UV and Thermal-Oxidative Ageing of SBS-Modified Binders

Abstract

Polymer-modified binders are widely used in asphalt pavements, but their long-term performance and recyclability depend on how they age under both thermo-oxidative and photo-thermal conditions. Within RILEM TC 307-PPB, Task Group 2 (TG2) has set up an interlaboratory programme to compare a reference RTFOT+PAV ageing condition (PAV40) with a well-defined RTFOT+UV condition (UVA72) for two industrial SBS-modified binders with different SBS contents. Ageing was carried out centrally at TU Delft and the binders were characterised in ten laboratories using FTIR spectroscopy, BTSV rheological measurements and fluorescence microscopy. FTIR band indices indicate that PAV40 and UVA72 bring both binders to a similar overall oxidation level, while the balance between matrix oxidation and polymer-related changes depends on SBS content. BTSV results show comparable high-temperature stiffening for PAV40 and UVA72, with binder-dependent but modest differences. The interlaboratory data reveal larger scatter of FTIR indices for UVA72, and additional tests on solid and homogenised UV-aged films point to finite UV ageing depth and sampling/homogenisation procedures as important contributors. Fluorescence microscopy provides a qualitative microstructural counterpart and confirms the sensitivity to preparation protocols. Together, these findings offer an interlaboratory reference for relating UV and PAV ageing of SBS-modified binders and underline the need for clearly defined UV ageing and sampling procedures in future TG2 pre-standardisation work.