Yan Tianhao, Turos Mugurel, Le Jia-Liang, Marasteanu Mihai
Department of Civil, Environmental and Geo- Engineering, University of Minnesota, Twin Cities, Minneapolis, MN 55455, USA.
Materials (Basel). 2022 Sep 1;15(17):6060. doi: 10.3390/ma15176060.
Compaction of hot mix asphalt (HMA) requires high temperatures in the range of 125 to 145 °C to ensure the fluidity of asphalt binder and, therefore, the workability of asphalt mixtures. The high temperatures are associated with high energy consumption, and higher NOx emissions, and can also accelerate the aging of asphalt binders. In previous research, the authors have developed two approaches for improving the compactability of asphalt mixtures: (1) addition of Graphite Nanoplatelets (GNPs), and (2) optimizing aggregate packing. This research explores the effects of these two approaches, and the combination of them, on reducing compaction temperatures while the production temperature is kept at the traditional levels. A reduction in compaction temperatures is desired for prolonging the paving window, extending the hauling distance, reducing the energy consumption for reheating, and for reducing the number of repairs and their negative environmental and safety effects, by improving the durability of the mixtures. A Superpave asphalt mixture was chosen as the control mixture. Three modified mixtures were designed, respectively, by (1) adding 6% GNP by the weight of binder, (2) optimizing aggregate packing, and (3) combining the two previous approaches. Gyratory compaction tests were performed on the four mixtures at two compaction temperatures: 135 °C (the compaction temperature of the control mixture) and 95 °C. A method was proposed based on the gyratory compaction to estimate the compaction temperature of the mixtures. The results show that all the three methods increase the compactability of mixtures and thus significantly reduce the compaction temperatures. Method 3 (combining GNP modification and aggregate packing optimization) has the most significant effect, followed by method 1 (GNP modification), and method 2 (aggregate packing optimization).
热拌沥青（HMA）的压实需要125至145°C范围内的高温，以确保沥青结合料的流动性，从而保证沥青混合料的可施工性。高温伴随着高能耗和更高的氮氧化物排放，还会加速沥青结合料的老化。在先前的研究中，作者开发了两种提高沥青混合料压实性的方法：（1）添加石墨纳米片（GNP），以及（2）优化集料堆积。本研究探讨了这两种方法及其组合对降低压实温度的影响，同时将生产温度保持在传统水平。降低压实温度有助于延长摊铺窗口、增加运输距离、减少再加热的能耗，并通过提高混合料的耐久性减少维修次数及其对环境和安全的负面影响。选择一种Superpave沥青混合料作为对照混合料。分别设计了三种改性混合料，方法如下：（1）按结合料重量添加6%的GNP，（2）优化集料堆积，（3）结合前两种方法。在两个压实温度下对这四种混合料进行旋转压实试验：135°C（对照混合料的压实温度）和95°C。提出了一种基于旋转压实的方法来估计混合料的压实温度。结果表明，所有三种方法均提高了混合料的压实性，从而显著降低了压实温度。方法3（结合GNP改性和集料堆积优化）效果最显著，其次是方法1（GNP改性）和方法2（集料堆积优化）。
