Effect of property deterioration in SBS modified binders during storage on the performance of asphalt mix

Abstract

SBS modified binders (SBS-MBs) are vulnerable to property erosion during storage and transportation in closed containers at temperatures exceeding 160 °C. If proper precautionary measures are not taken, the quality of pavements may also be affected. This investigation is focused on determining the effect of property deterioration in SBS-MBs during storage in closed metal containers on the performance of the asphalt mixture. In the first phase, optimum SBS content was determined based on binder and mixture studies. In the second part, studies were carried out comparing the performance of asphalt mixes prepared using fresh (0 days stored) and stored SBS-MBs at 150 °C and 180 °C for 14 days in closed metal containers. The asphalt mix performance was assessed through Marshall stability, rut depth, and fatigue tests. The results show that the properties of the SBS-MB remained stable during storage at 150 °C, and the performance of the asphalt mixes prepared using such SBS-MBs remained intact. On the contrary, during storage at 180 °C, significant erosion in the properties of the SBS-MBs with 4.5 wt% SBS content (optimum dosage) was observed. Gel permeation chromatography (GPC) results clearly showed chain scission of SBS polymer due to the non-oxidative thermal degradation. It can be concluded that the decline in the performance of the asphalt mix prepared using 4.5 wt% SBS-MB stored at 180 °C was substantial (50–100%). The Marshall stability value of the mixes decreased by up to 30% and rut depth increased by almost 50% when the asphalt mix was prepared using SBS-MB stored at 180 °C for 7 days. Such a massive reduction in the performance of asphalt mixes will severely impact the overall life and stability of the pavements, and contribute to its premature failure.