• International Journal of Highway Engineering
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• v.19 no.5
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• pp.117-129
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• 2017

PURPOSES : The purpose of this study is to analyze the performance life of hot central plant recycling (HCPR) and hot in-place recycling (HIR) pavements applied to the National Highway for the past 20 years and compare it with conventional hot-mix asphalt (HMA) pavement. METHODS : In order to analyze the performance life of recycling asphalt pavements, a comprehensive literature review was conducted to investigate the government law and official system for the use of recycling asphalt pavement in Korea and foreign countries. Next, the application information of using a hot central plant recycling and hot in-place recycling pavements in the national highway is collected from the database of pavement management system (PMS) and then their field condition is visually surveyed. Finally, the performance life of recycling asphalt pavements in the national highway is analyzed and compared with conventional hot-mix asphalt pavement. RESULTS :Institutions are encouraging the promotion of using recycled asphalt pavement through various legal systems in Korea as well as abroad. Based on analysis results for the average performance life of hot central plant recycling pavement applied to the national highway, the average performance life is estimated to be 10.2 years. However, the average performance life of in-place recycling pavement is estimated to be 6.5 years. However, it is expected to increase performance life after the HIR construction system is modified. CONCLUSIONS : Based on the limited data analysis of the performance life of recycled asphalt pavements, HCPR shows similar performance life to conventional asphalt pavement but HIR shows shorter performance life than conventional asphalt pavement. However, it is noted that all performance life data is very limited and it should be monitored and analyzed further.

• International Journal of Highway Engineering
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• v.19 no.5
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• pp.43-48
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• 2017

PURPOSES : The purpose of this study is to verify the effects of fiber grid reinforcement on the thickness reduction of asphalt pavement. Test sections were constructed on the national highway to evaluate the structural capacity of asphalt pavement with the reinforced fiber grid and normal asphalt pavement. METHODS : Falling Weight Deflectometer (FWD) tests were performed to measure the structural capacity of test sections. The loads of the FWD test are 4.1 ton, 8.0 ton, 10.0 ton, and loaded twice, respectively. The test sections consist of a reference asphalt pavement section, an asphalt pavement section reduced with a 5-cm base layer thickness, and a fiber grid reinforced asphalt pavement section reduced with a 5-cm base layer thickness. In addition, strain data was collected using strain gauges installed in the test sections. RESULTS : The results of the FWD tests showed that the deflections of the pavement section reinforced with the fiber grid was reduced by about 14% compared with that of the reference asphalt pavement section. The strain at the bottom of the asphalt surface layer of the pavement section reduced to a 5-cm base thickness and reinforced with a fiber grid was similar to that at the bottom of the asphalt layer of the reference asphalt pavement. CONCLUSIONS : The results of the FWD and strain tests showed the possibility of the pavement thickness reduction by reinforcement with a fiber grid.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.1-8
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• 2018

PURPOSES : Case studies of an asphalt-overlay project with a performance-based contract method were conducted on a national highway in Korea to evaluate the effect of the method on asphalt pavement maintenance. This study evaluated the procedure of the performance-based contract method. METHODS : In this study, an asphalt-pavement maintenance project for a national highway was assessed with a performance-based contract to investigate the advantage of the new contract procedures. This is the first trial applying the performance-based contract to a pavement-rehabilitation project in Korea. In the four case studies, the warranty period of the performance-based contract was designed for seven years. The research team monitored the construction site to compare the normal contract method with the performance-based contract method. The case studies' project sites were investigated after the end of the construction. RESULTS : Based on the limited case studies, the performance-based contract method could extend the service life of the asphalt pavement and reduce the pavement-maintenance budget because the quality control was well managed by the contractors. However, a few construction laws would be necessary to apply the performance-based contract method in the future. CONCLUSIONS : Using the performance-based contract, the construction company made great efforts to guarantee the warranty period and to apply the optimal maintenance method, based on the pavement distress condition. The contractor and the agency would need to understand the new performance-based contract system for it to be activated. Therefore, a proper education program for the performance-based contract system would be needed to educate the stakeholders regarding the procedures and their effects on the pavement management and maintenance.

• International Journal of Highway Engineering
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• v.4 no.3 s.13
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• pp.25-33
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• 2002

Most national highways are paved with asphalt. Since increased traffic volume and high temperature have reduced the service life of pavements, modified asphalt pavements or stone mastic asphalt (SMA) have gradually been adopted. However, pavement engineers have difficulty to select pavement types due to lack of standard specifications for these new pavement types. In this study, service lives of general asphalt pavements based on traffic volume were analyzed using the inventory data of pavement management system (PMS) collected for last 10 years. The results showed 9.5 and 5.6 year average service lives for new constructed pavements and overlays, respectively. The traffic volumes for the design life of 10 years was presented based on confidence levels using service life distributions of current pavements. For the confidence level of 90%, 2,300 ESAL was obtained; 1,500 ESAL for the confidence level of 80%. This indicates that modified asphalt pavements should be considered for sections with the higher traffic volume.

• International Journal of Highway Engineering
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• v.15 no.2
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• pp.1-9
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• 2013

PURPOSES : The PMS(Pavement Management System) has been utilized in order to efficiently allocate the limited budget for the maintenance of national highway system. In the PMS of national highway, surface pavement condition is evaluated by using the VI (Visual Index). However, the VI is determined only by considering the cracking rate (%) and rut depth (mm), which is not reflecting the IRI (International Roughness Index) that is known as an important factor of pavement performance. In this study, the NHPCI (National Highway Pavement Condition Index) which includes the cracking rate (%), rut depth (mm), and IRI (m/km) is suggested for determining the rehabilitation methods group. METHODS : First, the rehabilitation methods performed between 2008 and 2010 on the national highway is classified and then, NHPCI is determined for each rehabilitation method. Next, the NHPCI for each rehabilitation method is grouped through the interval estimation of the population mean and T-test analysis. RESULTS : According to NHPCI range, the rehabilitation methods are divided into four categories: Not Required, Preventive Maintenance, Overlay Treatment (with or without cutting), and Full-scale Treatment (i.e., reconstruction). CONCLUSIONS : Based on this study, it is recommended that the appropriate NHPCI range should be determined through the combination of the rehabilitation categories and Decision Procedure of Pavement Distress Condition Visual Index.

• International Journal of Highway Engineering
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• v.11 no.2
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• pp.37-44
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• 2009

Currently the reasonability of threshold values for rutting and cracking does not clearly defined at the Pavement Rehabilitation Decision Tree on national highway PMS(Pavement Management System). The goal of this study is to provide the reasonable threshold values for the national highway asphalt concrete pavement rehabilitation. To achieve this goal, test section that represents typical asphalt concrete pavement of national highway was selected and pavement export were participated. Pavement condition survey has been conducted and pavement performance data at the selected roadway section were analyzed. From this study, reasonable threshold values of Pavement Rehabilitation Decision Tree were suggested based on the pavement expert's engineering judgement. In terms of crack repairs, the application of overlay after cutting is required to deteriorated area where existing crack ratio is over 35% and just overlay is required to where crack ratio is over 20%. On rutting, rut depth over 13mm is required to overlay after cutting and rut depth over 10mm is just needed to overlay.

• International Journal of Highway Engineering
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• v.18 no.4
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• pp.19-28
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• 2016

PURPOSES : Long-life asphalt pavements are used widely in developed countries. In order to be able to devise an effective maintenance strategy for such pavements, in this study, we evaluated the performance of the long-life asphalt pavements constructed along the national highways in South Korea. Further, an economic evaluation of the long-life asphalt pavements was performed based on a life-cycle cost analysis. We aimed to devise a model for evaluating the performance of long-life asphalt pavements using the national highway pavement management system (PMS) database as well as for analyzing the economic feasibility of such pavements, in order to promote their use in South Korea. METHODS : The maintenance history and pavement performance data were obtained from the national highway PMS database. The pavement performances for a total of 292 sections of 10 lanes (5 northbound lanes and 5 eastbound lanes) of national highways were used in this study. Models to predict the performances of hot mix asphalt (HMA) and long-life asphalt pavements under two distinct traffic conditions were developed using a simple regression method. Further, the economic feasibility of long-life asphalt pavements was evaluated using the Korea Pavement Management System (KoPMS). RESULTS : We developed service-life prediction models based on the traffic volume and the equivalent of single-axle load and found that long-life asphalt pavements have service lives 50% longer than those of HMA pavements. Further, the results of the economic analysis showed that long-life asphalt pavements are superior in terms of various economic indexes, including user cost, delay cost, total cost, and user benefits, even though their maintenance cost is higher than that of HMA pavements. A comparison of the economic feasibilities of the various groups showed that group A is superior to HMA pavements in all aspects except in terms of the maintenance criterion (crack 20% or higher) as per the NPV index. However, the long-life asphalt pavements in group B were superior in terms of the maintenance criterion (crack 25% or higher) regardless of the economic feasibility. CONCLUSIONS : The service life of long-life asphalt pavements was found to be approximately 50% longer than that of HMA pavements, regardless of the traffic volume characteristics. The economic feasibility of long-life asphalt pavements was evaluated based on the KoPMS. The results of the economic analysis were the following: long-life asphalt pavements are exceptional in terms of almost all factors, such as user cost, delay cost, total cost, and user benefit; however, the exception is the maintenance cost. Further, the economic feasibility of the long-life asphalt pavements in group B was found to be better than that of the HMA pavements (crack 25% or higher).

• International Journal of Highway Engineering
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• v.20 no.2
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• pp.57-65
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• 2018

PURPOSES : The study aims to predict the service life of national highway asphalt pavements through deep learning methods by using maintenance history data of the National Highway Pavement Management System. METHODS : For the configuration of a deep learning network, this study used Tensorflow 1.5, an open source program which has excellent usability among deep learning frameworks. For the analysis, nine variables of cumulative annual average daily traffic, cumulative equivalent single axle loads, maintenance layer, surface, base, subbase, anti-frost layer, structural number of pavement, and region were selected as input data, while service life was chosen to construct the input layer and output layers as output data. Additionally, for scenario analysis, in this study, a model was formed with four different numbers of 1, 2, 4, and 8 hidden layers and a simulation analysis was performed according to the applicability of the over fitting resolution algorithm. RESULTS : The results of the analysis have shown that regardless of the number of hidden layers, when an over fitting resolution algorithm, such as dropout, is applied, the prediction capability is improved as the coefficient of determination ($R^2$) of the test data increases. Furthermore, the result of the sensitivity analysis of the applicability of region variables demonstrates that estimating service life requires sufficient consideration of regional characteristics as $R^2$ had a maximum of between 0.73 and 0.84, when regional variables where taken into consideration. CONCLUSIONS : As a result, this study proposes that it is possible to precisely predict the service life of national highway pavement sections with the consideration of traffic, pavement thickness, and regional factors and concludes that the use of the prediction of service life is fundamental data in decision making within pavement management systems.

• International Journal of Highway Engineering
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• v.17 no.3
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• pp.69-76
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• 2015

PURPOSES : Performance evaluation of four types of asphalt concrete overlays for deteriorated national highways. METHODS : Pavement distress surveys for crack rate and rut depth have been conducted annually using an automated pavement survey vehicle since 2007. Linear and non-linear performance prediction models of the asphalt concrete overlays were developed for 43 sections. The service life of the asphalt overlays was defined as the number of years after which a crack rate of 30% or rut depth of 15mm is observed. RESULTS : The service life of the asphalt overlays was estimated as 17.4 years on an average. In 90.7% of the sections, the service life of the overlays was 15 years or more which is 1.5 times the life of conventional asphalt concrete overlays used in national highways. The performance of the overlays was dependent on the type of asphalt mixture, traffic volume levels, and environmental conditions. CONCLUSIONS : The usage of stone mastic asphalt (SMA) and polymer-modified asphalt (PMA) for the overlays provided good resistance to cracking and rutting development. It is recommended that appropriate asphalt concrete overlays must be applied depending on the type of existing pavement distress.

• International Journal of Highway Engineering
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• v.4 no.1 s.11
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• pp.123-134
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• 2002

Special pavement test sections were selected to develop a distress prediction model on asphalt pavement of National Highway. Experimental design was conducted for the selection of LTPP sections on in-service pavement(new and overlaid pavement) using several variables affecting pavement performance. Preliminary sections that satisfied the design template were chosen from the national highway database, and final selection was fixed through field inspection. The number of monitoring section is 95 including 47 overlaid pavement. A pavement distress data such as crack and rutting were collected for two years. An interim pavement performance analysis was peformed to show feasibility of performance monitoring program. Data related pavement such as traffic, weather, material characteristic and crack etc. should be collected for next project years and distress prediction model will be developed through the statistical analysis.