Field Performance and Cost-Effectiveness of Chip Seals and Asphalt Concrete Overlays with and without Asphalt Concrete Stripping Damage

Abstract

The objective of this study was to evaluate the effects of asphalt concrete (AC) stripping damage on the field performance and cost-effectiveness (CE) of chip seals and AC overlays in pavement maintenance and rehabilitation. To achieve this objective, in-service pavement sections were selected from the Louisiana pavement management system (LaPMS) database and the presence of moisture damage was confirmed through the visual inspection of extracted cores. Sections were categorized according to traffic volume and their pavement condition index before treatment (PCI^-). Road sections in each group were then divided into two groups as stripped and non-stripped sections. The average deterioration rate (ADR), extension in pavement service life (ΔPSL), average condition improvement over the treatment service life (PI), and CE were compared for stripped and non-stripped sections. Results showed that for chip seal sections, moisture damage negatively affected the performance of the sections with PCI^- < 80 and low traffic volumes. For sections with PCI^- > 80, similar performance was observed for stripped and non-stripped sections. For AC overlays, moisture-induced damage significantly affected the long-term pavement performance at all traffic levels. On average, moisture-induced damage decreased ΔPSL, PI, and CE of AC overlays by 5 years, 24%, and 0.5%, respectively. Overall, results of the study demonstrated that moisture damage has a significant effect on the performance of chip seal and AC overlay. Therefore, it is critical to identify and repair stripped sections before the maintenance and rehabilitation of in-service pavements to ensure adequate performance and optimum CE.

Keywords

pavement management systems pavement management pavement preservation pavements

The presence of moisture in a pavement structure is a matter of great concerns, as it is responsible for significant distresses such as stripping, fatigue cracking, rutting, and poor durability. Asphalt concrete (AC) stripping, which is a chronic problem in flexible pavements in the Southern United States, refers to the loss of bond between the aggregate and asphalt binder and is caused by the accumulation of moisture underneath the pavement surface ( 1 , 2 ). Once moisture damage has occurred, structural degradation of AC accelerates, which is usually accompanied by cracking and permanent deformation in the AC layer caused by the reduction of the binder and mastic stiffness through diffusion ( 3 ).

In Louisiana, shallow groundwater table (GWT) and heavy rainfall conditions (average annual rainfall of 1,524 mm [60 in.]) throughout the year make the pavement highly vulnerable to water entrapment and moisture damage ( 4 ). The effect of AC stripping is manifested in the roadway through poor durability of the mixes, accelerated increase in surface roughness, and shorter service life. Transportation agencies, including Louisiana, typically apply chip seal and AC overlays based on surface conditions regardless of the underlying conditions of the existing pavement. Therefore, the performance of maintenance and rehabilitation (M/R) treatments such as chip seal and AC overlays may be adversely affected when placed on moisture-damaged pavements.

While previous studies have extensively evaluated the use of laboratory test methods to assess moisture damage in AC, the effects of below-the-surface water accumulation on the field performance of asphalt pavements have not been well-documented in the literature ( 5 – 8 ). In addition, and given the challenges of addressing this issue in the field, most pavements are built to ensure that the surface layer is impervious while attempting to achieve adequate drainage conditions in the granular and subgrade layers. Nevertheless, the presence of below-the-surface water accumulation can cause a substantial loss of serviceability and performance in the field.

Objectives

The objective of the study was to evaluate the effects of moisture-induced damage (AC stripping) on the long-term pavement performance and cost-effectiveness (CE) of two main treatments (i.e., chip seal and AC overlay) in hot and humid climates. In this study, the effects of traffic volume and pavement surface conditions before treatment on the performance and CE of chip seal and AC overlays with and without AC stripping damage were investigated.

Background

Asphalt Concrete (AC) Stripping Failure Mechanism

Moisture damage can be defined as the reduction of strength and durability of the pavement structure caused by the effects of moisture ( 9 ). Moisture damage in pavements can occur in two primary forms: softening and AC stripping ( 10 ). Softening is the loss in strength and stiffness of an asphalt mixture as a result of the reduction in cohesion. Stripping, on the other hand, is related to the loss of adhesion, which causes separation of the binder and the aggregate in the pavement surface layer. It has been suggested that the adhesion resistance of asphalt binder is directly related to its surface free energy (SFE) ( 11 ). NCHRP Synthesis 175 characterized stripping as a three-stage process of reduction in contact angle between the asphalt and aggregate surface ( 12 ). In this process, the contact angle gradually decreases until the binder loses contact with the aggregate leading to adhesion failure in the mixture.

Moisture damage permeates and weakens the mastic and makes the pavement structure more susceptible to damage under traffic. Repeated loading on a stripped pavement may cause severe cracks, permanent deformation, and failure of the pavement. Moreover, wearing courses placed over a stripped flexible pavement are likely to exhibit potholes and raveling because of adhesion failure. A wide range of physical processes have been identified as the cause of stripping, including detachment, displacement, spontaneous emulsification, and pore pressure, all of which lead to the gradual progress of moisture damage in the AC layer ( 12 ).

The Louisiana Pavement Management System (LaPMS)

In Louisiana, the pavement network is surveyed every 2 years to assess and monitor pavement surface conditions. The Automatic Road Analyzer (ARAN), which is equipped with computers, lasers, cameras, and sensors to capture and store high definition digital images of pavement right of way and surface conditions in both the primary and secondary travel directions, is used. The control sections are divided into log miles to provide a reference location system to the distress data for all pavements ( 13 ). The cracks are identified by the type (i.e., fatigue, longitudinal, reflective, and so on) and severity (i.e., low, medium, and high).

Collected data are reported every 1/10th of a mile and are analyzed to calculate different distress indices on a scale from zero to 100 (100 being perfect conditions). These indices include the pavement condition index (PCI), alligator cracking index (ALCR), rutting index (RUT), random cracking index (RNDM), roughness index (RUFF), and patch index (PTCH). For flexible pavements, the PCI is calculated as follows ( 14 ).

\begin{matrix} P C I = M A X \\ [\begin{matrix} M I N (R N D M, A L C R, P T C H, R U F F, R U T), \\ {A V G (R N D M, A L C R, P T C H, R U F F, R U T) \\ - 0.85 S D (R N D M, A L C R, P T C H, R U F F, R U T)} \end{matrix}] \end{matrix}

(1)

where RCI is the random cracks index, ALCR is the alligator cracking index, PTCH is the patch index, RFI is the roughness index, RTI is the rutting index, and SD is standard deviation.

Methodology

Figure 1 illustrates the general outline of the research methodology. Chip seal and AC overlay road sections were identified using the Louisiana Department of Transportation and Development (LaDOTD) pavement management system (PMS) databases. For these sections, core reports were then reviewed and analyzed to identify the occurrence of moisture-induced damage in the underlying AC layers before applying the chip seal or AC overlays. Distress and roughness data were then extracted from the PMS and the PCI values were calculated according to Equation 1. Performance curves, which were fitted to the PMS data, were then used to calculate four field performance and economic indicators, which were the average deterioration rate (ADR), the extension in pavement service life (ΔPSL), average condition improvement over the treatment service life (PI), and CE. The last step consisted of conducting a statistical analysis to evaluate the effects of moisture-induced damage on the long-term pavement performance and CE of chip seal and AC overlays.

Figure 1.

General outlines of the research methodology.

Data Collection

Approximately 496 mi (800 km) of Louisiana roads were identified and included in the data analysis. For chip seal sections, data from 228 mi (367 km) of in-service roads were used in the analysis. Based on core reports, 160 mi (257 km) were identified as non-stripped chip-sealed sections while the remaining 110 km (68 mi) were classified as stripped sections (with moisture damage) (see Figure 2). Similarly, 268 mi (430 km) of AC overlay sections were used in the analysis; 117 mi (188 km) were stripped sections and 151 mi (242 km) were non-stripped sections.

Figure 2.

Examples of core data extracted by Louisiana Department of Transportation and Development (LaDOTD): (a) non-stripped pavement and (b) stripped pavement.

Distress and roughness data were obtained from the LaDOTD PMS databases for the selected sections. Based on ARAN pavement condition surveys conducted biennially, data for every 0.1 mi (0.16 km) were used to calculate the PCI values, which in turn were used to calculate the different performance and economic indicators as discussed below.

Data Processing

The condition of the existing pavement was evaluated based on the PCI since it adequately reflects pavement surface condition over time. In addition, many agencies throughout the United States and Canada use it to assess the performance of the road sections and their level of service ( 15 ). PCI is calculated as a function of the different LaDOTD indices as presented in Equation 1. Based on the calculated PCI, a regression model describing pavement performance before and after the treatment was fitted for each pavement section as illustrated in Figure 3.

Figure 3.

Fitted performance curves and remaning service life calculations: (a) before treatment and (b) after the treatment.

Performance Indicators

In this study, four performance indicators were used to compare the long-term performance of stripped and non-stripped sections after the application of chip seal and AC overlays. These indicators are classified into two categories; benefits-only indicators and benefit-cost indicator. The benefit-only approach includes ADR, ΔPSL, and PI. On the other hand, CE was used as a benefit-cost indicator in the current analysis.

Average Deterioration Rate (ADR)

The ADR of pavement conditions, in regard to PCI, was compared for the stripped and non-stripped pavement sections. The deterioration rate between two successive survey cycles was calculated using Equation 2. It should be noted that LaDOTD collects field collected data biennially; therefore, the cycle length is two years ( 16 ). ADR was then calculated based on Equation 3.

D R i (%) = \frac{{P C I}_{i} - {P C I}_{i + 1}}{Y_{i + 1} - Y_{i}} * 100

(2)

where i is the number of cycle (i.e., i = 0 when a survey is conducted just after construction), DR_i is the deterioration rate (%) in the cycle of (i + 1) of the treatment age, PCI_i is the PCI value at the cycle of (i) after applying the treatment, PCI_i+1 is the PCI value at the cycle of (i + 1) after applying the treatment, Y_i is the treatment age at PCI value of PCI_i, and Y_i+1 is the treatment age at PCI value of PCI_i+1.

A D R (%) = \frac{\sum_{i = 1}^{n} {D R}_{i}}{n}

(3)

where n is the number of surveys.

Extension in Pavement Service Life (Δ PSL)

Pavement service life (PSL) is defined as the age at which a given pavement condition, in regard to PCI, reaches a selected threshold value ( 17 ). Based on this definition, PSL can be calculated by extrapolating the pavement performance curve to a point at which pavement condition reaches a specified threshold or cutoff value. ΔPSL calculations consisted of several steps. First, performance curves were fitted between PCI values and pavement age (years) before and after a given treatment (see Figure 3). As shown in Figure 3a, the remaining PSL (PSL_R) of the pavement before the treatment was calculated by extrapolating the performance curve before the treatment to the selected cutoff value. Similarly, the treatment PSL (PSL_T) was computed by extrapolating the performance curve after the treatment until it reached the same cutoff value. Finally, ΔPSL was calculated by subtracting PSL_R from PSL_T considering a PCI threshold value of 60 as suggested by LaDOTD PMS ( 18 , 19 ).

Average Condition Increase (PI %)

In the present analysis, the improvement in average pavement condition for chip seal or AC overlays service life relative to the condition of the road before the treatment (PCI^-) was used to evaluate the effect of moisture damage on chip seal and AC overlay performance. Equation 4 was used to calculate PI ( 20 , 21 ). It can be noted from Equation 4 that, the higher the PI value, the greater the long-term performance of the treatment ( 20 ):

P I (%) = \frac{{P C I}_{a v g} - {P C I}^{-}}{{P C I}^{-}} * 100

(4)

P C I_{a v g} = \frac{\sum_{i = 1}^{n} 0.5 * (P C I_{i} + P C I_{i + 1}) * Δ Y}{Y_{n} - Y_{1}}

(5)

where PCI _avg is the average PCI value over the treatment service life (Equation 5) ( 20 ), PCI _i is the PCI value at the time of i, ΔY is the period between i and i + 1, Y₁ is the year when chip seals or AC overlays were placed, Y_n is the last measurement year, and PCI^- is the PCI value before treatment.

CE

CE analysis typically compares the relative efficiency of several alternatives from a budgetary perspective to help decision-makers select the optimum alternative ( 22 ). However, instead of conducting a CE analysis to compare the efficiency of different treatments, CE analysis was used to evaluate the effect of moisture-induced damage on the cost efficiency of chip seal and AC overlay treatments. The CE of a treatment strategy for a road section was calculated using Equation 6 as follows:

C E (%) = \frac{A_{1} - A_{2}}{U n i t C o s t ($)} * 100

(6)

Where A₁ is an area that represents the benefits of a given treatment (see Figure 3a) until reaching a cutoff value, A₂ is an area that represents the remaining benefits of the existing pavement (see Figure 3b) until reaching the same cutoff value, A₁–A₂ is an area that indicates the net benefits of treatment application (see Figure 3b), and Unit Cost ($) is the unit cost of the treatment, which was obtained from LaDOTD database.

Data Analysis Strategy

Figure 4 presents the data analysis strategy adopted in the study. For chip seal and AC overlay sections, traffic volume and pretreatment conditions (PCI^-) were used to categorize the road sections into groups. In regard to traffic volume, pavement sections were categorized into two groups as sections with low traffic level (average daily traffic [ADT] < 1,100) and medium traffic level (1,100 < ADT < 5,300) (see Figure 4a). In addition, pre-treatment conditions, in regard to PCI^- values, were used to classify the pavement sections as sections with PCI^- < 80 and PCI^- > 80, as shown in Figure 4b. The threshold of 80 was selected to categorize different subgroups for two reasons. First, it represents the median of PCI values before the placement of chip seal sections used in this study. Second, it is located at the middle range of LaDOTD specifications for the roadways that are considered in acceptable conditions ( 14 ). Pavement sections in each group were then categorized into two different subgroups based on the presence of moisture damage before treatment (i.e., stripped and non-stripped sections). The performance of the road sections was then compared statistically for the defined subsets to assess the significance of moisture-induced damage on the predicted field performance. It is worth noting that, for AC overlays, the majority of the road sections had pre-treatment conditions (PCI^-) ranging from 65 to 70, which hindered the possibility of assessing the effects of this factor on the performance of the overlays.

Figure 4.

Analysis procedure for chip-sealed sections based on (a) traffic volume and (b) pretreatment conditions.

Results and Discussion

Chip Seal Sections

Average Deterioration Rate (ADR)

Figure 5a shows the effects of moisture-induced damage on the ADR of chip seal sections for different PCI^- conditions. For roads with PCI^- less than 80, the ADR was 6.5% and 3.5% for pavement sections with and without moisture damage, respectively. These results validate the accelerated deterioration of flexible pavements exhibiting moisture damage. For pavements with PCI^- > 80, the ADR was almost the same for both stripped and non-stripped sections (see Figure 5a). The reason behind these trends is twofold. First, pavement sections with PCI^- > 80 were in good conditions before the treatment and were not affected significantly by the presence of moisture damage in the underlying layers. Second, ADR was calculated based on performance curves that were fitted to the first four survey cycles (i.e., 8 years). At an early age, structurally sound pavements may not experience a significant impact caused by moisture damage. Therefore, similar ADR values were observed for stripped and non-stripped sections for PCI^- > 80.

Figure 5.

Impact of moisture damage on the performance and cost efficiency of chip seals based on (a) Average Deterioration Rate (ADR) and pretreatment conditions; (b) Average Deterioration Rate (ADR) and traffic volume; (c) Extension in Pavement Service Life (ΔPSL) and pretreatment conditions; (d) Extension in Pavement Service Life (ΔPSL) and traffic volume; (e) Average Condition Increase (PI) and pretreatment conditions; (f) Average Condition Increase (PI) and traffic volume; (g) Cost-Effectiveness (CE) and pretreatment conditions; (h) Cost-Effectiveness (CE) and traffic volume.

An analysis of variance (ANOVA) test was conducted at 95% confidence level (α = 0.05) followed by a Tukey’s honest significant difference (HSD) test in to evaluate the impact of moisture-induced damage on the ADR of chip seal sections. Pavement sections with PCI- < 80 and PCI- > 80 were divided into two subgroups as sections with stripping damage and sections without stripping damage to analyze the effect of moisture damage for different PCI-conditions. As shown in Figure 5, the average value of each performance indicator was represented by letters A, B, or C. Different assigned letters indicate that the two groups are statistically different. As shown in Figure 5a, the ADR of chip seal sections with PCI- < 80 was significantly affected by the presence of moisture-induced damage. However, the effect of moisture-induced damage was insignificant for pavement sections with PCI- > 80.

Figure 5b presents the ADR of stripped and non-stripped road sections for different traffic levels. When ADT was less than 1,100, stripped sections exhibited an ADR of 5% compared with 2% for the non-stripped sections; this difference was statistically significant. However, for medium traffic level, moisture-induced damage increased the deterioration rate by about 1.5%; however, this difference was not statistically significant.

Extension of Pavement Service Life service (ΔPSL)

Figure 5c presents the effects of moisture-induced damage on ΔPSL for the sections treated with chip seal for different pre-treatment conditions. For sections with PCI^- less than 80, chip seal extended PSL by approximately 9.5 years when placed on pavement sections without moisture-induced damage. This extension was only 5 years when the chip seal was applied on stripped pavements at the same PCI^- level. Tukey’s HSD results indicated that moisture damage decreased the service life of chip seals significantly, as illustrated in Figure 5c. For pavements with PCI^- > 80, both stripped and non-stripped sections exhibited similar ΔPSL (about 5 years). The results in Figure 5c are consistent with the results presented in Figure 5a. As previously noted, sections that are in good conditions before treatment were not significantly affected by the presence of moisture damage in the underlying layers. In addition, previous results by the authors also found that chip seal had minimal impact on the condition and deterioration rate of pavements when the PCI^- is greater than 80 ( 14 ). Therefore, the presence of moisture damage did not result in a significant impact on the performance curve of chip seal for all the sections with PCI^- > 80, which eventually led to the same ΔPSL. Figure 5d presents the effects of moisture damage on the service life of chip seal at two different traffic levels. At low traffic level (ADT < 1,100), moisture damage decreased chip seal service life significantly by 8 years, as implied by Tukey’s HSD test results. At medium traffic level (1,100 < ADT < 5,500), moisture damage decreased chip seals service life by 3 years; however, the impact of moisture damage was not statistically significant.

Average Performance Increase Over Treatment Life (PI) Relative to Pre-Treatment Condition

Figure 5e presents the effects of stripping damage on the PI for different pre-treatment conditions. For the sections with PCI^- less than 80, PI was 16.5% and 1.4% for non-stripped and stripped sections, respectively. These results indicate that the use of chip seal resulted in a 16.5% improvement in pavement conditions over its service life compared with the pavement conditions before chip seal for non-stripped sections. However, the average condition of the stripped sections was improved by only 1.4%. For the sections with PCI^- > 80, PI was 7.5% when chip seal was placed over pavement sections without moisture damage. On the other hand, stripped sections exhibited an overall condition enhancement of 6.2% after applying chip seal. Similarly, the application of chip seal on sections without moisture damage improved the average pavement conditions by 18.0% and 6.4% for low and medium traffic, respectively (see Figure 5f). However, PI was 3.5% for sections at both low and medium traffic levels when chip seal was applied to pavement sections with moisture damage.

CE

As shown in Figure 5g, non-stripped and stripped pavements achieved a CE of 1.3% and 0.5%, respectively at PCI^- < 80. However, sections with and without moisture damage exhibited similar CE of 0.6% when PCI^- was greater than 80. This trend agrees with the results presented in Figure 5a and b . As shown in Figure 5g, moisture damage decreased the CE of chip seal significantly especially for sections with PCI^- < 80. In addition, moisture damage reduced the CE of chip seal at both traffic levels (see Figure 5h). At the low traffic level, the presence of AC stripping significantly decreased CE from 1.2% to 0.3%. For sections with the medium traffic level, moisture damage decreased CE by 0.1%, which was not statistically significant.

AC Overlay Sections

AC Overlay Average Deterioration Rate (ADR)

Table 1 summarizes the effects of moisture damage on the ADR of AC overlays. The ADRs were observed to be 4.0% and 9.4% for pavements without and with moisture damage, respectively. In Figure 6a, ADR was observed to be lower for sections without moisture damage than that of the sections with moisture damage at all traffic levels. In Table 1, the P-value of 0.00094 obtained from a two-tailed t-test (at a confidence level of 95%) indicates a significant effect of moisture damage on the ADR of AC overlays. This significance is also illustrated by the results of Tukey’s HSD test as shown in Figure 6a.

Table 1.

Impact of Moisture Damage on Overlay Average Deterioration Rate (ADR)

Statistical factor	ADR (%)
Statistical factor	Without moisture damage	With moisture damage
Mean ADR	4.0	9.4
P-value	0.00094

Figure 6.

Impact of moisture damage on the performance and cost efficiency of asphalt concrete (AC) overlays based on (a) Average Deterioration Rate (ADR) and traffic volume; (b) Extension in Pavement Service Life (ΔPSL) and traffic volume; (c) Average Condition Increase (PI) and traffic volume; (d) Cost-Effectiveness (CE) and traffic volume.

Extension of Pavement Service Life Service (ΔPSL)

The effect of stripping damage on the service life of the AC overlay is presented in Table 2 and Figure 6b. As shown in this figure, AC overlays extended PSL by 13.3 and 8.7 years, on average, for pavements without and with moisture-induced damage, respectively (see Table 2). Figure 6b shows the effects of moisture-induced damage on the PSL of AC overlays. As shown in this figure, the non-stripped sections outperformed stripped sections with an average increase in the PSL of 13 years at all traffic levels.

Table 2.

Impact of Moisture Damage on Pavement Service Life (PSL)

Statistical factor	PSL (years)
Statistical factor	Without moisture damage	With moisture damage
Mean extension in pavement service life (ΔPSL)	13.3	8.7
P-value	0.037

In Table 2, a P-value of 0.037 was obtained from a two-tailed t-test, at a confidence level of 95%, indicating a significant impact of moisture damage on AC overlay PSL. The different assigned letters (A and B) for stripped and non-stripped sections in Figure 6b also show the significant effect of moisture damage, except at a traffic level greater than 16,000 vehicles per day (vpd). These results imply that moisture damage had a significant impact on the service life of the AC overlays.

Average Performance Increase for AC Overlays

Figure 6c and Table 3 show the impact of moisture-induced damage on the PI of the sections treated with AC overlays at different traffic levels. For pavement sections without moisture damage, the range of PI was between 35% (at traffic volume between 4,000 and 8,000 vpd) and 12.5% (at traffic volume between 8,000 and 12,000 vpd). For stripped sections, PI ranged from −1.2% to 7.5%. The negative sign means that, at a traffic level of ADT < 4,000, the average pavement condition after placement of AC overlay was less than the PCI^- by 1.2%. It worth noting that all non-stripped sections performed better in regard to PI than the stripped sections. The stripped and non-stripped sections also exhibited significantly different PI values as can be inferred from the two-tailed t-test with a P-value of 0.002 shown in Table 3 and the Tukey’s HSD results presented in Figure 6c.

Table 3.

Impact of Moisture Damage on the Average Condition Improvement over the Treatment Service Life (PI) of Asphalt Concrete (AC) Overlay

Statistical factor	PI (%)
Statistical factor	Without moisture damage	With moisture damage
Mean cost-effectiveness (CE)	28.0	5.0
P-value	0.0022

CE

The effect of moisture damage on the CE of AC overlays is presented in Table 4 and Figure 6d. The average values of CE were 1.1% and 0.6% for non-stripped and stripped pavements, respectively, when treated with an AC overlay. In Figure 6d, the CE of AC overlays was significantly lower for AC overlays constructed on sections with existing moisture damage than for AC overlays placed on non-stripped sections. A P-value of 0.004 obtained from the two-tailed t-test results (at a confidence level of 95%) indicated a significant impact of moisture damage on the CE of AC overlays (see Table 4). The significance is also supported by the different assigned letters (A and B) obtained from Tukey’s HSD test for stripped and non-stripped sections as shown in Figure 6d.

Table 4.

Impact of Moisture Damage on Overlay Cost-Effectiveness (CE)

Statistical factor	CE (%)
Statistical factor	Without moisture damage	With moisture damage
Mean CE	1.10	0.60
P-value	0.004

Summary and Conclusions

The performance and CE of in-service pavement sections were evaluated to assess the effects of AC stripping on the performance of chip seal and AC overlay treatments in hot and humid climates. Pavement sections were categorized and analyzed according to their pre-treatment conditions, traffic volume, and moisture damage in the underlying pavement. Based on the results of the analysis, the following conclusions were drawn:

PSL, the average performance increase, and CE decreased significantly when chip seal was applied on moisture-damaged pavements with a pre-treatment PCI of less than 80. Results also validate the accelerated deterioration of the treatment when applied on sections with moisture damage.

The effect of AC stripping damage on the performance of chip seal treatment was observed to be insignificant on the performance indicators including PSL, ADR, average condition increase, and CE for pavement sections with a pre-treatment PCI greater than 80.

AC overlays extended PSL by 13 years when placed on non-stripped pavements but only performed adequately for 8.7 years when moisture damage was present in the underlying AC layers.

Stripping damage decreased the CE of AC overlays from 1.1% to 0.6%. Furthermore, for pavement sections without moisture damage, the range of PI was between 35% and 12.5% but it was −1.2% to 7.5% for sections with moisture damage.

In summary, these results indicate that pavement-underlying conditions including AC stripping damage should be taken into consideration in the PMS decision and treatment selection process. Furthermore, moisture damage should be effectively corrected before the application of maintenance or rehabilitation strategies, including chip seal and AC overlays, for more durable pavements and optimum use of available funds.

Footnotes

Acknowledgements

The authors would like to acknowledge Louisiana Transportation Research Center (LTRC) through Project Number 18-4P.

Author Contributions

The authors confirm contribution to the paper as follows: study conception and design: M. Elseifi, H. Abohamer; data collection: H. Abohamer, M. Elseifi; analysis and interpretation of results: H. Abohamer, M. Elseifi; draft manuscript preparation: H. Abohamer, N. Dhakal, M. Elseifi, Z. Zhang. All authors reviewed the results and approved the final version of the manuscript.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was funded by the Louisiana Transportation Research Center (LTRC).

Data Availability Statement

Some or all data, models, or code that support the findings of this study are available from the corresponding author on reasonable request.

ORCID iDs

Hossam Abohamer

Mostafa A. Elseifi

Nirmal Dhakal

Christophe N. Fillastre

The contents of this paper do not necessarily reflect the official views or policies of LTRC or LaDOTD.

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