Quantification of recycled rubber content of end-of-life tyres in asphalt bitumen by total-reflection X-ray fluorescence spectrometry

This article presents a new methodology developed to quantify the amount of crumb rubber used in asphalt bitumen by Total-reflection X-Ray Fluorescence (TXRF) spectrometry. For the evaluation of the crumb rubber content in rubberized binders, the samples were completely digested by microwave-assisted acid digestion in a mixture of HNO3:HF acids. TXRF spectrometry has proven to be a powerful analytical technique capable to detect up to 12 elements in these matrixes with detection limits of only a few ppb's (μg/L). From those elements, Zn was elected as indicator of recycled crumb rubber and used for its quantitative correlation. The results obtained show that the proposed methodology is capable of quantifying the content of recycled crumb rubber in asphalt bitumen in a robust, accurate and reproducible way. [Display omitted] •TXRF as innovative tool for quantifying the amount of crumb rubber in asphalt bitumen.•TXRF detects 12 elements in bitumen/rubber matrices with detection limits of few ppb's.•Strong correlation between crumb rubber and Zn contents.•The standard uncertainty of the crumb rubber content has been modelled.•A method for controlling the use of recycled crumb rubber from ELT in road works.