In order to prevent early distress in asphalt pavement and save on subsequent operational and maintenance costs, modifying asphalt is an effective approach. Styrene–butadiene–styrene (SBS) block copolymers, due to their excellent physicochemical properties, have become a mature and widely used asphalt modifier. Carbon nanotubes (CNTs) possess advantages such as a large specific surface area and high modulus, which, when incorporated into asphalt, can enhance its deformation resistance. To analyze the effect of incorporating CNTs on SBS-modified asphalt (SBS-A), this study analyzed the influence of different CNT concentrations on the high and low-temperature performance and aging properties of SBS-A through penetration, softening point, ductility, dynamic shear rheometry, and short-term aging tests. The optimal CNT concentration was determined to be 1.0%. Furthermore, the changes in the modified asphalt during the aging process were analyzed using infrared spectroscopy.

PURPOSES: The study objective was to evaluate rheology and physical properties of SBS-modified warm-mix asphalt (WMA) binders in comparison with hot-mix asphalt (HMA) binders. METHODS : Four different SBS polymers were used to prepare polymer-modified asphalt (PMA) binders, and three different warm-mix additives (WAD) were used to prepare a total of 12 WMA PMA binders. The kinematic viscosity was measured at 115, 135℃. The PG was determined using DSR and BBR. The pass/fail (P/F) temperatures for high and low PG grading were evaluated for HMA PMA and WMA PMA binders. RESULTS: PG 76-22 binders could be prepared by modifying the base binder (PG 64-22) using 4.5 wt% of SBS. The kinematic viscosity (KV) of SBS PMA was increased by 3 times higher than that of base asphalt. The SBS PMA with WAD showed 10% lower KV than that of the normal SBS PMA at 115℃ The high P/F temperatures showed almost no difference between HMA PMA and WMA PMA binders. The high P/F temperature showed very high correlations with KV (R2 > 0.97). The result of SBS modification caused increase of low P/F temperature by 2.7℃ on average. CONCLUSIONS : Since the PMA with WAD showed 10% lower KV than normal (HMA) PMA at 115℃, reducing PMA mixture temperature down to a WMA level was possible in this study. The higher KV binders showed the higher P/F temperature. There was almost no change in high P/F temperature due to the use of WAD. The SBS PMA, showing an increased low P/F temperature, might show somewhat poorer performance at low-temperature, even though the lower PG grade was staying at the same level, i.e., -22℃.

골재의 입도에 따른 SBS 개질 아스팔트 혼합물의 점탄성 물성 및 피로공용 특성을 소개하였다. 아스팔트 바인더와 혼합물의 열역학적 거동분석을 위해 DSR 시험과 일축인장 크립시험을 실시하였다. 골재의 입도와 SBS 개질재가 피로공용성에 미치는 영향을 평가하기 위하여 7종의 아스팔트 혼합물에 대해 일축인장 피로시험을 실시하였다. DSR 및 일축인장 크립시험결과, 골재의 입도에 관계없이 SBS 개질 아스팔트 혼합물이 일반 아스팔트 혼합물에 비해 고온에서 소성변형에 대한 저항성이 큰 것으로 나타났다. Superpave 아스팔트 바인더 규격의 피로인자 $G^*sin\delta$는 아스팔트 혼합물의 피로 공용성 평가에 사용하기에는 부적절한 것으로 사료된다. 일축인장피로시험결과, 골재의 입도(밀입도, Superpave입도, SMA입도)에 관계없이 SBS 개질 아스팔트 혼합물이 일반 혼합물에 비해 약 10배 이상 피로수명이 큰 것으로 나타났다. 장기노화후의 경우에 있어서도 SBS 개질 혼합물의 피로수명이 일반 혼합물에 비해 높게 나타났다. 골재의 입도변화는 SBS 개질재에 비해 피로공용성에 미치는 영향이 적었다. SMA 혼합물에 첨가한 셀룰로오스 섬유는 혼합물의 점탄성 물성이나 피로공용성에 미치는 영향이 미미하였으나, Draindown을 방지하는 데는 효과적이었다. SMA 입도에 SBS 개질아스팔트를 사용할지라도 Draindown 방지를 위해서는 셀룰로오스 섬유를 첨가할 필요가 있을 것으로 사료된다.