisions forevaluating effects of various wheel loads, configurations, tire pressures andmixture temperatures.

Several models exist which relate laboratory fatigue characteristicsof asphalt bound materials to mixture properties such as stiffness (dynamicmodulus, complex modulus, etc.) and air voids. These models will be evaluatedand modified as necessary to improve their reliability. If currentlyavailable models are considered unsatisfactory, new models will be developed.

In addition to material properties, including those of asphalt andasphaltic concrete, the model shall.consider: wheel loads and configurations,time of loading, effect of mixed traffic, tire pressure and temperaturecycles.

Models have been developed for the predi cti on of low temperaturecracking. These models relate the occurrence of transverse cracking toasphalt properties and asphalt mixture properties. In selecting the lowtemperature transverse cracking model (s), consideration will be given to rateof change in temperature (i.e., temperature drop), the influence of frictionbetween the supporting layer, and age hardening of asphalt and asphalt-aggregate combinations.

The low temperature model will be capable of predicting cracksresulting from a single thermal cycle as well as repeated cycles over longperiods of time, i.e., 15 to 20 years. The model will provide some means forpredicting the cracking index or average expected frequency (spacing) ofcracks.

This project does not involve any testing; it is primarily aninvestigation of models; mechanistic, mechanistic-empirical or empirical whichcan be used to predict specific types of performance based on asphaltproperties or asphalt-aggregate properties.

Specific requirements for this task includ~:

1)

2)

Develop performance prediction models for each of the three typesof distress identified.Describe methods for validation of models including the need forand type of field data required.

TRA 1-46

r

A total of 0~5 million dollars has been allocated to this task.

Task 3.2 Asphalt Performance Studies

Objective: The objective of this' task will be to obtain as muchdocumented performance information as possible from as many sources aspossible in an effort to establish criteria which will be used for asphaltspecifications and for the design of asphalt-aggregate mixtures.

Scope: The scope of this task includes: 1) observations of fieldperformance, 2) collection of samples and performances of tests necess~ry .toevaluate prediction models and 3) development of empirically based flttlngcoefficients to calibrate models to observed performance. Emphasis in datacollecting, sampling and testing will be given to projects with long termperformance records and for which samples of the original asphalt andaggregate are available for testing.

The task will include the following activities:

1 )2)3)

4)

Develop a sampling and testing program for in-service pavements.Summarize and analyze field and laboratory data.Develop empirical coefficients to adjust theoretical models from3.1 to applied prediction models.Develop procedures for updating empirical coefficients.

Pl anni ng for thi s task wi11 requi re a well-pl anned experiment whichwill provide information indicative of differences due to materials andenvironments.

This task will involve collection of performance data from any ~ou~ceconsidered useful for evaluation of prediction models and for establlShlngspecification or mixture design requirements. A laboratory testing programnecessary to support prediction models will be required.

Specific requirements for this task include:

1 )

2)

Obtain samples of asphalt-aggregate materials from designated in-service pavements.Conduct necessary testing program to develop information requiredto evaluate prediction models for a) fatigue cracking, b)permanent deformation, c) low temperature cracking and d)reflection cracking.Analyze performance information and test data to establishspecification requirements and criteria to be used with asphalt-aggregate analysis system.

3)

A total of 3.0 million dollars has been allocated to this task.

Task 3.3(3) Evaluation Procedures for Prediction Models

Objective: This task will provide guidelines for state high~ayagencies to maintain and update performance prediction models and to modlfyspecification requirements recommended in task 4.2.

TRA 1-47

Scope: The scope of this task will include the development ofmethods for interpreting information from the Long Term Pavement Performanceresearch area (TRA 2) as it app1ies to TRA1 objectives, and to develop acomprehensive satellite SHRPprogram for future enhancement of specificationsbased on a well-planned experiment design and data acquisition requirements.

This task will involve methods to be used for obtaining and analyzingresearch information useful for updating (improving) prediction models and forrevising specification requirements for binders of all types, i.e., asphalt,recycled asphalt or modified asphalt. Criteria and recommended procedures tobe used in establishing local or national satellite SHRPresearch will bedeveloped. Mathematical examples with hypothetical or real data will beanalyzed to illustrate the recommended procedures. No testing, laboratory orfield, will be required for this task although data useful in illustratingprocedures may be acquired from other tasks within TRA1.


Develop mathematical guidelines to be used for evaluation ofprediction models from performance data. Relate such proceduresto future interpretation of LTPPdata.Prepare a step by step procedure for estab1 i shing datarequirements and analysis procedures to be used in updatingspecification requirements and design criteria for incorporationin the asphalt-aggregate mixture analysis system.Prepare experiment design recommendations for use at the local ornational level for obtaining information required to increase thedata base of information useful for future updating of goal sestablished for TRA 1; in effect, a planned SHRP satelliteprogram.III ustra te the step by step procedures for interpretinginformation from experiment design in items 3 above; usehypothetical or real data as is available and is appropriate.


1)

2)

3)

4)

Project 1-4 Preparation of Performance-Based Specifications and an Asphalt-AggregateMlxture Analysis~ystem - -

This project will prepare performance-based specifications forasphalt and recommendations for a comprehensive mixture design method to bereferred to as an asphalt-aggregate mixture analysis system (AAMAS).

For purposes of thi s project, a performance-based specifi cati on forasphalt must satisfy the following requirements:

1)

2)

It must be based on standardized tests which have been shown tosatisfy requirements of ASTMand AASHTO.It should include measurements (test data) which have beenrelated to performance.It should be based on types of performance which can be definedquantitatively.

The aspha1 t-aggregate ridxture ana1ysi s system wi 11 descri belaboratory procedures and requirements for the laboratory evaluation of

3)

TRA 1-48

r<t

asphalt binders, virgin, recycled or modified, and aggregate to minimize theoccurrence of fatigue cracking, low temperature cracking and permanentdeformation. The system will be sensitive to asphalt binder properties,aggregate properties and regional factors which could influence mixtureperformance.

The project will be divided into two tasks: 1) performance-basedspecifications for asphalt and 2) development of an asphalt-aggregate mixtureanalysis system.

~.'i!Ii

F

"

The performance-based spec i fi cati ons for asphalt and aspha 1t-aggregate systems will incorporate the findings of each of the projectsincluded in this research area. It is acknowledged that a limited amount offield performance information will be available during the term of theproject, i.e., five years. It will, therefore, be necessary to develop aninterim or model specification for recommendation at the completion of theproject but which can be modified (improved) as additional information becomesavailable.

Task 4.1(3) Performance-Based Specifications for Asphalt

Objective: The objective of this task will be to developperformance-based specifications for asphalts, with and without modification.A sufficient number of specifications will be formulated to accommodate a widevariety of conditions which can be encountered in the United States.

Scope: The development of the asphalt specifi cati ons wi11 fullyconsider the following requirements.

1) Will be tolerant to a wide range of mixing temperatures withoutdamaging the asphalt and adversely affecting its desirable mixingand placing characteristics or its long-term performance in-service.

2) Will not be adversely affected by the chemical and physicalproperties of the aggregate used in the mix.

3) Will develop the needed adhesion (i .e., bond) to aggregates ofdifferent compositi on at different temperatures and degrees ofwetness.

4) Will be resistant to migration (i .e., bleeding) at hightemperatures.

5) Will be res i stant to the adverse effects of agi ng (i. e., long-term durability).

6) Will remain flexible at in-service temperatures and resistant tocracking at low temperatures.


1)

2)

Select significant properties and their related test methods foruse.in the specifications.Specify limits for the pj"operties measured by the applicable testmethods for each type. and grade of asphalt included.

3) Provide guidelines for selecting asphalt grades for use indifferent environments, types of construction and characteristicsof traffic.

TRA 1-49

Each specifi cati on wi11 be the result of that combinati on of theabove requirements considered to be "optimal," all factors considered.

A total of 3.0 million dollars has been allocated for this task.

Task 4.2(3) Performance-Based Specification for an Asphalt-AggregateMixture AnaTY"sis System (AAMAS) --

Objective: The objective of this task will be to develop aperformance-based specification for an asphalt-aggregate mixture analysissystem (AAMAS),utilizing asphalts with and without modification.

Scope: The asphalt-aggregate mixture analysi s system wi11 i ncl udegui del i nes for specifyi ng the properti es of the asphal t-aggregate mixturewhich will produce a mix with the following characteristics:

1-2.

3.4.

Resistant to creep and permanent deformation (i.e., rutting).Resistant to repeated bending stresses and strains (i .e.,fatigue).Resistant to low temperature cracking (i.e., thermal cracking).Resistant to aging in-service at relatively high air voids (i.e.,long-term durability).Resistant to the effects of moisture and water (i .e., watersens iti vi ty) .Compactible over a wide temperature range.

5.

6.


1)

2)

Sel ect test methods consi dered necessary and suffi ci ent for usewith AAMAS.Desi gnate requi red specificati on 1imi ts for properti es measuredby the applicable test method for the full range of designconsiderations.Provide guidelines for implementing AAMAS.3)

Typical examples of the application of AAMAS to situationsrepresentative of the variety of environments, types of constructionand traffic loading characteristics encountered throughout the UnitedStates will be presented.


Project 1-5 Coordination

The objective of the coordination project is to assure that thecombined effort from each task will adequately focus on the requirements forTRA1. In order to achieve this objective, coordination has been divided intofive tasks as described herein.

Task 5.1 TRA!. Research Project Coordination

The objective of this task will be to monitor the activities of eachproject and task and to establish a mechanism for interaction between eachongoing research activity.

TRA 1-50

An important responsibility for the TRA1 project coordination willbe to interface the work under NCHRP10-26(A) and 9-6(1) with activities inTRA 1. These two projects could contribute to the work under the followingtasks:

2.2 - Testing and measuring methods for asphalt-aggregate systems2.3(2) - Relationships between asphalt properties and asphalt-aggregate

mixture properties3.2 - ¥sphalt pavement performance studies4.2 -/Performance-based specifications for asphalt-aggregate mixture

analysi s system

~endi ng on the results from these two NCHRPprojects, it may bedesirable to modify the scope of work under any of the above tasks or, in thecase of ask 4.2, to accelerate activities by at least one year.


1 ) Schedul e monthly meeti ngs for representati ves from each acti veresearch task or subtask in order to exchange and di scussspecific accomplishments and problems.Assist in resolving problems in order to achieve on time results.Organi ze quarterly meeti ngs of user-producer advi sory committeeto summarize results of research acti viti es. (Note: If thi scommittee is organized, it would be appointed by SHRPoffice withapproval by the Task Force).Provi de quarterly executi ve summari es of progress on eachresearch activity in progress indicating achievements, problemsand overall evaluation.

/2)3)

4)

A total of 1 million dollars has been allocated to this task.

Task 5.2 Operate Materials Reference library

The objective of this task will be to develop and maintain a"l ibrary" of asphalts, aggregates and modifiers for use by contract agenciesand other interested and authorized organizations.

The contractor will be required to procure asphalts and aggregates insuitable quantities to support the TRA 1 research activities. The cost ofprocurement, transport, storage, cataloging, packaging and shipping will beincluded in this project.

The specific requirements for this task include:

1 )

2)

Procure samples of asphalts, aggregates and modifiers necessaryto support research and long term requirements for TRA1.Store materials in proper containers or areas to minimize anychanges in properties with time.Package and ship materials to authorized users and in sufficientquantity to support specified research activities.Monitor properties of materials in order to determine if specificproperties are changing and by how much and if additionalprecautions are necessary to assure stable properties.

3)

4)

TRA 1-51


Task 5.3 ExperimentDesign

The objective of this task will be to develop a statistically soundexperimental design for each research activity and to prepare a coordinatedplan for selecting and testing materials. As a minimum the following itemswill be considered:

1.2.3.

4.

data requirements,data storage and transmittal to the central data bank,type and number of materials required to satisfy objectives ofTRA1 anddata analysis methodology.


1 )

2)

Provide input and coordinate experiment desi gn requi rements foreach task and subtask.Provide assistance in planning for data acquisition and dataanalysis for each task and subtask.Provide assistance in furnishing data to the central data bank tobe established for SHRPprojects.Coordinate plans for the asphalt study area with requirements forthe Long Term Pavement Performance Study Area.


3)

4)

Task 5.4 Economic Considerations--The objective of this task will be to provide expertise in evaluating

the economic consequences of implementing specific findings from TRA 1research activities. Preliminary indications from knowledgeable persons fromboth user and producer groups suggest that efforts to improve the propertiesof binders by introducing new asphalt specifications, or by the use ofmodifiers may increase the unit cost of binder systems. If this increasedcost can be offset by either more rel i abl e performance or an extended 1Hecycle the overall benefits of increased initial cost would be justified.

A defensible method for making life cycle cost or benefit-costcomparisons will need to be established.

Specific requirements of this task include:

1) Provide a centralized group to study and evaluate theeffectiveness of introducing new asphalt specifications andasphalt-aggregate requirements.Prepare reports summarizing economic analysis proceduresincluding assumptions required to estimate life cycle costanalysis and benefit-cost ratios.Prepare estimates of the possible national benefits ofi ntroduci ng speci fi c changes in asphal t-aggregate mixturerequirements.

2)

3)

.TRA 1-52

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In order to encourage and facilitate implementation of the researchfindings, it will be necessary to assemble information appropriate for use byuser agencies into a series of implementation packages. Such information willinclude as a minimum:

1.2.

3.

preparation of material for SHRPto use in newsletters,preparation of reports detailing the benefits of researchfindings andconduct of regional workshops to explain research findings and torecommend procedures for implementation.

Specific requirements of this task include:

1 ) Prepare information regarding how to obtain materials and prepareconstruct i on spec i fi ca t ion s for i ncorpora t i on of resea rchfindings.To provide a step by step procedure for implementing researchfindings to be applieg/to site specific conditions.Prepare specific information for use by SHRPofficials in makingpresentations to Congres~, AASHTOor other selected groups.Prepare information for use by SHRPin preparing news releases.Pl lIn linn ronnllrt. work e:;hone:; in thp fi ft.h ~Pi'lr of ~HRP to pxnl i'li nfindings and benefits available by implementing research results.

2)

3)

4)~)


TRA 1-53

and modified as necessary to improve their reliability ...spave/old/mcdaniel/shrp/tra1_46-53.pdf ·...

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