Mechanical properties and enhancement mechanisms of cold recycled mixture using waterborne epoxy resin/styrene butadiene rubber latex modified emulsified asphalt

Abstract

• CRM containing only fresh aggregate and WSEA has better mechanical properties; • WER/SBR modifier can provide the strengthening and toughening effects on CRM; • Dissipation energy ratio and relaxation time can better evaluate the CRM toughness; • The added fresh aggregates favor toughness rather than mechanical strength of CRM; • Asphalt syncretization occurs in the outermost three layers at RAP aggregate surface. To better understand the enhancement mechanisms of waterborne epoxy resin/styrene butadiene rubber latex modified emulsified asphalt (WSEA) on the mechanical properties of cold recycled mixture (CRM), four types of CRM specimens were prepared to systematically discuss the mechanical property changes based on nanoindentation tests. Then the syncretization state between aged asphalt and WSEA, as well as the microstructures of asphalt-aggregate interfaces were analyzed by Fourier transform infrared spectroscope and scanning electron microscope tests, revealing the performance enhancement mechanisms. Results indicated that the mechanical properties of CRM prepared by fresh aggregate and WSEA were better. Also, the toughness of CRM could be accurately characterized by the dissipation energy ratio and relaxation time rather than the creep compliance. Additionally, the syncretization occurred in the asphalt samples of the outermost three layers at RAP aggregate surface. The added fresh aggregate was beneficial to forming WSEA-fresh aggregate interface, improving the anti-cracking property and moisture stability. Finally, the result reliability of the nanoindentation test was verified by indirect tension tests and conventional tests of pavement performance.