PURPOSES: This study aims to develop a repair material that can enhance pavement performance, inducing rapid traffic opening through early strength development and fast setting time by utilizing MgO-based patching materials for repairing road pavements. METHODS : To consider the applicability of MgO-based patching materials for repairing domestic road pavements, first, strength development and setting time of the materials were evaluated, based on MgO to KH2PO4 ratio, water to binder ratio, and addition ratio of retarder (Borax), by which the optimal mixture ratio of the developed material was obtained. To validate the performance of the developed material as a repair material, the strength(compressive strength and bonding strength) and durability (freezing, thawing, and chloride ion penetration resistance) was checked through testing, and its applicability was evaluated. RESULTS : The results showed that when an MgO-based patching material was used, the condensation time was reduced by 80%, and the compressive strength was enhanced by approximately 300%, as compared to existing cement-based repair materials. In addition, it was observed that the strength (compressive strength and bonding strength) and durability (freezing and thawing, and chloride ion penetration resistance) showed an excellent performance that satisfied the regulations. CONCLUSIONS : The results imply that an emergent repair/restoration could be covered by a rapid-hardening cement to meet the traffic limitation (i.e. the traffic restriction is only several hours for repair treatment). Furthermore, MgO-based patching materials can improve bonding strength and durability compared to existing repair materials.

PURPOSES : This study primarily focused on evaluating the performance characteristics of 4.75-mm nominal maximum aggregate size (NMAS) asphalt mixtures for their more effective implementation to a layered flexible pavement system. METHODS: The full-scale pavements in the FDOT’s accelerated pavement testing (APT) program, including 4.75-mm mixtures at the top with different thicknesses and asphalt binder types, were considered for the faster and more realistic evaluation of the rutting performance. The results of superpave indirect tensile (IDT) tests and hot-mix asphalt fracture mechanics (HMA-FM) based model predictions were used for cracking performance assessments. RESULTS: The results indicated that the rutting performance of pavement structures with 4.75-mm mixtures may not be as good as to those with the typical 12.5-mm mixtures, and pavement rutting was primarily confined to the top layer of 4.75-mm mixtures. This was likely due to the relatively higher mixture instability and lower shear resistance compared to 12.5-mm mixtures. The energy ratio (ER) and HMA-FM based model performance prediction results showed a potential benefit of 4.75-mm mixtures in enhanced cracking resistance. CONCLUSIONS : In relation to their implementation, the best use of 4.75-mm mixtures seem to be as a surface course for low-trafficvolume applications. These mixtures can also be properly used as a preservation treatment that does not necessarily last as long as 12.5-mm NMAS structural mixes. It is recommended that adequate thicknesses and binder types be considered for the proper application of a 4.75-mm mixture in asphalt pavements to effectively resist both rutting and cracking.

A rapid urbanization has increased the portion of paved layer that results in the change of water circulation system. This change leads to frequent events of flooding, drought, and urban heat island. To resolve these issues, permeable pavement system based on Low Impact Development (LID) concept is being applied to international urban areas. Therefore it is necessary to establish a rational design procedure for the permeable pavement system that reflects our environmental conditions. iDue to inherent characteristics of permeable pavement system, water infiltrates thorough the layers so it may reduce the bearing capacity of sub-layers. In this study, an effort was made to investigate the effectiveness of geogrid reinforced crushed stone subbase layer based on field experimental program along with a limited numerical analysis. It reveals that geogrid reinforced sections improve the bearing capacity by close to 20%. In addition, a light weight deflectomenter (LWDT) appears to be promising for the compaction quality control of crushed stone subbase layer in order to construct qualified permeable pavement systems.

PURPOSES: This study intends to develop an inorganic soil pavement material using industrial by-products and to evaluate its applicability as a road pavement material. METHODS: In this study, a compressive strength experiment was conducted based on the NaOH solution molarity and water glass content to understand the strength properties of the soil pavement material according to the mixing ratio of alkali activator. In addition, the strength characteristic of the inorganic soil pavement material was analyzed based on the binder content. The performance of the soil pavement was evaluated by conducing an accelerated pavement test and a falling weight deflectometer (FWD) test. RESULTS: As a result of the soil pavement material test based on the mixture ratio of alkali activator, it was identified that the activator that mixed a 10 M NaOH solution to water glass in a 5:5 ratio is appropriate. As a result of the inorganic soil pavement materials test based on the binder content, the strength development increased sharply when the amount of added binder was over 300 kg; this level of binder content satisfied 28 days of 18 MPa of compression strength, which is the standard for existing soil pavement design. According to the measured results of the FWD test, the dynamic k-value did not show a significant difference before or after the accelerated pavement testing. Furthermore, the effective modulus decreased by approximately 50%, compared with the initial effective modulus for pedestrian pavement. CONCLUSIONS: Based on these results, inorganic soil pavement can be applied by changing the mixture proportions according to the use of the pavement, and can be utilized as road pavement from light load roads to access roads.

PURPOSES : The purpose of this study is to develop a deicing pavement system using carbon fiber or graphite with high electrical conductivity and thermal conductivity. METHODS: Based on literature reviews, in general, conventional concrete does not exhibit electrical and thermal conductivity. In order to achieve a new physical property, experiments were conducted by adding graphite and carbon fiber to a mortar specimen. RESULTS: The result of the laboratory experiment indicates that the addition of graphite can significantly reduce the compressive strength and improve the thermal conductivity of concrete. In the case of carbon fiber, however, the compressive strength of the concrete is slightly increased, whereas, the thermal conductivity is slightly decreased against the plain mortar irrespective of the length of the carbon fiber. In addition, a mixture of the graphite and carbon fiber can greatly improve the degree of heating test. CONCLUSIONS : Various properties of cement mortar change with the use of carbon fiber or graphite. To enhance the conductivity of concrete for deicing during winter, both carbon fiber and graphite are required to be used simultaneously.

PURPOSES : A finite difference model considering snow melting process on porous asphalt pavement was derived on the basis of heat transfer and mass transfer theories. The derived model can be applied to predict the region where black-ice develops, as well as to predict temperature profile of pavement systems where a de-icing system is installed. In addition, the model can be used to determined the minimum energy required to melt the ice formed on the pavement. METHODS : The snow on the porous asphalt pavement, whose porosity must be considered in thermal analysis, is divided into several layers such as dry snow layer, saturated snow layer, water+pavement surface, pavement surface, and sublayer. The mass balance and heat balance equations are derived to describe conductive, convective, radiative, and latent transfer of heat and mass in each layer. The finite differential method is used to implement the derived equations, boundary conditions, and the testing method to determine the thermal properties are suggested for each layer. RESULTS: The finite differential equations that describe the icing and deicing on pavements are derived, and we have presented them in our work. The framework to develop a temperature-forecasting model is successfully created. CONCLUSIONS : We conclude by successfully creating framework for the finite difference model based on the heat and mass transfer theories. To complete implementation, laboratory tests required to be performed.

The purpose of this paper is to find an limitation to detect the defect of damaged asphalt pavement structures for infrared thermography. We use heat source of a natural light to detect the defect efficiently. The heat source was applied to the asphalt specimens. Four asphalt specimens were used: one was the asphalt containing depth of 1cm internal timber, two was the asphalt containing depth of 2cm internal void, Three was the asphalt containing depth of 3cm internal timber and four was not the asphalt containing internal timber. It was found that the depth of 3cm internal timber could be detected by this method. In addition, we used the image processing to make the damage zone displayed clear in the image obtained from the thermographic operation.

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 use of environmentally friendly construction methods has been recently encouraged to reduce fuel consumption and the effects of global warming. For this purpose, the roller compacted concrete pavement (RCCP) construction method has been developed. RCCP is more environmentally friendly and economically efficient than general concrete by reducing the amount of CO2 generated through the application of a smaller amount of cement. RCCP has a number of advantages such as an easy construction method, low cost, high structural hydration performance, and aggregate interlocking. However, mix design standards and construction guidelines of RCCP are required for domestic application. In addition, a study on aggregate selection, which has an effect on the characteristics of RCCP, is necessary owing to a limited number of researches. Thus, the aggregate effect on the performance of RCCP in securing the required strength and workability was evaluated in consideration of domestic construction. METHODS : Sand and coarse aggregates of both 19mm and 13mm in maximum size were used in this study. Four types of aggregate gradations (s/a = 30%, 58%, and 70% for the sand and coarse aggregate of 19mm in maximum size, and s/a = 50% for a combination of the three types of aggregates) were set up to investigate the effects of the PCA band on the RCC characteristics. The conditions of s/a = 30% and 70% were evaluated to check the gradation effect outside of the recommended band. The conditions of s/a = 58% and 50% were used because they are the optimum combination of the two and three types of aggregates, respectively. RCCP gradation band was suggested gradation with a proper construction method of RCCP by synthetically comparing and analyzing the correlation of optimum water content, maximum dry density, and strength of requirements through its consistency and compaction test. RESULTS : The lower and upper limit lines are insufficient to secure a relatively strong development and workability compared to an aggregate gradation in the RCCP gradation band region. On the other hand, the line in the RCCP gradation band and the 0.45 power curve in the RCCP gradation band region were satisfactory, ensuring the required strength and workability. CONCLUSIONS: The suitable aggregate gradation on RCCP process should meet the RCCP gradation band area; however, fine particles passing through a #60 sieve do not need to be within the recommended gradation band because the influence of this region on such fine particles is small.

PURPOSES: To ensure appropriate RCC properties with sufficient strength development and workability, it is necessary to secure a proper level of consistency. It is also necessary to secure maximum dry density, which is an important factor for increasing the interaction of aggregate interlocking, leading to an augmentation of RCC strength. On the other hand, the dry density of RCC can be changed owing to the compaction conditions, water content, and particle size distribution. A Proctor test and a modified Proctor test were used for determining the optimum water content needed to achieve maximum dry density with different amounts of compaction energy. A Vebe test, on the other hand, was used for checking the level of consistency, which is important for producing a workable mixture. METHODS : To confirm the degree of compaction at various particle sizes, RCC mixtures with different sand/aggregate ratios were evaluated. The Proctor test and modified Proctor test were applied to these mixtures to check the effect of the aggregate gradation and compaction energy on the maximum dry density and optimum water content. During each test, three specimens were produced for all types of water content under each aggregate gradation. A compaction curve and the optimum water content and maximum dry density for each aggregate gradation were then obtained for both tests. The range of water content for the appropriate consistency of each aggregate gradation was determined through a Vebe test. The optimum water content was then evaluated based on this range. RESULTS : The compaction test results show that the modified Proctor test provides a higher maximum dry density and lower optimum water content compared with the standard Proctor test. For the modified Proctor test, two cases of aggregate gradation (s/a = 30% and 70%) had the optimum water contents outside of the appropriate water content range. For the standard Proctor test, on the other hand, none of aggregate gradations provided the optimum water content within the desired range. CONCLUSIONS : The modified Proctor test should be used for an RCC mixture design because it can provide adequacy between maximum dry density and consistency. Moreover, the compaction roller has become highly developed for higher compaction energy.

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.

Cracking is an inevitable fact of asphalt concrete pavements and plays a major role in pavement deterioration. Pavement cracking is one of the main factors determining the frequency and method of repair. Cracks can be treated with a number of preventative maintenance actions, including overlay surface treatments such as slurry sealing, crack sealing, or crack filling. Pavement cracks can show up as one or all of the following types: transverse, longitudinal, fatigue, block, reflective, edge, and slippage. Crack sealing is a frequently used pavement maintenance treatment because it significantly extends the pavement service life. However, crack sealant often fails prematurely due to a loss of adhesion. Because current test methods are mostly empirical and only provide a qualitative measure of the bond strength, they cannot accurately predict the adhesive failure of the sealant. This study introduces a laboratory test aimed at assessing the bonding of hot-poured crack sealant to the walls of pavement cracks. A pneumatic adhesion tensile testing instrument (PATTI) was adopted to measure the bonding strength of the hot-poured crack sealant as a function of the curing time and temperature. Based on a limited number of test results, the hot-poured crack sealants have very different bonding performances. Therefore, this test method can be proposed as part of a newly developed performancebased standard specification for hot-poured crack sealants for use in the future. PURPOSES : The purpose of this study was to evaluate both the adhesion and failure performance of a crack sealant as a function of its curing time and curing temperature. METHODS: A pneumatic adhesion tensile testing instrument (PATTI) was adopted to measure the adhesion performance of a crack sealant as a function of the curing time and curing temperature. RESULTS: With changes in the curing time, curing temperature, and sealant type, the bond strengths were found to be significantly different. Also, higher bond strengths were measured at lower temperatures. Different sealant types produced completely different bond strengths and failure behaviors. CONCLUSIONS: The bonding strength of an evaluated crack sealant was shown to differ depending on various factors. Two sealant types, which were composed of different raw materials, were shown to perform differently. The newly proposed test offers the possibility of evaluating anddifferentiatingbetweendifferentcracksealants.Basedonalimitednumberoftestresults,this test method can be proposed as part of a newly developed performance-based standard specification for crack sealants or as part of a guideline for the selection of hot-poured crack sealant in the future.

PURPOSES: This paper describes the expansion caused by the alkali-aggregate reaction (AAR) in concrete pavement currently in service. It also discusses the effects of joints installed to release the stress induced by the AAR expansion. METHODS: The expansion effect on concrete pavement was verified by a visual inspection and long-term measurement of the joint width of a cut-section. The behaviors of 16 newly installed joints were monitored as part of the investigation and long-term monitoring was carried out for three years after cutting. RESULTS: The behavior of a bridge was affected when AAR occurred in the connected pavement. The newly installed joints shrank in the longitudinal direction of the bridge after cutting. The width of the joints decreased over the six months after cutting. A large portion of the joint width (8.5cm) was found to have closed nine months after cutting. It had ultimately shrunk by about 92 percent when the final measurement was taken. CONCLUSIONS : The expansion of the pavement due to AAR was quantitatively described by visual inspection and the long-term monitoring of the newly cut joints. However, the width of the new joints decreased over the six to nine months after cutting. Additional research should be conducted to determine a means of controlling the expansion due to AAR in the pavement.

온도하중에 기인하는 교량의 수평거동의 구속을 최소화하기 위해 도로 포장과 교량의 접속부에는 줄눈, 신축이음 및 배수시설을 설치하며, 이로 인하여 도로에는 불연속면이 발생한다. 이는 노면의 평탄성에 영 향을 주어, 이용자들의 승차감을 저하시키고 경우에 따라 안전을 위협하기도 하는 요인이 된다. 교량의 교대 주변의 지반은 다짐이 용이하지 않아 장기침하가 발생하기 쉬우며, 이로 인하여 접속 슬래브에 균열 이 발생하고 신축이음이 손상되기도 한다. 또한 손상된 신축이음부에 강수 및 제설제 침투로 인한 2차적 인 피해가 발생하기 때문에 유지관리비가 요구되는 실정이다. 이러한 문제점을 해결하기 위한 방법으로 줄눈과 신축이음의 설치 없이 교량부와 포장을 일체로 시공 하는 Seamless Pavement 공법이 호주 WM7 고속도로의 Russell Bridge에서 시공되어 매우 우수한 성능 을 보인 것으로 확인되었다(Griffiths et al, 2006). 불연속면을 제거하여 줄눈, 신축이음 및 배수시설을 없애 초기 시공비를 줄일 수 있었고, 불연속면이 없어져 운전자의 쾌적성이 개선되었으며, 이 위치에서의 파손이 없어 유지관리비가 적게 소요된 것으로 나타났다. 미국의 경우 호주의 Seamless Pavement 공법 의 우수성을 확인하여 SHRP2 연구단에서 연구를 시작하여, 교량설계시 이를 고려할 수 있는 방안을 연 구하였다. 본 연구는 토공부와 교량 사이의 불연속면을 없애는 Seamless Pavement 공법을 국내에 도입하기에 앞서 이에 대한 이론적 배경과 설계 논리 등을 검토하여 보았다.

PURPOSES: The purpose of this study is to analyze the service life of expressway pavement based on both traffic volumes and use of deicing chemicals. METHODS: A database was built using expressway rehabilitation history information from over the last decade. In order to estimate the service life of expressway pavement, various analysis methods were considered, and a decision was made to perform analysis using a method based on an accumulated rehabilitation ratio. The service life of expressway pavement was then analyzed by classifying the scale of traffic volume and extent of de-icing chemicals used. RESULTS: The service life of PMA and SMA ranged from 7.8 to 10.6 years and from 9.9 to 12.0 years, respectively. The service life of JCP ranged from 16.0 to 22.2 years, and the service life of CRCP was 33.5 years on average. Results of assessing service life according to traffic volumes and de-icing chemicals showed that the lower the traffic volumes were, the greater the service life of PMA and JCP, and the less that de-icing chemicals were applied, the greater the service life of JCP. CONCLUSIONS : The dependence of expressway pavement service life on traffic volumes and de-icing chemicals makes it possible to apply LCCA for regional maintenance plans and cost-effective selection of expressway pavement type.

PURPOSES : Recently, attempts have been made to evaluate tire-pavement noise based on a measure of Mean Profile Depth (MPD). However, equivalent values of MPD appear to correspond to different levels of tire-pavement noise, which indicates that other factors such as texture wavelength need to be included to improve the accuracy of noise prediction. A single index to represent texture wavelength is proposed in this study. A consistent relationship between tire-pavement noise and texture wavelength on asphalt concrete pavement is observed. METHODS: Profile data and tire-pavement noise data were collected from a number of expressway sections in Korea. In addition, texture wavelength was defined by a Peak Number (PN), which was calculated using profile data. Statistical analysis was performed to find the relationship between the PN and tire-pavement noise. RESULTS: As a result of this study, a linear relationship between PN and tire-pavement noise is observed on asphalt concrete pavement. CONCLUSIONS: Tire-pavement noise on asphalt concrete pavement can be predicted from PN information.

PURPOSES: The objective of this study is to evaluate the tack-coating material’s properties using the bitumen bond strength(BBS) test and damping test as function of changed curing times. In this study, bonding strength tests were performed according to the curing time of tack coating materials. METHODS : In order to investigate bonding characteristic of tack coating materials, the Pneumatic Adhesion tensile Testing Instrument(PATTI) device is used to measure the bond strength between the tack coating materials and aggregate substrate based on the AASHTO TP-91. Also, damping test as in situ test was used to determine an appropriate traffic openting time for construction vehicle. Four different tack-coating materials were used in this study. The BBS tests were performed a one hour curing and testing temperatures of 5℃, 15℃, and 25℃. Damping test was conducted at 30min, 60min, 90min, and 120 min of curing times with temperatures of 20℃ and 30℃. RESULTS and CONCLUSIONS : The BBS test results show various bond strength as function of tack coat materials. At the same testing condition, A tack coat material shows almost two times higher than D tack coat materials although both materials are satisfied the criteria of material’s physical properties. Also, Dampting test results shows similar trend with BBS test result. The damping test result was significantly changed as function of tack coat materials. Based on this study, the tack coating material’s curing time is very important. Therefore, both curing time and the bond strength’s characteristic has to be considered in standard specification.

PURPOSES: The objective of this paper is to select the confidential intervals by utilizing the second moment reliability index(Hasofer and Lind; 1974) related to the number of load applications to failure which explains the fatigue failure and rut depth that it indicates the permanent deformation. By using Finite Element Method (FEM) Program, we can easily confirm the rut depth and number of load repetitions without Pavement Design Procedures for generally designing pavement depths. METHODS : In this study, the predictive models for the rut depth and the number of load repetitions to fatigue failure were used for determining the second moment reliability index ( ). From the case study results using KICTPAVE, the results of the rut depth and the number of load repetitions to fatigue failure were deducted by calculating the empirical predictive equations. Also, the confidential intervals for rut depth and number of load repetitions were selected from the results of the predictive models. To determine the second moment reliability index, the spreadsheet method using Excel’s Solver was used. RESULTS : From the case studies about pavement conditions, the results of stress, displacement and strain were different with depth conditions of layers and layer properties. In the clay soil conditions, the values of strain and stresses in the directly loaded sections are relatively greater than other conditions. It indicates that the second moment reliability index is small and confidential intervals for rut depth and the number of load applications are narrow when we apply the clay soil conditions comparing to the applications of other soil conditions. CONCLUSIONS : According to the results of the second moment reliability index and the confidential intervals, the minimum and maximum values of reliability index indicate approximately 1.79 at Case 9 and 2.19 at Case 22. The broadest widths of confidential intervals for rut depth and the number of load repetitions are respectively occurred in Case 9 and Case 7.

PURPOSES: The purpose of this study is to evaluate the degree of restraint (DOR) of longitudinal steel at continuously reinforced concrete pavement (CRCP) against environmental loadings. METHODS : To measure the longitudinal steel strain, 3-electrical resistance and self-temperature compensation gauges were installed to CRCP test section (thickness = 250mm, steel ratio = 0.7%) and continuously measured 10 min. intervals during 259 days. In order to properly analyze the steel strains first, temperature compensation process has been conducted. Secondly, measured steel strains were divided into 12 phases with different events such as before paving, during concrete hardening, and after first cracking, etc. RESULTS : Thermal strain rate (TSR) concept is defined as the linear strain variations with temperature changes and restraints rate of longitudinal steel against environmental loadings (especially thermal loading) with different cases is defined as degree of restraint(DOR). New concept of DOR could be indirect indicator of crack width behaviors of CRCP. CONCLUSIONS: Before paving, DOR of longitudinal steel is almost same at the coefficient of thermal expansion of steel (12.44m/m/℃) because of no restraint boundary condition. After concrete pouring, DOR is gradually changed into -1 due to concrete stiffness developing with hydration. After first cracking at crack induced area, values of DOR are around -3~-5. The negative DOR stands for the crack width behavior instead of steel strain behavior. During winter season, DOR reached to -5.77 as the highest, but spring this values gradually reduced as -1.7 as the lowest. Based on this observation, we can presume crack width decreased over time within the time frame of this study. This finding is not consistent with the current theory on crack width variations over time, so further study is necessary to identify the causes of crack width reducing. One of the reasons could be related to concrete stress re-distribution and stress relaxation.