A novel method to improve the anti-ageing ability of bitumen by organic LDHs/SBS composite: Preparation, performance evaluation and mechanism analysis

γ-aminopropyltriethoxy silane organic layered double hydroxides (LDHs) and SBS were combined into LDHs/SBS composite to improve anti-ageing performance of SBS modified bitumen (SMB). XPS and SEM showed that organic LDHs (OLDHs) was successfully grafted onto SBS, and OLDHs could be more evenly distributed in SBS, which was conducive to improve the anti-degradation capability of SBS. Compared with SBS and LDHs/SBS composite, the interaction between OLDHs/SBS composite and bitumen was stronger, resulting in the better stabilization of SBS and LDHs in bitumen. Furthermore, OLDHs/SBS composite could enhance the high-temperature property of SMB. SMB became hard and brittle during ageing, the physical and rheological properties were remarkably deteriorated. LDHs/SBS and OLDHs/SBS composite could alleviate the damage of ageing on the high- and low-temperature performance of SMB and enhance the anti-ageing capacity, particularly OLDHs/SBS composite. Then, the improvement mechanism of OLDHs/SBS and LDHs/SBS composite on the anti-ageing capability of SMB was analyzed at microscopic scale. LDHs/SBS and OLDHs/SBS composite could hinder the infiltration of oxygen into bitumen and decrease the oxygen content, and simultaneously decelerate the oxygen diffusion rate in bitumen. The synergistic combination of these two functions conspicuously diminished the probability of oxygen colliding with bitumen or SBS, which relieved the ageing of bitumen and the degradation of SBS, and ultimately improved the anti-ageing capability of SMB. Furthermore, due to the better stability, the effectiveness of OLDHs/SBS composite was more notable than LDHs/SBS composite, OLDHs/SBS composite demonstrated superior improvement on the anti-ageing capability of SMB than LDHs/SBS composite.