Characterization of Storage Stability of EPDM Rubberized Asphalt with Tire Pyrolytic Oil and Sulfur

Abstract

Automobile/industrial waste ethylene-propylene-diene monomer (EPDM) rubber has attracted considerable interest as a potential asphalt binder modifier. A rubberized asphalt binder must have adequate storage stability to assure homogeneity during storage and hauling and attain the desired performance after construction. This study focused on the application of tire pyrolytic oil (TPO) derived from the pyrolysis of scrap tires as an additive for composite modification to enhance the storage stability of the EPDM rubberized binder. Sequential and pretreatment were the two different approaches employed to produce the TPO-EPDM rubberized asphalt binders in this work. Furthermore, the effect of a crosslinking agent (sulfur) on the compatibility of the TPO-EPDM rubberized binder was investigated for both sequential and pretreatment approaches. In all total, 18 different combinations of rubberized binders with EPDM, TPO, and sulfur were fabricated for storage stability characterization. Various empirical, rheological, chemical, and microstructural analyses based separation parameters indicated that TPO usage enhanced the storage stability of rubberized asphalt binder. Both sequential and pretreatment approaches increased the storage stability of EPDM rubberized binders with an increase in TPO dosages; however, the pretreatment approach outperformed the sequential approach. The addition of sulfur further improved the compatibility of rubberized binders. The results of Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM)–based separation parameters were similar to those found using empirical and rheological tests. Grey relational analysis (GRA) was used to rank the binders according to their separation parameters. GRA showed the best results in both sequential and pretreatment approaches with and without sulfur for an optimal TPO dosage of 6%. The enhanced storage stability performance of rubberized binders with the incorporation of TPO in the pretreatment approach of binder preparation was attributed to the achieved preswelling of rubber particles during premixing and conditioning processes.