Low temperature cracking of asphalt pavement occurs in the cold region of Hokkaido, resulting in reduced speed and increased vibration acceleration for emergency transportation. In this study, road surface properties, FWD measurement, excavation survey, and core sampling were conducted on asphalt pavements with many cold cracks in Hokkaido, Japan. The results of FWD measurements indicated that the bearing capacity of the asphalt mixture layer in the vicinity of the cold cracks was about 20% of that of the sound part. The open-cut investigation revealed that the cracks penetrated through the asphalt mixture layer, and that the lower part of the asphalt mixture layer had been converted to sediment. The cracks penetrated through the asphalt mixture layer, and the lower part of the asphalt mixture layer was graded. The core sampling results showed that the more the surface cracks progressed, the more the interior damage progressed.

 It is concerned that the degree of deterioration of the pavement recycled material currently in use progresses due to repeated recycling. Therefore, care must be taken to recycle that material. There are standard values for recycled aggregate, which indicate whether the pavement recycled material can be used for reclaimed asphalt pavement or not. However, these standard values are not suitable for evaluating different types of asphalt such as straight asphalt and polymer modified asphalt. In this study, we considered that the evaluation by asphalt tensile work such as toughness and tenacity is effective and tried to confirm the relationship between asphalt properties and the fatigue failure resistance of the asphalt mixture. As a result, a good correlation was confirmed between the tenacity and the total dissipative energy in the condition by using new asphalt. In addition, by experiments in the condition by using recovered asphalt, it was suggested that the tenacity is effective as an evaluation index for recycled aggregates.

 The main cause of road cave-ins is cavities under the road surface. With the aging of infrastructure and the recent increase in the severity and frequency of natural disasters, the number of subsurface cavities is expected to increase further, and rationalization of countermeasures has become an important issue. As one of the measures against cave-ins, the authors have conducted joint research on a reinforcement method of the road surface above the cavities. In this paper, in addition to the results of previous studies, the method is evaluated based on the load-bearing capacity at its limit (when only the reinforcement sheet is left after the pavement underneath has collapsed) by cyclic loading tests and its long-term durability on actual roads. The effectiveness of the method was verified where the formation of unevenness in the surface was prevented where this method was applied to the road surface with subsurface cavities, thereby increasing the safety of the pavement until its rehabilitation.

 One damage progression mechanism that should be noted for asphalt pavements is the loss of bearing capacity caused by damage to individual pavement sections due to water intrusion into the pavement. On the other hand, it is still unclear how the damage to each pavement section affects the bearing capacity of the pavement. In this study, laboratory tests were conducted on granular roadbed and asphalt stabilized mixture to investigate the effect of water penetration into the pavement on the pavement structure. As a result, it is found that the bearing capacity of the former pavement decreases due to the increase of fine grains, and that the strength of the asphalt stabilized mixture decreases significantly due to water intrusion in the latter pavement. Furthermore, a 3DFEM analysis was conducted considering the test results, and the effect of water intrusion into the pavement on the pavement body was verified using a theoretical design method.

 In this study, model experiments were conducted to simulate pavement pumping, aiming to visualize the process of subbase erosion under repeated wheel loads. In the experiments, an acrylic plate with a slit aperture, simulating a pavement slab with a transverse joint, was placed on saturated silica sand layer, and a rubber tire repeatedly applied a wheel load onto the plate. The soil container, made of clear acrylic, enabled vertical cross-sectional view of pavement plate deflection and movements of sand grains. Fluorescently stained grains were mixed into the sand layer to serve as tracking targets for experimental video processing. The observation revealed that pumping is caused by the combined effects of gradual deflection in the approach slab and rapid deflection in the leave slab under wheel loading; the former pushes the sand grains beneath the approach slab toward the transverse joint, while the latter pumps out the sand grains through the joint aperture. When the slabs are unloaded and deflect upward, turbulent water flow forms beneath the slabs, particularly scouring the subbase surface beneath the joint.

 In recent years, the stripping of asphalt pavement has become apparent on expressways, ordinary roads and overseas road construction projects of Official Development Assistance (ODA). Therefore, countermeasures against stripping of accelerating the structural damage of the asphalt pavement are required. Currently, various evaluation methods are proposed based on such as the strength ratio before soaking and after soaking of asphalt mixtures. On the other hand, the causal relationship between the physical and chemical properties of the materials used and loss in strength is not clear. In this study, we investigated physical and chemical properties of twelve aggregates including overseas production focused on the interface between the aggregate and asphalt binder. And, evaluated influence of the stripping for various laboratory mechanical tests.

 Concrete waste is mainly used as recycled roadbed material for pavement, but a wide range of applications other than recycled roadbed material are required in the future. In this study, full-scale test specimens of 100% recycled stable roadbed material and 100% recycled concrete, in which all materials including solidifiers were used as by-products, were fabricated for application to pavement materials. As a result, it was confirmed that each recycled material can be constructed using general construction methods. Wheel load running tests were conducted on the full-scale specimens. As a result, it was confirmed that the 100% recycled stable roadbed material and 100% recycled concrete have durability equivalent or superior to that of pavement using ordinary cement stable roadbed material, and can be applied as pavement materials.

 The present study evaluated physical properties of recycled asphalt mixtures containing reclaimed asphalt pavements (RAP) with various degrees of aging and examined presence of aged asphalt that no longer functions as a binder material. Furthermore, a new mix design procedure was introduced to confirm the mixture properties when new asphalt was added to compensate for the aged asphalt. The results showed that the recycled asphalt mixture containing low quality RAP had aged asphalt that did not function effectively and decreased cracking resistance. The proposed mix design attitude was valid for recycled asphalt mixtures to use substandard RAP.

 As part of efforts to address the "2050 Carbon Neutral Declaration" and promote the effective utilization of asphalt resources, one initiative in the field of road pavement is the further promotion of recycled hot asphalt mixtures. While asphalt recycling has maintained high levels of performance in the past, recent years have seen instances of multiple recycling events, raising concerns about a decline in asphalt quality. In view of sustainability efforts in the road sector and the need to mitigate the deterioration of asphalt quality, the authors have developed an emulsion for rejuvenating deteriorated asphalt simply by spraying it onto existing pavement surfaces. Through various investigations, the rejuvenation effects of asphalt mixtures that have undergone long-term outdoor exposure were demonstrated.

 The present study measured the dissipated energy obtained from time series data of FWD deflection measurements (FWD dissipated energy) for asphalt pavements. Correlation between the FWD dissipated energy and the crack ratio measured by visual inspection of the pavement surface was investigated. As a result, it was confirmed the FWD dissipated energy increases as the damage state of asphalt pavements progresses and the crack ratio increases. In addition, viscoelastic fatigue parameters were measured by repeated compressive-tensile tests using cut cores collected at the FWD measurement points. The dissipated energy of the cut cores was compared with the FWD dissipated energy. Based on the results, this study indicated that fatigue damage state of asphalt pavements can be evaluated using the FWD dissipated energy.

 The longitudinal profile of a road surface is expected to change over time due to service conditions and the influence of the bearing capacity of the entire pavement. In order to maintain and manage the road surface over a long period of time, it is important to clarify the relationship between the longitudinal profile and the bearing capacity of the pavement over time. In this study, the relationship between longitudinal profiles tracked from 2014 to 2022 and the amount of FWD deflection was analyzed as part of the activities of the Pavement Diagnosis Research Group. As a result, a negative correlation was found between the deflection D0 and D150 and the difference in profile height, confirming a high degree of influence on the profile change in a specific wavelength region. The results also indicated the possibility of predicting future longitudinal profile changes based on the bearing capacity of the pavement at a given point in time.

 The results of subgrade resilient modulus (Mr) test are used in the theoretical structural design of pavements, such as Mechanical and Empirical Pavement Design Guide. However, since it takes a lot of time and money to conduct Mr test, it is desirable to estimate Mr using a field test such as portable FWD test. Therefore, if we can understand the relationship between the measurement results of portable FWD tests and Mr on pavement subgrades used as roadways, it will be possible to contribute to the spread and advancement of theoretical structural design of pavements. In this study, we conducted forward analysis of portable FWD test using multilayer elastic theory, targeting an asphalt pavement subgrade. The results revealed that the deflection at the center of loading obtained from a forward analysis using a correction coefficient β that takes into account dynamic effects agrees well with the deflection measured by portable FWD.

 In expressway pavement, damage that propagates to deep layers of the pavement structure has been confirmed.Under these circumstances, in order to sustainably provide safe, secure, and comfortable road surface, it is necessary to comprehensively grasp information on the soundness of pavement structures and reflect it in pavement management. In this study, we investigated a road surface deflection measurement method using a light section method that can continuously acquire high-precision height information for the development of a mobile deflection measurement device for high-speed driving.Specifically, the loading method was determined by FEM analysis to be a single-axle, single-wheel type, and a prototype vehicle was built that could carry a 10-ton axle weight while satisfying the general limits of the Vehicle Restriction Ordinance and continuously acquiring the road surface profile at the position where the wheel passes. Then, we conducted test measurements on an actual expressway, and confirmed that the measurement results approximated the FWD survey.

 Currently, the porous asphalt mixture is used for the surface course of pavements on many highways in Japan. Damage called "stripping," where the asphalt peels off from the aggregate, caused by rainwater infiltrating through the surface course, has occurred in the binder course beneath the surface layer formed by the porous asphalt mixture. If this type of damage occurs, partial subsidence will often appear on the surface course of the pavement. Road inspections on highways in Japan evaluate the soundness of the road surface by checking 3 indices (the amount of rutting, crack rate, and International Roughness Index). It is difficult to quantitatively capture and evaluate partial subsidence caused by stripping of the binder course beneath the porous asphalt surface layer with these check items. Therefore, we have developed a new index “5mσmax” to evaluate the partial subsidence. This index is derived from the transverse profile data of the road surface, measured by the road surface condition measurement vehicle. This index can predict the occurrence of partial subsidence in one to two years. Therefore, this index can be used in road surface management and repair planning.

 In snowy and cold regions, potholes occur frequently during the snowmelt season, requiring regular road patrols and systematic repairs based on road surface conditions. In recent years, in-vehicle cameras and AI have been introduced to improve the efficiency of road patrols . However, it is difficult to find a method to evaluate complex and significant road surface damage during the snowmelt season. In this study, we developed a method to detect potholes and further evaluate their road surface damage using image recognition AI (VGG16) and saliency map (Score-CAM). First, our method can detect potholes with an accuracy of more than 85% using AI trained on road surface images taken during the winter season. Next, we showed that the saliency map can evaluate road surface damage by extracting the shape of pothole areas in detail. Finally, we conducted periodic road patrols and planned network-level repairs using the proposed method. As a result, our findings can contribute to the efficiency and improvement of winter pavement maintenance and management.

 In Hokkaido, many potholesoccur on the road surface during the snowmelt season, and a great deal of labor and cost are required for repair (remedial measures). In this study, we devised a method for estimating the risk of road surface damage progressing from the point cloud data of the Mobile Mapping System in order to realize preventive maintenance of pavement.We found a correlation between road surface damage extracted by this method and crack length. Obtained the progress of pothole from the pothole areas before and after winter, and clarified the relationship between this and the flow accumulation of road surface water. In addition, we extracted the road surface damage points from the point cloud data, and estimated the progress of the road surface damage from the flow accumulation of the road surface water flowing through the points. We have also shown that this is correlated with the progress of cracking.

 As the demand for bicycles increases, it is an urgent issue to establish a method for evaluating and maintaining road surfaces for riding comfort. In this study, we calculated BRI, which is a road surface evaluation index from the viewpoint of a bicycle, and visualized it on a map together with road surface properties, using actual road profiles obtained by MPM and image data from an action camera. As a result, it is possible to visualize the road surface evaluation from the viewpoint of a bicycle. In addition, the difference between the IRI and BRI calculated from the actual road profile was examined, and the consistency between the wavelength component of the profile and the IRI and BRI calculation results was confirmed. These results indicate that a road surface maintenance method that takes into account the evaluation characteristics of BRI in addition to the conventional IRI is necessary for the maintenance and management of roadways that are comfortable for both automobiles and bicycles.

 E-scooter is a micro-mobility device that has been rapidly gaining popularity around the world in recent years. In Japan, roads are shifting from being vehicle-centered to people-centered, and a new road environment is required. The International Roughness Index is often used as a management index for roadways, but it is known that the road surface wavelength that affects electric E-scooter is affected by textures that are shorter than the roughness wavelength. Therefore, a new evaluation index is needed to evaluate the riding comfort of E-scooter. In this study, we conducted driving experiments to develop a vibration model of an E-scooter and to construct a new evaluation index, and measured the vibration response of the vehicle and evaluated the ride comfort by subjective evaluation. The results showed that there is a high correlation between the evaluation index based on vibration response and subjective evaluation, and that this index is useful as a new index for micromobility.

 In recent years, localized surface roughness on expressway road surfaces which occurs below current maintenance standards have become a factor that reduces the comfort of driving vehicles. In this study, we examined the human-centered evaluation of road surface deformation based on stress-related physiological responses of vehicle occupants, such as heart rate variability and electrodermal activity, by conducting a driving test using a driving simulator. As a result of this study, we clarified the range of road wavelength dominance associated with transient stress corresponding to localized roughness, and newly defined cumulative values consistent with stress in the entire evaluation section and variance values consistent with transient mental stress, which led to rational human-centered road surface evaluation based on physiological responses.

 The Pavement Inspection Procedure, developed in 2016, indicates the importance of protecting the layers below the base by timely repair of the surface and base layers to extend the life of the pavement and reduce life cycle costs. It also indicates that a detailed investigation should be conducted in early deteriorated sections because damage to the layers below the base layer is suspected. As the main detailed investigation, the FWD deflection survey is widely utilized, and the method to evaluate the bearing capacity of the entire pavement by D₀ deflection or the method to evaluate the elastic modulus by inverse analysis based on the multi-layer elasticity theory are commonly used. In this paper, we focus on the compressive strain on the top surface of granular base layer, which is reported by NCHRP (National Cooperative Highway Research Program) in the U.S., and discuss its application to the evaluation method of asphalt pavements.

 A detailed excavation survey of the low temperature cracking area was conducted in Shiranuka, and it was confirmed that the surface of lower subbase course in the damaged area had turned black. This is because a part of the asphalt mixture breaks into fine-grained particles due to degradation, and the fine grains migrated and sedimented on the lower subbase course. It is thought that the asphalt stripped from the aggregate by the action of water as well. In this study, samples were picked from the surface of the subbase course, and asphalt content and its areal distribution was confirmed. Property tests were also conducted to evaluate the degree of oxidation degradation. In addition, the properties of the asphalt degradation were evaluated for all asphalt mixture courses according to the depth distribution, comparing with the properties of the sedimented asphalt on the subbase course.

 The authors have developed a construction method to extend the service life of expressways by creating the highly durable stabilized base course. However, the properties of the highly durable recycled base course material constructed by this method vary depending on the water content of the existing base course. For this reason, when applying the method on site, it was necessary to establish the method for determining the design water content that would ensure the target performance and adjusting the water content of the existing base course to the design water content. Therefore, the authors determined the design water content of the existing base course based on workability and strength characteristics and found the method to adjust the water content of existing base course to the design water content by adding porous ceramics, thereby ensuring the target performance of highly durable recycled base course material. Furthermore, the simple method for evaluating the workability of highly durable recycled base course material was also examined, and the method for evaluating consistency using cone penetrometer and management target value was determined.

 By concentrating on the application of geosynthetics as base course reinforcement, this study aims to create a novel technique for prolonging the service life of asphalt pavements. In this study, FEM analysis and small tank tests were conducted using two types of geosynthetics and base course materials that had distinct woven fabric and geogrid qualities. Rainwater infiltration through asphalt layer cracks was replicated in the small tank experiment. The findings demonstrated that the base course's deformation and reduction in bearing capacity may be controlled by using geosynthetics.

 As roads often have a residual settlement on soft foundations, reducing the weight of the subbase course is an alternative way to solve this problem. In this study, the applicability of lightweight geo-materials made from expansive shale and sewage sludge to pavement subbase was investigated by conducting CBR tests, and triaxial tests under two types of confining pressure and with or without 10,000 cycles of cyclic loading on three samples that were simply adjusted in particle size by mixing with silica sand.

 The test results showed that there was a clear trend between the mixing ratio and CBR, and that under all conditions, the strength did not decrease, showing a similar trend to crushed stone, and by applying cyclic loading, the deformation modulus increased from the same level to about 20% at the maximum load equivalent axial strain level. In addition, an appropriate particle size with both stiffness and lightness was proposed.

 As part of efforts to reduce greenhouse gas emissions, the fixation of carbon dioxide in cementitious materials is being considered. In this study, the fixation performance of carbon dioxide in artificial crushed stone of cementitious material applied to roadbeds was investigated, and the change of mechanical performance of their crashed stone was examined. To investigate both performances, the crushed stones and the column specimens made by same mix proportion were subjected to carbonation curing, then the carbonation depth measurement, the thermogravimetry-differential thermal analysis, the pH measurement and the compressive strength test were carried out.

 As the results, it was confirmed that all section of the artificial crushed stone with grain size of 50 mm absorbed carbon dioxide when the carbonation curing was performed during 7 days. Furthermore, it was confirmed that the reduction of compressive strength by carbonation curing was suppressed by adequate hydration promotion before carbonation curing.

 In order to realize high durability and long life of cocrete pavements, proper maintenance is necessary. In this study, specific repair materials and methods were proposed for various types of damage to concrete pavements, and the physical properties of the various repair materials were examined in laboratory tests, the effectiveness of the newly proposed local replacement method was verified in analytically, and the long-term durability was examined on full-scale specimens under running load of a load truck. As a result, it was confirmed that all the repair material studied in this research can be sufficiently applied as repair materials for concrete pavements by using epoxy adhesives to ensure the integrity with the existing concrete. The newly proposed localized replacement method was confirmed to be more effective in reducing vertical displacement and strain than the existing method through analytical investigation. Furthermore, full-scale specimen tests confirmed that the proposed method maintained generally good serviceability even after 850, 000 wheel loadings of 49 kN equivalent.

 In precast prestressed concrete(PPC) slab pavement for airports, port container yards and roads, conventional joint structure has problems of causing pumping phenomenon at joints or breaking PPC slab pavement. In order to solve them, we have developed a joint structure in which a joint is easily replaceable when PPC slab pavement is damaged, by adopting wedge mechanism and introducing compressive force for the purpose of preventing pumping phenomenon at joints. In this study, fixed point fatigue load test, single joint shear strength test and replacement test were carried out to verify the required performance of joint. As a result, we have confirmed that the load transmission performance is equal to or better than that of conventional joints, that the joint structure can be expected to prevent the occurrence of pumping phenomenon, and that partial replacement is feasible.

 This manuscript discusses the improvement of embedded pipe snow melting system pavement, which is one of the heavy-snow countermeasures used in snowy and cold regions. In order to efficiently transfer heat from heat dissipation pipes installed in the concrete pavement to the road surface, we proposed replacing part of the fine aggregates in concrete with synthetic graphite, which has high thermal conductivity. Laboratory tests were conducted on the compressive strength, flexural strength, and abrasion resistance of concrete added with the synthetic graphite. It was shown that the flexural and compressive strength satisfied the design values. However, it was found that abrasion resistance of the concrete decreased by adding the synthetic graphite. And then, large-scale test was conducted outdoors in snowy cold region. A significant snow melting effect was confirmed when the synthetic graphite was used. Furthermore, it was shown that when 10 to 20% of the fine aggregate in concrete was replaced with the synthetic graphite, it was possible to increase the amount of heat transferred from the heat dissipation pipes to the concrete pavement by 1.5 to 2.5 times.

 In expressway pavement, damage that extends to deep layers of the pavement structure has been confirmed.Under these circumstances, in order to sustainably provide safe and comfortable highway pavement, it is necessary to accurately understand the causes of pavement deterioration and take measures to extend its service life. In this study, the thickness of the asphalt mixture layer was adopted as the structural condition, rainfall characteristics and aggregate delamination resistance were quantifiedas local environmental and material conditions, and their effects on the degradation rate of expressway pavements were analyzed. As a result, it was statistically clarified that pavement deteriorates faster in sections where the thickness of the asphalt mixture layer is thin, in areas with high rainfall, and in areas where aggregates with poor delamination resistance are collected.Furthermore, using the estimated parameters of the mixed Markov deterioration hazard model, a pavement structure design that takes into account the local environmental and material conditions was proposed.

 In Japan, a super-aging society, it is important to improve walking spaces that can be used safely and comfortably by everyone. In this study, we focused on the profile slope and the International Roughness Index (IRI) as a physical property of the pavement surface and the muscle action potential, which is one of the indices to evaluate the impact of walking on the pavement surface. Therefore, we compared the impact of the pavement surface on the human body and the physical properties of the pavement surface, and conducted a rational evaluation of the walking surface from the human body's point of view. The results suggest that the amount of muscle activity of pedestrians is correlated with the International Roughness Index (IRI). It was also found that profile slopes of ±2% were unlikely to affect pedestrians. We also found the possibility of predicting the points where pedestrians feel likely to stumble.

 This study conducted hydraulic model experiments to elucidate the flood control performance of lateral inflow pavements, where stormwater drainage flows into the granular subbase laterally through the gutter sidewall. Comparing inflow under two-conditions - when the subbase surface was exposed to atmospheric pressure and when sealed with acrylic plates—showed a significant reduction in inflow with the sealed surface. Adequate ventilation proves crucial for ensuring a seamless lateral flow into the pavement, necessitating actions like installing exhaust vents at elevated positions.

 80% of Hanshin Expressway consists of viaducts, and Wangan Route has lots of steel deck structures. For the base layer of pavement on a steel deck, a guss asphalt mixture has been conventionally used because it has high followability of steel deck deflection, and well workability by pouring to fill into uneven parts on the deck. In recent years, road pavement companies have developed new guss asphalts that are more durable and lower odor than conventional guss asphalt mixtures, and put them into practical use. This paper reports new regulations for the guss asphalts from its production to construction, which is organized by considering required standard values based on the results of performance tests, the results of pilot construction using new guss asphalt under the regulations, and the calculated life-cycle cost based on its performance.

 The warm-mix asphalt technology is expected to reduce carbon dioxide emissions when manufacturing asphalt mixtures, improve workability, and reduce asphalt fumes. The effects of the number of repeated cycles and the composition of rejuvenators on the properties of recycled mixtures have been clarified, and it is necessary to clarify these effects on recycled warm-mix asphalt mixture. In this study, the properties of recycled warm-mix asphalt mixture made from repeatedly recycled aggregate and foamed asphalt binder was compared with those of a normal recycled asphalt mixtures. As a result, at the high-temperature Cantabro loss rate was often higher in the recycled warm-mix asphalt mixture than in the recycled mixture, indicating the possibility of lower cracking resistance. However, by using rejuvenator with a high aromatic content, it was found that the decrease in cracking resistance at high temperature, and the properties became equivalent to those of the ordinary recycled asphalt mixture.

 Although the degree of compaction is controlled by the core density, etc. for the asphalt pavement surface layer, it is not for finding local places with poor compaction over a wide area and aspects. Through surface discontinuities, e.g. cracks, construction joints, structure boundaries, deterioration factors such as water and oxygen enter the pavement structure along these discontinuous lines. For surface layer discontinuities, joint adhesiveness is ensured during paving work, and injection materials such as crack seals are applied as maintenance, however, it is difficult to confirm actually the watertightness. This paper states the results on the evaluation of air void content and adhesiveness applying a double-chamber-type vacuum permeability tester for asphalt pavement, referring to the surface layer permeability test used for concrete structures.