PURPOSES : The objective of this study is to evaluate the feasibility of applying properties of asphalt binder other than absolute viscosity (AV) to evaluate the rejuvenation level of the binder from reclaimed asphalt pavement (RAP) in recycled asphalt mixtures (RAMs). METHODS : The G*/sin and critical temperature (CT) for determining high performance grade by DSR, and the large molecular size (LMS) using gel-permeation chromatography (GPC) were measured simultaneously with the AV of two virgin asphalt binders (58–22 for RAM and 64–22 for normal mix) and recovered binders from a RAP and four RAMs. Based on mix design, 20%, 30%, 40%, and 50% recycled RAMs were prepared, and the deformation strength (SD) of the RAMs were measured. The AV, LMS, G*/sin , and CT were measured from the recovered binders from each RAM of the SD-tested specimens. Regression analyses were performed between the LMS and AV, G*/ sin and AV, and CT and AV to determine the correlation of each property with the AV. The feasibility of evaluating the rejuvenation level of the RMA binder using the three properties (LMS, G*/sin , and CT) was evaluated. Regression analysis was performed between SD and AV, and the feasibility of using SD instead of AV ≤ 5,000 poise (p) was analyzed to evaluate the rejuvenation level of the RAM. RESULTS : The AV, LMS, G*/sin , and CT of RAM binders increased with the recycling ratio. Mixes with recycle ratios of 20% and 30% satisfied the AV ≤ 5,000 p criterion, unlike mixes with higher recycle ratios. The regression analysis results showed that the R2 values between the LMS and AV, G*/sin and AV, and CT and AV exceeded 0.96. Since these regressions showed extremely high R2 values, it can be inferred that the estimation of binder rejuvenation level using the LMS, G*/sin and CT, i.e., instead of the AV criterion, is applicable. Because SD exhibits high correlation with the binder stiffness, and the regression between SD and AV indicated R2 > 0.98, SD can be applied instead of the AV for binder rejuvenation level estimation. The main advantage of using the LMS and SD is to estimate the binder rejuvenation level without recovering the binder from the mix. CONCLUSIONS : For the binder rejuvenation level estimation of recycled mixes, it is concluded that the LMS by GPC and G*/sin and CT by DSR, and SD can be applied instead of the AV criterion. However, since this study was performed using limited materials, further studies involving many other materials may be performed to generalize the current conclusion.

PURPOSES : The purpose of this paper is to develop an evaluation method for aged reclaimed asphalt pavements using RAP mortar specimen and FTIR method. METHODS: To evaluate the low-temperature behavior of aged reclaimed asphalt pavements, an indirect tensile strength test was adopted with an RAP mortar specimen. The RAP mortar specimen without a rejuvenator was fabricated with two fine aggregate types as a function of passing sieve sizes. The fabricated RAP mortar specimen was frozen for 24 h at -20℃. The indirect tensile strength was measured as a function of different absolute viscosities. The indirect tensile strength and displacement were varied as functions of the dosage of the rejuvenator. The spectroscopy analysis of four asphalt binders was performed under attenuated total reflection. The four asphalt binders comprised of a virgin binder, two extracted RAP binders, and a mixed virgin and extracted RAP binder. To evaluate the oxidation of the binder, the carbonyl index was calculated. RESULTS : The four extracted RAP binders were measured with an extremely wide range of absolute viscosity from 30,000 poise to 170,000 poise. The indirect tensile strength of the RAP mortar decreased as the absolute viscosity increased. This means that at lower temperatures, the indirect tensile strength can indicate the oxidation of RAP. Also, the indirect tensile strength and displacement changed sensitively as the dosage of the rejuvenator was changed. Based on the FTIR principle, a good relation was observed between the dosage of the rejuvenator and the FTIR absorbance peak. It can be used to estimate the dosage of the rejuvenator in hot reclaimed asphalt mixture. Also, the carbonyl index of the RAP binder was calculated to evaluate asphalt oxidation using the FTIR principle. CONCLUSIONS : There is a good relation between the indirect tensile strength of RAP mortar and its absolute viscosity. This indicates that RAP mortar can be used to estimate the properties of aged RAP. Also, the usage of rejuvenator can be evaluated with both the indirect tensile strength and FTIR absorbance peak. The carbonyl index can be used to predict asphalt oxidation.

PURPOSES: Using recyclable materials in asphalt pavement industry is one of the essential tasks not only for saving construction budgets but also for mitigating environmental pollutions. Over the past decades, several efforts have been made by road maintenance agencies to incorporate various recyclable materials into virgin asphalt paving mixtures. As a result, reclaimed asphalt pavement (RAP), which consists of old pavement material was selected as one of most widely used recyclable materials. In this paper, the effects of using different amounts of single-recycled RAP (SRRAP) and double-recycled RAP (DRRAP) on the low-temperature characteristics of asphalt mixtures were investigated. METHODS: To evaluate the low-temperature characteristics of SRRAP and DRRAP mixtures, two experiments, the bending beam mixture creep test and semicircular bending fracture test were performed. The experimental parameters: creep stiffness, m-value, thermal stress, critical cracking temperature, fracture energy, and fracture toughness were computed then compared. RESULTS : RAP mixtures (SRRAP or DRRAP) showed lower mechanical performance compared with conventional asphalt mixtures. The differences became distinct with increased RAP addition. However, the performance differences between SRRAP and DRRAP mixtures were not significant in all cases, which indicate the possible application of re-recycling technology (DRRAP) in the asphalt pavement industry. CONCLUSIONS : The addition of RAP to virgin asphalt can mitigate low-temperature performance despite the improvement in fracture performance observed in some cases. Therefore, using RAP (SRRAP or DRRAP) mixtures on inter or sublayer construction, but not on the surface layer, is recommended. Moreover, the possibility of applying double-recycling technology in asphalt pavement industry can be introduced in this study because not significant performance differences were found between SRRAP and DRRAP mixtures especially at low temperature.

Generally, remarkable amount of Reclaimed Asphalt Pavement (RAP) is produced annually by pavement surface cutting: due to early distress on asphalt pavement layer and remodelling construction work on existing aged-asphalt pavement layer. In South Korea, various types of research on proper and optimized RAP material development and field application (including evaluation process) are performed because of increase of existing road maintenance budget and technology. The major material of RAP is recycled aggregate coated with aged asphalt binder. The advantages of application of RAP on asphalt pavement are recyclable material proportion can be increased due to re-using of existing aggregate and eco-friendly characteristics. However, more amount of specific additives (and/or agent) needs to be implemented during production with increase amount (and/or proportion) of RAP on virgin asphalt material inevitably. This action is highly needed because of recovery of penetration grade and absolute viscosity of final production. The required amount of additives tends to be vary based on different aging level of RAP, amount of RAP and types of virgin asphalt binder. But it is well known that required amount of additives tends to be increased with increase of RAP proportion compared to virgin asphalt mixture. Moreover, it also should be known that mere increase of additives on RAP asphalt can provide negative effect on its quality and mechanical performance. In this study, high penetration grade asphalt binder: contains between 200 and 300 level of penetration grade, was used for producing RAP asphalt mixture with small amount of required additive application. After the sample preparation, various characteristics of RAP asphalt were analysed with extensive experimental work.

The aged asphalt binder included in RAP due to the oxidative aging, repeated vehicle load, climate process affects to the recycled asphalt mixture property and performance (stripping, port hole and premature cracking initiation) after paving. The rejuvenator commonly is used to recover the aged binder in hot mix asphalt (HMA) containing RAP; the effect of rejuvenator in HMA had been proven according to many studies for over the past several decades. Also, there are many methods for using RAP in asphalt mixture in aspects of HMA, cold asphalt mixture (CMA) and worm mix asphalt mixture (WMA), and a foamed asphalt mixture is one of them. Employing the foamed asphalt manufacturing technology, the content of RAP in recycled asphalt mixture can be increased more. The objectives of this study are to evaluate of rejuvenator influence on foamed asphalt mixture using 100% RAP based on strength change of test sample and stiffness change of recovered binder from RAP and specimen. As the results, when rejuvenator was added to make foamed asphalt mixture, MS and ITS values decreased clearly as compared with the foamed asphalt mixture without rejuvenator use. The use of rejuvenator up to 6% showed a tendency of the decrease of strength and stability remarkably. The use of rejuvenator over 6% did not decrease the strength and stability. DSR test results, the use of rejuvenator in making a foamed asphalt mixture using 100% RAP showed a recovery effect of the foamed asphalt mixture. And recovered binder from the specimen that was made adding the 6, 12 and 18% rejuvenator showed lower stiffness obviously compared to the recovered binder from RAP adding same dosage of rejuvenator.

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 purpose of this study is to estimate the optimum content of an inorganic additive for cold-recycled asphalt mixtures and evaluate its performance. METHODS: An indirect tensile test, a tensile-strength ratio test, and an indirect tensile-fatigue test were conducted on cold-recycling asphalt mixtures with various additives. RESULTS: The laboratory performance tests indicated that granulated blast-furnace slag mixed with inorganic and cement activators provided optimum performance. The performance results of the cold-recycled asphalt pavement were similar to the inorganic and cement activators’ performance in terms of the indirect tensile strength, tensile strength ratio, and indirect tensile-fatigue test. CONCLUSIONS : Overall, the performance of a cold-recycled asphalt mixture using inorganic additives and emulsion asphalt was comparable to a warm-recycled asphalt mixture. However, more experiments aimed at improving its performance and studying the effect of the inorganic additives must be conducted.

본 연구는 노후된 폐아스콘으로부터 폐아스팔트를 추출하여 ASTM방법을 이용해서 폐아스팔트의 화학적 조성을 성분별로 분리하고, 이들을 신제아스팔트의 구성성분과 비교하여 노후시 변화하는 성분들을 파악하였다. 이러한 분석결과를 토대로 폐아스팔트의 성상복원을 위한 재생첨가제를 제조하여 재생첨가제를 10%, 20% 첨가했을 때 폐아스팔트의 복원정도를 침입도$(25^{\circ}C)$, 신도, 연화점, 점도의 네 가지 시험을 수행하여 폐아스팔트의 물성 변화 특성을 고찰하였다. 연구결과에 의하면 아스팔트의 노화시 아스팔텐의 함량이 하고, 방향족성분의 함량이 감소함을 알 수 있었고, 증가한 아스팔텐의 함량을 줄여주기 위해 아스팔트의 방향족 성분자 화학적으로 비슷한 아로마틱기유를 사용하여 재생첨가제를 제조했다. 그리고 제조된 재생첨가제를 노화가 진행된 폐아스팔트에 무게 비로 20% 첨가했을 때, 신제아스팔트 (AP-3)와 유사한 정도로 성상이 복원됨을 확인할 수 있었다.