PURPOSES : The type and degree of structural conditions and influencing factors distributed across representative sections should be similar to those distributed across entire sections as the representative sections have been predominantly used for developing performance prediction models, which substitute entire sections of road pavement. Therefore, a logic that selects the representative sections with similar distributions of structural conditions and the influencing factors with those of entire expressway asphalt pavement sections requires development. METHODS : The logic developed in this study to select the representative sections of asphalt pavements comprised three steps. First, the data on the structural conditions of the pavement and the influencing climate conditions and pavement materials were collected and organized. Consequently, in the second step, the candidate sections were selected, with the severity of the structural conditions of the pavement distributed widely and evenly. Finally, in addition to the widely and evenly distributed pavement conditions, the representative sections with climatic conditions and pavement materials were selected. RESULTS : A total of 6,352 ordinary asphalt pavement sections and 596 composite asphalt pavement sections were selected as entire expressway asphalt pavement sections and the data were collected and organized according to the logic developed in this study. Three times the representation sections were selected as candidate sections and, finally, 85 sections were selected as representative sections. The distribution of structural conditions and influencing climate conditions and pavement materials in the representative sections were similar to those in the entire sections. In addition, the representative sections were spread evenly across the country. CONCLUSIONS : The sections presenting similar distributions of structural conditions and the influencing factors of entire expressway asphalt pavement sections could be selected in this study. Using the representative sections selected in this study, a remodeling index model will be developed for predicting the asphalt pavement sections that require large-scale repair.

PURPOSES : The purpose of this study is to evaluate the performance characteristics of stone mastic asphalt (SMA) pavement by comparison with polymer modified asphalt (PMA) pavement and conventional asphalt pavement, to check the performance characteristics according to the pavement type, pavement materials, traffic volume, and environmental factors and to analyze the quality variation characteristics according to the pavement materials using data extracted from the database of the expressway long-term pavement performance. METHODS : Approximately 10% outlier data of pavement performance data were excluded in order to increase the reliability of the analysis results before evaluating the asphalt pavement performance. The performance model was developed through linear regression analysis by setting the performance period as the independent variable and the highway pavement condition index (HPCI) as the dependent variable. Descriptive statistic analysis of HPCI using the static package for social science (SPSS) tool and the analysis of variance was performed to identify the quality variation characteristics according to the pavement materials. The amount of de-icing agent and traffic level of service were classified as two levels in order to check the influence of traffic volume and environmental factors on the performance characteristics of the asphalt pavement. RESULTS : The tentative pavement performance lives were calculated at 19.3 years for new the SMA pavement (GPS-2), 14.3 years for the SMA overlay on the asphalt pavement (GPS-6), and 10.3 years for the SMA overlay on the concrete pavement (GPS-7). In case of the asphalt overlay, the tentative performance lives were calculated at 8.2 years for the PMA overlay on the asphalt pavement (GPS-6), 7.2 years for the PMA overlay on the concrete pavement (GPS-7), 7.2 years for the conventional asphalt overlay on the asphalt pavement (GPS-6), and 5.5 years for the conventional asphalt overlay on the concrete pavement (GPS-7). CONCLUSIONS : It was confirmed that the SMA pavement showed better performance and quality variation characteristics than the PMA and conventional asphalt pavement. The performance characteristics of the asphalt pavement (GPS-2) was better than the asphalt overlay pavement, and the asphalt overlay on the asphalt pavement (GPS-6) had better performance characteristics than the asphalt overlay on the concrete pavement (GPS-7). It was observed that the asphalt overlay on the asphalt pavement (GPS-6) was strongly influenced by the traffic volume and the asphalt overlay on concrete pavement (GPS-7) was strongly influenced by the traffic volume and de-icing agent.

PURPOSES: Investigating road pavement conditions using an investigation vehicle is challenging especially if repeated driving is required on the by-lane, and the traffic in the investigation section is heavy. A technology used to investigate the road pavement conditions is studied herein using image data obtained by drone photography. METHODS : Flight plans were made for the survey areas, and ground control point measurements were performed. The research section was filmed using drones. The acquired image data were modeled using Pix4Dmapper. The images taken by the drones were used to investigate the road pavement cracks. A digital surface model was extracted from the Pix4Dmapper modeling results using the Global Mapper program to investigate plastic deformation and flatness. As regards plastic deformation, the elevation of each point was extracted at intervals of 50 cm and 10 cm in the longitudinal and lateral directions, respectively, for 20 m× 10 m of the entire road. In terms of flatness, the elevation values for each point were extracted at intervals of 5 cm and 10 cm for the wheel path and 20 m for the entire roadway. RESULTS: This study compared drone-captured images, which were consistent, and vehicle scan images and confirmed that the former can detect a large number of cracks on road surfaces. The results showing the difference in the elevation values of the road surface indicate that the section, wherein the plastic deformation occurs throughout the entire road surface, can be identified and evaluated. With regard to flatness, in future studies, the long-directional elevation value of the target segment extracted using Global Mapper is likely to be derived from the International roughness index, which is the international flatness index used in the ProVAL program developed and used by the Federal Highway Administration. CONCLUSIONS : The road pavement status investigation conducted herein by utilizing drone-acquired images showed that repeated driving in a section is not required, and various analyses can be made in a single shot. If technologies, such as artificial intelligence, big data, and Internet of Things, which are the key components of the Fourth Industrial Revolution, are adapted, they can be used to investigate road pavement conditions and inspect completely constructed road lines and major road facilities.

PURPOSES : The recent increase in the application of reclaimed asphalt pavement (RAP) calls for more research focusing the evaluation of pavement performance. For this matter, this study aims at evaluating pavement performance using the application rate of RAP. METHODS: To obtain mixtures with RAP aggregate application rates of 10%, 25% and 30%, the gyratory compaction method was applied regarding the mix design process for determining the optimum asphalt content (OAC). Additionally, the in-direct tension (IDT) test, deformation strength test (DST), tensile strength ratio (TSR) test and dynamic modulus (DM) test were conducted to verify the effect of RAP application rate on pavement performance. Based on the above-mentioned results, performance evaluation was done to these RAP application of design or utilization to construction site. The performance evaluation analysis was performed using the Korean Pavement Research Program (KPRP) of second level for the pavement design. RESULTS: From the DST results, the rutting resistance was improved as the application rates of RAP were increased. Additionally, all the IDT and toughness results satisfied the quality standards of the asphalt concrete pavement. However, the results did not conform with the tensile strength ratio standards with the application rates of RAP of 25% and 30%. This means that the standards, which should be considered when the addictive regeneration material is applied to the mixture when the RAP application rate is over 25%, were reflected. CONCLUSIONS : The predicted performance decreased from the second level performance analysis with the increase in the RAP application rates. All the cases satisfied the design standards (fatigue cracking, rutting depth and international roughness index (IRI)). However, the results of them closed to these standards (up to 94% (Fatigue)).

PURPOSES: This paper presents the noise reduction effect of asphalt concrete pavement using steel slag aggregate. METHODS: Steel slag aggregates induce various mechanical effects because of their high stiffness and specific gravity. It is also known that the noise reduction effect is due to its high specific gravity and porous nature. In this study, the noise reduction in a steel slag asphalt concrete pavement section was measured and analyzed. RESULTS : On average, an asphalt concrete pavement with steel slag reduces road traffic noise by about 2 dB(A). In addition, the analysis of sound pressure levels by frequency showed lower sound pressure levels in steel slag asphalt concrete pavement than general HMA in all frequency ranges (from low to high frequencies). An analysis of the benefits with regard to noise, by assuming a road-traffic noise reduction of 2 dB(A) with asphalt concrete pavement using steel slag, shows that the noise abatement cost approach can save 1.6 million won a year over soundproof wall costs. In addition, the noise damage cost approach results in cost savings (with regard to noise) of between 19 and 60 million won per year depending on the population density. CONCLUSIONS: The use of steel slag aggregate as an asphalt concrete mixture material not only improves the mechanical performance but also has a noise reduction effect. It is expected that the steel slag asphalt concrete pavement can reduce the environmental burden by utilizing resources and provide a safer and more comfortable pavement condition to the road users.

PURPOSES : This study establishes a pay adjustment factor scheme that will penalize or provide incentives to contractors after pavement construction in Seoul City. METHODS: Random sampling was conducted, wherein acceptable quality characteristics (AQCs) of the field mixture such as the aggregate gradation, asphalt binder content, pavement thickness, field air void, and IRI (International Roughness Index) were determined. Using the acquired field data, the percent within limit (PWL) values of each AQC were determined. RESULTS : Weight factors were used to consider the effect of each AQC, since field data varies depending on the field condition. The total pay factor (PF) was determined by combining the PF material and PF construction. PF material considers the asphalt binder content and the aggregate gradation, while PF construction considers the field air void, pavement thickness, and field IRI. CONCLUSIONS: A pay adjustment factor was established by determining the PWL of each AQC and calculating the corresponding pay factor. Based on the results, it is found that PWL is a reasonable and acceptable method for evaluating the pavement quality and determining the pay factor.

PURPOSES: Using recyclable materials in asphalt pavement industry is one of the essential tasks not only for saving construction budgets but also for mitigating environmental pollutions. Over the past decades, several efforts have been made by road maintenance agencies to incorporate various recyclable materials into virgin asphalt paving mixtures. As a result, reclaimed asphalt pavement (RAP), which consists of old pavement material was selected as one of most widely used recyclable materials. In this paper, the effects of using different amounts of single-recycled RAP (SRRAP) and double-recycled RAP (DRRAP) on the low-temperature characteristics of asphalt mixtures were investigated. METHODS: To evaluate the low-temperature characteristics of SRRAP and DRRAP mixtures, two experiments, the bending beam mixture creep test and semicircular bending fracture test were performed. The experimental parameters: creep stiffness, m-value, thermal stress, critical cracking temperature, fracture energy, and fracture toughness were computed then compared. RESULTS : RAP mixtures (SRRAP or DRRAP) showed lower mechanical performance compared with conventional asphalt mixtures. The differences became distinct with increased RAP addition. However, the performance differences between SRRAP and DRRAP mixtures were not significant in all cases, which indicate the possible application of re-recycling technology (DRRAP) in the asphalt pavement industry. CONCLUSIONS : The addition of RAP to virgin asphalt can mitigate low-temperature performance despite the improvement in fracture performance observed in some cases. Therefore, using RAP (SRRAP or DRRAP) mixtures on inter or sublayer construction, but not on the surface layer, is recommended. Moreover, the possibility of applying double-recycling technology in asphalt pavement industry can be introduced in this study because not significant performance differences were found between SRRAP and DRRAP mixtures especially at low temperature.

PURPOSES: In this study, algorithms were proposed for determining the crack condition of an asphalt pavement image using deep learning methods. METHODS: For the configuration of a deep learning network, the study used a Convolution Neural Network and You Only Look Once algorithms. To obtain input data for analysis, a camera was mounted on the bonnet of the vehicle to obtain images of asphalt pavement and to mark the ground-truth cracks in the asphalt pavement image. In addition, an algorithm suitable for the automatic determination function of Deep Learning was proposed in order to calculate the crack ratio and crack rating. RESULTS: The result of analysis showed that the recall rate of cracks in this system was higher from FPPW 5.0E-06 to 96.03%. Furthermore, the accuracy of the grading system was found to be 100%, enabling the determination of very accurate ratings. The rate of processing per image was 0.4448 seconds on average, and the real-time analysis of pavement images presented no problem because the assessment took place within a short time. CONCLUSIONS : Applying this system to the pavement management system is expected to reduce the time required in finishing work and to determine a quantitative crack rating.

지난해 2월말 경 용산역 근처 공사현장 인근 인도에서 도로함몰이 발생하여 보행자가 추락하여 부상을 입는 사고가 발생했다. 이를 계기로 서울시는 도로함몰의 조기예방을 위해 세계 최고수준의 기술을 보유 한 일본 업체와 협력하여 차량형 GPR(Ground Penetrating Rader : 전자파를 지표에 투과하여 지하의 빈 공간 형상 데이터를 수집하는 레이더 장치)을 이용한 도로하부 동공탐사 용역을 실시하였다. 서울시 동공탐사용역을 계기로 현장적응 시운전과 기술진의 분석훈련을 거쳐 실질적 탐사는 지난해 12 월부터 시작되었으며 약 4개월 동안 도로함몰 개연성이 높은 주요 간선도로 48km구간에서 105개의 공동 을 발견하였으며 금년 말까지는 약 200여개를 포함해 총 300여개의 공동이 발견될 것으로 예상했다. 이번 조사로 발견된 공동 중 위험도가 가장 높은 A급 공동이 약 60%로 61개가 발견되었고 그보다 낮은 등급의 B급 공동이 35개가 발견되어 5월 말까지 복구할 예정이며 도로함몰 가능성이 그나마 낮은 C급 공동 8개는 연구를 위해 일정 기간 관찰 후 복구할 예정이라고 밝혔다. 서울시 자치구별 공동 발견 현황을 살펴보면 송파구가 약 30%인 32개로 가장 많은 공동이 발견되었고 뒤이어 용산구 21개, 종로구 19개 순으로 나타났 다. 본 연구는 상용 유한요소해석 프로그램인 ABAQUS를 이용하여 공동 규모에 따른 아스팔트 포장도로 의 거동에 대한 분석을 실시하였다. 이를 위해 공동의 규모는 공동 위험도 평가 등급에 따른 A, B ,C 등급 으로 분류하였으며 공동의 발생 범위는 1.5m 이내로 설정하였다. 해석을 위한 단면 구성은 아스팔트 콘크 리트 층, 보조기층, 노상의 구조로 이루어져 있으며 접합상태를 의미하는 tie contact를 선택하고 각 층의 재료에 대한 입력물성은 일반적으로 아스팔트 콘크리트 포장구조체에 사용되는 범위를 적용하였다. 해석 모델은 연직하중만이 작용하는 Axisymmetric으로 구성하였으며 해석에 사용된 하중은 포장도로 설계시 사용되는 원형 등분포하중으로 설정하였다. 해석은 각 층의 단면, 재료물성과 하중 그리고 공동의 규모를 변화시키며 실시하였고 아스팔트 포장체의 표면 처짐, 변형률 등을 분석하였다.

아스팔트 덧씌우기는 어느 정도 파손이 진행된 아스팔트 포장이나 시멘트 콘크리트 포장 위에 아스팔 트 혼합물을 포설하는 포장 보수 공법으로 지난 2006년에는 탄소섬유와 유리섬유를 느슨한 격자막 형태 로 직조한 토목섬유 보강재를 노면에 부착하여 아스팔트 포장체의 균열저항성을 증진시킬 수 있는 섬유그 리드 보강 덧씌우기 공법이 개발되어 현재까지 136km의 달하는 구간에 시공되었다. 그에 따라 최근 국내 에서는 섬유그리드 보강 덧씌우기 포장의 효과를 확인하기 위한 연구가 활발히 진행되고 있다. 김광우 외 (1999)는 아스팔트 콘크리트 덧씌우기에서 야기되는 반사균열에 대한 저항성 향상을 위한 연구를 통해 유 리섬유 그리드로 보강된 아스팔트 혼합물이 반사균열 저지에 효과적이라는 연구결과를 보였다. 도영수 외 (2005)도 아스팔트 덧씌우기 포장에 나타나는 반사균열 제어를 목적으로 시멘트 콘크리트 포장과 아스팔 트 덧씌우기 포장 경계면에 보강재의 부착 방법을 달리하여 실내실험을 진행하였으며, 불포화 폴리에스터 수지 부착이 가장 효과인 것을 확인했다. 또한 박상구 외(2010)는 이러한 섬유보강 아스팔트 포장 부착의 전단강도를 개선하여 섬유보강 아스팔트 포장의 성능을 극대화하기 위한 연구를 진행하여 현장에서 지켜 야 할 만한 규정을 제안하였다. 국내에서의 섬유그리드 보강 덧씌우기 포장공법은 비교적 최신의 기술이기 때문에 일반 아스팔트 덧씌 우기 포장공법과의 장기적인 공용성 비교가 제대로 이루어지지 않은 실정이다. 따라서 본 연구에서는 섬 유그리드 보강 덧씌우기 포장 공법의 장기공용성 조사를 위해 재령 8년이 된 국내 고속도로 콘크리트 포 장의 PMS 데이터를 확보하여 추적조사와 구조해석을 실시하였다. 결과 분석을 통해 기존 콘크리트 포장을 섬유그리드로 보강하고 덧씌웠을 때가 그렇지 않은 경우보다 수명이 증진되는 것으로 나타났으며, 섬유그리드가 반사균열에 저항하는 것을 확인하였다.

PURPOSES : The hydrated lime-modified asphalt, which improves moisture resistance, is normally used for pavements to reduce the number of potholes. However, the method of applying the material properties of the lime-modified asphalt mixture for use in pavements is not covered in the Korean Pavement Research Program (KPRP). The objective of this research is to find a method for the design application of lime-modified asphalt’s material properties to the KPRP. METHODS: The section for test design is selected in some conditions which are related to the level of design regarding Annual Average Daily Traffic (AADT). To define the application methods of hydrated lime in the KPRP, the models of fatigue, rut and international roughness index (IRI) are determined based on the M-EPDG test results from some earlier research results. Moreover, it is well known that dynamic moduli of the unmodified mixture are not different from those of the lime-modified mixture. RESULTS: The performance results of hydrated lime-modified asphalt pavement were not very much different from those of the unmodified pavement, which meant the limited design regulations regarding fatigue failure, rutting deformation and IRI. CONCLUSIONS: The KPRP uses the weather model from the data for previous 10 years. It implies that the KPRP cannot predict abnormal climate changes accurately. Hence, the predictive weather data regarding the abnormal climate changes are unreliable. Secondly, the KPRP cannot apply the moisture resistance of asphalt mixtures. Therefore, a second level of design study will have to be performed to reflect the influence of moisture. It means that the influence on pavement performance can be changed by the application of hydrated lime in asphalt mixture design.

PURPOSES : The objective of this study is to evaluate the performance properties of chip seals and fog seals with polymer-modified emulsions. METHODS : The performance of chip seals and fog seals was evaluated on the basis of common issues in surface treatments. Granite aggregate and four types of asphalt emulsions (one of the unmodified and three of the modified emulsions) were used considering the usage in field. A Vialit test was performed to determine the aggregate retention, and the MMLS3 (Third Scale Model Mobile Load Simulator) test was conducted to determine the aggregate retention, bleeding, and rutting. In addition, the fog seal specimens were tested by the BPT (British Pendulum Test) to evaluate skid resistance. RESULTS AND CONCLUSIONS : Overall, the polymer-modified emulsions (PMEs) showed better aggregate retention and bleeding resistance for both chip seals and fog seals. When comparing the performance of the PMEs, the difference was not considerable. In addition, PMEs present significantly better rutting resistance than unmodified emulsions. For skid resistance, if the recommended mix design is applied, the specimens do not cause issues with skid resistance. Although all of the fog seal specimens were over the criteria for skid resistance, the specimen fabricated by the high emulsion application rate (EAR) of the unmodified emulsion was nearly equivalent to the skid value criteria. Therefore, the use of an unmodified emulsion with a high EAR should be carefully applied in the field.