Information on Materials and Practices for Improving Highway Pavement Performance

Published by the Government Accountability Office on 2012-11-14.

Below is a raw (and likely hideous) rendition of the original report. (PDF)

United States Government Accountability Office
Washington, DC 20548

           November 14, 2012

           The Honorable John J. Duncan, Jr.
           Subcommittee on Highways and Transit
           Committee on Transportation and Infrastructure
           House of Representatives

           The Honorable Frank LoBiondo
           Subcommittee on Coast Guard and Maritime Transportation
           Committee on Transportation and Infrastructure
           House of Representatives

           Subject: Information on Materials and Practices for Improving Highway Pavement

           The nation’s more than 4 million miles of roads are key to the economy, facilitating the
           movement of goods and people. Although highways are highly durable and can last for
           decades, they deteriorate from traffic wear and tear, inadequate drainage, construction
           deficiencies, and weather. Keeping them in good condition requires substantial resources:
           public entities spent more than $180 billion in 2008 on highways, with about $40 billion
           coming from the federal government. Despite these outlays, the Federal Highway
           Administration (FHWA) estimates that these funding levels are insufficient to maintain or
           improve the condition of the nation’s highways through 2028. 1 Further, the major source of
           federal surface transportation funding—federal motor fuel tax revenues deposited into the
           Highway Trust Fund—is eroding. 2 The Congressional Budget Office estimates that, as of
           March 2012, to maintain current spending levels and account for inflation from 2013 to 2022,
           the Highway Trust Fund will require more than $125 billion over what it is expected to take in
           during that period. 3
           As a result, state highway agencies, the entities that are ultimately responsible for keeping
           most major highways in good repair, will need to develop strategies for doing so at reduced
           costs. 4 One potential strategy is using more cost-effective materials and practices. With
           this in mind and in response to your request, this report describes (1) selected materials and
             U.S. Department of Transportation, Federal Highway Administration, 2010 Status of the Nation’s Highways,
           Bridges and Transit: Conditions and Performance Report to Congress (Washington, D.C.).
             The Highway Trust Fund is an account established by law to hold and distribute federal highway user taxes
           (e.g., federal excise taxes on fuel) that are dedicated for highway- and transit-related purposes. It is composed of
           two accounts: the Highway Account and the Mass Transit Account. See GAO, Highway Trust Fund: All States
           Received More Funding Than They Contributed in Highway Taxes from 2005 to 2009, GAO-11-918
           (Washington, D.C.: Sept. 8, 2011).
             Congressional Budget Office, March Fiscal Year 2012 Baseline Projections for the Highway Trust Fund
           (Washington, D.C.: 2012).
             Each of the 50 states, plus Washington, D.C., and the Commonwealth of Puerto Rico, has a highway agency.

                                            GAO-13-32R Materials and Practices for Improving Pavement Performance
practices that states can use or are using to improve the performance of pavements,
including what is known about their costs and benefits, if any, and (2) challenges, if any, to
using these materials and practices.
To address our objectives, we first conducted a literature search to identify potential
materials and practices that were reported to increase the durability and the life of
pavements, thereby improving performance. To supplement the materials and practices
identified in our literature search, we reviewed and analyzed relevant documentation and
interviewed officials from FHWA headquarters, asphalt and concrete industry groups, a
tollway authority, and the American Association of State Highway Transportation Officials
(AASHTO), as well as pavement researchers from four transportation research
organizations. 5 We then identified and interviewed officials from seven state departments of
transportation (DOT)—chosen based on their reported use of materials and practices to
improve pavement performance, the number of highway miles they managed, and
geographic diversification—to obtain additional information about materials and practices
and challenges to their use. 6 The selection of states was intended to provide a strong
understanding of states’ experiences and was not intended to be generalizable.
Through these efforts, we identified and compiled a list of potential materials and practices
for further evaluation. We assessed each potential practice on whether it (1) has the
potential to cost-effectively improve pavement performance by increasing durability or
extending pavement life or has the potential to reduce life-cycle costs—costs associated
with constructing and maintaining a pavement over its lifetime, and (2) is currently available
for states to use. We eliminated materials and practices that did not meet these criteria. We
also identified available cost information and additional benefits provided by these materials
and practices using the same resources.
We then verified the accuracy and completeness of the list by identifying a list of
stakeholders who have relevant expertise in the use of materials and practices with the
potential to improve pavement performance. We identified potential stakeholders with a
range of expertise in concrete, asphalt, and highway operations from government, industry
groups, and transportation research organizations. From this group, we selected nine
stakeholders who represented a range of expertise and affiliations, and provided them a
data collection instrument that displayed the initial list of materials and practices we had
compiled for their review and comment. We asked them if they concurred, did not concur, or
did not know whether each material and practice has the potential to cost-effectively
improve pavement performance by increasing durability or extending pavement life, or
reduce life-cycle costs. We also asked them to identify any materials and practices that meet
these criteria that we did not include in the list. We received eight responses, which we
analyzed to identify any materials and practices that a majority of the respondents did not
concur with. As a result of these responses, we removed two practices from our list and did
not add others. We organized the materials and practices into five categories to facilitate
their presentation, shown in tables 2 through 6. In addition, after each table, we discuss
some considerations associated with the choice of materials or practices by highlighting a
few examples. Prior to distributing the data collection instrument, we tested our validation
process with three officials from FHWA and one individual from a private engineering firm.
We made modifications to the instrument as a result of these tests. We believe our resulting
list reflects materials and practices that may have the potential to improve pavement
performance; however, the list was not meant to be exhaustive, and we acknowledge that
there may be some materials and practices we did not identify.

  We interviewed officials from the National Center for Asphalt Technology, National Concrete Pavement
Technology Center, Texas A&M Transportation Institute, and Western Research Institute.
  We interviewed DOT officials from Georgia, Iowa, Minnesota, Tennessee, Texas, Utah, and Washington.

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To identify challenges to using these materials and practices that states might encounter,
we conducted a literature search and interviewed DOT officials from seven states. We
analyzed the information we obtained and categorized challenges into four areas.
We conducted this performance audit from January 2012 to November 2012 in accordance
with generally accepted government auditing standards. Those standards require that we
plan and perform the audit to obtain sufficient, appropriate evidence to provide a reasonable
basis for our findings and conclusions based on our audit objectives. We believe the
evidence obtained provides a reasonable basis for our findings and conclusions based on
our audit objectives.
In summary, our literature review and discussions with stakeholders having relevant
expertise resulted in the identification of 40 materials and practices that may contribute to
improving the performance of pavements, extending service life, and reducing life-cycle
costs. These materials and practices cover a range of uses and applications across the
stages of a pavement’s life cycle, from initial design and construction through maintenance
and preservation cycles, and at the time of reconstruction. Several challenges exist to
states’ use of these materials and practices. In particular, some materials and practices
may not be applicable or beneficial to all states, a decentralized and segmented highway
industry may impede change, and resource constraints and procurement methods may limit
states in implementing new approaches to building and maintaining their highways.
However, FHWA, AASHTO, and states have developed several programs that address
these challenges through research, training, and information and outreach programs.

In the United States, state and local governments own about 96 percent of the more than 4
million miles of roads. State DOTs are responsible for constructing, repairing, and
maintaining most major highways, including the Interstate Highway System. These
agencies generally contract with private sector companies to perform these activities. The
federal government provides funding to states through a series of programs collectively
known as the federal-aid highway program. Each program that provides funding specifies
how it can be used—such as for construction, reconstruction, and preventive maintenance
activities—and specifies eligible project types. Highways supported by federal aid represent
about one-fourth of all roads, but about 85 percent of all miles traveled annually occur on
them (see table 1).

Table 1: Ownership of U.S. Roads by Length in Miles and Vehicle Miles Traveled, 2008

    Owner                            Miles supported          Miles not supported          Total miles
                                     with federal aid         with federal aid

    Federal                          6,596                    124,962                      131,559 (3%)
    State                            562,170                  222,141                      784,311 (19%)
    Local                            418,564                  2,667,888                    3,086,452 (76%)
    Other                            7,188                    49,832                       57,020 (1%)
    Total                            994,518 (24%)            3,064,823 (76%)              4,059,341 (100%)
    Vehicle miles traveled           2,534,647 (85%)          458,058 (15%)                2,992,705 (100%)
Source: GAO analysis of FHWA data.

Note: Percentages may not add due to rounding. Other includes state park, state toll, other state agency, other
local agency, and roadways not identified by ownership. Road lengths and vehicle miles traveled include Puerto

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Highway pavement consists of several layers of durable material. Lower layers of a
pavement typically consist of crushed, compacted rock (base or subbase) built on a
compacted earthen roadbed (subgrade). The surface layer, upon which vehicles travel, is
typically constructed of asphalt or concrete. According to FHWA, of all of the miles of roads
supported with federal aid, about 91 percent have asphalt surfaces, about 5 percent have
concrete surfaces, and 4 percent are unpaved. 7 Figure 1 illustrates a typical pavement
Figure 1: Typical Pavement Structure

All pavements deteriorate over time but numerous factors—including increased traffic, water
intrusion into the pavement layers, freeze/thaw cycles or other weather events, and
instability of the roadbed or base layers—can accelerate this aging process. Truck traffic, in
particular, contributes to pavement deterioration, because heavier loads are many times
more damaging than lighter loads. Evidence of deterioration may be apparent on the
surface layer, as shown in figure 2.

Figure 2: Examples of Deterioration in Asphalt and Concrete Pavements

The activities performed by state and local governments, or their contractors, to build and
keep pavements in good condition can be organized into four stages, corresponding to
different points of a pavement’s life: (1) design, (2) construction, (3) maintenance and
preservation, and (4) reconstruction (see figure 3).

  Federal Highway Administration, Highway Statistics 2008: Federal-Aid Highway Length – 2008 Miles by Type
of Surface (Table HM-31), (October 2009), the most recently available data.

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Figure 3: Stages of a Pavement’s Life Cycle

Designs that appropriately consider factors specific to the highway, such as anticipated
traffic levels, and construction that meets the design specifications are essential to ensuring
long-lasting roads. Likewise, maintenance and preservation activities can improve the
performance of deteriorated pavements and prolong their life by preventing minor problems
from getting worse and correcting major problems that accelerate deterioration. Over time,
a pavement may undergo multiple cycles of maintenance and preservation before
reconstruction is necessary. In addition, throughout these stages, states and contractors
perform a number of tests, such as testing asphalt and concrete materials before they are
applied to a road, and use quality assurance and quality control practices, such as testing
the thickness of new asphalt or concrete, to ensure that pavements meet established

Materials and Practices That Can Improve Pavement Performance, Reduce Life-Cycle
Costs, and Provide Other Benefits
Selected Materials and Practices
Our review of existing literature and discussions with stakeholders having relevant expertise
resulted in the identification of 40 materials and practices—6 materials and 34 practices—
that may contribute to improving the performance of pavements, extending service life, and
reducing life-cycle costs. Of the 40, 6 are materials that could be used in the construction,
maintenance and preservation, or reconstruction stages of a pavement’s life. The remaining
34 are practices; 9 of the practices relate to design and testing, 13 are practices that could
be used in the maintenance and preservation stage, 8 are practices that could be used in
the construction or reconstruction stages, and 4 could be used as part of quality assurance
and quality control activities affecting construction, maintenance and preservation, or
reconstruction work.

         Pavement Materials
Table 2 describes six pavement materials that could be used in projects during the
construction, maintenance and preservation, or reconstruction stages of a pavement’s life
cycle to affect performance. Some can improve the performance of the pavement and base
materials and increase the durability of the road, while other materials—such as reclaimed

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asphalt or recycled concrete—may yield roads with performance characteristics similar to
those constructed with new materials but at a lower cost.

Table 2: Pavement Materials

 Material                                                       Description
 Modified asphalt binders     Synthetic or natural material added to asphalt to enhance pavement properties.
                              Includes polymers, chemical modifiers, rubber, fibers, fillers, and
 Reclaimed or recycled        Re-use of materials into new pavements. Includes asphalt and concrete
 material                     pavement, asphalt shingles, and ground tire/crumb rubber.
 Blended or performance       Material added to the more typical portland cement to enhance concrete
 cements                      pavement properties or reduce costs. Includes pozzolans, slag cement, fly ash,
                              and limestone.
 Concrete curing compounds Material applied to newly poured concrete to inhibit water evaporation and
                           ensure proper concrete curing.
 Geosynthetics                Synthetic polymeric materials used for a variety of purposes in pavement
                              structures, such as reinforcement, separation, and drainage. Includes
                              geotextiles, geomembranes, geogrids, geocells, and erosion control products.
 Corrosion-resistant          Materials that resist corrosion and deter corrosion-related damage to concrete.
 reinforcement for concrete   Includes fiber-reinforced polymer bars, discrete fibers, stainless steel, and
 pavement                     epoxy-coated steel.
Source: GAO.

In reference to reclaimed or recycled materials, officials from each of the states we met with
said that they allow the use of reclaimed asphalt in asphalt paving projects, typically allowing
it to comprise up to 20 percent of the asphalt, and some states have investigated use of
higher levels. Reclaimed asphalt can replace other, more expensive materials when making
asphalt for pavements. For example, Washington estimates it saves $15 million to $20
million annually by using reclaimed asphalt. Similarly, recycled concrete is commonly used
in base or subbase layers of pavement structures and in a more limited capacity in new
concrete mixes. Using recycled concrete may be less costly, in part because of reduced
disposal and transportation costs. Georgia officials told us that they not only use recycled
concrete but have approved a recycling center to accept concrete from sources other than
pavements for use in road construction.
Concerning use of geosynthetics, officials from all the states we talked with have used
geosynthetics in base or subbase layers of a pavement structure. Used in this way, the
materials can improve the stability and strength of those layers. Geoynthetics can also be
used in the surface layers of asphalt pavements where it may keep water from penetrating
to the lower pavement layers and may reduce the transfer of cracks from an old pavement
to a new pavement overlay. However, officials from two states expressed concerns that
using geosynthetics in this way may create challenges for future pavement repair. For
example, one pavement preservation practice involves milling, or removing the surface layer
of an existing asphalt pavement, and replacing it with a new layer of asphalt (see table 4).
According to one official, geosynthetics used in pavement surface layers might interfere with
operation of the milling equipment and lead to additional effort to separate geosynthetic
material from the asphalt millings before they are reclaimed.

           Pavement Design and Material-Testing Practices
Table 3 describes nine design and material-testing practices affecting pavement
performance that correspond to the design stage of the pavement life cycle. These include

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using different pavement types, such as the use of warm-mix asphalt (WMA) or two-lift
concrete pavements, and tools that designers could use to predict pavement performance.

Table 3: Pavement Design and Material Testing Practices

 Practice                                                        Description
 Performance testing of        Testing to predict how the binder in asphalt will perform, using procedures such
 asphalt binder                as the Multiple Stress Creep Recovery test and the Asphalt Binder Cracking
 Performance testing for       Testing to predict how asphalt design mixes will perform using equipment such
 asphalt design mix            as the Asphalt Mixture Performance Tester.
 Using Mechanistic-Empirical A tool that predicts the performance of a pavement being designed based on
 Pavement Design Guide       mechanistic-empirical principles.
                             Consideration of aggregate (granular material, such as sand, gravel, crushed
 Optimizing aggregate used stone, or recycled concrete) characteristics—such as shape, angularity, and
 in pavements                texture—in the mix design of asphalt and concrete pavements to improve
                             Asphalt mix produced and placed at lower temperatures—ranging from 30 to 120
 Warm-mix asphalt (WMA)
                             degrees Fahrenheit lower—than traditional hot-mix asphalt.
                             Asphalt mix consisting of coarse aggregate, high asphalt cement content, filler,
 Stone matrix asphalt
                             and fibers.
 Continuously reinforced     Concrete pavement without contraction joints that is reinforced using continuous
 concrete pavement (CRCP) steel bars throughout its length.
                             Concrete pavement made of two layers: a thick lower layer that can include
 Two-lift concrete pavement materials that are less resistant to wear and a thinner surface layer made of
                             more wear-resistant materials.
                             Sections of concrete pavement that are made off-site and assembled on-site for
 Precast concrete panels
                             construction and repairs.
Source: GAO.

In reference to the practice of using WMA, FHWA included it as part of its Every Day Counts
Initiative to promote innovation; FHWA reported that, as of 2009, more than 40 states had
constructed WMA projects. 8 All of the states we spoke with have constructed WMA
projects. According to the National Asphalt Pavement Association, WMA comprised at least
15 percent of the asphalt pavement market as of 2010, and in combination with reclaimed
asphalt, WMA’s use offers significant potential for maintaining well-performing pavements at
reduced costs.
In addition, according to FHWA, the use of precast concrete panels in highway projects may
provide pavements in less time and at lower total cost—considering both construction and
user costs—than using traditional cast-in-place concrete construction methods. For
example, an FHWA Highways for Life demonstration project used precast concrete panels
to replace sections of I-66 in Virginia. 9 FHWA reported that the as-built project yielded
about a 7 percent savings over the estimated cost of the alternative reconstruction method
using cast-in-place concrete. Also, Utah officials said that they use precast concrete panels
in areas requiring rapid pavement repair, such as on highly trafficked highways.

           Pavement Maintenance and Preservation Practices
Table 4 describes 13 maintenance and preservation practices affecting pavement
performance that could be used during the maintenance and preservation stage of the
pavement life cycle. These practices include approaches to monitoring the condition of

  FHWA’s Every Day Counts Initiative is designed to get effective, proven, and market-ready technologies into
widespread use. This and other FHWA programs are discussed later in this report.
  FHWA’s Highways for Life is a grant program to demonstrate and promote innovative technologies and
accelerate their adoption by the highway community.

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pavements and examples of specific maintenance and preservation treatments that can be
used to cost-effectively sustain road networks.

Table 4: Pavement Maintenance and Preservation Practices

 Practice                                                            Description
                               Using tools such as deflection testing devices (e.g., falling weight deflectometer),
 Evaluating pavement
                               ground penetrating radar, ultra-sonic and impact echo devices, and other
 condition using non-
                               nondestructive testing devices that can be used to noninvasively evaluate the
 destructive technology
                               condition of pavements.
 Pavement                      A network-level, long-term strategy that uses an integrated, cost-effective set of
 management/preservation       pavement maintenance and preservation practices.
 Thin or ultra-thin asphalt    Applying a thin (generally 1.5 inches or less) layer of asphalt over an existing
 overlay on asphalt            asphalt pavement.
 Mill asphalt pavement and     Removing the surface layer of an existing asphalt pavement and replacing it with
 resurface with asphalt        a new layer of asphalt.
 Cold in-place recycling of    Removing existing asphalt pavement, mixing it with new asphalt, and placing the
 asphalt pavement              re-mixed material as a base layer for a subsequent asphalt overlay.
 Surface preservation          Various thin surface treatments applied to asphalt pavement, involving the
 treatments for asphalt        application of liquid asphalt and, in most cases, aggregate.
 Microsurfacing for asphalt    Spreading a thin mixture of polymer-modified asphalt emulsion, mineral
 pavement                      aggregate, mineral filler, water, and other additives on an asphalt pavement.
 Diamond grinding for          Removing surface imperfections of a concrete pavement using diamond saw
 concrete pavement             blades.
 Dowel bar retrofit for        Installing metal reinforcing bars across joints or cracks that exhibit poor load
 concrete pavement             transfer.
 Partial-depth repair for      Removing and replacing small, shallow areas of a concrete pavement to restore
 concrete pavement             localized areas of deterioration.
 Full-depth repair for         Removing and replacing a segment of concrete pavement through the depth of
 concrete pavement             the concrete slab to restore areas of deterioration.
 Joint sealing for concrete    Applying sealant material to the spaces between jointed concrete pavement
 pavement                      sections.
 Crack sealing for asphalt     Applying sealant material to cracks in asphalt or concrete pavements.
 and concrete pavements
Source: GAO.

In reference to maintenance and preservation practices, according to FHWA, applying
treatments to roads in good condition is more economical than reconstructing them after
they deteriorate: each dollar spent now on pavement preservation could save up to six
dollars in the future. However, FHWA reports that state DOTs have historically allowed
pavements to deteriorate to fair or poor condition before taking steps to reconstruct them—a
costly, time-consuming activity. Pavement management/preservation systems can help
states monitor the condition of their roads and make decisions to optimize the use of
resources by applying appropriate preservation treatments at the proper time.
Several states we spoke with (Georgia, Utah, and Washington) are expanding their use of
lower-cost surface preservation treatments. Georgia, for example, began using a
preservation practice involving thin asphalt overlays in 2007. 10 According to Georgia
officials, the cost of this practice is significantly less than the cost of a thicker asphalt overlay
that they would otherwise place. In addition, Washington has begun using an asphalt
pavement surface preservation treatment typically used on low volume highways to maintain
higher-volume asphalt highways. The treatment—known as a “chip seal”, in which liquid

  Georgia DOT officials referred to their practice as “micromilling”—removing a thin layer of asphalt from a road
and replacing it with a new, thin layer of asphalt.

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asphalt sprayed on a pavement is covered with aggregate and rolled to embed it—generally
provides less additional service life to a pavement than milling and replacing the asphalt
surface. 11 However, the life-cycle cost of a chip seal treatment is about one-third that of
milling and replacing the asphalt surface, according to state officials, and the treatment’s
use should result in lower maintenance and preservation costs over the life of the pavement.

           Pavement Construction and Reconstruction Practices
Table 5 describes eight practices that could be used during the construction and
reconstruction stages of the pavement life cycle to affect pavement performance. These
practices include specific approaches to building or rebuilding roads that may enhance their

Table 5: Pavement Construction and Reconstruction Practices

 Practice                                                             Description
 Subbase and base layer         Using cement, asphalt, geosynthetics, or other materials to improve the subbase
 treatments                     or base layers of a roadway.
                                Using compaction equipment that measures compaction levels and provides
 Intelligent compaction         feedback to allow adjustments to ensure base materials and asphalt are
                                compacted completely and correctly.
 Asphalt structural overlay for Adding pavement layers to increase the pavement’s load-carrying capacity.
 asphalt pavement
 Full-depth reclamation for     Pulverizing the existing asphalt pavement and mixing it with the underlying base
 asphalt pavement               material for use as the base for a new asphalt surface layer.
 Concrete overlay               Applying a layer of concrete (generally 2-11 inches) over an existing asphalt
 (whitetopping) for asphalt     pavement.
 Asphalt overlay for concrete Applying a layer of asphalt over an existing concrete pavement.
 Rubblization/crack and seat Fracturing existing concrete pavement into small pieces (less than 3 feet) and
 with asphalt overlay for       placing a new asphalt pavement over this base.
 concrete pavement
 Concrete overlay for           Placing a layer of concrete (generally 2-11 inches) over an existing concrete
 concrete pavement              pavement.
Source: GAO.

According to FHWA, properly compacting pavement materials, such as subbase rock and
asphalt, is one of the most important elements in constructing long-lasting pavements.
Compacting equipment with intelligent compaction systems can ensure that pavement
material is compacted correctly and completely. Three of the seven states we met with
(Georgia, Minnesota, and Texas) participated in a study aimed at accelerating the
implementation of intelligent compaction, working with equipment suppliers, for example, to
increase awareness of the technology.
In addition, since the early 1990s, according to FHWA, the use of whitetopping has grown
significantly in the U.S., as newer techniques for bonding the new concrete to the old
pavement have allowed for use of thinner concrete layers (2 to 6 in.) over existing asphalt
pavements. A potential benefit to whitetopping repair is the durability of concrete, which
results in a greater interval between reconstruction treatments compared to use of an
asphalt overlay. Colorado has conducted many whitetopping projects and, of the states we
spoke with, Iowa officials said that whitetopping is used extensively on county roads in their

     “Aggregate” is granular material, such as sand, gravel, crushed stone, or recycled concrete.

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           Quality Assurance and Quality Control Practices
Table 6 describes four quality assurance and quality control practices that could be used
during the construction, maintenance, or reconstruction stages of a pavement’s life cycle to
affect performance. These practices include specific devices that can be used and actions
that can be taken to ensure constructed work meets the level of quality intended by the

Table 6: Quality Assurance and Quality Control Practices

 Practice                                                            Description
 Infrared thermography for     Devices that non-destructively measure temperature variation in asphalt as
 asphalt pavement              pavements are constructed to identify possible quality problems.
                               A system of devices that provides on-site, real-time recommendations to achieve
 Smart Cure System
                               optimal concrete curing based on ambient conditions.
 Magnetic imaging              A non-destructive testing device that determines the thickness of fresh concrete
 tomography                    pavement.
                               A warranty establishes the expected performance of a product (such as a newly
 Warranties                    constructed road or repair of an existing road) and the responsibility to repair or
                               replace defects for a defined period.
Source: GAO.

According to FHWA, “infrared thermography”—equipment that measures the temperature of
asphalt as it is placed by a paving machine—can help ensure asphalt is placed at the
appropriate temperature, which is a critical factor in preparing uniform, high-quality
pavements. Knowing the temperature helps to better identify and immediately correct parts
of the road where temperatures are not sufficiently uniform and failures are likely to occur.
Officials in four of the states we spoke with (Georgia, Minnesota, Texas, and Washington)
said their states have experimented with the use of infrared equipment on paving machines.
A Minnesota DOT evaluation of infrared thermography (see table 6) and intelligent
compaction (see table 5) concluded that both practices can be used as effective quality
assurance tools to improve pavement performance.
In addition, FHWA encourages the use of pavement warranties and notes that the most
benefit comes from long-term performance warranties (generally ranging from 10 to 20
years). While use of warranties shifts some risk to the contractor—which can raise project
costs —FHWA notes that increased contractor responsibility should allow greater freedom
for innovation. None of the states we spoke with said they are currently using warranties.
Officials from five states that had used or considered using warranties noted that contractors
may be challenged to provide long-term warranties because of the cost of holding a bond
over the term of the warranty. 12

Potential Cost Savings of These Materials and Practices Varies and Can Be Assessed
Using Life-Cycle Cost Analysis
By improving the durability or extending the service life of pavements, the materials and
practices described in the preceding tables may decrease the life-cycle costs of a
pavement—that is, the costs associated with constructing and maintaining a pavement over
its lifetime. 13 The cost of a pavement is dependent on a range of factors that may be
specific to an individual state or project, including climate, traffic, and geologic conditions.

   A bond, secured through a surety, guarantees contractor performance throughout the warranty period.
   GAO will be conducting work during the next year on best practices for calculating life-cycle costs and benefits
for federally funded highway projects, as mandated by the recent adoption of 23 U.S.C. § 503(b)(3)(D)(ii) by the
Transportation Research and Innovative Technology Act of 2012. Pub. L. No. 112-141, Div. E, Title II,
§ 52002(b), 126 Stat. 405, 866-875 (July 6, 2012).

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For example, constructing a pavement in a northern state that experiences frequent freeze-
thaw cycles may involve different factors than constructing a pavement in a southern state
that rarely does. Likewise, constructing a pavement to accommodate high levels of truck
and other vehicle traffic may involve different factors than constructing a pavement to
accommodate relatively low levels of traffic.
A state DOT may conduct a life-cycle cost analysis to compare construction and
maintenance alternatives—and the possible materials and practices associated with each—
in determining approaches to building and maintaining pavements. For each alternative, the
analysis provides projections based on initial costs, such as material and construction costs,
and future costs—such as maintenance, user, and reconstruction costs—over the life of a
project. For example, a state may perform life-cycle cost analysis to compare the costs of
using asphalt or concrete as surface layer materials to construct or reconstruct a road.
Some states we met with had used life-cycle cost analysis to inform key decisions. For
example, in 2005, Utah DOT assessed two of its existing asphalt surface preservation
treatments—an open-graded surface course and a chip seal—and found the chip seal
treatment to be much more cost-effective. 14 The analysis showed that expanding the use of
chip seals and limiting use of open-graded surface courses to certain high volume roads
could result in a savings of over $2 million per year. Similarly, the Georgia DOT conducted
a life-cycle cost analysis to compare the costs of using conventional asphalt and stone
matrix asphalt (see table 3). While stone matrix asphalt is more expensive than
conventional asphalt, it is highly durable and can provide a 30 to 40 percent increase in
pavement life. In its analysis, Georgia considered that the stone matrix asphalt would need
less frequent maintenance and repair, resulting in estimated annualized costs that were 37
percent less than using conventional asphalt. This analysis led Georgia to select use of
stone matrix asphalt based on its overall lower life-cycle cost.

Some Materials and Practices May Provide Additional Benefits
Some of the materials and practices described in the preceding tables offer additional
benefits, beyond improving pavement performance, for example:
     •    Incorporating reclaimed or recycled materials (see table 2) into highway pavements
          provides an environmental benefit by making use of a material that might otherwise
          be disposed of and reducing the amount of new material needed.
     •    Using precast concrete panels (see table 3) can provide a benefit to users of the
          road under repair. Concrete that is placed on-site may take several days to cure,
          and during that time, affected lanes must remain closed to traffic. Conversely,
          precast panels may be driven on immediately, thereby reducing the inconvenience to
     •    Following the principles of a pavement management/preservation system (see table
          4) can provide sustainability benefits because these tools seek to minimize the
          amount of natural resources used over a pavement’s life cycle.

Potential Challenges to Implementing Materials and Practices
Although the materials and practices identified in this report may offer states opportunities
for savings and improved pavement performance, certain factors could prevent states from
implementing them. In our review of literature regarding these factors, we identified
challenges in four areas that could affect the extent to which state DOTs implement
  An “open-graded surface course” is an asphalt pavement treatment that is water-permeable. Its use can
reduce spray from water on the road and provide a quieter ride.

Page 11                        GAO-13-32R Materials and Practices for Improving Pavement Performance
materials and practices. In our interviews with state DOTs, officials also identified challenges
in these same areas. FHWA and others have developed several ongoing programs and
efforts to overcome these challenges.

Literature Review Identified a Range of Challenges
Our literature review identified challenges in the following four areas that might prevent state
DOTs from implementing materials and practices:
     •    Suitability of Materials and Practices: In some cases, a particular material or practice
          may not be applicable or beneficial to all states. Because of differences in climate,
          sources of raw materials, and other factors, a material or practice that works well for
          one state may not work well for another. For example, two-lift concrete pavement
          (see table 3)—which allows lower quality aggregates to be used in a lower level of
          the pavement—may be beneficial in a state where good aggregates for pavement
          have to be transported in at a high cost. However, in a state with an abundant
          supply of good aggregates, using two-lift construction may not be cost-effective. In
          other cases, a state may find that a material or practice has not been sufficiently
          tested, or that the results of testing are not sufficiently quantifiable. This is in part
          because, given the long-lasting nature of pavements, the results of testing or using a
          practice may not be known for 10 years or more. Finally, highway pavement
          systems are complex, and interaction between different components makes it difficult
          to understand how the implementation of a material or practice may affect other
     •    Structure and Culture of the Industry: As we and others have previously reported, the
          highway industry is highly decentralized and segmented. 15 There are about 35,000
          different federal, state, and local entities responsible for constructing, operating, and
          maintaining U.S. highways. In addition, there are many private companies of many
          sizes and specialties that carry out highway design work and much of the highway
          construction work, and that supply materials, equipment, and services used by public
          agencies. As a result, it takes time to overcome implementation challenges in each
          agency to achieve widespread use of a material or practice. In addition, a number of
          reports have pointed to a cultural resistance to change in the highway industry.
          State DOTs and other public agencies are risk averse because success can bring
          minimal rewards and the cost of failure can be high. As a result, an agency’s
          leadership may not provide sufficient support and direction to encourage innovation.
          Likewise, highway contractors may be reluctant to invest in new technologies without
          an assurance that a state DOT will share the risk of using them.
     •    Resources: Insufficient funding to implement new materials and practices can limit
          states’ use of them, as the budget or cost required may exceed the level
          management is willing to support. Limited staff resources because of decreased
          agency size, staff turnover, or lack of staff with technical expertise may also prevent
          a state DOT from implementing a material or practice. As a result, staff may not
          have time or expertise to take on the additional workload required to implement a
          material or practice, such as writing new specifications for the practice.

  GAO, Highway Technology: The Structure for Conducting Highway Pavement Research, GAO/PEMD-88-2BR
(Washington, D.C.: Nov. 13, 1987); GAO, Highway Infrastructure: Federal-State Partnership Produces Benefits
and Poses Oversight Risks, GAO-12-474 (Washington, D.C.: Apr. 26, 2012); Transportation Research Board,
Special Report 261 The Federal Role in Highway Research and Technology (Washington, D.C.: 2001); and
Transportation Research Board, Special Report 296 Implementing the Results of the Second Strategic Highway
Research Program: Saving Lives, Reducing Congestion, Improving Quality of Life (Washington, D.C.: 2009).

Page 12                        GAO-13-32R Materials and Practices for Improving Pavement Performance
   •      Procurement and Specifications: Public agencies use procurement methods that can
          inhibit them from implementing new materials and practices. The low bid system,
          whereby a state DOT accepts the lowest bid that meets the terms of a public
          proposal, may limit both the state’s and contractors’ ability to introduce innovation
          that might cost more to construct, but have a lower life-cycle cost. Some agencies
          use an initial cost criterion to determine whether to use a new practice; although a
          new practice can be initially more costly than an existing practice, it might provide
          lower costs over its lifetime. Implementing a new technology may require a DOT to
          revise its specifications to allow its use. Most highway agencies have their own
          specifications and revising them may require the coordination of several
          organizational entities, increasing the difficulty of the task. Finally, state DOTs may
          find it is not always easy to use proprietary products. These products are usually not
          allowed, because they could limit competition and may not conform to a state’s
          standard design specifications.

State DOTs Identified Challenges Similar to Literature Review
In our interviews, state officials identified challenges they experienced in implementing new
materials and practices similar to the suitability, culture, resources, and procurement areas
identified above. Most examples they provided, however, involved issues with the suitability
of materials and practices.
   •      Suitability of Materials and Practices: In at least three instances, state officials
          reported that they had success with a practice that had not worked well in another
          state. For example, in Texas, officials stated they use CRCP (see table 3)
          extensively and have had good experiences with them. However, Iowa officials said
          they have used CRCP in the past but believe them to be cost-prohibitive and have
          experienced good performance with jointed concrete pavements. In addition,
          Georgia has used stone matrix asphalt (see table 3) on its Interstates and other high-
          volume highways because of its durability. However, in the neighboring state of
          Tennessee, officials stated that they evaluated stone matrix asphalt, decided the
          initial cost was too high, and have not widely adopted its use.
          A state DOT may be less willing to implement a practice that is not well-understood
          or not perceived to have sufficient benefits. For example, Minnesota officials said
          they tried requiring extended warranties (see table 6) but found the costs prohibitive
          for contractors to bond the projects over the warranty period. Because these costs
          are passed on to the DOT in the form of higher bids on contracts, the officials said
          they determined that the increased costs were greater than the benefit provided by
          the warranties and discontinued the practice. Also, Washington officials stated that
          they have not used two-lift concrete (see table 3) because they know their locally
          available materials and current construction practices work well.
          Materials and practices that have not been sufficiently tested may present a
          challenge. For example, Washington officials told us that even though there might
          be research on a particular practice, they will not necessarily implement it until they
          verify reasonable performance and that the practice will work on their state’s roads.
          In addition, Tennessee officials stated they used recycled shingles (see table 2) on a
          few projects and are planning more, but additional testing is needed. They stated
          that specifications routinely allowing the recycled shingles could be up to a year
          Potential or actual interactions between different paving materials may also present a
          challenge to implementing new materials and practices. According to state officials,
          Georgia specifications allow up to 40 percent reclaimed asphalt pavement (see table

Page 13                       GAO-13-32R Materials and Practices for Improving Pavement Performance
          2), but contractors typically use less—about 25 to 30 percent—because using more
          can prevent them from complying with other specifications designed to decrease
          pavement deterioration. Similarly, Utah specifications allow blended cements (see
          table 2), and state officials said that they generally perform as well as standard
          concrete mixes. However, these officials have found that blending cement with
          locally sourced limestone does not allow the concrete to strengthen quickly and thus
          should not be used in cases where this characteristic is desired. 16
          A negative experience with a practice may prevent a state from using the practice
          again. Tennessee officials said they used recycled tire rubber (see table 2) in three
          asphalt paving projects in 1993 and 1998, and two of the pavements failed early, so
          they did not adopt further use of the material. 17 Utah officials said they stopped
          using geosynthetics (see table 2) in pavements because they found it was not as
          effective in inhibiting the transfer of cracks from the old pavement to the new
          pavement overlay as expected.
     •    Structure and Culture of the Industry: Tennessee officials stated that they are open
          to looking at new materials and practices but are not willing to get too far ahead of
          everyone else. In addition, states may meet resistance from contractors when
          implementing materials and practices that are new to them. Georgia and Minnesota
          officials stated that they had received resistance from contractors to implementing
          the use of intelligent compaction (see table 5) or infrared thermography (see table 6).
          For example, Georgia DOT officials stated that they had received resistance from
          contractors to implementing the use of intelligent compaction because the costs to
          purchase the equipment is high, and the investment in equipment, without a
          requirement from a state for its use, is difficult to justify. Minnesota DOT officials
          said that they had also received resistance from some contractors to implementing
          the use of infrared thermography because it brings added complexity and the
          investment in equipment without a commitment from the state for its future use was
          difficult to justify. While one of the contractors that purchased an infrared paving bar
          has continued to use it, another contractor only used it on the job for which it was
          required. Similarly, Utah officials stated that while the use of optimized grading of
          aggregates for concrete pavement (see table 3) could be beneficial, the
          implementation has been very slow due to industry’s resistance to making costly
          required changes to concrete plants. Utah officials noted that while they are
          modifying their specifications to allow the use of a wider range of materials and
          practices, it is up to the contractors to include them in their bids to the state.
     •    Resources: Minnesota officials stated there are more materials and practices they
          would like to evaluate than available funds or staff to do it. As a result, they use
          professional engineering judgment to select materials and practices to evaluate
          based on the likelihood of implementation. Georgia officials stated that with the
          continued downsizing of staff, they will have little expertise remaining in their
          organization to change specifications to allow new materials and practices. Iowa
          officials noted that reduced travel because of budget reductions is sometimes a
          challenge, resulting in a reduction of the staff’s ability to adequately understand new
          materials and practices and implement them.
     •    Procurement and Specifications: Minnesota officials wanted to try intelligent
          compaction (see table 5) on a project but could not require its use because they
          lacked a specification. As a result, they worked with an equipment manufacturer and
   This characteristic, known as “high early strength,” refers to concrete that achieves its specified strength at an
earlier age than normal concrete. High early strength concrete used in repair or construction projects, for
example, can carry traffic within a few hours after the concrete is placed.
   Tennessee officials told us that they used recycled tire rubber in an asphalt paving project in 2011 that is
currently performing satisfactorily.

Page 14                           GAO-13-32R Materials and Practices for Improving Pavement Performance
          distributor to outfit compaction equipment with intelligent compaction systems and
          conducted two pilot projects. Based on these pilot projects, officials developed
          contract specifications pertaining to intelligent compaction systems. They expect to
          start using these specifications in contracts beginning in 2013. Texas officials stated
          they wanted to use a promising new aggregate in their concrete pavements that
          improves concrete quality. However, the material is only produced by one
          manufacturer, limiting their ability to specify it in requests for contract proposals.
          Similarly, Utah officials wanted to use proprietary asphalt materials in their cold in-
          place recycling (see table 4) and full-depth reclamation (see table 5) practices.
          Although they cannot specify proprietary products, the officials said that their effort to
          change to performance-based specifications might enable them to overcome this
          challenge. Performance specifications require a contractor to meet functional criteria
          such as strength and durability, without prescribing use of specific materials or
          practices. As a result, contractors may choose to use proprietary materials or
          practices to meet performance requirements.

Agencies Have Implemented Various Programs and Efforts to Overcome These Challenges
FHWA, the Transportation Research Board (TRB), AASHTO, and states have developed
several programs that address the challenges of developing new materials and practices
through research, training, information and outreach programs, demonstration projects, and
other incentives. 18 The following are some of the programs the agencies and organizations
have in place to promote the use of pavement materials and practices and other highway

FHWA works with state, industry, and trade associations’ stakeholders to develop and
implement new materials and practices through the following programs:
     •    Advanced Concrete Pavement Technology Products Program: A national
          technology transfer effort to improve the long-term performance and cost-
          effectiveness of the nation's concrete pavement highways by identifying, refining,
          and delivering the available technologies that can enhance the performance of
          concrete highways. Some of the materials and practices the program is advancing
          include mechanistic-empirical concrete pavement design (see table 3), concrete
          overlays (see table 5), and the use of recycled materials (see table 2).
     •    Every Day Counts Initiative: A program designed to get effective, proven, and
          market-ready technologies into widespread use. Warm-mix asphalt (see table 3) is
          one of the practices the program has featured.
     •    Highways for Life: A grant program to demonstrate and promote innovative
          technologies and accelerate their adoption by the highway community. 19 We
          observed a demonstration project partially funded by this program that included four
          of the materials and practices we identified in the previous section of this report,
          including use of optimized aggregate (see table 3 and fig. 4), intelligent compaction
   TRB is a unit of the National Research Council within the National Academy of Sciences whose mission is to
provide leadership in transportation innovation and progress through research and information exchange. TRB
is supported by state transportation departments, federal agencies, including the component administrations of
the U.S Department of Transportation, and other organizations and individuals interested in the development of
   This program was authorized as a pilot program under section 1502 of the Safe, Accountable, Flexible,
Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU), Pub. L. No. 109-59, 119 Stat 1144,
1236-1237 (2005).

Page 15                         GAO-13-32R Materials and Practices for Improving Pavement Performance
          (see table 5), geosynthetics (see table 2), and curing compounds (see table 2 and
          fig. 5). 20

Figure 4: Concrete Plant Producing Optimized Aggregate Concrete for the Highways for Life Project in
Tarrant County, Texas, 2012

Figure 5: Application of Concrete Curing Compound at the Highways for Life Project in Tarrant County,
Texas, 2012

     •    Long-term Pavement Performance Program: A 20-year study of in-service
          pavements across North America. The program’s goal is to extend the life of
          highway pavements through various designs of new and rehabilitated pavement
          structures using different materials and under different loads, environments,
          subgrade soils, and maintenance practices. One of the more recent results of this
  The project included construction of a 2.2 mile section of continuously reinforced concrete pavement in Tarrant
County, Texas, on FM 1938 from SH 114 to Randol Mill Road. FHWA, through its Highways for Life Program,
provided a grant of $1 million on this estimated $16.5 million project.

Page 16                          GAO-13-32R Materials and Practices for Improving Pavement Performance
          study is guidance on selecting the most effective pavement preservation treatments
          for asphalt pavement (see table 4).
     •    Transportation Pooled Fund Program: Interested states, FHWA, and other
          organizations may pool funds and other resources for new areas of research,
          planning, and technology innovation or to provide information that will compliment or
          advance previous efforts in these areas.
     •    International Technology Scanning Program: 21 An FHWA program to help states and
          industry access innovative materials and practices from other countries. The
          program helped entities adapt and put into practice highway innovations without
          spending research funds to re-create advances already developed by other
          countries. Past scans included providing information on asphalt and concrete
          pavements, pavement preservation (see table 4), superior materials, reclaimed or
          recycled materials (see table 2), and many other non-pavement related topics.
     •    Technology Innovation and Deployment Program: Section 503(c)(3)(C) of Title 23,
          United States Code, now requires that the Secretary of Transportation obligate at
          least $12 million per year to accelerate the deployment and implementation of new
          pavement innovations and technology. 22

TRB also has several programs that are providing additional research to and helping to
share information regarding new materials and practices with states.
     •    National Cooperative Highway Research Program (NCHRP): Conducts research in
          problem areas that affect highway planning, design, construction, operation, and
          maintenance nationwide. Its efforts include helping state DOTs put the findings to
          early use in the form of policies, procedures, specifications, and standards. Two
          subprograms are involved within NCHRP:
          •   The Innovations Deserving Exploratory Analysis program funds research into
              innovations for design, construction, materials, operations, maintenance, and
              other areas of highway systems.
          •   The U.S. Domestic Scan Program is designed to identify materials and practices
              being used within the United States that might be beneficial to other states and
              then disseminate those materials and practices to others.
     •    Strategic Highway Research Program (SHRP): The first Strategic Highway
          Research Program (1988 to 1993) changed asphalt pavement design by producing a
          new method for designing pavements that reduced distress, resulting in better
          performing and longer lasting pavements. The second Strategic Highway Research
          Program (SHRP 2) (2006 to 2015) was authorized by Congress to address some of
          the needs related to the nation’s aging highway system, including renewal of roads
          through construction methods that produce long-lived facilities. Some of the work
          related to pavements undertaken in SHRP 2 includes precast concrete pavement
          technology (see table 3), infrared thermograpghy (see table 6), and ground
          penetrating radar (see table 4).

   This program was conducted under section 5206 of SAFETEA-LU, known as the International Highway
Transportation Outreach Program, Pub. L. No. 109-59, 119 Stat., 1795-1796.
   23 U.S.C. § 503(c)(3)(C) as amended by the Transportation Research and Innovative Technology Act,
§ 52003, 126 Stat., 879-880.

Page 17                        GAO-13-32R Materials and Practices for Improving Pavement Performance
AASHTO has groups to assist DOTs in overcoming the challenges of implementing
materials and practices.
       •   National Transportation Product Evaluation Program: Evaluates materials, products,
           and devices for use in highway and bridge construction. The program’s goal is to
           provide cost-effective evaluations for state DOTs by eliminating duplication of testing
           and auditing by the states and manufacturers that provide products. Some of the
           materials and practices being evaluated include warm-mix asphalt (see table 3), joint
           sealing for concrete pavement (see table 4), crack sealing for asphalt pavements
           (see table 4), concrete overlays (see table 5), concrete curing compounds (see table
           2), and geosynthetics (see table 2).
       •   Technology Implementation Group: Identifies and champions the implementation or
           deployment of a select few proven technologies, products, or processes that are
           likely to yield significant economic or qualitative benefits to the users. Some of the
           pavement technologies promoted include precast concrete pavement slabs (see
           table 3) and hot in-place asphalt pavement recycling.

           State DOTs
Officials at some of the state DOTs we interviewed said that in addition to working with
FHWA and others, they had their own efforts under way to evaluate and implement new
materials and practices. For example, Minnesota officials told us the state created a $20
million innovation program in 2010 which can pay for the incremental costs associated with
using practices such as intelligent compaction (see table 5). 23 In one case, the state paid a
contractor to outfit its construction equipment to use intelligent compaction, thus reducing
the reluctance of the contractor to bid the project and buy equipment it might not use again.
In another instance, the state used the funding to pay for a new asphalt-patching material for
use by its maintenance division. This purchase allowed the state to become familiar with
the product and develop specifications for potentially continuing its use.

Agency Comments
We provided U.S. Department of Transportation (DOT) with a draft of this report for review.
U.S. DOT did not comment on the draft report. We also provided each of the seven state
DOTs we spoke to with a draft of relevant sections of this report for review. Each provided
technical comments, which we incorporated as appropriate.
We are sending copies of this report to congressional committees with responsibilities
for surface transportation issues, the Secretary of Transportation, the Administrator of the
Federal Highway Administration, and other interested parties. In addition, this report is
available at no charge on the GAO website at http://www.gao.gov.

     The program was funded with $15 million in 2012.

Page 18                           GAO-13-32R Materials and Practices for Improving Pavement Performance
If you or your staff have any questions about this report, please contact me at (202) 512-
2834 or stjamesl@gao.gov. Contact points for our Offices of Congressional Relations and
Public Affairs may be found on the last page of this correspondence. GAO staff who made
key contributions to this correspondence are Michael Armes, Hal Brumm, William Carrigg,
Bert Japikse, Justin Jarrett, Les Locke, Amy Rosewarne, Travis Thomson, and Elizabeth

Lorelei St. James
Director, Physical Infrastructure Issues


Page 19                    GAO-13-32R Materials and Practices for Improving Pavement Performance
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