A Study on Chemical Composition, Colloidal Stability, and Rheological Properties of Ethylene Vinyl Acetate–Modified Binders

AbstractThe rheological properties and performance of binders are often explained using the chemical composition of binders. The present study explored the effect of SARA fractions (saturates, aromatics, resins, and asphaltenes) and colloidal stability on the rheological properties of ethylene vinyl acetate (EVA) modified binders. The effect of short-term and long-term aging on SARA fractions and colloidal stability of EVA-modified binders was also examined. The base bitumen (VG40) was modified with EVA-18 polymer (1% to 7%, varied with an increment of 1%) to produce EVA polymer-modified binders. Penetration, softening point, elastic recovery, complex shear modulus (G*), phase angle (δ), Superpave rutting parameter (G*/sinδ), temperature and frequency sensitivities of the Superpave rutting parameter, and multiple stress creep and recovery (MSCR) test parameters of the binders were determined and correlated with the polar components (resins and asphaltenes) of EVA-modified binders. The elastic recovery, percent recovery measured in the MSCR test, temperature and frequency sensitivities of Superpave rutting parameter, and fatigue lives of binders estimated from the linear amplitude sweep (LAS) test were correlated with the colloidal stability index of binders. The temperature and frequency sensitivity of the binders decreased with EVA polymer modification. Colloidal stability of bitumen increased with increased content of the EVA polymer modifier in base binder VG40. The effect of aging demonstrated a decrease in the colloidal stability of bitumen. The polar fractions (resins and asphaltenes) of binders were found to correlate well with (1) different consistency/stiffness parameters such as penetration, softening point, and complex modulus (G*); (2) elastic response represented by elastic recovery, phase angle, and percent recovery measured in the MSCR test; (3) permanent deformation (rutting) resistance measured by G*/sinδ and nonrecoverable creep compliance (Jnr) measured in the MSCR test; and (4) temperature and frequency sensitivities of Superpave rutting parameter. The correlations obtained for resins are observed to be better than those developed with asphaltenes. Colloidal stability index is found to correlate well with elastic recovery, percent recovery measured in the MSCR test, temperature and frequency sensitivities of the Superpave rutting parameter, and fatigue lives of binders estimated from the LAS test.