In South Korea, the level of Highway Pavement Management System (HPMS) was developed since early 2000. During this time numbers of professional pavement condition monitoring equipment were developed and applied in the actual field. One of the remarkable results is 3D Pavement condition Monitoring profiler vehicle (3DPM) designed and developed in Korea Expressway Corporation Research Division (KECRD). Thanks to this equipment, The surface condition of current pavement can successfully be monitored and proper following management strategy cab be established. However, the inner condition of pavement layer cannot be monitored dur to limitation of 3DPM equipment. In this paper, Bending Beam Rheometer (BBR) mixture creep test was performed to verify the effectiveness of current 3DPM equipment. It was found that the current 3DPM equipment has reasonable feasibility on surveying pavement condition.

최근 국내 겨울철 블랙아이스(Black Ice)로 인해 발생하는 교통사고가 증가하는 추세이며, 한국 도로교통공단 조사 결 과 2016～2020년 겨울철까지 블랙아이스로 인한 사고는 총 4,868건이며, 사상자는 8,938명인 것으로 조사 되었다. 도로상 태에 따라 건조대비 동결상태에서 교통사고 발생시 치사율이 43%로 높게 나타났다. 이러한 사고는 기온이 떨어지는 12 월부터 급증하여, 최저기온이 가장낮은 1월까지 증가한다. 블랙아이스는 도로에 쌓인 눈이 융해(해설)과 동시에 도로 위 각종 이물질과 결합 후 재동결하여 흑색 동결막을 형성하는 것을 말한다. 그 특성상 운전자가 차량내부에서 도로의 상태 를 쉽게 파악할 수 없으며 대부분의 운전자가 차량이 미끄러지기 시작함과 동시에 인지하여 사고가 발생하게 된다. 이에 본 연구에서는 기존 포장체의 미끄럼 저항도를 상태별로 비교 분석하였다. 포장체의 미끄럼 저항성 정도를 파악하기 위 해 영국식 미끄럼저항 시험기 (British Pendulum Tester ; BPT)를 사용하였으며, 포장체의 종류로는 일반적인 밀입도 아스팔트 포장, 배수성 아스팔트 포장, 그루빙(포장 표면에 일정한 규격의 홈을 형성)을 적용한 콘크리트 포장, 그루빙이 없는 콘크리트 포장을 적용하였다. 미끄럼저항 실험은 관련 KS규격 및 ASTM규격에 준하여 실시하되 블랙아이스를 모 사하기위하여 표면온도 영하 2～3℃ 샘플에 강우를 모사한 물을 분사하며 영하 9℃로 10분 동결 후 2mm강수량을 모사 한 수분을 재 분사한 후 시험을 실시하였다.

PURPOSES : The purpose of this study is to investigate the tendency of material property estimation under different concrete distress conditions and curling conditions when non-destructive tests such as rebound hammer and surface deflection test are applied to concrete pavement. METHODS : Nondestructive tests using Schmidt hammer and Falling Weight Deflectometer were performed to inspect the expressway concrete pavements constructed more than 20 years ago. Some results were compared with core tested elastic modulus and compressive strength. RESULTS : As a result of the rebound test, the section with Alkali-Silica Reaction(ASR) distress was outside the range of the existing estimation formula, but the control section was found to be within the range of the existing estimation formula. As a result of the physical property estimation through deflection test, the section with ASR distress showed greater fluctuations in the estimated material properties and deflection ratio compared to the control section, showing that the ASR damage seems to affect the slab deflection behavior. CONCLUSIONS : The rebound test may not sufficiently reflect the decline in material properties due to concrete damage. The deflection test can obtain results that reflect the deterioration of material properties, but it was confirmed that significant variability may occur, so it seems to necessary to perform complementary indoor core tests with nondestructive testing(NDT) tests.

PURPOSES : Previously, the expansion state of the concrete pavement in which AAR occurred could not be determined. Because the current situation has not been evaluated, it has been difficult to prepare an appropriate response. In this study, a method for calculating the expansion amount of concrete pavement using the stiffness damage test (SDT) is proposed. METHODS : The SDT method was examined through a literature review. For the laboratory tests, specimens that generated AAR were produced based on the mix design (2018) of the Korea Expressway Corporation. SDT was used to calculate various mechanical properties, and their correlation with the expansion amount was reviewed. RESULTS : Using the SDT, various mechanical properties(elastic modulus, hysteresis area, plastic deformation, plastic deformation index, stiffness damage index, and nonlinear index) were calculated based on the expansion rate of the AAR. The elastic modulus was evaluated as the best predictor of the expansion rate. Thus, if the elastic modulus is calculated using SDT, a prediction equation can be used to calculate the amount of AAR expansion. This equation will need to be supplemented by further research. CONCLUSIONS : SDT was used to confirm that the expansion state due to the AAR of the concrete pavement could be indirectly evaluated. Among the mechanical properties related to SDT, the elastic modulus was found to be the most suitable for predicting the amount of expansion.

PURPOSES : The evaluation of the low-temperature performance of an asphalt mixture is crucial for mitigating transverse thermal cracking and preventing traffic accidents on expressways. Engineers in pavement agencies must identify and verify the pavement sections that require urgent management. In early 2000, the research division of the Korea Expressway Corporation developed a three-dimensional (3D) pavement condition monitoring profiler vehicle (3DPM) and an advanced infographic (AIG) highway pavement management system computer program. Owing to these efforts, the management of the entire expressway network has become more precise, effective, and efficient. However, current 3DPM and AIG technologies focus only on the pavement surface and not on the entire pavement layer. Over the years, along with monitoring, further strengthening and verification of the feasibility of current 3DPM and AIG technologies by performing extensive mechanical tests and data analyses have been recommended. METHODS : First, the pavement section that required urgent care was selected using the 3DPM and AIG approaches. Second, asphalt mixture cores were acquired from the specified section, and a low-temperature fracture test, semi- circular bending (SCB) test, was performed. The mechanical parameters, energy-release rate, and fracture toughness were computed and compared. RESULTS : As expected, the asphalt mixture cores acquired from the specified pavement section ( poor condition – bad section) exhibited negative fracture performances compared to the control section (good section). CONCLUSIONS : The current 3DPM and AIG approaches in KEC can successfully evaluate and analyze selected pavement conditions. However, more extensive experimental studies and mathematical analyses are required to further strengthen and upgrade current pavement analysis approaches.

PURPOSES : The purpose of this study is to establish a scientific and rational structure pavement maintenance technique and management standard through field investigation and analysis method development for measuring damage to structure pavement such that fundamental quality improvement can be promoted and the life of pavement prolonged. METHODS : In this study, the crack, plastic deformation, IRI, and SPI values measured using the existing RoadScanner of a corresponding section, as well as the relative dielectric constant values of a lower deck measured using a ground penetrating radar are reduced. The results of a small impact load test are verified by comparing the modulus of elasticity measured. RESULTS : In the Hongjecheon Overpass, when comparing the suspicion points of deterioration between the center of the lane and the 25 measurement data points of the wheel pass section based on the elastic modulus of the light falling weight deflectometer (LFWD), it is discovered that the lane comprises four centers (16%) and 18 wheelpaths (72%). The percentage of suspected deterioration points in the center is higher than that in the wheelpath. In addition, in the case of the Seoho Bridge, by comparing the suspicious points of deterioration for 11 measurement data points in the middle of the lane and the wheelpath section based on the elastic modulus of the LFWD, it is discovered that five points (45%) in both the middle of the lane and the wheel pass are similar. CONCLUSIONS : In this study, a comparative analysis of the LFWD elastic modulus and SPI factors (crack rate, plastic deformation, and IRI) of the Hongjecheon Overpass and Seoho Bridge is conducted to confirm the factors of pavement breakage. Among them, it is confirmed that it affects the pavement condition the most; however, to consider the LFWD elastic modulus as an evaluation criterion for future structure pavement, the data points must be verified via additional experiments to ensure high reliability.

PURPOSES : On a thin epoxy overlay pavement, epoxy is placed on the existing bridge deck pavement, followed by the spraying of aggregates on it. The bond strength between the existing pavement and overlay pavement is an important factor representing the performance of the thin epoxy overlay pavement, in addition to the skid resistance and roughness. Therefore, the bond strength, skid resistance, and roughness of a thin epoxy overlay pavement constructed for field tests under various field conditions are examined in this study. METHODS : The usability of epoxy and aggregates on a thin epoxy overlay pavement is identified by testing their material properties in a laboratory. A construction test is performed using the pretreatment conditions of the existing pavement surface and the number of layers of overlay pavement as variables. The bond strength, skid resistance, and roughness are analyzed 3 d after constructing the test pavement, and immediately before and after applying repetitive traffic loadings at 6 months. RESULTS : When the existing pavement is in good condition, as in this study, the bond strength of the thin epoxy overlay pavement is affected more significantly by the existing pavement condition than the material properties of epoxy, in which destruction is indicated in the existing pavement. The skid resistance is affected primarily by the condition of the aggregates sprayed on the epoxy. The pavement on which the aggregates are well sprayed indicate a high skid resistance. The roughness is not affected by any variables, such as the pretreatment conditions, number of thin pavement layers, and repetitive traffic loadings. CONCLUSIONS : A long-term evaluation of the bond strength, skid resistance, and roughness will be conducted on a test pavement. In addition, another construction test will be performed to investigate the performance of a thin epoxy pavement overlaid on a bridge deck pavement under inferior conditions.

PURPOSES : Given that large-scale repair works of expressway bridge pavements have high maintenance cost and long traffic blocking time, the thin overlay method that maintains the existing pavement is attracting attention. In this study, because the bridge thin overlay has not been introduced in Korea yet, the basic physical properties of the epoxy thin overlay, which is mainly used for the bridge thin overlay, were investigated, and the skid resistance and bond performance were analyzed. METHODS : Basic physical property tests were performed on each of the epoxy binders, aggregates, and mixtures used in epoxy thin overlay. They were also compared and reviewed against foreign standards. The epoxy binders were tested for viscosity, gel time, and thermal compatibility. The aggregates were tested in terms of water absorption, specific gravity, and gradation. The compressive and flexural strengths of the mixtures were investigated. The epoxy thin overlay has the possibility of detachment of aggregates, so the skid resistance was tested according to the paving phase. In addition, to investigate the bond performance, which is the most important performance of the epoxy thin overlay, the bond strength test was performed by varying the moisture condition and treatment condition of the existing layer surface. RESULTS : The basic physical properties of the materials used in the epoxy thin overlays satisfied foreign standards except for the gradation of aggregates. The skid resistance did not satisfy the standard when the epoxy was exposed, whereas the skid resistance did satisfy the standard when the aggregates were exposed, even after the abrasion test. The bond strength of the epoxy thin overlay satisfied the standard in all cases. The bond strength was the highest when the relative humidity of the existing layer surface was 60%. CONCLUSIONS : The materials of epoxy thin overlay that could be obtained in Korea satisfied the basic physical property standards except for aggregate gradation. Given that the aggregate gradation could be adjusted, it can be concluded that the epoxy thin overlay could be introduced in Korea. In addition, it was confirmed that the skid resistance and bond strength of the epoxy thin overlay were high enough to be used in general road conditions. It was determined that the existing layer surface should maintain an optimal relative humidity of approximately 60% because the moisture condition affects the bond strength.