Reducing the moisture susceptibility of recycled hot‐mix asphalt mixture with composite modification technology

Styrene–butadiene–styrene block copolymer (SBS)‐modified asphalt is a key material for constructing recycled hot‐mix asphalt mixtures (RHMAs). However, these mixtures still risk insufficient moisture stability. To this end, this study investigates the feasibility of asphalt composite modification technology to enhance RHMA performance. SBS, high‐viscosity agent (HVA) and crumb‐rubber materials (CRM) were used to prepare SBS‐HVA‐ and SBS‐CRM‐modified asphalt, with SBS‐modified asphalt as the control group, and the adhesion properties of the asphalt were evaluated using surface free energy tests. RHMAs with 50% reclaimed asphalt pavement were then prepared with each type of modified asphalt. The moisture susceptibility of these mixtures was analyzed using moisture‐induced sensitivity, freeze–thaw splitting and immersion Marshall tests. It was found that HVA significantly enhanced the adhesion of SBS‐modified asphalt under dry conditions, while CRM had a minimal effect. Compared to RHMA with SBS‐modified asphalt, HVA and CRM additives are crucial for enhancing the moisture stability of RHMA in the immersion Marshall test. However, CRM does not improve the moisture stability of RHMA in the moisture‐induced sensitivity and freezing–thaw splitting tests. From the conducted study, it can be proposed that SBS and HVA composite‐modified asphalt can be utilized in RHMAs to achieve higher moisture stability. © 2024 Society of Chemical Industry.