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<p>Polymer-modified asphalt binders (PMBs) produced with styrene–butadiene–styrene (SBS) are increasingly used to extend pavement service life, particularly in highly modified asphalt (HiMA™) applications. Because both SBS dosage and polymer architecture influence long-term durability, this study evaluated PMBs prepared with three SBS architectures—linear (LSBS), radial (RSBS), and branched (BSBS)—across a range of SBS contents, along with a base binder (VG40). Binders were tested in unaged, short-term aged, and long-term aged conditions using conventional, rheological, and microstructural characterization techniques. Fluorescence microscopy was employed to examine the dispersion and network development of SBS within the asphalt matrix, providing insight into the structural changes associated with increasing polymer dosage. Conventional properties—penetration value and softening point temperature—showed that LSBS and RSBS produced greater stiffness, improved aging resistance, and lower temperature susceptibility than BSBS, particularly in the HiMA region (SBS &gt; 8%). True failure temperature trends revealed a phase-reversal behaviour in LSBS beyond 8% SBS, where the formation of a continuous polymer network enabled superior high-temperature performance compared with RSBS and BSBS. In contrast, differences among architectures were not statistically significant within the conventional modification range (2–6% SBS). Complex-modulus master curves demonstrated a strong polymer network at low frequencies and elevated reference temperatures. Aging indices decreased for all PMBs, indicating enhanced resistance to oxidative hardening. Stress-dependent unrecoverable creep compliance (J<sub>nr</sub>) highlighted polymer yielding, chain alignment, and strain hardening in LSBS and RSBS, whereas BSBS exhibited early saturation due to weaker chain entanglements. Saturation dosages were identified from percentage recovery (%R) trends. Linear amplitude sweep (LAS) testing showed that increased SBS dosage improved failure strain and ductile response through controlled polymer yielding. Steady shear flow (SSF) testing further characterized viscosity behaviour and was used to determine the mixing and compaction temperatures of the modified binders. Overall, LSBS emerged as the most effective modifier in the HiMA zone (8–10%), simultaneously improving rutting resistance at high temperatures, fatigue performance at intermediate temperatures, and resistance to thermal and aging effects.</p>

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Effect of aging on SBS-modified and highly modified asphalt binders: A comprehensive evaluation using rheological and mechanical indices

  • 期刊论文

  • 发表日期：

    2026年6月1日

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  • Mohanshu Bhardwaj,
  • Praveen Kumar,
  • Nikhil Saboo

摘要

Polymer-modified asphalt binders (PMBs) produced with styrene–butadiene–styrene (SBS) are increasingly used to extend pavement service life, particularly in highly modified asphalt (HiMA™) applications. Because both SBS dosage and polymer architecture influence long-term durability, this study evaluated PMBs prepared with three SBS architectures—linear (LSBS), radial (RSBS), and branched (BSBS)—across a range of SBS contents, along with a base binder (VG40). Binders were tested in unaged, short-term aged, and long-term aged conditions using conventional, rheological, and microstructural characterization techniques. Fluorescence microscopy was employed to examine the dispersion and network development of SBS within the asphalt matrix, providing insight into the structural changes associated with increasing polymer dosage. Conventional properties—penetration value and softening point temperature—showed that LSBS and RSBS produced greater stiffness, improved aging resistance, and lower temperature susceptibility than BSBS, particularly in the HiMA region (SBS > 8%). True failure temperature trends revealed a phase-reversal behaviour in LSBS beyond 8% SBS, where the formation of a continuous polymer network enabled superior high-temperature performance compared with RSBS and BSBS. In contrast, differences among architectures were not statistically significant within the conventional modification range (2–6% SBS). Complex-modulus master curves demonstrated a strong polymer network at low frequencies and elevated reference temperatures. Aging indices decreased for all PMBs, indicating enhanced resistance to oxidative hardening. Stress-dependent unrecoverable creep compliance (Jnr) highlighted polymer yielding, chain alignment, and strain hardening in LSBS and RSBS, whereas BSBS exhibited early saturation due to weaker chain entanglements. Saturation dosages were identified from percentage recovery (%R) trends. Linear amplitude sweep (LAS) testing showed that increased SBS dosage improved failure strain and ductile response through controlled polymer yielding. Steady shear flow (SSF) testing further characterized viscosity behaviour and was used to determine the mixing and compaction temperatures of the modified binders. Overall, LSBS emerged as the most effective modifier in the HiMA zone (8–10%), simultaneously improving rutting resistance at high temperatures, fatigue performance at intermediate temperatures, and resistance to thermal and aging effects.