Aging characterization of rheology and morphology evolution of SBS-modified asphalt

Abstract

Aging behavior has always been a key issue in the asphalt industry, and the undetermined extent of the residual modification effect in aged SBS-modified asphalt can lead to uncertain performance. The relationship between the modification effect and aging mechanism has not been well examined, which leads to whether aged asphalt can be regarded as modified asphalt or conventional asphalt. To overcome this issue, this paper conducted fluorescence microscopy tests, dynamic shear rheometer tests, multiple stress creep recovery tests and toughness and tenacity tests on aged SBS-modified asphalt. Five quantization parameters were proposed to determine the phase structure and modified effect. Multinomial logistic regression analysis was performed to categorize the phase structure with increasing aging time. Based on the results, it was found that the aging process can be divided into three regions according to the modification effect. The first region presented a slower aging rate, and copolymer relaxation appeared, but chemical crosslinking still existed during this period. Aging dominated the second region, in which copolymers dissolved out and the polymer network was destroyed, and the quantization parameters sharply changed, eventually, the network structure was completely destroyed in the third region. The failure of the modification effect is also determined by evaluating the toughness curve. It is reasonable to assume that there is no difference between SBS-modified asphalt and conventional asphalt after RTFOT 6 h in terms of toughness curve. It is suggested that the toughness curve parameter can be used as one of the critical indicators to determine whether aging asphalt can be regarded as modified asphalt or conventional asphalt.