PAVEMENT DESIGN AND PERFORMANCE by mercy2beans112

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									Canadian Strategic Highway Research Program (C-SHRP)

           PAVEMENT DESIGN AND PERFORMANCE:
              Current Issues and Research Needs

November 2000                                                                   Millennium Research Brief #2


To mark the approach of the new millennium, the                 FLEXIBLE PAVEMENT DESIGN [1]
Transportation Research Board (TRB) technical com-
mittees mounted a special effort to capture the cur-            The state of the art in flexible pavement design is mani-
rent state of the art and practice, as well as their per-       fested in mechanistic, or mechanistic-empirical (M-
spectives on future directions in their respective ar-          E) based design procedures that incorporate the treat-
eas of focus. Each of these “millennium papers” pro-            ment of life-cycle costs and design reliability. State-
vides a comprehensive view of transportation in the             of-the-practice methods, however, rely on empirical
United States as it exists today and can be expected            correlations with past performance, index-value char-
to evolve as the new century unfolds.                           acterizations of material properties and engineering
                                                                judgment for design strategy selection. In addition,
In September 1999, the Transportation Association
of Canada (TAC) released “A National Agenda for Tech-           these procedures have been used for traffic load lev-
nological Research and Development in Road and                  els and environments well beyond their observational
Intermodal Transportation.” The agenda identifies               base. The AASHTO Guide for Design of Pavement
trends, opportunities and needs, as well as specific            Structures is commonly used to design pavements
                                                                with traffic loadings greater than 50 million equiva-
high priority R&D projects, relevant for advancing
                                                                lent single axle loads (ESALs), while the basic design
Canadian highway transportation. The focus of the
                                                                equations were developed from traffic loadings of less
Agenda is on identifying R&D opportunities to opti-
mize the management of the road system and                      than 2 million ESALs. Mechanistic procedures can
intermodal transportation, and minimize the cost of             have several important advantages, including:
road transport while maintaining or improving safety.           ♦ Better capability to characterize material proper-
To further the dissemination of current North Ameri-               ties and assess existing pavement structural
can highway technology and future research needs,                  capacity (through laboratory testing, nondestruc-
C-SHRP has prepared this special series of technical               tive testing, and backcalculation),
briefs, called the Millennium Research Briefs, based
on information published in the TRB millennium                  ♦ ability to evaluate and compare different design
papers and the TAC agenda. One brief has been de-                  alternatives on a fair (defensible) basis,
veloped for each of the four original C-SHRP/SHRP
                                                                ♦ ability to rigorously account for stochastic vari-
technology areas - Asphalt, Concrete and Structures,
                                                                   ability or uncertainty in the design process.
Pavement Performance and Highway Operations.


  The Canadian Strategic Highway Research Program (C-SHRP) was established in 1987 to systematically extract the
  benefits from research undertaken by the Strategic Highway Research Program (SHRP) in the United States. SHRP
  was initiated in response to the continuing deterioration of highway infrastructure with the intention of making
  significant advances in traditional highway engineering and technology through the concentration of research funds
  in key technical areas. C-SHRP aims to solve high priority highway problems in Canada that are related to SHRP
  topics. The goal of both SHRP and C-SHRP is to improve the performance and durability of highways and make
  them safer for motorists and highway workers.


                                                            1
The primary disadvantage of the mechanistic proce-            still needed to develop better and more realistic mod-
dures (as reported by the users) is that they are more        els that can predict performance.
complicated, time-consuming, and costly to apply
because they require additional information that is           Traffic Loading Simulation Models
not typically collected by highway agencies.                  Currently the variety of wheel loads in the traffic
The anticipated 2002 Guide for Design of New and              stream and their cumulative applications are con-
Rehabilitated Pavement Structures - currently un-             verted into a single number of 80-kN ESAL applica-
der development through the National Cooperative              tions using a load equivalency factor (LEF) concept
Highway Research Program (NCHRP) under Project                that was developed over 40 years ago. This method-
1-37A - will advance the state of the art over current        ology still has validity, however, it has several weak-
practices in several key areas including the use of           nesses when considering the impacts of new tire types,
axle load spectra for traffic modeling, the use of fi-        higher tire pressures and axle configurations. Fur-
nite-element (FE) analysis for response prediction,           thermore, the current AASHTO LEFs were developed
and the incorporation of reliability in life-cycle cost       solely on the basis of how wheel loads affected over-
assessment. Perhaps its greatest benefit will be the          all pavement serviceability and not individual dis-
widespread introduction of M-E based design to the            tresses. The new axle load-spectra approach is ex-
transportation industry.                                      pected to replace the ESAL concept in the 2002 Guide
                                                              to address some of these problems.
Analytical Models
                                                              Material Characterization Methodologies
Analytical models are used to predict the state of
stress in a pavement under simulated wheel and en-            One of the benefits of M-E methodologies is that they
vironmental loading conditions. Most models are               rely upon one or more fundamental engineering prop-
based on multi-layer elastic (MLE) theory and/or FE           erties of the individual pavement and soil layers to
analysis. The MLE models are considered satisfac-             determine the state of stress and predict pavement
tory for predicting flexible pavement response under          performance. One of most important properties is
external wheel loads and are also relatively easy to          the elastic modulus. The elastic modulus has many
operate. However, they are not capable of predicting          benefits over other index properties such as AASHTO
pavement response associated with environmental               layer coefficients, R-value, and CBR since it has a di-
loading (i.e. that due to daily temperature changes,          rect effect in the analytical models used to predict
temperature gradients, moisture variations, etc.). FE         the state of stress. Despite this key advantage, there
models are capable of considering both wheel and              are some significant problems associated with its use.
environmental loading conditions, however, they are           First, bituminous pavement materials are not elas-
relatively complicated to operate and time-consum-            tic. Accordingly, a surrogate for elastic modulus (re-
ing. Prior to the 2002 Guide, FE analysis was not             silient modulus) is used to characterize a given layer
widely used for flexible pavement design.                     material’s bending resistance under the state of stress
                                                              that it will experience in-situ. Another problem con-
Transfer Functions                                            cerns the difficulty in accurately measuring resilient
                                                              modulus in the laboratory. Although improvements
A multitude of relationships have been developed to           to the laboratory-based resilient modulus test method
relate the state of stress in a pavement to its overall       are anticipated, a second method involving the use of
performance. The primary transfer functions used              nondestructive testing and backcalculation analysis
for current flexible pavement design procedures are           also holds promise. In this latter approach, measure-
those that relate: (a) maximum wheel load tensile             ments of surface deflection are obtained
strain in the hot-mix asphalt (HMA) surface layer to          nondestructively in the field and then evaluated
fatigue cracking; and (b) wheel load compressive              mechanistically (using a computerized process known
stress (or strain) at the top of the subgrade layer to        as backcalculation) to determine each layer’s in-situ
rutting. These models are typically derived through           resilient modulus. This process is especially useful
statistically based correlations of pavement response         for rehabilitation design, but also has some applica-
with observed performance of laboratory test speci-           tion for new pavement design if the nondestructive
mens, full-scale road test experiments, or both. Trans-       test measurements are obtained along the planned
fer functions are the most important component of             road alignment.
an M-E design procedure and significant efforts are

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Life-Cycle Cost Model                                          every year on both the preservation of the highway
                                                               infrastructure and trucking activities, one approach
Life cycle cost (LCC) analysis is considered a state-          is to determine the combination of maximum axle
of-the-art component in a pavement design procedure,           load (or gross vehicle load) and the cost of infrastruc-
although it is not at all tied to the M-E design prin-         ture restoration to optimize the overall benefits to the
ciples discussed thus far. LCC analysis provides a             taxpayer.
sound basis for economically evaluating a number of
feasible pavement design alternatives.
                                                               PAVEMENT MANAGEMENT [2]
Reliability Model
                                                               Support for pavement management among transpor-
Reliability is a feature that was incorporated into the        tation agencies continues worldwide; however, recent
1986 AASHTO Guide in order to account for the un-              changes in (US) legislation that no longer mandates
certainty in determining design inputs and predict-            the use of pavement management systems have re-
ing pavement performance. Like LCC analysis, it is             duced the support of senior management personnel.
not a process that is related to the M-E pavement              Many practitioners have expressed the need to re-
design principles. However, it is a process that comple-       gain or maintain the support of top-level management
ments M-E design well and is planned for use in the            through increased communication and technology
2002 Guide. The process associated with reliability            transfer.
involves an assessment of stochastic variability of the
                                                               Other challenges surround the technical aspects of
design inputs as well as prediction error within the
                                                               pavement management, including more standardiza-
transfer functions so that a structural design can be
                                                               tion in data collection procedures and more training
established with an associated level of confidence.
                                                               for pavement management personnel. Broader chal-
                                                               lenges that have been identified include:
FUTURE DIRECTIONS IN                                           ♦ The need for increased standardization in the data
PAVEMENT DESIGN                                                   collection processes to facilitate communication
                                                                  of data between agencies on a more consistent
Incorporation of LTPP/C-LTPP Findings                             basis.
Under the current schedule, field data collection as-          ♦ Allowances for flexibility in the customization of
sociated with the Long-Term Pavement Performance                  pavement management programs so that
(LTPP) studies in the United States will be completed             agencies can tailor their systems to the manage-
within the next seven or eight years, while the Cana-             ment philosophy and resources available.
dian counterpart (C-LTPP) will be completed in April
2004. Some preliminary data analyses are under way             ♦ The lack of practical pooled-fund studies to
or envisioned and the eventual completion of field                address research concerns that are common to
monitoring and finalization of the databases will set             several agencies.
the stage for more comprehensive data analyses.
These research efforts will have a variety of different        ♦ Continuous turnover in pavement management
goals, including the development of new transfer func-            personnel, requiring the need for more training
tions, prediction models, and M-E design procedures               and innovative forms of training.
that would likely be incorporated into future pave-
ment design guides.                                            ♦ The need for a better link between network-level
                                                                  and project-level management decisions.
Vehicle-Pavement Interaction
                                                               ♦ The increased need to sell pavement management
Vehicle-pavement interaction has received some at-                results to the individuals responsible for making
tention over the years but has not significantly im-              program, policy, and budget decisions.
pacted flexible pavement design. Past studies have
focused either on the effect of vehicle dynamics to-           Future Directions
ward accelerated pavement deterioration or the ef-
                                                               Several goals and objectives for taking pavement man-
fects of rough pavements on truck damage. Consid-              agement into the new millennium have been identi-
ering the hundreds of billions of dollars that are spent       fied:


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♦ The program development process, which                      volumes of data much more manageable and user
   includes pavement management system recom-                 friendly. However, only pavement ride quality and
   mendations, should become more formalized                  rut depth data can be collected with acceptable levels
   within transportation agencies, with decisions             of accuracy, resolution, and precision in real time (at
   made on a more objective basis.                            normal highway speeds). Research and development
                                                              are under way to advance the state-of-the-art in the
♦ The use of pavement management systems should               collection of structural capacity data, while the auto-
   be expanded beyond large transportation agen-              mated collection of pavement surface condition data
   cies to include cities, counties, and airports.            remains at an unacceptable level.
♦ A clearinghouse for pavement management                     Information Gaps
   information should be developed so that agencies
   have immediate access to information that                  Many agencies have yet to determine when structural
   documents best practices and the use of new                capacity data are truly needed. For example, should
   technology in pavement management.                         structural capacity data be obtained for project de-
                                                              signs alone, or can such data be used to supplement
♦ Processes and procedures should be developed                management decisions? Can the cost of collecting
   to facilitate improved coordination between trans-         such data at a network level be justified? How should
   portation agencies in pavement management                  the data be summarized and represented in such a
   through shared activities and pooled-fund                  network-level application?
   studies.
                                                              Needs for surface condition assessment continue to
♦ Research is needed in order to improve the                  be a source of uncertainty for agencies. For example,
   status of existing pavement data collection                what level of detail is required for network-level sur-
   technology.                                                face condition assessments? How many different dis-
                                                              tresses and severity levels are truly required? Are the
♦ Additional training programs should be developed            locations of the distresses important or just average
   for both practitioners and top-level managers.             quantities? What kinds of decisions require severity
   Innovative approaches to training should be con-           levels and additional distress types?
   sidered because of restrictions on travel and the
   ongoing nature of the need for technology trans-           Similarly, analysis of visual distress data collection
   fer programs.                                              for pavement management remains a significant ab-
                                                              straction to many agencies. For example, should a
♦ Efforts should focus on linking asset management            threshold value be incorporated? Should rehabilita-
   components, which include pavements, into an               tion be completed when the rate of deterioration in-
   integrated decision-making model that can be               creases? How detailed should the data collection be
   used by transportation agencies for all infrastruc-        to ensure that the analysis is meaningful? Do com-
   ture assets.                                               posite scores maximize the value of data collection
                                                              efforts? Will programs such as pavement preserva-
                                                              tion require additional data? The ability to store and
PAVEMENT MONITORING, EVALUATION,                              process large volumes of data has advanced consid-
AND DATA STORAGE [3]                                          erably, however this may simply be fostering signifi-
                                                              cant inefficiencies.
There is a need to collect pavement performance data
more expeditiously and reliably. Automation technol-          Data Consistency
ogy continues to advance at an exponential rate of            Consistency of data across individual transportation
growth, with current technologies capable of collect-         agencies remains a significant problem to this indus-
ing structural capacity information, ride quality data,       try. Although research is being conducted on the op-
and surface distresses. Advances in computer tech-            timum strategies for collection of data, agencies must
nology have facilitated the volumes of data that can          make interim decisions. As they address their cur-
be collected and stored. Similarly, greater access to         rent needs, trends are established that cannot easily
positioning satellites has made the location of data in       be redirected. The challenge of persuading agencies
the field more accurate, which has assisted in mak-           to convert to new or universal systems grows larger
ing the storage, retrieval, or both, of the increasing        with each passing year.

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Looking Ahead                                                 investments in FS/APT programs have been commit-
                                                              ted by FHWA, the US Army Corps of Engineers, and
The desire to have an “all-in-one” pavement-monitor-          several states. In addition, the Federal Aviation Agency
ing vehicle remains. Profile data can already be col-         (FAA) is currently commissioning the largest APT ma-
lected in real time and structural capacity data will         chine in the world. The state of Florida and the Na-
likely be obtainable in a similar fashion within the          tional Center for Asphalt Technology (NCAT), in col-
next decade. Steps must be taken, however, to pro-
                                                              laboration with the Alabama Department of Trans-
duce a clearer set of objectives for collection of sur-
                                                              portation, have both initiated major FS/APT efforts,
face condition data to allow for its automation. If ex-
                                                              which are likely to be the first new APT programs of
tremely detailed pavement surface distress data are
                                                              the 21st century. In Canada, the Université Laval has
truly needed, advances in image resolution will be
required. If a standard set of critical distresses can        established an accelerated test facility for low volume
be agreed upon (with a specified tolerance for accu-          roads, and efforts are underway at the University of
racy), industry should be able to focus on those dis-         Waterloo to establish a roads and pavements test fa-
tresses and develop some consistency in their collec-         cility. FS/APT affords rapid evaluation of potential
tion. The quality and accuracy of the data appear to          solutions in a number of current and enduring prob-
be of greater concern than the ability to collect these       lem areas including asphalt concrete rutting, quality
data rapidly. However, the industry as a whole con-           control and assurance procedures, warranty con-
tinues to struggle without a definitive statement of          struction, performance-based specifications, im-
minimum data quality and accuracy. Until these is-            proved maintenance procedures, and nondestructive
sues are adequately addressed, pavement monitor-              pavement evaluation procedures.
ing will not be able to capitalize on the advancements
in automation technology.                                     In the immediate future, the most beneficial develop-
                                                              ment for FS/APT would be improved coordination of
                                                              effort to ensure the most effective application of re-
PAVEMENT MAINTENANCE [4]                                      sources without duplication. This goal requires sig-
                                                              nificant standardization of distress definition and data
There is a shortage of data that reflect the effective-
                                                              collection procedures.
ness (cost and performance) of pavement mainte-
nance treatments. Although data may be collected,
documentation is sparse, and the data is not often            PAVEMENT REHABILITATION [6]
analyzed in an organized fashion. The various man-
agement systems that currently exist (pavement man-           The achievement of longer-lasting pavement rehabili-
agement, maintenance management, project manage-              tation while efficiently managing heavy traffic through
ment, etc.) must be integrated to effectively manage          construction zones is an ongoing challenge. As such,
pavement information and to improve pavement                  continuous improvements in technology are needed
maintenance planning, programming, and schedul-               to improve the entire process of pavement rehabilita-
ing. Some agencies are already integrating manage-            tion. The key areas that will benefit from such im-
ment systems, but more emphasis is needed. Inte-              provements include the following:
grated systems will also promote the implementation
of effective pavement preservation programs.                  ♦ Assessment of the in-situ condition of existing
Quality assurance for pavement maintenance activi-               pavements. Use of ground-penetrating radar,
ties has been relatively slow to evolve. While some              seismic techniques, and other nondestructive
agencies have adopted quality assurance programs                 techniques needs to be expanded to complement
for maintenance, much work remains to be done. As                FWD testing. There is a need to standardize
more agencies outsource maintenance activities to                pavement evaluation and testing protocols,
contract workers, better specifications and quality
assurance will become more important.                         ♦ Use of durable paving and repair materials that
                                                                 can carry truck traffic within a few hours after
                                                                 placement.
FULL-SCALE/ACCELERATED PAVEMENT
TESTING [5]                                                   ♦ Use of zero-clearance paving equipment that will
                                                                 minimize extensive lane closures.
A renewed interest in FS/APT programs has been ob-
served worldwide. In the United States alone, major

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♦ Development of rehabilitation design procedures              which are believed to provide a long-lasting seal in
   that clearly address mitigation of specific distress        new pavements, during the new construction of air-
   types and rationally account for future truck               field pavements.
   traffic loading.                                            New materials will continue to be developed for seal-
                                                               ing cracks and joints in flexible and rigid pavements
♦ Concrete pavement restoration techniques (e.g.,
                                                               in an effort to provide a more effective seal. As new
   dowel bar retrofit technique) and reflection crack-
                                                               products become available, it will be important to
   ing mitigation techniques.
                                                               verify their performance in specific applications. The
                                                               real challenge will be to identify material properties
JOINT- AND CRACK-SEALING [7]                                   and develop testing procedures that can assess seal-
                                                               ant performance in the field. Procedures and concepts
Pavement joint and crack sealants are designed to              developed during the Strategic Highway Research
prolong pavement life by minimizing water infiltra-            Program (SHRP) for performance grading of asphalt
tion and preventing the accumulation of debris. Re-            cements, as well as adhesion (to substrate) tests may
search has indicated that, in conjunction with main-           allow the development of performance-based specifi-
                                                               cations. Performance-based specifications provide
tenance techniques such as slurry seals and chip
                                                               two advantages. First, the performance of newly de-
seals, crack sealing will extend the life of a flexible
                                                               veloped materials could be more rapidly assessed
pavement. A major challenge facing the sealant in-
                                                               against the known performance of existing sealants.
dustry is to quantify the effectiveness of joint sealing
                                                               Second, the most appropriate sealant could be ob-
in rigid pavements and its cost-to-benefit ratio when          jectively selected for a specific set of conditions. How-
considering the life cycle cost. Another challenge is to       ever, new material specifications alone will not im-
identify the appropriate sealant for a specific job. The       prove the performance of crack and joint sealants in
third challenge is training of contractors and users           the field. Application procedures and equipment also
concerning the types of materials, the correct instal-         play a vital role in the field performance of materials.
lation geometry, and the procedures that are required
to clean the joint or crack and install the sealant.
                                                               PAVEMENT TECHNOLOGY ISSUES AND
Materials and Specifications                                   OPPORTUNITIES IN CANADA [8]
Different kinds of pavement (from both the material            The following pavement technology issues were iden-
and use perspectives) require different sealant mate-          tified in the TAC National Agenda through an exten-
rials. Hot-applied modified asphalt-based sealants are         sive consultative process.
the most effective and widely used sealant materials
for use on flexible pavements. Other materials—such            Pavement Preservation
as emulsified, cutback, and chemically curing prod-
ucts—will continue to be used in specific applications         Until recently, decisions concerning how and when to
where the costs or material characteristics of the prod-       rehabilitate pavements were essentially based on ex-
ucts are justified. Sealant materials used for rigid           pert judgement. The rapid emergence of pavement
pavement applications vary more widely than those              management technologies and systems have assisted
used for flexible pavements. Historically, the hot-ap-         the decision-making processes greatly, however, these
plied asphalt-based materials have been the most               systems and technologies have evolved unevenly over
commonly used materials for these applications.                the past few years. A few key technologies have still
However, silicone-based sealants and preformed com-            not reached industry expectations and are restrict-
pression-seal materials have gained increased accep-           ing the potential of modern pavement management
tance and have become the preferred choice of a sig-           tools. The key issues and opportunities are related
nificant number of US agencies.                                to pavement data, pavement management, and con-
                                                               tracting methods.
Materials resistant to jet fuel and aircraft exhaust are
commonly required for airfield pavements. The use              Durability of Pavement Materials
of silicone-based materials for airfield pavements that
                                                               Increased traffic loads and the deterioration and age-
are exposed to intermittent or limited fuel spillage is
increasing for civil and military applications. The U.S.       ing of materials used in pavement construction in the
military typically uses preformed compression seals,           1960’s and 70’s have promoted the need to develop


                                                           6
more resistant and durable pavement materials. Re-              Policies and procedures for spring load restrictions
cent developments in engineered asphalts, Superpave
binder and mix specifications, and high performance             Bearing capacity loss during spring thaw period has
concrete have helped to resolve several pavement                long been recognized as a major factor toward pave-
performance problems. Improvements are still                    ment deterioration. Most Canadian highway agencies
needed in many aspects of material performance in               use springtime load restrictions to mitigate the detri-
the Canadian context. The growing preoccupation with            mental effect of heavy vehicles during spring thaw.
environmental considerations and sustainable devel-             However, procedures and criteria to establish the
opment during the last decade has forced the rapid              beginning, the duration, and the magnitude of the
development of technologies and procedures for re-              restrictions vary considerably from one agency to the
cycling pavement and other materials in road con-               other. The development and promotion of a standard
struction. Research is still needed to refine the exist-        approach to spring load restrictions would greatly
ing recycling processes and to develop new ones. The            benefit both the highway agencies and the transpor-
key issues and opportunities in this area are the de-           tation industry.
velopment of surfacing materials resistant to reflec-
tive cracking, developing performance-based specifi-            CONCLUDING REMARKS
cations for pavement materials, and recycling meth-
odologies.                                                      This brief highlights the state of the art and some of
                                                                the critical issues facing the pavement design and per-
Design procedures for new and
                                                                formance fields as identified by the Transportation
rehabilitated pavements
                                                                Research Board and the Transportation Association
Major developments are currently underway led by                of Canada. The interest and awareness of this field
TRB-NCHRP, FHWA and C-SHRP. These developments                  have grown progressively over the last fifty years. Most
will produce improved technologies for the design of            notably, the LTPP/C-LTPP initiatives and SHRP/C-
new and rehabilitated pavements based on mecha-                 SHRP research focused the attention on the challenges
nistic principles and distress-specific empirical trans-        of the pavement industry in the past decade. The
fer functions calibrated to local conditions. It is ex-         majority of issues identified in the pavement design
pected that significant improvements will result from           and performance field relate to data quality and man-
these ongoing research endeavours. Important efforts            agement, standardization of distresses, practices and
will, however, be required in order to adapt and cali-          quality control procedures, and performance based
brate research results to Canadian conditions.                  specifications. There is an evident need for increased
                                                                research and development in this area. Continued
Variability of pavement design factors                          collaboration and partnerships between the pavement
                                                                industry, research institutes, and transportation agen-
The AASHTO and the OPAC 2000 design methods                     cies will provide solutions to many of these issues.
have incorporated the concept of reliability in pave-
ment design. This concept, based on the quantifica-
tion of the variability of significant design factors, is
likely to be incorporated in other design methods in
the future.




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REFERENCES

[1] Seeds, S.B. “Flexible Pavement Design: Summary of the State of the Art.” TRB
Committee on Flexible Pavement Design, TRB Millennium Paper Series, 2000.

[2] Zimmerman, K., Botelho, F., and Clark, D. “Taking Pavement Management into
the Next Millennium.” TRB Committee on Pavement Management Systems, TRB
Millennium Paper Series, 2000.

[3] Daleiden, J.F. “Pavement Monitoring, Evaluation, and Data Storage.” TRB Com-
mittee on Pavement Monitoring, Evaluation, and Data Storage, TRB Millennium
Paper Series, 2000.

[4] Moulthrop, J.S., and Smith, R.E. “State of the Art and State of the Practice in
Pavement Maintenance.” TRB Committee on Pavement Maintenance, TRB Millen-
nium Paper Series, 2000.

[5] Coetzee, N.F., Nokes, W., et al. “Full-Scale/Accelerated Pavement Testing: Cur-
rent Status and Future Directions.” TRB Task Force on Full-Scale/Accelerated Pave-
ment Testing, TRB Millennium Paper Series, 2000.

[6] Tayabji, S.D., and Brown, J.L., et al. “Pavement Rehabilitation.” TRB Commit-
tee on Pavement Rehabilitation, TRB Millennium Paper Series, 2000.

[7] Lynch, L., and Steffes, R. “Joint- and Crack-Sealing Challenges.” TRB Commit-
tee on Sealants and Fillers for Joints and Cracks, TRB Millennium Paper Series,
2000.

[8] Hajek, J., Mealing, N., Colavincenzo, O., Billing, J., Dore, G., Carter, P., Smiley,
A., Harmelink, M., Comfort, G. “A National Agenda for Technological Research
and Development in Road and Intermodal Transportation.” Transportation Asso-
ciation of Canada, Ottawa, Canada. September 1999.




            This technical brief has been prepared and distributed by:

            Canadian Strategic Highway Research Program (C-SHRP)
            2323 St. Laurent Blvd.
            Ottawa, Ontario K1G 4J8

            Tel. : (613) 736-1350
            Fax : (613) 736-1395
            www.cshrp.org

            ISBN 1-55187-064-9



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