PURPOSES : In this study, the resources and energy consumed to produce hot mix asphalt mixtures and hot mix reclaimed asphalt mixtures in asphalt concrete plants were estimated and the emissions from the detailed processes of the production process were evaluated based on TRACI(the tool for the reduction and assessment of chemical and other environmental impacts). METHODS : To estimate the energy consumption of the aggregate drying process, which consumes a significant amount of energy in the production process, an energy consumption calculation model based on the thermal equilibrium equation was used, and the energy consumed for material transportation, storage, and operation of other facilities was cited from the literature. RESULTS : For the system boundary conditions established and the inventory considered, the emissions to produce one ton of hot mix reclaimed asphalt mix are greater than the emissions to produce one ton of hot mix asphalt mix for a number of key impact categories. The process of producing hot mix reclaimed asphalt mixtures was evaluated to consume more resources and energy in the production of recycled aggregates and heating for drying than in the production of hot mix asphalt mixtures, but less resources and energy in the production of binders and natural virgin aggregates and the heating to heat these materials. CONCLUSIONS : The results of the emissions assessment using the life cycle inventory for the production of hot mix asphalt mixtures were generally similar to the results understood in the field and in much of the literatures, confirming the reliability of the methodology. However, in order to evaluate the dominance of specific processes or mixtures, it is believed that the construction of a wide range of inventory databases after inventory redesign is necessary for a specific and rigorous assessment.

PURPOSES : There has been increasing interest in South Korea on warm-mix asphalt (WMA) and cold-mix asphalt (CMA) technologies that allow production of asphalt pavement mixtures at comparatively lower temperatures than those of hot-mix asphalt (HMA) for use in pavement engineering. This study aims to evaluate the feasibility of replacing HMA pavement with WMA pavement with the goal of reducing CO2 emissions associated with asphalt production for road construction. METHODS : Changes in the dynamic modulus characteristics of WMA and HMA according to short-term and long-term aging were evaluated. In addition, the effects of water damage were evaluated for short- and long-term aging stages. RESULTS : For WMA, in the process of mixing and short-term aging, early-age dynamic modulus decreased owing to low temperature and reduced short-term aging (STA) time. This could result in early damage to the asphalt pavement depending on the applied traffic load and environmental load. CONCLUSIONS : Mastercurves of the dynamic modulus were used for comparative analysis of WMA and HMA. Compared to the dynamic modulus after STA of HMA, the estimated aging time determined by experiments for WMA to achieve the required stiffness was more than 48 hours, which is equiva-lent to approximately 4 to 5 years real service life when converted. It is considered that further studies are needed for performance optimization to achieve early-age performance of the asphalt mixes.

PURPOSES : This study was performed to evaluate the short-term aging (SA) protocols of the normal hot-mix asphalt (HMA) mixture, to explore problems, and to suggest proper procedures based on fundamental principles of SA in terms of the SA temperature (T) and length of time (Lt) in existing specifications in several countries including Korea. METHODS : As the SA in our lab is a simulation of field SA, which is an inevitable procedure occurring naturally in the current field practice, major SA guidelines of foreign countries and Korea were reviewed to investigate problems that showed discrepancies with field practice. The aging quantity (Aq) model was introduced as a function of T and Lt, based on the correlation with absolute viscosity (AV) to estimate Aq by T and Lt. The normal SA (NSA) was suggested through an example procedure inducing binder aging level similar to the RTFOtreated binder AV or Aq. Based on the NSA Aq level, lower, proper, or higher SA conditions were discovered from the existing SA guidelines. RESULTS : As Aq has excellent correlation with AV, the proper T and Lt for NSA as an example was suggested based on the AV of RTFOtreated binder to induce an Aq range of 19,000-25,000 min.℃. It was found that there were several problems in the existing guidelines in USA and Korea. These included lower T, shorter or longer Lt, and air blowing or stirring the mix during SA, which were not matched with the practical condition of loaded HMA mixtures that were short-term aged under hot temperatures in trucks. CONCLUSIONS : It was concluded that there are several problems in the current SA guidelines, which do not provide proper HMA temperature to mixtures for proper (modal) length of time. Therefore, these guidelines should be reevaluated carefully and revised based on the fundamental field SA principle. The NSA condition should be suggested using proper HMA T and modal Lt for better simulation of field SA practice.

PURPOSES : The use of reclaimed aggregate has been recently increasing with the increase in the amount of waste asphalt concrete. The application of these materials can reduce the properties of the asphalt pavement when compared with the case when recycled aggregate is not used. The objective of this study is to evaluate the performance of the asphalt mixtures with various mix ratios of reclaimed aggregate. METHODS : To measure the performance, the following tests using the mixtures prepared in accordance with the Korea Standards were conducted: Hamburg wheel-tracking test, third-scale model mobile loading simulator test, and dynamic modulus test. RESULTS : The test results of the Hamburg wheel-tracking test indicate that the water resistance was similar in each mixture and the plastic deformation resistance was good in the high-ratio reclaimed aggregate mixture. In the case of the third-scale model mobile loading simulator test, the plastic deformation demonstrated a high resistance in the high-ratio reclaimed aggregate mixture. The results were similar to those of the Hamburg wheel-tracking test; however, the cracking resistance was poor with a high recycled aggregate incorporation ratio. The dynamic modulus test results demonstrated excellent resistance to plastic deformation at a relatively high ratio of reclaimed aggregate admixture. The crack resistance was weakened when a high ratio of reclaimed aggregate mixture was used. CONCLUSIONS: As the reclaimed aggregate content increased, the plastic deformation resistance increased and the crack resistance decreased.

PURPOSES : Asphalt concrete pavement is damaged by various causes such as traffic and environmental loads. The distressed pavement should be maintained by various methods to provide a comfortable and safe pavement for the driver. This study evaluates the effect of adding a mixing procedure to enhance the mixture quality in the hot in-placement recycled asphalt pavement method, which is an asphalt-pavement maintenance method. METHODS: Various test methods such as Marshall stability and dynamic stability, were employed to estimate the recycled asphalt mixture with and without an additional mixing, using the hot in-placement recycled asphalt pavement method. RESULTS : The mixture samples used in this study were taken before and after the addition of the mixer in the hot in-placement recycled asphalt pavement method (HIR) at field construction sites in GongJu and JinJu in South Korea. The test results of both mixtures satisfied the asphalt-mixture standard specifications. CONCLUSIONS: This study confirmed that adding a mixer in the HIR method results in a well-mixed new asphalt mixture, rejuvenator, and reclaimed asphalt mixture.

This study evaluates the healing performance of asphaltmixture via microwaves heating method. Three different conductive additive types with various percentages were used, includingsteel wool fibers (SF), carbon fibers (CF), and graphite (G). The healing performance of asphalt mixture wasinvestigated through 10 damage-heal cycles of semi-circular samples using three-point bending test. The infraredcamera was also employed to recordthe heat transmitting in the test samples. The test results indicated that the healing effectiveness reduced after every healing cycles. It was found that microwave radiation provided great healing performance for almost all test samples. Among all types of conductive additives, SF mixtures achieved the highest healing performance with the healing level of higher than 50 percent after 10 cycles. However, microwaves heating may promote the faster aging of asphalt binder at late cycles which lead to the brittle behavior of samples. Finally, homogenous mixing is a critical factor to avoid the cluster formation of conductive additives which causes the overheating of asphalt binder.

OBJECTIVES : The objective of this research is to determine the moisture resistance of the freeze-thaw process occurring in low-noise porous pavement using either hydrated-lime or anti-freezing agent. Various additives were applied to low-noise porous asphalt, which is actively paved in South Korea, to overcome its disadvantages. Moreover, the optimum contents of hydrated-lime and anti-freezing agent and behavior properties of low-noise porous asphalt layer are determined using dynamic moduli via the freeze-thaw test. METHODS: The low-noise porous asphalt mixtures were made using gyratory compacters to investigate its properties with either hydratedlime or anti-freezing agent. To determine the dynamic moduli of each mixture, impact resonance test was conducted. The applied standard for the freeze-thaw test of asphalt mixture is ASTM D 6857. The freeze-thaw and impact resonance tests were performed twice at each stage. The behavior properties were defined using finite element method, which was performed using the dynamic modulus data obtained from the freezethaw test and resonance frequencies obtained from non-destructive impact test. RESULTS: The results show that the coherence and strength of the low-noise porous asphalt mixture decreased continuously with the increase in the temperature of the mixture. The dynamic modulus of the normal low-noise porous asphalt mixture dramatically decreased after one cycle of freezing and thawing stages, which is more than that of other mixtures containing additives. The damage rate was higher when the freeze-thaw test was repeated. CONCLUSIONS : From the root mean squared error (RMSE) and mean percentage error (MPE) analyses, the addition rates of 1.5% hydrated-lime and 0.5% anti-freezing agent resulted in the strongest mixture having the highest moisture resistance compared to other specimens with each additive in 1 cycle freeze-thaw test. Moreover, the freeze-thaw resistance significantly improved when a hydrated-lime content of 0.5% was applied for the two cycles of the freeze-thaw test. Hence, the optimum contents of both hydrated-lime and anti-freezing agent are 0.5%.

PURPOSES: It is theoretically well known all over the world, that porous hot mixed asphalt (HMA) with hydrated Lime improves moisture and rutting resistance, and reduces pothole occurrence frequency, as well as the life cycle cost (LCC). METHODS : Addictive in the two different formations of the liquid anti-stripping Agent and powder Hydrated-Lime was applied in this investigation in order to obtain relatively clear results according to their types and conditions. Firstly, the moisture conditions were set, and applied to the porous HMA mixtures with hydrated lime (anti-stripping agent). Next, it was followed by a non-destructive test with the application of three freeze-thaw cycles, which were individually carried out thrice to compare the results of the dynamic moduli. Lastly, the hydrated lime effect related to moisture sensibility to porous HMA has been verified through the analysis of the modulus results regarding the change rate of dynamic modulus per n-cycle. RESULTS: It is clear from this investigation, that the dynamic modulus is inversely proportional to the change in temperature, as the graph representing the rigidity of the thermorheologically simple (TRS) material showed gradual decline of the dynamic modulus with the increase in temperature. CONCLUSIONS: The porous HMA mixture with the anti-stripping agent (hydrated Lime) has been found to be more moisture resistant to freezing and thawing than the normal porous HMA mixture. It is clear that the hydrated lime helps the HMA mixture to improve its fatigue resistance.

PURPOSES: A tack coat has been utilized to increase the bond performance between the surface layer and base course (intermediate course) at various road pavement sites. This is similarly true in other nations. Based on this connection, the objective of the present study is to evaluate the properties of hot mix asphalt (HMA) mixtures with an RSC-4 or BD-Coat and determine the application rate of the tack coat. METHODS: The HMA specimens were manufactured using superpave gyratory compaction. The HMA mixtures were composed of a 5-cm thick surface layer and a 10-cm thick base course. An impact hammer resonance test (IHRT) and a static load shear test were conducted to evaluate the performance of the HMA mixtures with a tack coat. From these tests, the dynamic moduli related to the high-frequency resistance and interlayer shear strength (ISS) of HMA could be obtained. RESULTS: The results of the dynamic moduli of HMA are discussed based on the resonance frequency (RF). To check the accuracy of the IHRT, we conducted a coherence analysis. A direct shear test using the application of a static load test was carried out to evaluate the interlayer shear strength (ISS) of HMA. CONCLUSIONS: The maximum ISS was demonstrated at an RSC-4 application rate of 462 gsm, and the maximum dynamic modulus was demonstrated at an RSC-4 application rate of 306 gsm. By averaging the results of the ISS, the maximum ISS values were obtained when a BD-Coat application rate of 602 gsm was applied.

아스팔트 포장도로의 공용수명을 연장하기 위해 다양한 방법이 소개되었으며, 대표적인 방법으로 화학 적 개질제를 이용하는 방법과 격자형태의 토목섬유를 이용하는 방법이 있다. 화학적 개질제를 이용하는 방법은 아스팔트 바인더에 석유계(SBS 또는 SBR) 폴리머 입자를 중합하여 아스팔트 바인더의 점도를 증 대시킨 방법이다. 이 방법은 고온에서 아스팔트 혼합물의 소성변형 저항성에 유리한 효과를 나타내기도 하지만, 과다한 비용, 품질관리의 어려움, 혼합물 생산 온도 증가에 따른 에너지 비용 증대, 탄소 이중결 합 (C=C) 존재로 산소와의 반응성이 커서 고분자 망상구조를 조기에 상실하여 연화점이 낮아지는 점, 및 저온에서 재료의 취성증대로 인한 균열 가능성 문제 등을 단점으로 제기할 수 있다. 또 다른 예로써 격자 형태의 토목섬유를 이용하는 방법은 하부층으로부터의 반사균열 저항에 유리한 효과를 나타내지만, 시공 과정이 복잡하여 공사기간이 길어지고, 공사비가 상승하며, 또한 상부 표면으로부터 3-5㎝ 표층 내부에 서 가장 큰 집중응력 또는 전단변형이 발생하는 경우에는 이에 대해 대응할 수 없다는 맹점이 있다. 최근 합성 또는 비합성 섬유를 활용하여 가열 아스팔트 혼합물의 인성 증대를 통해 소성변형 또는 균열 등에 대한 저항성능을 향상시키기 위한 연구가 활발하게 수행되고 있다. 미국의 경우, 열가소성 또는 열 경화성 섬유를 동시에 혼입하여, 열가소성 섬유와 아스팔트 바인더의 바람직한 상용성으로 작업성 개선 및 열경화성 섬유의 인성증대 특성을 활용하여 아스팔트 바인더의 고분자 개질 없이도 그에 상응하는 개 선된 물리적 성능을 발현하는 섬유보강 혼합물을 개발하여 적용하고 있다. 그러나, 상기와 같은 섬유를 아스팔트 혼합물에 적용할 경우, 혼합물 생산시 섬유의 효과적인 분산을 해결해야하는 최우선 과제로 판 단할 수 있다. 본 연구에서는 상기와 같은 문제를 해결하기 위한 것으로, 경제적이면서 우수한 물리적인 특성을 가지는 75μm이하의 미세 유리섬유 파분을 펠렛 또는 입자 형태로 한 석분 치환용 보강재와 여러 가닥의 유리섬유를 폴리프로필렌과 같은 수지재로 코팅하여 다발형으로 만든 섬유 보강재를 혼합한 구성 으로 이루어져, 비중이 일반 골재와 유사하게 되어, 간편하게 현장 플랜트에서 투입이 가능하다. 가열 아스팔트 혼합물 내에서 섬유의 뭉침 현상이 없는 유리섬유 복합 보강재료와 이를 이용한 가열 아 스팔트 혼합물의 Hamburg Wheel 시험 및 간접인장강도 시험결과, 유리섬유 치환·보강 혼합물의 경우, 20,000회 재하동안 평균 3.5mm의 매우 작은 변형을 나타낸 반면, 일반 혼합물의 경우, 5,000회 이전에 파괴되었으며, 간접인장강도의 경우, 건조 및 동결융해 시편 모두에서 유리섬유 보강 시편이 2배 이상의 향상된 강도 증진 효과를 나타내어, 유리섬유 보강 아스팔트 혼합물의 현장 적용시, 우수한 공용수명 증 진 효과를 기대한다.

PURPOSES: This study is to investigate the Hot In-Place recycling asphalt mixture in Korea using field produced materials. METHODS: Hot In-Place reclaimed asphalt mixture was investigated to evaluate the mixture properties based on various test results such as Marshall Test, Indirect Tensile Test, TSR, and Wheel Tracking Test. These test values were compared with domestic standard specification. RESULTS: The result of the laboratory experiment indicates that the Hot In-Place Reclaimed(HIR) asphalt mixture produced at the field constrution site was satisfied all of the test criteria such as Indirect tensile test, Marshall and TSR test, and wheel tracking test. During the test, the research team found that current HIR system is required an extention of mixing time to improve quality and to reduce variation of sample to sample. Although the current HIR mixture was passed the test criteria, there is a potential capability to enhance the mixture properties as extend mixting time. CONCLUSIONS: Based on these laboratory test results, It would be concluded that domestic HIR mixture's properties were satisfied all standard specification related with evaluation of recycling asphalt mixtures. Based on this case study result, there is a chance to save construction cost and increase the usage of reclaimed asphalt concrete in the future.

아스팔트 콘크리트 포장은 많은 곳에서 쓰여지는 것을 볼 수 있다. 도심지 도로, 고속도로, 주차장, 그리고 자전거 도로에 이용되고 있다. 사용재료의 성질을 보면 비교적 온도에 민감한 재료로 분류될 수 있다. 여름철에는 유연한 성질을 보여주고 있고 겨울철에는 강성의 성질을 보여주고 있다. 포장관리의 측면에서는 손상된 부분에 대해서는 비교적 쉽게 보수할 수 있는 점을 들 수 있다. 그리고 일반적인 아스팔트 포장의 색깔은 검정과 회색으로 구성되어 있음을 알 수 있는데 이들 아스팔트 포장은 다양한 칼라로 표현할 수 있는데 크게 두 가지의 방법으로 칼라포장을 시공할 수 있다. 첫 번째로 시멘트 형태의 칼라도료를 아스팔트 포장에 칠하는 방법으로 도료가 벗겨지는 것을 방지하기 위해서는 주위를 요하는 시공이 요구된다. 두 번째의 방법은 칼라 첨가제를 이용한 칼라 아스팔트 시공을 들 수 있다. 본 방법은 원하는 아스팔트 층에 대해 전체적으로 색을 입히는 방법으로 장점으로는 일반적으로 쓰고 있는 혼합물 배합설계를 이용할 수 있다는 점이다. 단점으로는 주로 빨간색 그리고 갈색으로만 색깔을 표현할 수 있는 것이다. 본 연구에서는 제시된 첨가제를 이용하여 영구변형, 수분민감도 및 피로균열에 대한 공용성을 평가하고자 한다.