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C H A P T E R 3
Development of Preservation Guidelines
for High-Traffic-Volume Roadways
The results of the literature review and the questionnaire sur- of the treatment selection process depicted in Figure 3.1.
vey are an excellent starting point for identifying the state of In this process, the current and historical conditions of the
the practice for preservation of high-traffic-volume facilities. existing pavement are first established through condition
The information indicates the types of treatments that can be surveys or the agency's pavement management system (PMS)
successfully used on pavements with high traffic volumes, and records or both. A preliminary list of preservation treatments
it also reveals much about other key factors that can influence that best address the deficiencies of the existing pavement
the selection of treatments at the project level. Specific insights is then developed. The candidate treatments are evaluated
obtained relate to the following: according to their ability to satisfy the performance needs and
construction constraints of the project. A final list of feasible
Performance Attributes treatments is then generated and these treatments are analyzed
· Effect of existing pavement condition (distress) and service- for cost-effectiveness and other considerations to arrive at
ability (smoothness) on treatment performance. the preferred treatment.
· Effect of traffic volume on treatment performance.
· Effect of climate and environment on treatment performance:
Preliminary Analysis of
Direct climatic and environmental stresses; and
Treatment Feasibility:
Stresses associated with snowplowing and studded or
Consideration of Existing
chained tire use.
Pavement Conditions
· Effect of treatment on pavement condition, serviceability,
safety (friction, surface drainage [splash/spray, cross slope]), Applying preservation treatments at the correct time is often
and noise. cited as a key to cost-effectively extending pavement service-
ability. If a treatment is applied too soon, funds are expended
Constructability Issues on roads that do not require treatment or do not exhibit
· Costs (agency and user). sufficient benefit to justify the costs. If a treatment is applied
· Complexity of construction. too late, the road may have deteriorated to the point that the
· Availability of skilled and experienced or qualified treatment is ineffective or does not add sufficient life to the
contractors. pavement to justify the cost. Thus, the correct time represents
· Need for specialized equipment or materials. a "window of opportunity" in terms of the condition or service-
· Availability of quality materials. ability of the pavement.
· Environmental constraints. Most practitioners agree that preservation treatments should
· Traffic disruption. be applied during the period when the pavement remains in
· Traffic control constraints. fair to good condition. A recent NCHRP survey on pavement
· Restrictions on available time for lane closures to complete preservation revealed that more than two-thirds of the report-
the work. ing agencies treat roads while they are still in fair to good
condition, whereas less than 5% treat pavements in very
This chapter draws upon the findings presented in Chap- poor condition (Peshkin and Hoerner 2005). This leads to
ter 2 and incorporates additional information, concepts, and the conclusion that most state agencies try to restrict treat-
ideas that convey the state of the practice within the backdrop ment to pavements in fair to good condition. Findings from
33
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Establish existing Determine Perform cost-effectiveness
pavement project needs analysis and evaluate economic
condition. and constraints. and noneconomic factors.
Identify preliminary Identify final set Identify
set of feasible of feasible preferred
treatments. treatments. treatment.
Figure 3.1. Process of selecting the preferred preservation treatment.
the SHRP SPS-3 and SPS-4 studies of PM on both HMA before an expected rehabilitation is assigned to each treatment,
and PCC support this, concluding that "treatments applied based either on the number of years remaining in the design
to pavements in good condition had shown good results" life of the existing pavement structure or on the projected
(Morian et al. 1997). performance trend (overall condition or smoothness curves
Preservation treatments have often been applied according and corresponding terminal and threshold levels), as illustrated
to a predetermined schedule based on a time (or a window in Figure 3.2.
of time) since original construction or the last major reha- An example of RSL-based windows of opportunity is
bilitation (e.g., crack seal at Year 5, apply a chip seal between featured in a report covering the development of a pave-
Years 7 and 10). In some cases, recurring intervals were estab- ment PM program in Colorado (Galehouse 2004). The recom-
lished (e.g., reseal joints every 7 years). This is also referred to by mended RSL criteria for various HMA- and PCC-surfaced
some agencies as cyclic maintenance. The schedule was usually treatments are listed in Table 3.1. These criteria are used in
established based on information obtained from maintenance conjunction with distress index scores (discussed later in this
surveys or on agency experience with the types and rates of chapter), which provide the direct tie-in needed with pave-
deterioration incurred by certain pavement types. However, ment condition.
whereas a schedule-based approach has the advantage of ease of With the advancements in PMSs in recent years, the iden-
budgeting and programming, it often results in poor treatment tification of candidate treatments can be more closely tied
choices for existing problems (Shober and Friedrichs 1998) to the existing pavement conditions. Using historical data
because pavement condition is only indirectly considered on overall condition (pavement condition index/rating [PCI/
through the proxy of time. PCR]), serviceability (present serviceability index/rating
A variation of the schedule-based approach is remaining [PSI/PSR]), or roughness (international roughness index
service life (RSL). In this approach, a minimum time period [IRI]), performance models can be developed for groups of
Existing
Pavement Minimum
Condition Treatment Application Remaining
Window Service Life
(RSL)
Terminal/Threshold Condition Level
Time
Projected Year of
Major Rehabilitation
Figure 3.2. Remaining service life approach to establishing treatment
application windows.
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Table 3.1. Recommended RSL Criteria for PM Treatments in Colorado
Flexible Pavements Rigid Pavements
Minimum RSL Minimum RSL
Treatment (years) Treatment (years)
Crack filling 9 Crack sealing 10
Crack sealing 10 Joint resealing 10
Sand seals 9 Diamond grinding 8
Chip seals 8 Partial-depth spall repair 10
Microsurfacing (single course) 12 Dowel bar retrofit 10
Microsurfacing (multiple course) 8 Full-depth concrete repair 7
Ultra-thin bonded wearing course 8
Thin HMA overlay 6
Mill and thin HMA overlay 6
Source: Galehouse 2004.
similar pavements (i.e., pavement families), which can then general guidelines for establishing condition-based windows
be used to set condition-based windows of opportunity for of opportunity for preservation treatments on high-traffic-
individual treatment types. As overall condition, serviceability, volume facilities.
or roughness is tracked at the project level, feasible treatments Two important considerations in the identification of
can be identified according to the established windows of treatments based on windows of opportunity are the rate
opportunity (see Figure 3.3). of deterioration and the gap between when a treatment is
Overall condition, serviceability, and roughness measures selected and when it formally gets constructed. Pavements
do not indicate specific pavement deficiencies or problems; showing abnormally high reductions in condition (say more
they can only provide a general indication of when specific than 4 to 5 PCI/PCR points per year or more than 7 to 8 in./mi
treatments should be considered for use. Hence, it is criti- (0.11 to 0.13 mm/m) of IRI per year) are likely being affected
cal that they be augmented with application criteria pertaining by structural or subsurface material issues that could greatly
to individual pavement distresses. The next section presents limit the effectiveness of a preservation treatment. If the gap
some examples in which overall pavement condition is eval- between treatment selection and construction is expected to be
uated in conjunction with detailed distress data in order to 1 year or more, the conditions of the pavement will likely have
identify candidate preservation treatments. It also presents changed enough to warrant the reevaluation of treatments.
Overall Condition,
Serviceability, or
Roughness
Condition/Serviceability Trendline
Appropriate Condition/
Serviceability Range
Condition-Based Windows
of Opportunity
Appropriate Roughness Range
Roughness Trendline
Time
Figure 3.3. Windows of opportunity based on age and overall condition.
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This is particularly true if the condition data upon which Table 3.2. Ohio DOT Condition Criteria
a treatment was selected did not fully reflect the conditions for PM Treatments
at the time of selection (i.e., the condition survey data were
collected or processed several months before the evaluation Pavement Condition Rating
(PCR) Rangea
or selection process).
Flexible Composite
PM Treatment Pavements Pavements
Windows of Opportunity
Crack sealing 75 to 95 75 to 95
Ohio, New York, and Alberta represent agencies that use Chip seal 75 to 90 75 to 90
overall pavement condition in conjunction with detailed
Microsurfacing 75 to 90 75 to 90
distress data to identify candidate preservation treatments. As (single course)
seen in Table 3.2, the Ohio DOT uses PCR ranges as criterion
Microsurfacing 75 to 90 75 to 90
for identifying candidate PM treatments for HMA-surfaced (double course)
pavements. The PCR ranges for five of the six treatments span
PMAC overlay 75 to 90 75 to 90
the same condition range defined by ODOT as good (75 to 90),
Thin HMA overlay 75 to 90 75 to 90
while the range for the sixth treatment, crack sealing, extends
partly into the very good condition category (90 to 100). As dis- Source: ODOT 2001.
Note: PMAC = Polymer-modified asphalt concrete.
cussed later, additional criteria, including detailed distress data a Condition categories listed in ODOT Pavement Condition Rating Manual:
and traffic levels, are also used by Ohio in identifying candidate 90100, very good; 7590, good; 6575, fair; 5565, fair to poor; 4055, poor;
treatments. 040, very poor.
The New York State DOT uses a 1-to-10 surface condi-
tion rating along with pavement roughness (IRI) to identify
candidate treatments (preventive and rehabilitation) for high- entail light to moderate forms of rehabilitation are candidates
traffic-volume roads. The performance curve and windows of for pavements with (a) condition ratings between 5.5 and 6.5
opportunity shown in Figure 3.4 provide a general basis for and IRI 95 in./mi ( 1.5 mm/m) or (b) condition ratings
the treatment selection matrix, which is shown in Figure 3.5. between 6.5 and 7.5 and 96 IRI 170 in./mi (1.51 IRI
Generally speaking, non-paving-type PM (i.e., crack sealing) 2.7 mm/m).
is prescribed for pavements with surface ratings between The Alberta Ministry of Transportation (MOT) uses pave-
7.5 and 8.5 and any level of roughness. Paving-type PM, such ment smoothness as the first level in the hierarchy of assessing
as ultra-thin and thin HMA overlays, are candidates for pave- and selecting preservation treatments (Alberta MOT 2006).
ments with condition ratings between 6.5 and 7.5 and with Rural highway pavements smoother than the following IRI
IRI 95 in./mi ( 1.5 mm/m). Multicourse treatments that levels are analyzed according to individual distress types,
Condition
Rating Do Nothing
Pavement Performance Curve and
10 Windows of Opportunity
Nonpaving PM
9
PM Paving
8
Multicourse
7
Major Rehab/
Recon
6
5 Time
Source: NYSDOT 2008.
Figure 3.4. Condition rating windows of opportunity for various forms
of pavement preservation for New York highways.
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9+ D D D D D D Flexible Overlay
1 Crack seal 8 CIPR (not used on high
8 1 1 1 1 1 1
volume)
Surf 7 5 5A 9 9 11 11 3 Thin overlay 9 Mill and fill
Rating 5 6.3 mm asphalt 11 Mill and fill
6 9 9 9 11 12 12
w/underlying pvt repairs
5A 6.3 mm asphalt 12 Major rehab: 2-course
5 9 9 11 12 12 13
mill and fill OL w/repairs
6 1.5 in. hot-mix overlay 13 Reconstruction: 3-course
60 6195 96135 136170 171220 >220
OL w/repairs
Ride Quality (IRI, in./mi) D Defer treatment
Pavement Surface Rating Based on Frequency and Severity Descriptions
Severity
Frequency Moderate Very Travel Is
None Slight Minor Moderate Severe Impassable
to Severe Severe Impaired
No distress is present. A single
None 10/9 - - - - - - - -
random defect per 0.10 mi is allowed.
Most of pavement is free of distress.
One or two cracks or distresses are Infrequent - 8 8 8 7 7 - - -
visible for the next 0.10 mi.
Much of pavement is free of Infrequent
cracking. Large blocks of distress- to - 8 7 7 7 6 6 - -
free pavement are present. occasional
Much (0.5) of the
pavement is cracked. Uncracked or
Occasional
undistressed blocks of pavement - 7 7 6 6 5 5 - -
to frequent
range from 20 to 30 ft/lane to 12
ft/lane.
Nearly all the pavement is cracked.
Uncracked or undistressed blocks of Frequent - 7 6 6 5 4 3 2 1
pavement are 12 ft2 or less.
Mostly cracked. Cracks or distress
Very
are continuous and spaced only a few - 6 6 5 5 4 3 2 1
frequent
feet apart.
Slight: Cracks are tight, single, and only a few feet long. Tight,
single longitudinal joint cracks, partial or continuous, are included.
Minor: Cracks are generally <0.125 in. wide, some with minor secondary
cracks, no or very few connected cracks. May have a few small spalls
(<1 ft2).
Moderate: Cracks are generally >0.125 in. wide, secondary cracking is common, some
cracks connected; may have some minor popouts or small (1 to 2 ft) to medium (3 to 4
ft) patching.
Moderate to Severe: Distresses vary from "moderate" to "severe."
Severe: Cracks are wide and/or have extensive interconnected secondary cracking;
holes, loose material, and/or patching are common; patches may have patches.
Very Severe: Cracks are very wide; holes and/or patching is extensive; patches extend
across the full lane or extend several feet along the lane; patches on patches are common.
Travel Is Impaired: Holes in pavement are large and/or pavement has so many
layers of patches that the section can be traveled only at reduced speed.
Impassible: Travel by ordinary car would risk damage to the vehicle.
Source: NYSDOT 2008.
Figure 3.5. Treatment selection matrix used for high-traffic-volume (AADT > 20,000 vpd)
HMA-surfaced Interstates and highways in New York.
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severities, and extents to determine candidate preservation adequately designed and constructed pavement, there is a fairly
treatments: consistent pattern to distress development and to the sequence
of treatments intended to address the distresses at various
AADT, vpd IRI Trigger, in./mi (mm/m) points in the deterioration cycle. The pattern is as follows:
<400 190 (3.0)
400 to 1,500 165 (2.6) · Within the first few years of HMA construction, various
environment-related distresses often begin to develop at the
1,501 to 6,000 145 (2.3)
pavement surface, causing the overall condition to reduce
6,001 to 8,000 132.5 (2.1)
slightly. Preventive treatments, like crack sealing and thin
>8,000 120 (1.9) surface seals, are best applied at this time in order to slow
or reduce the severity of these distresses.
Pavements rougher than these levels are analyzed for struc- · As environment-related distresses continue to develop and
tural capacity to determine treatment thickness requirements. other non-load-related distresses emerge, a further reduction
Candidate treatments are then identified based on detailed in overall condition occurs and some roughness becomes
assessments of individual distress types, severities, and extents. apparent. Consequently, more significant treatments, like
Depending on the structural needs and specific deficiencies chip seals and thin overlays, become more suitable for use.
to be addressed, the candidate treatments may range from low- · Further distress development (and possibly the initial onset
cost preventive treatments to expensive major rehabilitation of some load-related distresses) reduces the overall condition
activities. Figure 3.6 illustrates the process used by Alberta. and increases roughness even more, making restorative treat-
ments, such as mill-and-overlay and in-place recycling, the
Guidelines for Condition-Based more appropriate preservation treatment options.
· As load-related distresses become more significant, mod-
Windows of Opportunity
erate to major forms of pavement rehabilitation become
Although overall condition, serviceability, and roughness appropriate.
indicators are not indicators of the specific forms of distress that
are present, they can effectively serve as preliminary identifiers Using the information just presented and the following
of candidate preservation treatments. This is because for an categories of PCI (USACE et al. 2004) and IRI (FHWA 2002),
Segment smoother than IRI (ride level) Segment rougher than
trigger value trigger value
20-year structural overlay
requirement--OL (20 yr)
OL (20 yr) > 40 mm
OL (20 yr) < 40 mm 40 mm < OL (20 yr) < 70 mm 70 mm < OL (20 yr) < 90 mm OL (20 yr) 90 mm
Preventive maintenance Preventive maintenance HIR OL (20 yr)
Thin OL Thin OL Mill and inlay
HIR HIR OL (10 yr)
Mill and inlay Mill and inlay IL (20 yr)
Two-lift OL OL (10 yr)
IL (20 yr)
Environmental/construction Traffic/load
distresses distresses
Potholes, dips, heaves, and Transverse Longitudinal Segregation Ravel
local distortion cracks centerline cracks
Rutting Longitudinal wheelpath Wheelpath
fatigue cracks flushing/bleeding
Source: Alberta MOT 2006.
Figure 3.6. Alberta guidelines for assessing pavement preservation treatments and strategies.
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Table 3.3. Recommended PCI Windows of Opportunity for
Pavement Preservation Treatments
HMA-Surfaced Pavements PCC-Surfaced Pavements
Treatment PCI Window Treatment PCI Window
Crack fill 75 to 90 Concrete joint resealing 75 to 90
Crack seal 80 to 95 Concrete crack sealing 70 to 90
Slurry seal (Type III) 70 to 85 Diamond grinding 70 to 90
Microsurfacing, single 70 to 85 Diamond grooving 70 to 90
Microsurfacing, double 70 to 85 Partial-depth concrete patching 65 to 85
Chip seal, single
Conventional 70 to 85 Full-depth concrete patching 65 to 85
Polymer modified 70 to 85
Chip seal, double
Conventional 70 to 85 Dowel bar retrofitting 65 to 85
Polymer modified 70 to 85
Ultra-thin bonded wearing course 65 to 85 Ultra-thin bonded wearing course 70 to 90
Ultra-thin HMAOL 65 to 85 Thin HMA overlay 70 to 90
Thin HMAOL 60 to 80
Cold milling and thin HMAOL 60 to 75
Hot in-place recycling
Surf recycle and HMAOL 70 to 85
Remixing and HMAOL 60 to 75
Repaving 60 to 75
Cold in-place recycling and HMAOL 60 to 75
Profile milling 80 to 90
Ultra-thin whitetopping 60 to 80
Note: HMAOL = Hot-mix asphalt overlay.
some basic guidelines for condition-based windows of oppor- treatment selection. Agency practices and experiences will
tunity have been developed and are presented in Table 3.3: generally dictate any adjustments or refinements that need
to be made.
Condition Description PCI
Good 86 to 100
Detailed Assessment of
Satisfactory 71 to 85
Treatments and Deficiencies
Fair 56 to 70
Because preservation treatments address pavement deficien-
IRI, in./mi (mm/m) Condition Description cies to varying degrees and no one treatment is best suited to
<95 (<1.5) Good ride quality and all conditions, a detailed assessment is needed that matches
good condition treatment capabilities with existing deficiencies. Ideally, this
95 to 119 (1.5 to 1.88) Acceptable ride quality, assessment should consider not only the specific distress types
fair condition present and their causes but also the severity and extent of each
120 to 170 (1.9) Acceptable ride quality, observed distress. Moreover, it should consider important
mediocre condition functional performance attributes, such as friction, splash-
spray, and pavement-tire noise.
The windows of opportunity listed in Table 3.3 can be Two approaches for identifying feasible preservation treat-
considered as starting points or reference values for agencies ments based on existing pavement deficiencies are decision sup-
that have not developed formal criteria for preservation port matrices and decision support trees. Both approaches rely
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Table 3.4. Example Decision Support Matrix for Identifying Flexible Pavement PM Strategies
Seal Coat Slurry Seal Microsurfacing Rut Depth
1. Traffic Treatment 1 in.
ADT < 2000 R R R 0.5 in.
2000 > ADT
Microsurfacingc One course Scratch Rut box and Multiple
< 5000 Ma Ma R
course final surface placement
ADT > 5000 NR NR R
and final with rut
2. Bleeding R R R surface box
3. Rutting NR R R Slurry seald One course One course Microsurfacing See note e
scratch course
4. Raveling R R R and final
5. Cracking surface
Few tight
cracks R R R
Extensive
cracking R NR NR
6. Improving
friction Yes Yes Yesb
7. Snowplow Most Moderately Least
damage susceptible susceptible Susceptible
Source: Jahren et al. 2000. Courtesy of Center for Transportation Research and Education, Iowa State University.
Note: R = Recommended; NR = Not recommended; M = Marginal.
a
There is a greater likelihood of success when used in lower-speed traffic.
b
Microsurfacing reportedly retains high friction for a longer period of time.
c
As recommended by International Slurry Seal Association.
d
Current practice in Iowa.
e
Sometimes successful (anecdotal evidence).
on a set of rules and criteria to identify appropriate preservation · Difficult to develop matrix that can incorporate multiple
treatments; the former uses a tabular structure like the one pavement distress types (i.e., do not always address the
shown in Table 3.4 and the latter, a more systematic graphical actual distress conditions);
approach like the one illustrated in Figure 3.7 (Peshkin and · Generally only designed to focus attention on one or two
Hoerner 2005). treatments that have worked well in the past and tend to
The benefits and limitations of these approaches were ignore or overlook new or improved treatments that may
previously identified by Hicks et al. (2000) as follows: be more effective;
· Do not include more comprehensive evaluation of various
Benefits feasible alternatives and life-cycle cost analysis (LCCA) to
· Make use of existing experience; determine the most cost-effective strategy; and
· Work well for local conditions; · Not good for network evaluation.
· Good as project-level tools;
· Reflect decision processes normally used by an agency; The last two limitations listed are not relevant in the present
· Flexible in modifying both the decision criteria and the study because the treatment selection framework and method-
associated treatments; ology developed and presented in this report are intended for
· Generate consistent treatment recommendations; and use at the project level and include a cost-effectiveness analysis
· Explain and program selection process with relative ease. component.
The rules and criteria behind decision support matrixes
Limitations or trees are based on an understanding (from past experience
· Not always transferrable from agency to agency; or historical performance data) of the ability of individual
· May be more difficult to innovate or introduce new treatments to fix or mitigate specific distresses. As illustrated
treatments; in Figure 3.8, a key step in developing rules and criteria is to
· Hard to incorporate all important factors (e.g., competing evaluate the primary purposes and functions of treatments in
projects, functional classification, remaining life); relation to the factors and causes of individual distresses, the
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Structural
M&R Surface Wear Environmental Deterioration Fatigue Cracking Rutting M&R
Treatment Severity Cracking Extent Extent Severity Treatment
Crack Low Low Mill/Fill
Seal 40 mm
Surface Moderate Low Low Moderate Mill/Fill
Treatment 50 mm
Crack Seal and High High Mill/Fill
40-mm OL 75 mm
Crack Low Low Mill 50 mm
Seal 75-mm OL
Crack Seal and Moderate Moderate No Yes Moderate Moderate Mill 75 mm
40-mm OL 100-mm OL
Mill/Fill High High Mill 100 mm
50 mm 125-mm OL
Mill/Fill Low Low Mill 100 mm
50 mm 150-mm OL
Mill/Fill Moderate High High Moderate Rem HMA, Repl
50 mm Base, Repave
Mill/Fill High High Total
50 mm Reconstruct
Source: Hicks et al. 1999.
Figure 3.7. Example decision support tree for identifying flexible pavement preservation
and rehabilitation strategies.
Treatment Purposes/Functions
Treatment
Prevent/delay Slow/reduce rate Restore integrity
Types
distress of distress and functionality of
development development pavement
Causes/Factors Causes/Factors
Environmental effects Distresses Traffic loading effects
(temp, moisture, UV) (frequency, intensity, type)
Causes/Factors
Causes/Factors
Material deficiencies
Structural
(design/construction
inadequacies
related)
(design related)
Subgrade
Figure 3.8. Matching of treatments with distress types through evaluation
of treatment purposes/functions and distress causes/factors.
