混合料试件中沥青微尺度力学性能原位判别方法研究

Study on In-situ Determination Method of Micro-mechanical Performance of Asphalt in Mixture Samples

为了实现在混合料试件中直接判别沥青微尺度力学性能的想法,确定沥青微尺度力学性能与混合料试件路用性能之间的相关关系,以不同老化程度沥青成型的混合料样本为研究对象。首先,采用冻融劈裂试验、60℃车辙试验和-10,15℃劈裂强度试验,对混合料的抗水损坏性能、高温性能、低温性能以及抗劈裂性能进行评价,研究了沥青老化程度对于混合料宏观尺度性能的影响;然后,采用低温冷冻再切割的方法制备混合料试件显微观测样本,针对选定的样本测试区域利用原子力显微技术(AFM),直接测试(原位)混合料中沥青的微尺度力学性能;利用AFM附带的专业分析软件提取力学图像中局部区域像素点的力学信息,分析了沥青微尺度模量和微尺度黏附力的量化表征方法,获取了混合料中老化沥青微尺度性质的演变规律;最后,基于统计分析方法,建立了沥青微尺度性能与混合料宏观性能的相关关系。研究表明:采用AFM技术可以实现混合料中沥青力学性质的原位测试,混合料中未老化沥青模量集中在420~500 MPa,黏附力集中在27~36 nN;随着沥青老化程度的加深,微尺度模量升高,微尺度黏附力降低。沥青微尺度力学性能的演变规律与混合料宏观尺度性能存在很好的一致性,证实了AFM技术用于混合料试件中沥青性能原位识别的可行性。

In order to realize the idea of directly determine the micro-scale mechanical property of asphalt in the mixture samples, and to determine the correlation between the micro-scale mechanical property of asphalt and the road performance of mixture,the mixture samples with different aged asphalts are used as research objects. First, freeze-thaw split test, rutting test at 60℃, and split strength test at -10℃ and 15℃ are conducted to evaluate the water damage resistant performance, high temperature performance, low temperature performance and split resistant performance of the mixture respectively. The effect of asphalt aging degree on the macro-scale performance of the mixture is studied. Then, the microscopic observation samples of the mixture are prepared by low-temperature freezing and re-cutting method, the micro-scale mechanical property of the asphalt in the mixtures (in situ) are directly tested by atomic force microscopy (AFM) for selected sample test areas. The professional analysis software attached to the AFM is used to extract the mechanical information of the local area pixels in the mechanical image. The quantitative characterization methods of micro-scale modulus and micro-scale adhesion for the asphalt are analyzed, and the evolution rule of micro-scale property of aged asphalt in the mixture is obtained. Finally, based on the statistical analysis method, the correlation between the micro-scale performance of the asphalt and the macro-performance of the mixture is established. The research shows that (1) the in-situ test of the mechanical property of the asphalt in the mixture can be achieved by AFM technology, the modulus of unaged asphalt in the mixture is concentrated at 420-500 MPa, and the adhesion is concentrated at 27-36 nN;(2) with the aging of asphalt, the micro-scale modulus increases and the microscale adhesion decreases. The evolution of micro-scale mechanical property of the asphalt is in good agreement with the macro-scale performance of the mixture, which verified the feasibility of AFM technology for in-situ determination of asphalt performance in mixture samples.