교통량이 증가하고 교량과 같은 특수구조물에 아스팔트 포장이 시공되는 사례가 증가함에 따라 일반적으로 사용되는 아스팔트보다 높은 성능을 가진 아스팔트에 대한 수요가 증가하고 있다. 일반 아스팔트 혼합물은 내구연한이 지나면 재생첨가제 등을 사용하여 다 시 도로포장재료로서 재활용할 수 있는 방안이 마련되어 있으나, 개질 아스팔트가 사용된 폐아스팔트 혼합물은 매립재로 사용하는 것 이외에는 별다른 대안이 없는 실정이다. 이에 본 연구에서는 국토부 지침에 규정된 재활용 아스팔트 혼합물 배합설계법을 적용하여 개질 폐아스팔트 혼합물을 재활용할 수 있는지를 검토해보고자 하였다. 이를 위해 개질 아스팔트를 활용하여 혼합물을 제작하였으며, 현장에서 수거되는 폐아스팔트 혼합물의 노화상태를 모사하기 위해 AASHTO R 30을 참고하여 강제 노화를 실시하였다. 노화 및 추출 과정에서 아스팔트의 물성 변화를 확인하기 위해 절대점도, DSR, MSCR 시험을 실시하였다. 시험결과, 추출 후 바인더의 절대점도는 감소하였으나 G*(복합전단계수)와 δ(위상각)은 증가하는 경향을 보였다. 소성변형 저항성을 확인하기 위해 MSCR(다중 응력 크리프 및 회복) 시험을 실시한 결과,  이 2배 가까이 증가하여 소성변형 저항성이 감소한 것을 확인할 수 있었다. 이러한 결과는 추출시 사용 되는 용매가 개질첨가제를 추출하지 못하여 기인한 결과로 판단된다. 따라서 개질 폐아스팔트 혼합물을 재활용하기 위해서는 기존과 는 다른 별도의 배합설계법이 개발되어야 할 것으로 판단되었다.

In order to prevent early distress in asphalt pavement and save on subsequent operational and maintenance costs, modifying asphalt is an effective approach. Styrene–butadiene–styrene (SBS) block copolymers, due to their excellent physicochemical properties, have become a mature and widely used asphalt modifier. Carbon nanotubes (CNTs) possess advantages such as a large specific surface area and high modulus, which, when incorporated into asphalt, can enhance its deformation resistance. To analyze the effect of incorporating CNTs on SBS-modified asphalt (SBS-A), this study analyzed the influence of different CNT concentrations on the high and low-temperature performance and aging properties of SBS-A through penetration, softening point, ductility, dynamic shear rheometry, and short-term aging tests. The optimal CNT concentration was determined to be 1.0%. Furthermore, the changes in the modified asphalt during the aging process were analyzed using infrared spectroscopy.

PURPOSES : This study was conducted to evaluate the physical properties of the RAP 50 asphalt mixture containing polymer modified rejuvenator and warm-mix additive to improve the recycling rate of RAP and reduce CO2 emission. METHODS : Mix design of Polymer Modified Warm-mix Asphalt Mixture(RAP 50), and Hot Mix Asphalt Mixture(RAP 30) were produced and the properties of asphalt mixture such as Marshall Stability, ITS, Deformation Strength, TSR, and Dynamic Stability were compared between the two asphalt mixtures. RESULTS : The RAP 50 asphalt mixture showed superior or similar performances compared to the RAP 30 asphalt mixture in all the tests conducted. The results of the Marshall stability and dynamic stability in particular were 13,045N and 3,826 pass/mm, which were 11.37% and 76.7% greater than the RAP 30 asphalt mixture, which indicated that high plastic deformation resistance may be expected. CONCLUSIONS : The results obtained from laboratory tests on the two types of mixtures indicated that the use of polymer modified rejuvenator and warm-mix additive not only allows to increase the proportion of RAP but also improves its properties under lower temperature condition than RAP 30 asphalt mixture. Additionally, it was confirmed that plastic deformation resistance was high and moisture resistance and crack resistance were improved for a RAP 50 asphalt mixture.

PURPOSES : In this study, we propose a mini-trench method, which involves using warm mix Guss mastic asphalt as a backfill material and an installation temperature of 160 ℃. The method is verified via a heat transfer analysis of a pavement using the finite element method. METHODS : First, the density, thermal conductivity, and specific heat required for heat transfer analysis were determined based on previous studies. Subsequently, the boundary conditions for convection and radiation to perform the heat transfer analysis were determined. The pavement temperature, which is the initial condition of the analysis, was determined based on the summer pavement temperature distribution using the temperature prediction program of the Korean pavement Research Program. Heat transfer analysis was performed by determining the temperature of the backfill material based on 160 °C and 200 °C for the heat load temperatures. The temperature change was observed on the backfill surface, and the temperature change of the conduit was observed directly. RESULTS : When the pavement surface temperature for traffic opening is 50 °C, the backfill thickness ranges from 50 to 250 mm, the warm mix Guss mastic asphalt requires 2 h to 5 h, 15 min until traffic opening, and the hot mix Guss mastic asphalt requires 2 h, 30 min to 6 h, 40 min until traffic opening. The limit temperature of the conduit evaluated based on KS C 8454 shows that the warm mix Guss mastic asphalt does not satisfy the standard when the backfill concrete cover is 50 mm thick, whereas the hot mix Guss mastic asphalt does not satisfy the standard when the concrete cover is 50 and 100 mm thick. CONCLUSIONS : The backfill depth of the mini-trench using warm mix Guss mastic asphalt as a backfill material should be less than 100 mm, considering the traffic opening time. Meanwhile, the thickness of the backfill concrete should be 100 mm or less.

PURPOSES : This study evaluates the mechanical properties of high-viscosity polymer-modified asphalt binders using PG and MSCR tests. METHODS : Using the Superpave asphalt binder performance grade (PG) and multi-stress creep recovery (MSCR) test methods, the linear (dynamic shear modulus, stiffness, and viscosity) and non-linear properties — i.e., non-recoverable compliance (Jnr) and recoverable shear strain % recovery — of 16 different types (SBS, SIS, PE, PP) of polymer-modified asphalt binders were assessed. RESULTS : Based on the viscosity testing results. Most PG 82 binders did not meet the criterion of 3 Pa ·s. This indicates that they need to increase the mixing and compaction temperatures to reduce the high viscosity. The MSCR % Jnr results demonstrated that PG 76, PG 82–22, and PG 82-28/34 binders were below 1.0, 0.5, and 0.2, respectively. In addition, the MSCR % recovery results showed that PG 76, PG82-22, and PG82-28/34 were above 35 %, 55 %, and 80 %, respectively. CONCLUSIONS : It was found that the % Jnr decreased with an increase in the high-temperature PG of the asphalt binder, whereas the % recovery increased as the low-temperature PG of the binder increased.

PURPOSES : This study aims to determine the type (e.g., melting point, freezing point, latent heat fusion) and optimal content of phase change material (PCM) based on the numerical and experimental analyses evaluating the effects of heat transfer in PCM-modified asphalt pavement systems. METHODS : The effect of PCM on the thermophysical properties of PCM-modified asphalt concrete can be taken as an effective volumetric heat capacity. The volumetric fraction of PCM was calculated using an iterative method. The numerical model was established and computed using the MATLAB 2020 software. The optimum PCM design tool was developed to select the type and contents of the PCM. The PCM was chosen based on the following criteria: black-ice-formation delay time, minimize temperature increase, and increase temperature area. To validate the numerical model, asphalt mixtures were modified with varying PCM contents, and the temperature response of the PCMmodified asphalt samples was examined via temperature test. RESULTS : The numerical results showed that incorporating PCM into the asphalt mixture can slow the cooling rate of the pavement system. The predicted results from the optimum PCM design tool were highly consistent with the measured values from the laboratory temperature test. CONCLUSIONS : The temperature of PCM-modified asphalt pavement can be predicted via numerical method. The effect of PCM on the thermophysical properties can be considered as effective volumetric heat capacity; while the volume fraction of PCM can be calculated via an iterative method. The accuracy of the numerical model was confirmed by a high agreement between the measured and predicted values.

Modified asphalt pavements are needed to resolve pavement distress problems like rutting, pot-hole and warm asphalt pavements are needed to solve energy saving, reduction of noxious gasses emission and early traffic opening. To present these two characteristics, we developed polymer-modified warm-mix asphalt binder and mixtures and evaluated their performance by optimizing polymer-modified warm-mix additive. As results, physical properties and rheological characteristics of polymer-modified warm-mix asphalt binder are similar to normal modified binder. And we confirmed that polymer-modified warm-mix asphalt mixtures satisfied quality standard of Ministry of Land, Infrastructure and Transport.

PURPOSES: The purpose of this study was to develop an urgent road-repair system and perform a field applicability test, as well as discover the optimum mix design for machine applications compared to the optimum mix design for lab applications. METHODS: According to reviews of the patent and developed equipment, self-propelled and mix-in-place equipment types are suitable for urgent pavement repair, e.g., potholes and cracks. The machine-application mix design was revised based on the optimum lab-test mix design, and the field application of a spray-injection system was performed on the job site. The mixture from the machine application and lab application was subjected to a wet-track abrasion test and a wheel-tracking test to calibrate the machine application. RESULTS and CONCLUSIONS : This study showed that the binder content could differ for the lab application and the machine application in the same setting. Based on the wet-track abrasion test result, the binder contents of the machine application exceeded the binder contents of the lab application by 1-1.5% on the same setting value. Moreover, the maximum dynamic stability value for the machine application showed 1% lower binder contents than the maximum lab-application value. Collectively, the results of the two different tests showed that the different sizes and operating methods of the machine and lab applications could affect the mix designs. Further studies will be performed to verify the bonding strength and monitor the field application.

PURPOSES: The main distress of asphalt pavements in monsoon climate regions are caused by water damage and plastic deformation due to repeated rain season and increased heavy vehicle traffic volume. In this study, the mechanical properties of polymer-modified warm mix asphalt (PWMA) materials are evaluated to use in monsoon climate regions such as Indonesia. METHODS: Comprehensive laboratory tests are conducted to evaluate moisture resistance and permanent deformation resistance for three different asphalt mixtures such as the Indonesian conventional hot-mix asphalt (HMA) mixture, the polymer-modified asphalt mixture, and the polymer-modified warm mix asphalt (PWMA) mixture. Dynamic immersion test and indirect tensile strength ratio test are performed to evaluate moisture resistance. The wheel tracking test is performed to evaluate rutting resistance. Additionally, the Hamburg wheel tracking test is performed to evaluate rutting and moisture resistances simultaneously. RESULTS: The dynamic immersion test results indicate that the PWMA mixture shows the highest resistance to moisture. The indirect tensile strength ratio test indicates that TSR values of PWMA mixture, Indonesian PMA mixture, and Indonesian HMA mixture show 87.2%, 84.1%, and 67.9%, respectively. The wheel tracking test results indicate that the PWMA mixture is found to be more resistant to plastic deformation than the Indonesian PMA. The dynamic stability values are 2,739 times/mm and 3,150 times/mm, respectively. Moreover, the Hamburg wheel tracking test results indicate that PWMA mixture is more resistant to plastic deformation than Indonesian PMA and HMA mixtures. CONCLUSIONS: Based on limited laboratory test results, it is concluded that rutting resistance and moisture susceptibility of the PWMA mixture is superior to Indonesian HMA and Indonesian PMA mixtures. It is postulated that PWMA mixture would be suitable for climate and traffic conditions in Indonesia.

The discontinuity movements of the Portland cement concrete (PCC) layer due to temperature fluctuations and traffic loading are primary causes of the reflection cracking in asphalt overlays. The thermal expansion and contraction of the discontinuities at the PCC layer induces tension at the bottom of the asphalt overlay layer creating excessive strains which causes cracking. The additional cyclic discontinuity movements from the thermal fluctuations and traffic loads propagates the cracks initiated until failure of the overlay layer. However, the crack behaviors of asphalt mixtures varies with temperature due to its viscoelastic property. As such, there is a need to investigate the cracking behavior of asphalt mixtures with varying temperatures and loading conditions. A modified overlay tester developed to evaluate the cracking resistance of asphalt mixtures in various loading directions and different confining temperatures was used to investigate the behavior of asphalt materials with various temperatures and loading conditions. The laboratory test was conducted in 2 segments. The first segment investigates the asphalt cracking behavior subjected to horizontal loading in 3 varying temperatures (10, 25 and 40C) which simulates the cyclic thermal contraction and expansion at the discontinuity. The second segment examines the cracking propagation of the asphalt mixture subjected to vertical loading in 3 varying temperatures. A load dissipation curve per loading cycle is generated in each test along with the images taken on the face of the specimen to monitor the crack propagation. Results have shown that asphalt mixtures undergo a 3-phase cracking behavior: initiation, propagation and failure. This is evident in the load dissipation curve when the initiation phase shows a rapid reduction of peak loads in first series of loading cycles which is followed by a slow and constant load reduction over a certain number of cycles. Failure occurs when there is a sudden decline in peak load and the percent reduction of the load is achieved. Figure 1 shows a fine dense grade asphalt mixture subjected to horizontal movement at 10C. Meanwhile, the load dissipation curve is further investigated by analyzing the images captured during testing. It can be seen that the first visible crack can be identified after 40 cycles which steadily propagates up to 600 cycles. However, between 600 and 700 loading cycles, there is a sudden dip in peak load which shows that at that the stage the crack has already propagated to the top of the test specimen as shown in Figure 2. Other tests have shown that the cracking patterns and load dissipation curves vary with different testing temperatures signifying that low temperature is more susceptible to early failure with constant differential movement. Further tests signify that using a general formula, parameters are calculated which refer to fracture properties of the material.

비가열식 상온 도로포장 재활용 공법인 상온 현장 재활용 공법(CIR), 상온 플랜트 재활용 공법(CCPR), 상온 전체 포장층 재활용 공법(FDR)들은 경제적으로 시공 비용이 저렴하고 공사기간을 단축시키며 환경오염 영향을 적게 미치는 장점이 있다. 상온 재활용 공법에 사용되는 아스팔트 바인더는 크게 유화아스팔트(emulsified asphalt)와 폼드 아스팔트(foamed asphalt)가 적용되며, 이들은 재생 아스팔트 혼합물의 재생첨가제 또는 안정제로서의 기능을 하기도 한다. 유화아스팔트는 물속에 아스팔트 바인더 입자(1-3μm)가 계면활성제(surfactant)에 의해 상분리 현상을 일으키지 않고 분산 상태를 유지하고 있는 액체 상태의 아스팔트이기 때문에 상온에서 별도의 가열 없이 편리하게 사용할 수 있다. 하지만 상온 재활용 아스팔트 콘크리트에 대한 공학적 구조 해석을 위한 정량적 데이터가 부족하여 공학적 공용성 분석이 이루어지지 못해 널리 활성화 되는데 한계점을 가지고 있다. 본 연구는 상온 재활용 아스팔트 콘크리트용 개질 유화아스팔트의 개발을 목적으로 개질재(천연고무, 합성고무 등)에 의한 유화아스팔트 바인더의 정량적 물성 성능 평가를 위하여 기초적 실험평가를 실시하였다. 아스팔트 바인더(AP-3)를 개질 첨가제인 천연고무, 합성고무 A와 B를 각각 3% 첨가하여 개질시키고 유화 과정을 시켜 개질 유화아스팔트를 제조하였다. 이렇게 제조된 개질 유화아스팔트의 증발잔류물(평균 61%)에 대해 침입도와 연화점 시험을 실시하였다. 시험결과 천연고무와 합성고무 B로 개질 유화아스팔트의 연화점이 66℃과 67℃로 합성고무 A(51℃)보다 높게 나타났고, 침입도는 천연고무로 개질된 유화아스팔트가 49로 합성고무(A) 66와 합성고무(B) 74로 측정되었다. 천연고무로 개질된 유화아스팔트의 물성 성능이 가장 우수하였고 혼합성 및 저장안전성도 양호하였다. 천연고무, 합성고무 A와 B를 적용한 개질 유화아스팔트의 물성 성능평가를 통해 기초적 자료를 확보하였고, 향후 상온 재활용 아스팔트 콘크리트 혼합물에 대한 공용성능 평가를 통해 공학적 공용성 분석을 진행할 예정이다.

PURPOSES :The purpose of this study was to determine the optimum mix design of the content of 100 % reclaimed asphalt pavement (RAP) for spray injection application with different binder types.METHODS:Literature review revealed that spray injection method is the one of the efficient and economical methods for repairing a small defective area on an asphalt pavement. The Rapid-Setting Polymer modified asphalt mixtures using two types of rapid setting polymers-asphalt emulsion and a quick setting polymer asphalt emulsion-were subjected to the following tests to determine optimum mix designs and for performance comparison: 1) Marshall stability test, 2) Retained stability test, 3) Wet track abrasion test, and 4) Dynamic stability test.RESULTS AND CONCLUSIONS :Type A, B, and C emulsions were tested with different mix designs using RAP aggregates, to compare the performances and determine the optimum mix design. Performance of mixtures with Type A emulsion exceeded that of mixtures with Type B and C emulsion in all aspects. In particular, Type A binder demonstrated the highest performance for WTAT at low temperature. It demonstrated the practicality of using Type A mixture during the cold season. Furthers studies are to be performed to verify the optimum mix design for machine application. Differences in optimum mix designs for machine application and lab application will be corrected through field tests.

OBJECTIVES: The objective of this research is to develop additives for the modification of Solvent DeAsphalting Residue (SDAR) to be used as pavement materials, and evaluate the performance of asphalt mixture manufactured using the SDAR modified by developed additives. METHODS: The SDAR generally consists of more asphaltenes and less oil components compared to the conventional asphalt binder, and hence, the chemical/physical properties of SDAR are different from that of conventional asphalt binder. In this research, the additives are developed using the low molecular oil-based plasticizer to improve the properties of SDAR. First, the chemical property of two SDARs is analyzed using SARA (saturate, aromatic, resin, and asphaltene) method. The physical/rheological properties of SDARs and SDARs containing additives are also evaluated based on PG-grade method and dynamic shear-modulus master curve. Second, various laboratory tests are conducted for the asphalt mixture manufactured using the SDAR modified with additives. The laboratory tests conducted in this study include the mix design, compactibility analysis, indirect tensile test for moisture susceptibility, dynamic modulus test for rheological property, wheeltracking test for rutting performance, and direct tension fatigue test for cracking performance. RESULTS : The PG-grade of SDARs is higher than PG 76 in high temperature grades and immeasurable in low temperature grades. The dynamic shear modulus of SDARs is much higher than that of conventional asphalt, but the modified SDARs with additives show similar modulus compared to that of conventional asphalt. The moisture susceptibility of asphalt mixture with modified SDARs is good if, the antistripping agent is included. The performance (dynamic modulus, rutting resistance, and fatigue resistance) of asphalt mixture with modified SDARs is comparable to that of conventional asphalt mixture when appropriate amount of additives is added. CONCLUSIONS: The saturate component of SDARs is much less than that of conventional asphalt, and hence, it is too hard and brittle to be used as pavement materials. However, the modified SDARs with developed additives show comparable or better rheological/physical properties compared to that of conventional asphalt depending on the type of SDAR and the amount of additives used.

OBJECTIVES : In this study, microstructural components of crumb rubber modified asphalt (CRMA) binder were investigated using environmental scanning electron microscope (ESEM). To clearly understand the elemental composition of the CRMA binder, energy dispersive X-ray spectroscopy (EDX) was employed on the ESEM samples. METHODS: CRMA binders were produced using open blade mixers at 177℃ for 30 min. The binders were artificially aged through a series of accelerated aging processes. Sample preparation was done by making a mold shape on the glass slide. Thereafter, the morphology of the CRMA binder was observed using the ESEM coupled with the EDX. RESULTS : The images captured from the ESEM indicate that the unaged CRMA binder appears to have a single-phase continuous nonuniform structure after the addition of crumb rubber particles, whereas the artificially aged CRMA binder was observed to have two different phases. ESEM coupled with EDX shows detailed internal structure of the modified binders compared to other technologies (i.e., optical microscopy, atomic force microscopy, and conventional scanning electron microscope). CONCLUSIONS: The captured images resemble the internal structures such as the viscous properties of the unaged CRMA binder and the interaction between the rubber particles and the base binder at aged condition. ESEM is a powerful instrument and with the introduction of EDX, it provided more details of the network microstructure of the asphalt binder. ESEM coupled with EDX is recommended for use in future investigation of microstructure of asphalt binders.

PURPOSES: The objective of this study was to determine the optimum ratio of mix design, for a reclaimed asphalt pavement (RAP) content of 100%, for spray injection application. METHODS: A literature review revealed that spray injection is an efficient and cost-effective application for fixing small defective regions of an asphalt pavement. Rapid-setting polymer-modified asphalt mixtures prepared from two types of rapid-setting polymer asphalt emulsion were subjected to Marshall stability and wet track abrasion tests, in order to identify the optimum mix designs. RESULTS and CONCLUSIONS : Different mix designs of type A and type B emulsions were prepared using RAP and virgin aggregates, in order to compare the performance and determine the optimum mix design. The performance of mixtures prepared with RAP was superior to that of mixtures containing virgin aggregates. Moreover, for optimum ratio of the design, the binder content prepared from RAP was set to 1~2% lower than that consisting of virgin aggregates. Compared to their Type A counterparts, type B mixtures consisting of a reactive emulsion performed better in the Marshall stability and wet track abrasion tests. The initial results confirmed the advantages associated with using RAP for spray injection applications. Further studies will be performed to verify the difference in the optimum mix design and performance obtained in the lab-scale test and tests conducted at the job site by using the spray injection machine.

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 objectives of this study were to develop a new polymer-modified emulsion for application to tack coats and to evaluate its properties by comparing it with other types of asphalt emulsions, with the goal of providing an enhanced tack coat material for use in construction. METHODS: Modified asphalt binders were developed from using SBS and SBR latex in the laboratory, and their fundamental properties, such as their penetration index and PG grade, were evaluated. Based on the properties, a new tack coat material was developed. To evaluate the newly developed asphalt emulsion, the bonding strength between the two layers of HMA was measured by applying a uniaxial tensile test and shear test. For the tests, a total of four different conditions were applied to the specimens, including the developed asphalt emulsion, latex modified asphalt emulsion, conventional asphalt emulsion, and non-tack coating. RESULTSAND CONCLUSIONS: Overall, the developed asphalt emulsion exhibits the best bonding strength behavior among all of the three types. Also, the two types of polymer-modified emulsions were found to be better for application for use as a tack coat than a conventional emulsion. Especially, at a high temperature (50℃), the conventional asphalt emulsion no longer acts as a tack coating material. Therefore, the polymer-modified emulsion should be considered for application to tack coat construction during the summer.