최근 이상기후 현상으로 인해 국지성 호우 발생이 증가되어 도로 미끄럼 사고 발생이 증가하는 추세이다. 콘크리트 포장에서는 미끄 럼 저항을 확보하기 위해 그루빙 작업을 실시하여 주행안전성을 향상시키고 배수를 원활하게 하여 수막현상을 억제한다. 본 연구에서 는 그루빙 작업에서의 홈의 방향을 종방향과 횡방향 뿐만 아니라 임의의 방향으로 구성할 수 있으며 다양한 홈의 형상을 구성할 수 있는 동시에 우수한 양생포 기능을 지닌 그루빙 양생 플레이트를 제작하였다. 이러한 그루빙 양생 플레이트를 사용하여 타원형, 삼각 형, 사각형으로 홈 형상을 구성한 콘크리트 공시체를 제작하였다. 공시체를 사용하여 그루빙 방향을 종방향, 횡방향, 45° 방향으로 구 성하였을 경우에 대한 미끄럼 저항성을 BPT 장비를 사용하여 분석하였다. 분석 결과, 그루브 형상이 타원형, 삼각형, 사각형 등으로 차이가 있더라도 BPN 값은 유사하게 측정되었으나 그루브 방향은 종방향, 횡방향, 45° 방향 순으로 BPN 값이 높게 분석되었다.

PURPOSES : The skid resistance between tires and the pavement surface is an important factor that directly affects driving safety and must be considered when evaluating the road performance. In especially wet conditions, the skid resistance of the pavement surface decreases considerably, increasing the risk of accidents. Moreover, poor drainage can lead to hydroplaning. This study aimed to develop a prediction equation for the roughness coefficient—that is, an index of frictional resistance at the interface of the water flow and surface material—to estimate the thickness of the water film in advance to prevent human and material damage. METHODS : The roughness coefficient can be changed depending on the surface material and can be calculated using Manning's theory. Here, the water level (h), which is included in the cross-sectional area and wetted perimeter calculations, can be used to calculate the roughness coefficient by using the water film thickness measurements generated after simulating specific rainfall conditions. In this study, the pavement slope, drainage path length, and mean texture depth for each concrete surface type (non-tined, and tined surfaces with 25-mm and 16-mm spacings) were used as variables. A water film thickness scale was manufactured and used to measure the water film thickness by placing it vertically on top of the pavement surface along the length of the scale protrusion. Based on the measured water film thickness, the roughness coefficient could be back-calculated by applying Manning's formula. A regression analysis was then performed to develop a prediction equation for the roughness coefficient based on the water film thickness data using the water film thickness, mean texture depth, pavement slope, and drainage path length as independent variables. RESULTS : To calculate the roughness coefficient, the results of the water film thickness measurements using rainfall simulations demonstrated that the water film thickness increased as the rainfall intensity increased under N/T, T25, and T16 conditions. Moreover, the water film thickness decreased owing to the linear increase in drainage capacity as the mean texture depth and pavement slope increased, and the shorter the drainage path length, the faster the drainage, resulting in a low water film thickness. Based on the measured water film thickness data, the roughness coefficient was calculated, and it was evident that the roughness coefficient decreased as the rainfall intensity increased. Moreover, the higher the pavement slope and the shorter the drainage path length, the faster the drainage reduced the water film thickness and increased the roughness coefficient (which is an indicator of the friction resistance). It was also evident that as the mean texture depth increased, the drainage capacity increased, which also reduced the roughness coefficient. CONCLUSIONS : As the roughness coefficient of the concrete road surface changes based on the environmental factors, road geometry, and pavement surface characteristics, we developed a prediction equation for the concrete pavement roughness coefficient that considered these factors. To validate the proposed prediction equation, a sensitivity analysis was conducted using the water film thickness prediction equation from previous studies. Existing models have limitations on the impact of the pavement type and rainfall intensity and can be biased toward underestimation; in contrast, the proposed model demonstrated a high correlation between the calculated and measured values. The water film thickness was calculated based on the road design standards in Korea—in the order of normal, caution, and danger scenarios—by using the proposed concrete pavement roughness coefficient prediction model under rainy weather conditions. Specifically, because the normal and caution stages occur before the manifestation of hydroplaning, it should be possible to prevent damage before it leads to the danger stage if it is predicted and managed in advance.

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.

PURPOSES : The purpose of this study was to identify the availability of Grip-Tester, which can be used as continuous friction testers, for estimating the skid resistance of pavements by examining its basic performance. METHODS : Based on a literature review, various factors influencing skid resistance on road surfaces were described, and the subject to be evaluated were proposed. Friction tests were conducted at various operating speeds to assess the water supply performance, repeatability, and reproducibility of the measurement results. Both the British pendulum number (BPN) and mean texture depth (MTD) were examined to confirm the relationship between the Grip Number(GN) and surface texture. RESULTS : The results of the watering test indicate that more than 91% of valid measurements can be obtained at the maximum operating speed of 90 km/h to maintain a water film thickness of 0.25 mm. The repeatability and reproducibility of the measured GN were derived from the cross-correlation analyses to be 90.9% and 87.4%, respectively. It was found that the variations in GN values according to operating speeds follow an exponential model similar to the commonly known Penn State model, which can be considered to be due to the effect of texture on skid resistance. CONCLUSIONS : The grip tester is suitable for continuously surveying the skid resistance because GN datasets are reliable at variable operating speeds and correlate with the surface texture. This method may provide objective data for making decisions regarding the maintenance of skid resistance through periodic full-scale investigations with the tester in the future.

PURPOSES: This study aimed to measure the skid resistance of the sidewalk in order to find out the relationship between different surface types and skid resistance. By using British Pendulum Tester, skid resistance of sidewalk was measured in a wet after snow-melt, sludgy, and snowy conditions. METHODS : The skid resistance was measured on surfaces including Concrete Interlocking Block Paving, Colour Asphalt Pavement, Granite Block Paving, Manhole, and Tactile Paving for Visually Impaired. Five trials at each measurement were made, and the average and standard deviation were derived. RESULTS: The skid resistance measured in wet after snow-melt, sludgy, and snowy conditions for the various surface types are summarized and compared. Reduction rates of skid resistance of sludgy and snowy against wet after snow-melt are also analysed. The skid resistance variation between measurement points which mimic pedestrian route in study site are analysed to check out the consistency of the skid resistance along the sidewalk. CONCLUSIONS : The study concluded that the skid resistance of sidewalk surfaces varied depending on the surface types and weather conditions. Secondly, reduction rates of skid resistance according to weather changes are varied depending on the surface types, Thirdly, consistency of skid resistance along the pedestrian route is hardly acquired in the study site at least. So, future study on the consistency evaluation for skid resistance along sidewalk is strongly recommended.

PURPOSES : Skid resistance on pavements plays an important role in reducing the risk of vehicle skidding on wet surface particularly. Almost 9.3 percent of traffic accidents were occurred under rainy condition and these are over-represented in terms of the severity of the crashes. Recently, unusual weather conditions referred widely as the intensified rainfalls justify the need of a systematic management of skid resistance. In this context, the study carried out the observational study on the skid resistance characteristics of different types of pavement with the time passage. METHODS : This study measured the skid resistance with Pavement Friction Tester at three times within five years. The skid resistance measurement has followed the method suggested by ASTM. RESULTS : As the main results under the scope of this study, skid resistance of asphalt concrete has not nearly reduced with time. On the contrary, skid resistance of cement concrete has been rapidly reduced with time though the highest resistance was gained at the early observation. Porous asphalt concrete shows a steady decrease of skid resistance with time, anyway, the reduction rate according to the increase of measurement speeds is relatively lower than the others. CONCLUSIONS : Based on our study, skid resistance of the pavement should be regarded as one of the pavement management system, so periodic measurement should be made to assure road safety as a whole.

미끄럼저항은 자동차의 타이 어 와 포장노면 사이에서 발생하는 미끄러짐을 방지하여 제동거리를 제어하고 주행 안전성을 확보하는데 중요한 역할을 한다. 우천시의 미끄럼저항 감소는 치명적인 교통사고를 유발할 수 있다. 노면위에 남은 토사 및 겨울철 제설재는 미끄럼저항을 감소시킬 수 있는 요소가 될 수 있다. 본 연구에서는 노면상의 잔류하는 이물질이 타이어와 포장노면사이에서 발생하는 미끄럼저항에 미치는 영향을 다양한 콘크리트 노면조직 형태 (횡방향타이닝, 종방향타이닝, 골재노출) 및 노면조직의 마모조건(신설노면, 마모된 노면)에 대하여 검토하였다. 노면상의 이물질로는 모래, 염화칼슘과 자동차에서 발생하는 폐 오일을 사용하였으며 각 경우별로 이물질의 양을 달리하여, 모래의 경우는 입도 및 양을 달리해가며 미끄럼저항에 미치는 영향을 검토하였다.