煤直接液化沥青基道路改性沥青老化性能研究

Study on the aging properties of coal direct liquefaction asphalt-road modified asphalt

煤直接液化沥青(DCLA)是煤直接液化过程的副产品,由约50%的沥青类物质和约50%的固体颗粒组成,以DCLA为基础改性剂复合SBS高分子聚合物,制备了道路改性沥青即DCLA-改性沥青。沥青组分对沥青的各项性能有直接影响,并最终体现为改性沥青路面使用性能的改变,因此,研究改性沥青老化后的性能更重要。通过沥青旋转薄膜加热试验(简称RTFOT)模拟DCLA改性沥青老化试验,并对DCLA-改性沥青的老化特性进行研究,建立其微观组分特性和宏观性能的联系。通过分析DCLA改性沥青原料及改性沥青老化前后的分子质量、红外光谱(FTIR)、氧含量等,发现DCLA-改性沥青的老化不是单一反应,是活性物质氧化、轻质组分挥发、沥青分子团聚、SBS分子断裂等多种反应的综合结果,表现为DCLA改性沥青平均分子质量由13 865 g/mol降到11 983 g/mol,氧含量由0.9%升至1.3%,SK90的平均分子质量由1 906 g/mol团聚增长到2 068 g/mol,SBS发生断裂平均分子质量由41 482 g/mol降至20 647 g/mol。DCLA-改性沥青老化性能的变化由体系中沥青质和胶质的变化量决定。沥青质能提高改性沥青的抗老化性,但同时会降低改性沥青本身的延度。为达到JTG F40—2017的I-D改性沥青延度标准,即5℃的延度不小于20 cm,则改性沥青体系中沥青质含量不能超过12.9%,其残留针入度比为72%。胶质能改善改性沥青的低温延度,但胶质是一个不稳定的物质,易被空气氧化生成沥青质,从而造成老化后残留延度降低,这体现在红外谱图中出现的羰基C=O与亚砜基S=O。当体系中胶质含量为28%时老化后延度降低率达到70%。控制原料沥青质含量并降低原料中胶质的反应活性是提高改性沥青老化后性能的有效途径。

Coal direct liquefaction asphalt(DCLA)is a by-product of the coal direct liquefaction process,which is composed of about50%asphalt and 50%solid particles.The road modified asphalt(DCLA-modified asphalt)is prepared by adding DCLA as the basic modifier with SBS polymer.The asphalt composition has a direct influence on the properties of asphalt,which is reflected in the performance of modified asphalt pavement.Therefore,it is more important to study the aging performance of modified asphalt.In this paper,the aging test of DCLA modified asphalt was simulated by rotary film heating test(RTFOT)and the aging characteristics of DCLA-modified asphalt were studied to establish the relationship between its microscopic properties and macroscopic properties,which provided a theory for improving the life of DCLA-modified asphalt pavement and increasing the amount of DCLA in the modified asphalt.By analyzing the molecular weight,FTIR,oxygen content of modified asphalt before and after aging and DCLA-modified asphalt raw materials,it was found that the aging of DCLA modified asphalt was not a single reaction,but a comprehensive result of many reactions,such as oxidation of active sub-stances,volatilization of light components,aggregation of asphalt molecule and fracture of SBS molecule.The results indicate that the DCLA-modified asphalt average molecular weight decreases from 13 865 g/mol to 11 983 g/mol,the oxygen content increases from 0.9%to 1.3%,the SK90 average molecular weight increases from 1 906 g/mol to 2 068 g/mol,and the SBS average molecular weight decreases from 41 482 g/mol to 20 647 g/mol.The performance of aged DCLR-road modified asphalt is affected by the asphaltene and resin.Asphaltene can improve the aging resistance but reduce the ductility of modified asphalt.In order to meet the JTG F40—2017 I-D standard,that is,the 5℃ductility is not less than 20 cm,and the asphaltene content in the modified asphalt system can’t exceed 12.9%,the residual penetration ratio is 72%.Resin can improve the low temperature ductility of modified asphalt,but resin is an unstable substance and is easily oxidized by air,which is reflected in the FTIR of carbonyl C=O and sulfoxide S=O .When the resin in the system is 28%,the aging ductility rate can be reduced by 70%.It is an effective way to improve the properties of aged modified asphalt by controlling the asphaltene content and reducing the resin reactivity in raw materials.