Investigation of Selected Properties of Crumb Rubber Modified Bitumens with Different Rubber Contents

The current paper investigates the characteristic properties of three crumb rubber modified bitumens (CRMBs) of Greek origin with different crumb rubber (CR) contents, i.e. 5, 10 and 15%, before and after aging. The virgin bitumen used for the production of the three modified bituminous binders, was a 50/70 paving grade bitumen. The characteristic properties examined were penetration, softening point, dynamic viscosity, storage stability and force ductility. Temperature sweep test was also performed, and certain rheological properties were determined. Additionally, results of characteristic and rheological properties of CRMB which was designed in the Czech Republic, by using activated rubber powder (10 and 15%), were presented. Results showed that although CR addition (5, 10 and 15%) affects the characteristic properties, only 10 and 15% of CR affects the rheological properties before and after aging. The overall effect is mainly hardening of the bitumen, rather than improvement of elastic behavior before aging. Only after aging and with respect to phase angle measurements CRMBs seem to present a more elastic behavior than the virgin bitumen. Activated rubber addition seems to lower the viscosity of the modified bitumen and at some cases (with respect to activation agent content and CR content) improves significantly the storage stability of the CR modified bitumen.