PURPOSES : This study aims to develop drainage minor-structure materials using asphalt mixtures, and to apply construction methods. METHODS : The AP-5, 120-150A, and 150-200A binders were adopted to select the optimal asphalt binder for the domestic application of asphalt concrete in curb construction. The mixture design of asphalt mixtures has applied the standard for evaluating asphalt curb mixtures in Korea. Test construction utilized asphalt curb equipment to evaluate asphalt mixtures, according to the type of asphalt binder. RESULTS : The results of the asphalt mixture design indicated that the optimum asphalt content was determined at 2–3% air void for each type of asphalt binder, and the quality of the asphalt mixture applied with asphalt curb binder was excellent. In addition, the quality difference was significant, depending on the temperature of the asphalt mixture at each phase of the asphalt curb construction. CONCLUSIONS : Asphalt curb construction using asphalt materials has a large impact on the quality, depending on the temperature of the asphalt mixture, therefore management at the appropriate temperature is important when applying it to the site. Further research is also required on the production, transportation, and dedicated equipment of asphalt mixtures.

PURPOSES : The purpose of this study is to evaluate the asphalt binder properties using FTIR analysis. METHODS : To investigate the chemical properties of asphalt binders, FTIR tests were performed. Recently, FTIR was used for quantification under various aging conditions. Three scans were averaged for each sample within the wavenumber range of 4000 to 400 cm-1, at a resolution of 4 cm-1 (default Simatech software settings). To determine the oxidation of the extracted asphalt binder and the remaining TCE solution in the extracted asphalt binder, the penetration test was adopted and compared. To track the changes in the chemical composition of the aged bitumens, the ATR spectrum of each sample was analyzed, both qualitatively and quantitatively. The qualitative analysis involved identifying characteristic absorption peaks for the functional group of interest, such as polymer components, carbon and sulfur oxidation products, and polar aromatics. RESULTS : The asphalt binder is easily oxidized in air during FTIR testing. To reduce the oxidization of the asphalt binder, the asphalt binder must avoid air contact to measure constant results. Sometimes, the extracted asphalt binder has a residual solvent (TCE), which affects the evaluation of the extracted asphalt binder rheology, such as absolute viscosity and penetration testing. To solve this problem, the research team adopted the FTIR test method. First, the TCE was scanned with FTIR to obtain the chemical characteristics of TCE. After that, the extracted asphalt binder was scanned and the FTIR spectra were compared with those of TCE. If there is a TCE in the extracted asphalt binder, a typical peak was found in the spectrum. Thus, it is possible to estimate the content of the TCE remaining in the extracted asphalt binder via the FTIR test method. CONCLUSIONS : It is possible to evaluate the aging of asphalt binder through FTIR analysis used for the analysis of the chemical structure of asphalt. In addition, during FTIR analysis, the sample is required to avoid air contact to obtain accurate results. FTIR analysis was conducted to confirm whether the solvent (TCE) remained in the extracted asphalt binder and it was confirmed that the penetration increased by a factor of two when the solvent remained. This suggests that it is difficult to control the quality of the asphalt mixture by controlling the amount of recycled additive, as well as the aging of the extracted asphalt binder.

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.

PURPOSES: Using recycled asphalt materials (called Reclaimed Asphalt Pavement: RAP) from existing asphalt pavement layers in newly constructed asphalt pavement is an essential option not only for lowering the construction budget but also for mitigating environmental pollution for society. For this reason, many pavement agencies in South Korea, the USA, and Canada have observed the effect of RAP on conventional asphalt pavement to evaluate and set proper material specifications and addable amounts. In this paper, effect of recyclable material on low-temperature performance of asphalt materials was investigated with two different mechanical tests. Among the recyclable material sources, RAP and Taconite Aggregate (TA), which is mainly produced in northern Minnesota (USA), were considered. METHODS : To evaluate the low-temperature mechanical performance of a RAP mixture, two different experimental tests (In-Direct Tensile (IDT) low temperature creep test and Semi-Circular Bending (SCB) test) were considered. The mechanical parameters creep-stiffness, relaxation modulus, fracture energy, and fracture toughness were computed then compared. RESULTS: More brittle characteristics were observed with RAP-added asphalt mixtures compared to the conventional asphalt mixtures, as expected. However, the differences of computed mechanical performances were not significantly distinct for RAP mixtures compared to conventional mixtures when the RAP proportion was around 20%, and with the addition of TA up to 20%. CONCLUSIONS : It can be concluded that up to 20% of RAP addition (along with TA up to 20%) in a virgin asphalt mixture does not provide significant performance reduction. This addable proportion can be viewed as a successful minimum level when considering the addition of RAP to hot-mix asphalt (HMA). Moreover, applying TA with RAP could offer a successful alternative for asphalt recycling and the materials industry.

PURPOSES : Thermal cracking (also called low-temperature cracking) is a serious stress for asphalt pavement, especially in eastern South Korea, the northern USA, and Canada. Thermal cracking occurs when the level of thermal stress exceeds the corresponding level of low temperature strength of the given asphalt materials. Therefore, computation of thermal stress is a key factor for understanding, quantifying, and evaluating the level of low-temperature cracking resistance of asphalt pavement. In this paper, two different approaches for computing thermal stress on asphalt binder were introduced: Hopkins and Hamming’s algorithm (1967) and the application of a simple power-law function. All the computed results were compared visually; then the findings and recommendations were discussed. METHODS: Thermal stress of the tested asphalt binder was computed based on the methodology introduced in previous literatures related to viscoelastic theory. To perform the numerical analysis, MATLABTM 2D matrix-correlation and Microsoft Excel visual basic code were developed and used for the function fitting and value-minimization processes, respectively. RESULTS : Different results from thermal stress were observed with application of different computation approaches. This variation of the data trends could be recognized not only visually but also statistically. CONCLUSIONS: It can be concluded that these two different computation approaches can successfully provide upper and lower limits (i.e. boundaries) for thermal stress prediction of a given asphalt binder. Based on these findings, more reliable and reasonable thermal stress results could be provided and finally, better pavement performance predictions could also be expected.

PURPOSES : A geo-grid pavement, e.g., a stress-absorbing membrane interlayer (SAMI), can be applied to an asphalt-overlay method on the existing surface-pavement layer for pavement maintenance related to reflection cracking. Reflection cracking can occur when a crack in the existing surface layer influences the overlay pavement. It can reduce the pavement life cycle and adversely affect traffic safety. Moreover, a failed overlay can reduce the economic value. In this regard, the objective of this study is to evaluate the bonding properties between the rigid pavement and a SAMI by using the direct shear test and the pull-off test. The predicted fractural energy functions with the shear stress were determined from a numerical analysis of the moving average method and the polynomial regression method. METHODS : In this research, the shear and pull-off tests were performed to evaluate the properties of mixtures constructed using no interlayer, a tack-coat, and SAMI with fabric and without fabric. The lower mixture parts (describing the existing pavement) were mixed using the 25-40-8 joint cement-concrete standard. The overlay layer was constructed especially using polymer-modified stone mastic asphalt (SMA) pavement. It was composed of an SMA aggregate gradation and applied as the modified agent. The sixth polynomial regression equation and the general moving average method were utilized to estimate the interlayer shear strength. These numerical analysis methods were also used to determine the predictive models for estimating the fracture energy. RESULTS: From the direct shear test and the pull-off test results, the mixture bonded using the tack-coat (applied as the interlayer between the overlay layer and the jointed cement concrete) had the strongest shear resistance and bonding strength. In contrast, the SAMI pavement without fiber has a strong need for fractural energy at failure. CONCLUSIONS : The effects of site-reflection cracking can be determined using the same tests on cored specimens. Further, an empiricalmechanical pavement-design analysis using the finite-element method (FEM) must be done to understand the appropriate SAMI application. In this regard, the FEM application analysis and bonding property tests using cored specimens from public roads will be conducted in further research.

국내 고속도로 포장의 종류는 크게 콘크리트 포장과 아스팔트 포장으로 구분 할 수 있다. 현재 콘크리트 포장은 공용 중 노후화로 인해 서비스지수가 일정수준 이하로 낮아질 경우 다양한 보수공법을 적용하여 개량 및 유지보수를 시행하여 공용기간을 연장시키는 방법을 택하고 있다. 이러한 노후화된 콘크리트 포장에 대한 보수공법 중 아스팔트 덧씌우기 공법은 기존 콘크리트 포장 위에 아스팔트를 약 50∼80mm정도 덧씌우기하여 기존 콘크리트 포장체는 기층재로 표층재는 신설AP로 하는 복합단면형태이다. 이러한 복합단면은 소음저감, 평탄성확보 등의 장점과 함께 하부 콘크리트의 줄눈부 거동으로 인한 반사균열 발생이 가장 큰 단점으로 지적되고 있다. 본 연구에서는 복합단면포장에 있어 경계면 접합처리 방식이 반사균열 발생에 미치는 영향을 검토하고자 일반포설 구간과 택코팅 동시포설 구간에 대한 하부 콘크리트의 깊이별 온도 및 줄눈부 거동을 2016년 11월 17일부터 2017년 8월 7일까지 계측하여 분석하였으며 그 결과, 표 1과 그림 1과 같이 분석되었다.

고속도로 포장의 불량연장은 지속적으로 증가하고 있는 반면 예산한계, 성능 저하로 인하여 포장상태가 고객 기대수준에 미치지 못하고 있는 실정에 대한 대책의 일환으로 고속도로 유지보수에 적용하고 있는 다양한 종류의 포장공법과 재료에 대한 장기공용성 관측구간을 운용하고 있다. 국내 고속도로 장기공용성 관측구간은 포장층의 구성, 환경인자, 교통하중 등과의 상관관계를 고려하여 총 292개소를 선정하였으며 매년 기본조사(자동조사장비를 이용한 파손정량화 및 현장도보조사)와 정밀조사(구조적 상태조사, 소음 및 미끄럼저항성 조사, 코어채취를 통한 실내시험)등의 추적조사를 수행하고 있다. 본 연구에서는 주행쾌적성이 확보되고 구조적으로 오래가는 장수명 복합포장공법 도입을 위해 장기공용성 관측구간 중 콘크리트 포장 위 아스팔트 덧씌우기 구간의 하부포장형식에 따른 공용성 변화추이 분석을 통하여 기존 복합포장구간의 문제점 도출 및 장수명 복합포장공법의 타당성을 확인하고자 한다. 콘크리트 포장 위 아스팔트 덧씌우기 구간의 하부포장형식에 따른 공용성 변화추이 분석을 위하여 크게 CRCP 위 아스팔트 덧씌우기 구간과 JCP 위 아스팔트 덧씌우기 구간을 선정하여 하부포장형식 및 덧씌우기 재료에 따른 공용성 변화추이를 분석하였다. 분석 결과 그림 1 및 그림 2에서 보는 바와 같이 전체구간(AC구간 : SMA구간 + 개질 아스팔트 구간) 및 재료별 분류에서도 JCP 위 아스팔트 덧씌우기 구간에 비해 CRCP 위 아스팔트 덧씌우기 구간의 공용성이 우수한 것으로 분석되었다. 이는 콘크리트 포장 위 아스팔트 덧씌우기 구간에서 하부포장형식이 공용성에 크게 영향을 미치는 것으로 사료되며 CRCP위 아스팔트 포장으로 구성된 복합포장 형식의 구조적 타당성을 확인할 수 있었다. 그러나 현재 공용중인 CRCP 복합포장의 경우 CRCP구간의 유지보수 개념으로 시공되어 기존 하부포장과의 부착문제 및 반사균열에 의한 조기파손 등에 취약하며 장수명 복합포장과 단면 구성이 상이하기 때문에 현재 시험시공중인 구간의 장기공용성 관측구간으로의 편입 및 추적조사가 필요할 것으로 사료된다.