Investigating the properties of crumb rubber modified bitumen using classic and SHRP testing methods

Considerable effect of crumb rubber on improving the original bitumen properties along with environmental and economical advantages, encouraged using this additive as an effective modifier. In this research, due to lack of enough information about the effects of crumb rubber produced in Iran on 0/70 bitumen properties, extensive laboratory investigations have been carried out using classic and SHRP testing methods. The results of classic tests showed that adding crumb rubber reduced penetration, temperature susceptibility, ductility and fraass breaking point and increased the softening point, elastic recovery and vialit adhesion. Rheological properties of modified specimens were investigated with DSR in temperature sweep and frequency sweep and creep tests before and after aging in RTFO. Results indicated that there was an inflection point or inflection interval in G∗, G∗/sinδ and G∗·sinδ diagrams. At higher temperatures and lower frequencies than the inflection point or inflection interval the aforementioned parameters increased by increasing the crumb rubber content and at lower temperatures and higher frequencies the reverse was true. Furthermore, increasing the crumb rubber content and aging in RTFO lead to reduce of creep and increase of viscosity quantity.

► Increasing the crumb rubber (CR) increased the elasticity of studied bitumen.
► Modified bitumen with CR had relatively poor storage stability.
► At a constant CR content, aged bitumen in RTFO had higher softening point and elastic recovery.
► Aging in RTFO had no detrimental effects on CR particles.
► Aging in RTFO led to increase of G∗, G∗/sinδ and G∗·sinδ parameters and decrease of tanδ parameter.