Investigating the performance, chemical, and microstructure properties of carbon nanotube-modified asphalt binder

Abstract

Carbon nanotubes (CNT) hold the potential to enhance the performance of construction materials such as asphalt binders and mixtures. With the goal of designing long-life asphalt pavements, this research report investigates the laboratory performance of CNT-modified asphalt. Mixing combination conditions including shearing time and shearing rate are studied in the first step. Then modified asphalts with different CNT contents are evaluated by penetration, softening point, and ductility indexes. Storage stability of modified asphalt is accessed using the separation test. After that, aged asphalts are obtained by using the thin film oven test (TFOT). Samples of base and CNT-modified asphalts before and after ageing are characterised by running the rotational viscosity (RV) test, dynamic shear rheometer (DSR) test, and bending beam rheometer (BBR) test. Furthermore, Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) are employed to characterise the functional groups and microstructures of base and modified asphalt binders before and after ageing. It is shown that shearing rate and shearing rate*shearing time interaction have a profound influence on the property of modified asphalt whereas shearing time does not. Conventional test results indicate that increasing CNT content would decrease penetration and ductility while increasing the softening point. The separation test shows that CNT may settle down during the storage process. Rheological test results show that the addition of CNT can improve the high temperature performance and ageing resistance while decreasing the low temperature performance. The functional groups in base and modified asphalt are found to be similar which indicates that there are no chemical reactions during modification. It demonstrates that CNT-modified asphalt has better anti-ageing property with a lower increase in sulphoxide index after ageing. AFM characterisation provides details of the CNT modification mechanism. This research provides useful guidance and potential problems on the use of CNT as a high performance modifier.