Microstructure analysis and mechanical performance of crumb rubber modified asphalt concrete using the dry process: Fid-Bau Portal

Microstructure analysis and mechanical performance of crumb rubber modified asphalt concrete using the dry process

Rodríguez-Fernández, Israel / Tarpoudi Baheri, Farrokh / Cavalli, Maria Chiara / Poulikakos, Lily D. / Bueno, Moises

Highlights • Crumb Rubber from waste tyre can be recycled in asphalt mixture production. • The effect of Crumb Rubber has been evaluated by relating mechanical performance with microstructural characterization. • Conditioning time have a significant influence on the asphalt mixture performance. • ESEM analysis show that the microstructure changes depend on the conditioning time. • After certain conditioning time there is less microstructure (bee) formation.

Abstract Globally, the vast majority of waste tires are landfilled, with catastrophic ecological consequences and in particular, serious threats to human health (e.g. fire, pests and soil contamination). Because of the increasing environmental awareness, the use of crumb rubber modified asphalt has become an important recycling strategy for waste tires. The so-called crumb rubber (CR), which is the recycled rubber from tires, has become a common additive in hot mix asphalt mixture due to its improvement of the mechanical performances of asphalt mixtures. The purpose of this study is to investigate the effect of adding crumb rubber to asphalt mixtures using the dry process by relating mechanical performances with microstructural characterizations. It was possible to observe the influence of conditioning process (time during which the asphalt mixture is kept at a high temperature after mixing) on the mechanical performance of the mixtures that depend primarily on the properties of the crumb rubber used. Specifically, it is shown that the conditioning time has an influence on the Marshall test results as well as the viscosity measurements. By using the Environmental Scanning Electron Microscope (ESEM), the distribution of the crumb rubber within the mixture has been investigated. In particular, the distribution of the crumb rubber by changing the conditioning time is of interest. The results showed that crumb rubber is well dispersed in the asphalt mixture when the conditioning time is increased. The effect of crumb rubber on the microstructure using Atomic Force Microscopy-Infrared Spectroscopy (AFM-IR) indicated that the main chemical change takes place in the para domain and catana or the so-called bee structures diminish on the CR modified bitumen as a consequence of more conditioning time.