Abstract: In order to investigate the reaction time on cross-linking process of modifier in SBS modified asphalt, based on the share stress versus time curve observed by shear test, the network intensity, a new concept used as an index was introduced to evaluate the network structure of modifier. The results, combined with the softening point test were used to study the relationship of network structure with performance at high temperature and storage stability. The network structure of the modifier forms through two stages: partial crosslinking and entire crosslinking. The partial crosslinking is a reversible process in a metastable state and only has limited effect on the improvement of storage stability and softening point. While the stability of entire crosslinking structure is much better and is a key factor to improve softening point. The changes of the softening point present a trend as the reaction time of the modifier with asphalt prolongs: first reduces and then elevates. This trend is resulted from both the modifier morphology and structure changes.

Key words: SBS modified asphalt, network structure, shear test, network intensity, softening point