Impact of Design Features on Pavement Response and Performance in Rehabilitated Flexible and Rigid Pavements

Performance of Rehabilitated Asphalt Concrete Pavements in the LTPP Experiments-Data Collected Through February 1997(FHWA-RD-00-029)(3)

• Nonwheel-path longitudinal cracking was the most prevalent distress in the early period (SPS-5).
• Fatigue cracking was the least observed distress (SPS-5).
• Nonwheel-path longitudinal cracks exceeded wheel-path longitudinal cracks (general pavement study (GPS)-6).
• GPS-6 data showed that fatigue cracking and longitudinal cracking in the wheel path are related. Specifically, the longitudinal cracking in the wheel path will propagate or evolve into fatigue cracking with continued traffic loading.

Rehabilitation of Asphalt Concrete Pavements-Initial Evaluation of the SPS-5 Experiment (FHWA-RD-01-168)(4)

• Four performance indicators were established: fatigue cracking, transverse cracking, rutting, and IRI.
• Fatigue cracking occurred most frequently on older sections.
• Transverse cracking occurred in all but four of the projects, all of which were less than 7 years old.
• Older sections showed moderate severity of transverse cracks even in a no-freeze climate.
• Test sections with extensive transverse and fatigue cracking had high IRIs.

LTPP Data Analysis: Effectiveness of Maintenance and Rehabilitation Options Web Document 47 (Project 20-50(3/4))(5)

• All SPS-5 overlay treatments reduced long-term roughness relative to the nonoverlaid sections.
• The rutting data from the SPS-5 and GPS-6B experiments indicated that on average, about 0.2 inches (6 mm) of rutting developed in the first year after placement of an asphalt overlay of an asphalt pavement.

Performance of Rehabilitated Asphalt Concrete Pavements in the LTPP Experiments-Data Collected Through February 1997 (FHWA-RD-00-029)(3)

• The nominal 5-inch (127-mm) overlays generally showed better performance than the nominal 2-inch (5l-mm) overlays, as expected (SPS-5).
• The thicker overlays generally exhibited less cracking distress than the thinner ones but had little effect on the occurrence of rutting and no apparent effect on roughness (SPS-5).
• The different type of mixtures (virgin or recycled asphalt concrete (AC)) appeared to have the least effect on performance of any of the factors included in this experiment (SPS-5).
• There was no advantage to using virgin versus recycled mixtures in reducing the number of transverse cracks.
• Compared to virgin mixes, recycled AC mixtures resisted longitudinal cracking outside the wheel path substantially better in at least five projects.
• Thicker pavement performed better (GPS-6).
• The thickness of the pavement was conversely correlated with the extent of nonwheel-path longitudinal cracks (GPS-6).
• Neither the age nor the condition of the pavement before the overlay seemed to be critical to cracking extent (GPS-6).
• Thicker overlays resisted rutting slightly better than thinner ones (GPS-6).
• AC mix properties were the most significant factors to limit rutting (GPS-6).
• Thicker overlays offered a slight advantage for roughness (GPS-6).
• GPS-6A (existing AC overlays on AC pavements) data showed that overlay designs that provided pavement structure consistent with traffic expectations can be expected to perform well for more than 10 years.

Rehabilitation of Asphalt Concrete Pavements-Initial Evaluation of the SPS-5 Experiment (FHWA-RD-01-168)(4)

• Overlay thickness did not appear to have a strong effect on the occurrence of longitudinal cracking in the wheel path and rutting (5 years after rehabilitation).
• There was no apparent effect of overlay thickness on roughness based on these early observations (5 years after rehabilitation).
• Age of overlay was found to be the leading contributing factor to four of the six distresses studied in the SPS-5 experiment (rehabilitation of AC pavements): fatigue cracking, rutting, transverse cracking, and initial pavement smoothness.

LTPP Data Analysis: Effectiveness of Maintenance and Rehabilitation Options (Project 20-50(3/4))(5)

• Overlay thickness and preoverlay roughness level were the two factors that most influenced the performance of asphalt overlays of asphalt pavements in the SPS-5 experiment with respect to roughness and fatigue cracking.
• No significant mean differences were detected in long-term roughness, cracking, and rutting between recycled mixes versus virgin mixes.
• No significant mean differences were detected in long-term rutting between minimal versus intensive preparation or thin versus thick overlays.
• Preoverlay cracking, age, and accumulated traffic loads significantly correlated to the difference in long-term cracking in nonoverlaid versus overlaid sections.

Reducing Flexible Pavement Distress in Colorado Through the Use of PMA Mixtures(6)

• Projects using modified HMA mixtures were found to have lower amounts of fatigue cracking, transverse cracking, and rutting.
• The use of modified HMA mixtures was found to extend the service life of HMA overlays by about 3 years, a 30 percent increase over the 10-year design life.

Construction Factors

Performance of Rehabilitated Asphalt Concrete Pavements in the LTPP Experiments-Data Collected Through February 1997 (FHWA-RD-00-029)(3)

• The test sections that had received intense surface preparation (patching and milling) prior to placement of the overlays generally performed better than test sections that had not. Reduced fatigue cracking, reduced longitudinal cracking in the wheel paths, and reduced transverse cracking were observed on intensely prepared sections.
• The amount of transverse cracking was dependent on the original pavement condition before overlay placement. The overlays placed on pavements classified in good condition exhibited less transverse cracking than on pavements classified in poor condition.
• No substantial difference was noted between longitudinal cracking outside the wheel paths, rutting, and roughness between the test sections with and without milling (SPS-5).
• Rutting was not affected by or related to the condition of the original pavement or age of the overlay (GPS-6).
• The condition of the original pavement prior to overlay appeared to have little effect on the occurrence of or increase in roughness (GPS-6).
• The amount of traffic affected the growth of roughness (GPS-6).

Rehabilitation of Asphalt Concrete Pavements-Initial Evaluation of the SPS-5 Experiment (FHWA-RD-01-168)(4)

• Fewer or shorter transverse cracks occurred on sections that had been milled.
• According to an analysis of variance (ANOVA), milling depth had an important effect on the length of transverse cracks.
• The IRI values of the overlay were lower for the overlays placed over pavements in the fair category and when the existing surface was milled before overlay.

LTPP Data Analysis: Effectiveness of Maintenance and Rehabilitation Options (Project 20-50(3/4))(5)

• Asphalt pavements overlaid when rougher tended to have somewhat
  more initial roughness after overlay than asphalt pavements overlaid
  when smoother.
• There was no significant mean difference in long-term roughness between overlays with minimal versus intensive preoverlay preparation.
• No significant mean differences were detected in long-term cracking between minimal versus intensive preparation.

Site Factors

Rehabilitation of Asphalt Concrete Pavements-Initial Evaluation of the SPS-5 Experiment(6)

• The age of the overlay and the climatic factors temperature and moisture had a significant effect on fatigue cracking.
• More fatigue cracking occurred on test sections in a climate with less precipitation but higher freeze indices.
• Longer transverse cracks occurred on the older pavements in areas with higher freeze indices.
• Freeze index had an effect on the length of transverse cracks.
• The age of the overlay and precipitation had an effect on rut depth. Sections with increased precipitation had larger rut depths.
• The age of the overlay, condition of the pavement before overlay placement, and surface preparation or milling depth were important factors relative to the IRI values.
• Milling offered no consistent advantage for resisting longitudinal cracking outside the wheel path during the early life of an overlay.

LTPP Data Analysis: Effectiveness of Maintenance and Rehabilitation Options (Project 20-50(3/4))(5)

• Overlay age and average annual precipitation had a significant effect on long-term rutting.
• A significant correlation was detected between average annual precipitation and the difference in long-term rutting in 2-inch (51-mm) versus 5-inch (127-mm) overlays.

LTPP Data Analysis: Effectiveness of Maintenance and Rehabilitation Options (Project 20-50(3/4))(5)

• The effectiveness of the rigid pavement rehabilitation treatments in the SPS-6 experiment can be ranked from most to least effective with respect to IRI, rutting, and cracking as follows: (1) 8-inch (203-mm) overlay of cracked/broken and seated pavement, (2) 4-inch (102-mm) overlay of either intact or cracked/broken and seated pavement with or without sawing and sealing of transverse joints and with minimal or intensive preoverlay repair, (3) concrete pavement restoration with diamond grinding, full-depth repair, and joint and crack sealing, and (4) concrete pavement restoration without diamond grinding but with full-depth repair and joint and crack sealing.
• Subdrainage retrofitting, undersealing, and/or load transfer restoration techniques did not produce significantly lower long-term roughness levels compared to sections that received only diamond grinding, full-depth repair, and joint and crack sealing.

Rehabilitation of Jointed Portland Cement Concrete Pavements: Initial Evaluation and Analysis (FHWA-RD-01-169)(7)

• The rehabilitation techniques in exposed Portland cement concrete (PCC) involve restoration techniques other than overlay including full-depth repair, diamond grinding, joint sealing, and addition of retrofitted edge drains.
• If the prerehabilitated section has significant roughness, diamond grinding should be considered or the section will retain its roughness. Full-depth repairs do not remove significant roughness from a jointed concrete pavement by themselves.
• Both routine and premium pavement preparation treatments reduce the amount of transverse cracking immediately after rehabilitation. Routine preparation treatment includes limited patching, crack repair and sealing, and stabilization of joints. Premium preparation treatment includes subsealing, subdrainage, joint repair and sealing, full-depth repairs with restoration of load transfer, diamond grinding, and shoulder rehabilitation.
• Premium pavement preparation with diamond grinding reduces the amount of faulting to zero immediately after rehabilitation.
• AC overlay of nonfractured PCC rehabilitation technique involves applying varying degrees of preoverlay repairs and placing an AC overlay.
• The AC overlay of nonfractured PCC reduces the roughness immediately after rehabilitation to a smooth level (5.28 ft/mi (1.0 m/km)).
• The sections with AC overlay of nonfractured PCC exhibit a faster increase in IRI over time than does the fractured PCC.
• The sections with AC overlay of nonfractured PCC exhibit a lower increase in IRI over time than do premium preparation nonoverlaid PCC sections.
• The routine and premium preparation sections with 4-inch (102-mm) AC overlays exhibited no reflective cracking within the first year after construction.

The LTPP Experiment SPS-3 5-Year Data Analysis (FHWA-RD-97-102)(8)

• Structural adequacy did not have a significant effect on the performance of SPS-3 treatments.
• Thin overlay had a significant effect in rutting and roughness reduction, while other treatment options were either slightly effective or not effective.

LTPP Data Analysis: Effectiveness of Maintenance and Rehabilitation Options (Project 20-50(3/4))(5)

• In the SPS-3 thin overlay sections, pavement age was the only factor studied that was found to be significantly correlated to the rate of rutting.
• In the SPS-3 crack sealed and chip sealed sections, average annual precipitation was the only factor studied found to significantly correlate to the rate of rutting.

The LTPP Experiment SPS-3 5-Year Data Analysis (FHWA-RD-97-102)(8)

• This report provides multiple regression models to develop prediction models for cracking, rutting, ride quality, friction, and pavement rating score.

Pavement Maintenance Effectiveness (SHRP-H-358)(9)

• This study developed a damage modeling approach with an index varying between zero and 1. The index is dependent on accumulated traffic/age, expected traffic/age to failure, and the shape of the performance trend.

LTPP Maintenance and Rehabilitation Data Review (FHWA-RD-01-019)(10)

• This report documents a survival analysis of SPS-3 sites in the Southern LTPP region in 1999 to obtain life expectancy of each treatment, effect of timing, and the benefit of treatment to the life span of the pavement.

LTPP Maintenance and Rehabilitation Data Review (FHWA-RD-01-019)(10)

• After 6 years of service, sections that received maintenance when in poor condition had a probability of failure twice as much as sections initially in fair or good condition.
• Sections in fair and good condition had about the same probability of failure.
• The overall median survival times for thin overlay, slurry seal, and crack seal were 7, 5.5, and 5.1 years, respectively.
• A median survival time for chip seal could not be determined because fewer than 50 percent of these sections had failed at the time of the analysis. Chip seals outperformed thin overlay, slurry seal, and crack seal treatments with respect to controlling the reappearance of distress.

LTPP Data Analysis: Effectiveness of Maintenance and Rehabilitation Options (Project 20-50(3/4))(5)

• In terms of roughness, rutting, and fatigue cracking, the most effective of the maintenance treatments was the thin overlay treatment, followed by the chip seal treatment, and then the slurry seal treatment.
• The thin overlay treatment was the only one of the four SPS-3 maintenance treatments to produce an initial small reduction in roughness, and the only one of the four to have a significant effect on long-term roughness, relative to the control sections.
• For the SPS-3 test sections, the thin AC overlay treatment was the only one of the four treatments (thin AC overlays, chip seals, slurry seals, and crack seals) that showed a significant initial effect on rutting. Thin AC overlays also had the most significant effect on long-term rutting control.
• For rougher pavements, there was some evidence that chip seals and slurry seals also had some effect on long-term roughness, rutting, and cracking relative to the control sections.
• Crack seals did not have any significance on long-term roughness, rutting, or fatigue cracking.

Pavement Treatment Effectiveness, 1995 SPS-3 and SPS-4 Site Evaluations National Report  (FHWA-RD-96-208)(11)

• The thin AC overlay treatments performed best after 5 years.
• In general, chip seal treatments also performed well. Chip seal performance was best in the Southern region, which has a predominantly wet no-freeze environment.
• The crack seal treatment performed very well in wet freeze environments where the wide shallow sealant reservoir was routed. Crack seal performance in the other two regions was not as successful.

LTPP Pavement Maintenance Materials: SHRP Crack Treatment Experiment  (FHWA-RD-99-143)(12)

• The most cost-effective treatments for crack seals are usually those consisting of rubberized asphalt placed in a standard or shallow-recessed band-aid configuration. The standard recessed band-aid method showed the longest estimated service life, followed very closely by the shallow recessed band-aid method.
• For long-term crack-seal performance (5 to 8 years) under the condition where 0.1 to 0.2 inches (2.5 to 5.0 mm) of horizontal crack movement occurred, a modified rubberized asphalt sealant should be installed in either a standard or a shallow recessed band-aid configuration.

LTPP Data Analysis: Effectiveness of Maintenance and Rehabilitation Options  (Project 20-50(3/4))(5)

• The review of construction problems and deviations in the SPS-3 experiment illustrated that more than 40 percent of the sites had problems in the application of maintenance treatments, mostly chip seal.

Pavement Treatment Effectiveness, 1995 SPS-3 and SPS-4 Site Evaluations National Report (FHWA-RD-96-208 (11)

• The question of timing cannot be resolved completely from the visual observation of the SPS-3 sites, but indications are that earlier application of the preventive maintenance treatments provides greater benefits than later application.

LTPP Data Analysis: Relative Performance of Jointed Plain Concrete Pavement with Sealed and Unsealed Joints (NCHRP Web Document 32 Project 20-50(2))(13)

• Joint spalling was quantified by several measures, including percentage of joints spalled within a pavement section, total length of joint spalling, percentage of total joint length spalled, and percentage of individual joint length spalled. In addition, weighted measures were used that take into account the severity of joint spalling as characterized by low-, medium-, and high-severity joint spalling.
• The faulting measure employed in most previous analyses of LTPP concrete pavement performance is average joint faulting, as measured in the outer wheel path. In addition, average absolute faulting was introduced in the study to account for negative faulting (the approach slab edge being lower than the leave slab edge). Absolute average faulting is calculated as the arithmetic average of the absolute values of the individual joint faulting measurements.
• An index of weighted sealant damage was developed to quantify overall transverse joint sealant condition as a weighted average of the numbers of joints within the section with low, medium, and high sealant damage ratings.

LTPP Data Analysis: Relative Performance of Jointed Plain Concrete Pavement with Sealed and Unsealed Joints (NCHRP Web Document 32 Project 20-50(2))(13)

• Based on 5 years of data collected at the five test sites built in Arizona, Colorado, and Utah (all in the dry region), the effects of sealed and unsealed joints on spalling were similar.

Pavement Treatment Effectiveness, 1995 SPS-3 and SPS-4 Site Evaluations National Report (FHWA-RD-96-208)(11)

• SPS-4 sealed joint sections performed better than unsealed sections.
• Unsealed joints also had significantly more joint spalling than the sealed joint sections.
• Unsealed joints in the control sections contained significantly more debris than sealed joint sections.

Concrete Pavement Maintenance Treatment Performance Review: SPS-4 5-Year Data Analysis (FHWA-RD-97-155)(14)

• No significant differences were identified between the control sections (unsealed) and the sealed-joint or undersealed (slab stabilization) sections. This observation was based on the 32 SPS-4 sites.
• Based on 5 years of data collected in Arizona, Colorado, Nevada, and Utah, no significant differences in initial pavement smoothness were identified among the three treatments consisting of sealed, undersealed, and unsealed joints in the SPS-4 experiment.
• In the analysis of SPS-4 performance through 1995, no significant differences were detected in IRI or joint faulting between sealed-joint and unsealed-joint sections.

Design and Construction of PCC Pavements, Volume 1: Summary of Design Features and Construction Practices that Influence the Performance of Pavements (FHWA-RD-98-052)(15)

• Neither presence nor type of sealant was found to be significant in the regression analysis of JPCP joint faulting in the GPS-3 experiment.

Common Characteristics of Good and Poorly Performing Pavements (FHWA-RD-97-131)(16)

• In statistical analyses of GPS-3 performance data, neither sealant presence or sealant type was found to be a significant variable in the prediction of dowelled or undowelled joint faulting in JPCP.

LTPP Pavement Maintenance Materials: SPS-4 Supplemental Joint Seal Experiment (FHWA-RD-99-151)(17)

• A comparison of joint sealant types among the SPS-4 supplemental test sections built in Arizona, Colorado, Nevada, and Utah between 1990 and 1995 showed that silicone seals outperformed the other two treatments for transverse joint seals (compression seals and hot pours).

Optimal Timing of Pavement Preventive Maintenance Treatment Applications (NCHRP Report 523)(18)

• Several studies researched the issue of optimum timing of the preventive maintenance treatments to achieve best maintenance effectiveness. These included earlier studies of SPS-3 and SPS-4 experiments and State transportation department studies in Arizona, Iowa, Montana, Texas, and South Dakota. None of these studies was successful in identifying the optimum timing of preventive maintenance treatments.

Optimal Timing of Pavement Preventive Maintenance Treatment Applications (NCHRP Report 523)(18)

• A methodology was developed to determine the optimal timing for the application of preventive maintenance treatments to flexible and rigid pavements. The methodology was based on the analysis of pavement performance and costs associated with maintenance treatment. It assessed the effectiveness of a particular preventive maintenance treatment in terms of both the benefit it provided and the cost required to obtain that benefit. The benefit was defined as the quantitative influence on pavement performance as measured by pavement condition factors. Condition indicators may be expressed by such measures as IRI, present serviceability index, or other custom-defined measure of pavement performance. The optimum application of a preventive maintenance treatment occurred at the point at which the benefit per unit cost was greatest.

Optimal Timing of Pavement Preventive Maintenance Treatment Applications (NCHRP Report 523)(18)

• One of the case studies conducted under NCHRP Project 14-14 was a review of the data from LTPP SPS-3 and -4 experiments.⁽¹⁹⁾ The conclusion from that case study was that LTPP data at that time could not be used to conduct the analysis of optimal timing. The reasons provided in the report include the counterintuitive performance trends, no improvement in performance as a result of treatment application, and not enough sections with treatments applied at different ages that exhibited the expected trends to support the analysis.

Preliminary Evaluation and Analysis of LTPP Faulting Data- Final Report (FHWA-RD-00-076)(20)

• Data analysis was performed to determine the usefulness of joint faulting and related data in identifying factors that affect joint faulting. As part of this study, an assessment of data availability and data quality was performed for the SPS-4 experiment. Data for a total of 422 jointed concrete pavement sections were available in the LTPP Information Management System (IMS) database at the time of the study. Of these, only 307 sections had records in the faulting data table MON_JPCC_FAULT, for a total of 24,108 records.

Rehabilitation of Asphalt Concrete Pavements: Initial Evaluation of the SPS-5 Experiment (FHWA-RD-01-168)(4)

• The data availability and completeness were good overall for the SPS-5 experiment with two exceptions: traffic and materials test data. These data deficiencies should be addressed before a comprehensive analysis of the SPS-5 experiment is conducted. Both of these data elements must be collected in order for the SPS-5 experiment to meet the expectations for calibrating and validating mechanistic models.

Rehabilitation of Jointed Portland Cement Concrete Pavements: SPS-6-
Initial Evaluation and Analysis (FHWA-RD-01-169)(7)

• Data availability and completeness for the SPS-6 experiment are good overall, but some data, such as traffic, climatic, and materials data, were not yet available in the IMS database. Three of the 14 sites were still relatively new and, therefore, did not have much data available. It was believed that the information was collected and in the process of being entered into the IMS database.

LTPP Data Analysis: Effectiveness of Maintenance and Rehabilitation Options (Project 20-50(3/4))(5)

• The data used in this research were the data available at all quality levels in LTPP data release 11.5 dated June 13, 2001.
• Efforts to analyze the SPS-3 experiment were hampered by data availability problems and the short times in which the treatments had been in service.
• In both the SPS-5 and -6 experiments, the long-term rutting data were so erratic that analysis of long-term trends was problematic.

LTPP Maintenance and Rehabilitation Data Review (FHWA-RD-01-019)(10)

• This publication provides a review of maintenance and rehabilitation data elements across all the experiments for data completeness and anomalies. The test sections were divided into three categories based on surface type: HMA, jointed concrete pavement, and continuously reinforced concrete pavement. The study was based on the 1999 third quarter LTPP data release. There were a total of 757 type sections, including SPS and GPS, for which maintenance and rehabilitation  techniques have been documented in the database.