Owing to recent emphasis on global carbon-neutrality flows and the importance of resource recycling, the utilization of various liquid and solid additives— such as modifying additives, anti-peeling agents, warm-mix additives, and rejuvenators—to restore the function of aging asphalt has increased in the domestic ascon industry. These additives critically govern the overall performance of road pavements and are categorized into pre-mix types, which are mixed and supplied by refiners in advance, and plant-mix types, which are directly injected during the production process at the asphalt mixing plant, depending on the input method. The plant-mixing method adopted by most ascon plants in Korea involves the direct addition of additives to an asphalt binder weighing tank or mixer. However, the mixing time of this approach is less than one minute per batch, thus resulting in a nonuniform dispersion of the asphalt binder and additive at the molecular level. Accordingly, this study evaluates the performance of an asphalt-binder mixer designed and manufactured for use in asphalt mixing plants. The key experimental variable is mixing time. Binder samples are obtained at five time intervals (0, 1, 3, 5, 7, and 9 min)—where 0 min represents the unmixed state—to monitor changes in the binder characteristics. Scanning electron microscopy (SEM), absolute viscosity tests, and multiple stress creep recovery tests (MSCRs) are conducted for performance evaluation. The MSCR test precisely analyzed the rheological properties of the binder—which cannot be captured easily via viscosity measurements alone—by simulating high-stress conditions of 3.2 kPa that represent actual pavement loading. The SEM results indicate local additive aggregation in the 1- and 3-min stirring samples; however, visual analysis alone proved insufficient for comprehensively quantifying the dispersion state of the liquid additives. The absolute viscosity test indicates that the decline in viscosity decelerated after 3 min of stirring, thus suggesting a tendency to converge toward a steady state. The MSCR test results show that the rejuvenator diffused more evenly into the binder as the mixing time increased, thus effectively softening the asphalt; accordingly, the Jnr value, which represents nonrecoverable deformation under repeated loading, continued to increase while the elastic recovery rate decreased. This study experimentally demonstrates that the conventional 1-min mixing time used in existing asphalt mixing plants fails to fully exploit the additive’s performance potential while simultaneously increasing quality uncertainty. Although absolute viscosity measurements alone may suggest an optimal duration, evaluating the binder’s comprehensive rheological properties and statistical significance reveals that a minimum mixing time of 7 min is essential to achieve uniform additive dispersion and optimize performance.

ABSTRACT
ABSTRACT
1. 서론
2. 연구배경 및 목적
    2.1. 실험재료
    2.2. SEM 분석
    2.3. 절대점도 시험
    2.4. 아스팔트 바인더의 유변학적 특성 평가
3. 결과 및 고찰
    3.1. 혼합시간별 SEM 분석
    3.2. 절대점도 시험결과
    3.3. 아스팔트 바인더의 유변학적 특성 결과
4. 결론
REFERENCES

• 윤상혁(전북대학교 공과대학 토목공학과 석·박통합과정) | Youn Sang hyeok
• 장대성(전북대학교 공과대학 토목공학과 박사 후 연구원) | Jang Dae seong
• 임치수(전북대학교 공과대학 토목공학과 박사 후 연구원) | Lim Chi su
• 은윤기(전북대학교 공과대학 토목공학과 박사과정) | Eun Yun ki
• 이재준(전북대학교 토목공학과, 공업기술연구센터(RCIT) 교수) | Lee Jae jun Corresponding author