Quantitative analysis of functional polymer in recycled tyre rubber used in modified asphalt binders

Abstract

Ground tyre rubber (GTR) has been employed to modify asphalt binders used in hot-mix asphalt construction since the early 1960s. Proper formulation of GTR-modified asphalt binders provides for substantial improvement in performance over conventional asphalt binders, while providing an outlet for disposal of waste tyres. Physical characteristics of GTR are considered to be vital to the final performance of the asphalt paving mixture, with some state agencies specifying chemical composition requirements for GTR used in binder modification. Adequate analysis and understanding of the functional polymer content, polymer available in GTR to improve asphalt binder properties, and other chemical characteristics of GTR remain lacking. Thermogravimetric analysis (TGA) is a method used to measure the change in mass of a material measured as a function of temperature or time facilitating acquisition of information on properties of the material and its composition. This paper introduces an instrumental TGA method to analyse recycled tyre rubber, also known as ground tyre rubber or GTR, for better understanding and quantification of the functional polymer content, as well as general chemical characteristics, of GTR used to modify asphalt binders.

Keywords:

• ground tyre rubber
• natural rubber
• styrene-butadiene rubber
• thermogravimetric analysis
• asphalt binder
• recycled tyre rubber

Acknowledgements

The authors would like to thank Dr Rafael Cueto and Dr Sreelatha Balamurugan of Louisiana State University, Baton Rouge, Louisiana for performing TGA analysis of rubber blends and the staff of Paragon Technical Services, Inc. (PTSi), Richland, Mississippi for sample preparation and assistance in testing in this study.