Effect of short-term and long-term ageing on the elastic and creep behaviour of modified binder containing different SBS copolymer

Performance of Styrene butadiene styrene (SBS) polymer modified asphalt binder under thermal exposure has been immensely explored pertaining to linear SBS, however there is limited study focusing on the efficacy of varying molecular structure of SBS copolymer modified binder. In order to address this, the current study is directed to monitor the performance of binder modified with four types of SBS co-polymer having linear SBS (L-SBS), branched SBS (B-SBS), high vinyl SBS (HV-SBS) and diblock SBS (DB-SB) under laboratory ageing condition. The change in rutting performance and chemical properties of the modified binders due to short-term and long-term ageing were measured by means of the multiple stress creep and recovery test and Fourier Transform Infrared Spectroscopy test, respectively. Results highlights that variation of performance parameters for RTFO ageing condition was minimal and studied SBS copolymer produces a negligible stress and temperature susceptible behavior. However, after PAV ageing L-SBS and B-SBS showed degradation of polymer chain by increment and decrement of Jnr and ER values, respectively. Higher polymer degradation index (PDI) also supports the same for aforesaid SBS copolymer. On the contrary HV-SBS and DB-SB copolymer attribute higher thermal stability due to the presence of high vinyl content and location of butadiene block in polymer structure. Performance deterioration of L-SBS and B-SBS polymers were observed during long-term ageing irrespective of similar binder properties; thereby inferring the pivotal role of molecular structure and orientation of polymers.