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 aims to determine whether machine learning techniques based on the results of chemical analysis experiments can be rationally applied to evaluate the aging of various asphalt binders used throughout the country. METHODS : We conducted chemical experiments such as FT-IR, H-NMR, C- NMR, and GPC for the three-stage aging levels of eight types of asphalt binders used in the country and utilized two artificial neural network models to determine valid chemical experimentation and conditions for the use of neural modeling through predictions. RESULTS : The M-prop model, which combined the findings from each neural network model into a single artificial neural network model, demonstrated superior predictive performance compared with the M-base model, which assessed aging using two cluster layers. In addition, the minimum amount of data required to achieve 100% predictive accuracy for the target asphalt binders, regardless of the artificial neural network model, was 18, and the amount of training data decreased to less than 50%. CONCLUSIONS : The predictive accuracy of the aging of asphalt binders was significantly enhanced when GPC data was used, indicating that GPC should be prioritized in evaluating the aging of asphalt binders.

PURPOSES : The objective of this study is to analyze the significance of binder aging in a hot-mix asphalt (HMA) mixture in an insulated camber for a long duration for repair works, where the absolute viscosity level and service life reduction (SLR) are assessed based on the haul time, as well as to suggest a methodology for reducing the aging level. METHODS : Because the HMA mixture is stored in an insulated box carriage at high temperature for repair works, if the binder in the mix is severely oxidized, then the repaired pavement will not exhibit a long service life. Therefore, the 13-mm dense-graded HMA mix with PG64-22 was aged in an oven at 160 °C for 1, 2, 4 and 8 h to evaluate its aging level. Gel-permeation chromatography was performed on the mixture particle without binder recovery to measure the large-molecular size ratio, from which the estimated absolute viscosity (EAV) was computed using a best-fit regression model. The SLR values of aged and repaired mixes were estimated to determine the amount of deterioration in the mixes caused by severe aging. Hydrated lime (HL) was introduced into the mix at a ratio of 1.5 wt% of the total mix. The aging level and SLR were compared with those of the repaired mix without HL. RESULTS : The binder EAV of the HMA mix increases significantly with the mixture aging duration. In particular, the binder EAV level of a 4-h aged mix is similar to the asphalt viscosity level of a pavement with approximately 7 years of service life. The service life expressed based on the aging level is interpreted as the reduced service life of the aged mix, which is already oxidized before it is used. Meanwhile, the binder of an 8-h aged mix without HL aged significantly and its SLR is approximately 11 years. However, its aging level and SLR reduced significantly when HL. is incorporated. CONCLUSIONS : The binder aging level of the repaired mix increases significantly with its storage duration in a hot chamber for carriage. However, since the aging level decreases significantly by the incorporation of HL, the use of HL is highly recommended when preparing new mix for repair works to be performed in a hot-chamber for a long duration.

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 hydrated lime or other liquid anti-stripping agents (ASA) is the most common method of improving the moisture susceptibility of asphalt mixes. ASAs are also known to have an anti-aging effect, according to several researchers. Therefore, the use of ASAs is expected to enhance the stability of asphalt pavements. The purpose of this study is to investigate the anti-aging effect of ASAs that are found in the domestic market. METHODS : In this study, an asphalt binder and a mixture mixed with typical domestic solid and liquid ASAs were prepared and aged to evaluate the physicochemical changes. A liquid additive developed by a Korean oil refinery was used as the liquid ASA, and hydrated lime was utilized as the solid ASA. The aging process of the asphalt was determined in the laboratroy based on previous studies to simulate the aging process inh te field. RESULTS : The result of the laboratory experiment indicates that both the solid and liquid ASAs have an anti-aging effect. Moreover, the liquid additive performed relatively better than the hydrated lime. CONCLUSIONS : If ASAs have an anti-aging effect in addition to the anti-stripping function, it is expected to improve the stability of the asphalt pavement significantly. However, few studies have been carried out on the anti-aging effect of ASAs found in the domestic market. In this study, we conducted a fundamental study on the anti-aging effect to help in the selection and use of ASAs in the domestic asphalt-paving industry.

PURPOSES : Asphalt pavements are damaged by various causes, such as cracks, potholes due to climate, and traffic environment. Asphalt aging has a significant effect on cracks, which may also form potholes. The purposes of this study are to estimate the change in asphalt binder and mixture performance and to correlate the physicochemical changes of the asphalt binder and mixture performance with aging. METHODS : The aging process of the asphalt was determined in the laboratory, based on the methods used in previous studies. In terms of consistency (stiffness), crack-resistance performance, moisture susceptibility, SK investigated the binder part, and Shoreki investigated the mixture part depending on the aging time. RESULTS : The consistency (stiffness) and brittleness of both the asphalt binder and mixture tended to increase with aging. In particular, the crack-resistance performance of the asphalt binder (G*sinδ, ductility, and ΔTc) and mixture (flexural fatigue test and Cantabro test) deteriorated because of asphalt aging. Furthermore, the aging mechanisms (oxidation and polymerization) were identified based on the chemical structure analysis. CONCLUSIONS : It is confirmed that the aging affected the chemical composition change and the physical properties of the asphalt. Asphalt pavements are significantly affected by the aging characteristics of the binder. It is concluded that the crack-resistance performance of the mixture decreases with aging due to these physical and chemical changes.

PURPOSES: The objective of this study was to investigate the effect of short-term aging level on the moisture resistance of a dense-graded asphalt mixture by measuring its deformation strength ratio (SDR). METHODS : Three short-term aging (STA) durations (1, 2, and 4 h) at two different temperatures (160℃ and 180℃) were used for the normal dense-graded hot-mix asphalt (HMA) mixtures prepared using PG 64-22 asphalt and 13mm aggregate with and without hydrated lime (HL). The specimens were prepared using a gyratory compactor, after each STA, to achieve a WC-1 gradation as defined by the Korean guide. The SDR was measured after freezing-and-thawing (F-T) conditioning, and submerging the specimen into water at 60℃ for 72 h. RESULTS: The results indicated that the moisture resistance decreased with the increase in STA duration. After STA at 160℃ and 180℃, the SDR values, measured after F-T treatment, or after submerging into 60℃ water for 72 h, decreased with the increase in STA duration. However, when HL was used in the same asphalt mixtures, the SDR improved, for identical STA conditions. Therefore, the moisture resistance of the asphalt mixture was affected by the short-term aging duration, and decreased with the increase in aging duration. However, HL effectively retarded aging, and the moisture resistance, as indicated by the SDR, improved in the HL-added mixes, which had aged lesser than the normal mixes. CONCLUSIONS : It was concluded that the moisture resistance of the asphalt mixture decreased with the increase in aging level, and hydrated lime was effective in preventing the degradation of the moisture resistance by reducing the age-hardening of the binder. However, since this study used a limited range of materials, further studies using more materials are required to reach a more generalized conclusion.

PURPOSES: This study evaluated the effect of fog seal treatment utilizing an agricultural oil-based asphalt concrete sealant (ABCS) on the long-term performance of an asphalt pavement. METHODS: Fog seal treatment using ABCS was applied on 800 m of the pavement section in the test section with a total length of 2,400 m; the remaining pavement section was not considered for this treatment. A series of laboratory and field tests were conducted on both sections, including a Marshall stability test, penetration test, viscosity test, skid resistance test, and pavement surface macrotexture test. In addition, the pavement condition index (PCI) was determined 8 years after the ABCS application to evaluate the effect of the ABCS treatment on the pavement’s long-term performance. RESULTS : The ABCS-treated section exhibited a PCI of 75, whereas the non-treated section exhibited a value of 64. Furthermore, a MicroPAVERTM‚ pavement management system determined that the pavement deterioration rates (i.e., drops in PCI) were 3.6 and 5.1 per year for the ABCS-treated and non-treated sections, respectively. CONCLUSIONS : The results of the series of laboratory and field tests revealed that the ABCS treatment increased the pavement performance life by approximately 3.5 years.

아스팔트 혼합물이 운반·대기 중에 단기노화(short-term aging: STA)되는 것은 잘 알려진 사실이며 노화정도는 혼합물의 온도가 높음에 따라 그리고 시간이 길어짐에 따라 지수 함수적으로 증가되는 것으로 알려져 있다. 또한 같은 온도와 시간에 같은 바인더, 골재 및 입도를 사용한 같은 혼합물이라도 사용되는 첨가제의 종류에 따라 노화도에 차이가 난다. 그리고 혼합물의 종류에 따라서도 노화도에 차이가 큰 것으로 알려져 있다. 따라서 본 연구에서는 박리방지제(anti-stripping agent: ASA)의 종류와 혼합물의 종류에 따른 노화도의 차이를 비교분석 하였다. ASA로는 박리방지효과가 우수한 분말의 소석회와 액상 ASA를 비교하였다. 혼합물은 밀입도 아스팔트 (dense-graded asphalt: DGA) 표층용 혼합물과 쇄석 매스틱 아스팔트 (stone mastic asphalt: SMA) 혼합물을 비교하였다. 노화도는 아스팔트 노화의 척도로는 가장 많이 쓰이는 절대점도(absolute viscosity: AV)를 이용하였다. STA 온도와 시간에 따른 AV의 차이를 STA 처리된 혼합물로부터 추출·회수하여 60℃에서 측정하였다. 시험결과 같은 온도와 시간으로 STA 처리된 혼합물에서 소석회가 사용된 혼합물의 노화도가 월등히 낮았으며, 혼합물의 종류로는 SMA 혼합물의 노화도가 DGA 혼합물보다 낮게 나타났다. 이는 소석회가 박리방지효과 뿐만 아니라 노화억제 효과가 크기 때문이며, SMA는 바인더 함량이 높아 골재를 피복한 아스팔트 필름의 두께가 두꺼워 노화도가 적게 나타난 것으로 판단되었다.

PURPOSES: This study aims to show the difference of the binder aging level in the hot-mix asphalt (HMA) mixture after short-term aging (SA) under different aging conditions, such as mixture temperature and duration in hour. METHODS: Three SA times (i.e., 1 h, 2 h, and 4 h) at two temperatures (i.e., 160℃ and 180℃) were used for the normal mixtures prepared using a PG64-22 asphalt. The field long-term aging (LA) was simulated by applying the same LA procedure (65 h at 110℃) to all compacted specimens, prepared at the air void of 7% using each SA-treated mixture, in a convection oven. The binder aging level was measured in terms of large molecular size by gel-permeation chromatography (GPC) from the mixture and the absolute viscosity (AV) from the recovered binder. The aging levels were evaluated using those two properties after SA and LA, and then compared based on the normal SA (NSA) mixture (1 h at 160℃). The service life reduction caused by SA in various conditions was estimated based on the aging level of the field cores from different locations in various service lives. RESULTS: The results of the laboratory evaluation indicated that the binder of the mixture, which was treated at longer SA time and higher temperature, showed a significantly higher aging level than the NSA mixture. The binder aging level from a longer time, such as 2 h and 4 h SA, or at a higher temperature (180℃), were estimated to be similar to that of the mixtures, which had already been in field service for several years. CONCLUSIONS : The HMA mixture should be produced at a moderate temperature, such as 160℃, and placed within a limited hauling and queuing time to avoid a significant short-term aging of the binder before placement in the field pavement. The SA for a longer time at a higher temperature than the NSA condition was found to be detrimental to the service life of the asphalt pavement.

최근 아스팔트 포장에 빈번히 발생하는 포트홀을 보수함에 있어서 포트홀 부위를 사전 가열하기 위하 여 적외선 방출 하향식 가스히터 장비(이하 적외선 가스히터)를 사용한 공법이 사용된다. 이 보수 공법은 포트홀 발생부위 일정 구역을 적외선 가스히터로 가열하고 가열된 부분을 굴착하고 신규 아스팔트 혼합물 (New asphalt mix: NAM)과 컷백아스팔트를 넣고 비벼서 고르게 펼친 후 다지는 것이다. 이때 최종 포 설된 혼합물(보수 혼합물, Repaired asphalt mix: RAM)은 기존 포트홀 부위에서 회수된 혼합물(RAP from pothole: RFP)보다 더 회생된 상태이어야 한다. 이를 위해서는 추가되는 NAM의 노화도가 낮아야 하고, 사전가열에 의해 표변부위가 타서 노화도가 심해지는 현상이 없어야 한다. 하지만 현재 대부분 현 장의 실정은 포트홀 보수 혼합물(RFP)의 노화특성, NAM의 운반 시간에 따른 단기노화도의 변화, 적회선 heating에 따른 표면 혼합물 노화 특성변화, 최종 보수된 혼합물(RAM)의 노화도 및 회생 정도 등에 대한 정보를 모른 상태로 수행된다. 이에 본 연구에서는 일부 포트홀에 실제 보수된 혼합물의 노화정보를 GPC 를 이용하여 수집하고 최종 포설된 RAM의 상태를 절대점도로 추정하여 평가하였다. 이를 위해 RFP의 노 화특성, 운반시간에 따른 NAM의 노화특성 변화, 사전가열의 영향 등이 RAP에 미치는 영향을 평가하고 필요한 개선 방안을 일부 제시하였다.

The effect of hydrated lime (HL) as an antioxidant (AO) for retarding aging of asphalt mixture using the large molecular size (LMS) of gel-permeation chromatogram (GPC) technique. A HL were used for preparing dense-graded asphalt (DGA) mixes to examine the effect of the HL on age retardation. The asphalt mixtures prepared with and without HL were aged artificially in two stages; the short-term aging (SA) for 1, 2, 4 hour at 160℃ and 180℃ on the loose mixes, and the long-term aging (LA) for 68 hours at 110℃ on the specimen. The specimen ( =100mm) of SA-treated mix was compacted to the air void of 7% using a gyratory compactor. The LMS values were used for estimating absolute viscosity (AV) for evaluating aging level and age- retardation effect in terms of viscosity. It was observed that the asphalt mixes which were short-term aged at 180℃ for over 2 hours were significantly aged, compared with the mix which was short-term aged for 1 hour at 160℃. It was also found that the use of 1.5% HL by wt. of mix resulted in a significant reduction of binder aging of SA and LA treated mixes. It was concluded that the HL did apparently have an effect of reducing aging of asphalt in the mixes after SA and LA. This result will be an applicable information for retarding aging of the field HMA mixture which is carried in the dump truck at hot temperature for 2-4 hours.

아스팔트는 잘 알려진 대로 골재와 혼합되고 아스팔트 포장으로 포설되어 공용되면서 2단계의 노화 (aging) 과정을 거친다. 첫째는 혼합물의 제조와 운반 및 포설 전까지 급속도로 일어나는 단기노화 (short-term aging) 과정이고 둘째는 이어지는 공용과정에서 시간이 지남에 따라 서서히 발생하는 장기 노화(long-term aging)과정이다. 이 두 과정은 연결되어 있으나 그 진행속도가 다르다. 국내의 경우 신 규바인더의 절대점도(absolute viscosity)가 약 1,800~2,000 poise인 60-80 아스팔트를 사용할 경우 단 기노화과정이 끝나면 약 5,000±1,000poise 정도로 높아진다. 그리고 이 혼합물의 포설되어 5~6년 정도 가 지나면 약 10,000±2,000poise 정도로 높아진다. 대게 이 정도의 노화가 바인더를 RTFO→PAV 처리 하여 얻어지는 점도이다. 이 상태에서 다시 5~6년이 지나면 아스팔트의 점도는 약 100,000poise 전후로 급속히 높아진다. 따라서 혼합물이 비벼지면서부터 단기노화를 거쳐 5∼6년 까지를 아스팔트 장기노화의 1단계, 그 이후를 2단계로 구분할 수 있다. 즉, 장기노화 1단계 까지는 점도 상 신규바인더의 약 5배, 그 리고 2단계는 신규바인더의 50배(1단계의 약 10배)의 노화가 진행 된다. 따라서 이의 예측 모델을 추정하 는 것은 쉬운 일이 아니다. 따라서 본 연구의 목적은 아스팔트 노화를 이와 같이 두 단계로 구분하여 각각 의 추정 가능 모델을 연구하는 것이다. 이를 위해서 아스팔트의 각종 특성인 stiffness (G*/sin δ), DSR pass/fail 온도, 침입도 등을 구하고 이들의 상관관계를 구하며, 노화아스팔트의 노화시간과의 상관관계 를 구하여 그 변화 양상을 보여준다. 그리고 노화 특성 지수로 가장 널리 사용되는 절대점도를 이용하여 2 단계별로 노화예측모델을 연구하고, 이 두 모델을 합성 도식화하여 제시함으로써 아스팔트의 노화에 따 른 점도 변화를 개념적으로 이해할 수 있도록 할 것이다.

아스팔트 포장의 경우 노화 (aging)로 인한 경화 (hardening) 및 취성 (brittleness) 증가로 인한 내구 성 약화는 균열 (cracking) 발생의 원인이 되고 수분침투에 의한 박리 (stripping)와 반복 윤하중은 포트 홀 (pothole) 등을 유발하게 된다. 이러한 손상은 최근의 이상 기온, 집중 호우 및 기록적 강설로 인해 가 속화되면서 유지보수에 소모되는 비용이 급격히 증가되고 있다. 아스팔트 혼합물은 제조와 운반 도중 단기노화 (short-term aging: STA)와, 시공 후 공용 중에 장기 적으로 노화(long-term aging: LTA)가 진행된다. 아스팔트의 노화는 혼합물의 제조와 운반 시 아스팔트 바인더가 고온의 골재와 혼합, 운반되는 짧은 시간 동안 얇은 박막 (thin film)의 형태로 공기 중에 노출 되고 산화와 휘발작용으로 단기간에 급격한 노화가 발생한다. 아스팔트의 노화로 인한 경화는 교통 개방 후에도 지속적으로 발생하며, 교통 하중에 의한 다짐으로 한계 밀도에 다다르는 동안 계속해서 진행된다 (아스팔트포장공학원론, 1999). 일반적으로 아스팔트 바인더의 상태는 노화 전 (original), 아스팔트 혼합물 제조 시 발생하는 단기노화 (주로 rolling thin film oven: RTFO으로 모사), 포설 후 공용 기간 중에 발생하는 장기노화 (주로 pressure aging vessel: PAV로 모사)로 구분할 수 있다. 아스팔트 혼합물의 노화는 노화 전 (no aging: NA), 아스팔트 혼합물의 제조 후 운반 과정에서 발생하는 단기노화 (STA), 공용 기간 중에 발생하는 장 기노화 (LTA)로 구분하여 고려한다. 본 연구에서는 노화 정도와 바인더 특성과의 상관성을 연구한 선행 연구 (kim et al. 1995, 2009)를 기초 로 하여 아스팔트 포장도로에서 공용기간에 따른 노화정도를 회수 바인더 특성과 상관성을 분석하여 평가하 였다. 노화 정도를 평가하기 위해서 현재 현장에 공용중인 도로에서 코어를 채취하여 분석하였다. 현장 코 어를 추출하여 바인더를 회수하고, 회수한 바인더를 침입도 (penetration), 점도 (viscosity), HP-GPC (High performance gel-permeation chromatography) 시험 결과 대형분자량 (large molecular size: LMS)의 비율, DSR (dynamic shear rheometer) 시험 결과 G* (복합전단계수) 및 sin δ(위상각)를 측정하 여 공용 기간에 따른 노화 정도를 평가하였다. 또한 다양한 조건에서 바인더 특성을 나타내는 특성치들과 공용기간에 따른 노화 수준을 가장 개관적으로 나타내는 특성치를 평가하였다.

PURPOSES: To characterize the aging effect on asphalt binder, dynamic shear modulus mastercurve of two typical asphalt binders are developed. METHODS: To develop dynamic shear modulus mastercurve, dynamic shear modulus at high temperature and creep stiffness at low temperature are measured by temperature sweep test and bending beam rheometer test, respectively. RESULTS: It is observed that the aging effect on asphalt binder can be clearly observed from dynamic shear modulus mastercurve and the mastercurve can be utilized to predict behavior of asphalt binder at wide range of temperature. CONCLUSIONS: It is confirmed that SBS 5% modified binder has more desirable mechanical property at low and high temperature as a pavement material comparing to PG64-22 binder and the mastercurve is an effective tool to evaluate the property of asphalt binder.