Research on the Foaming Characteristics and Rheological Properties of Warm-Mix Foamed Polymer-Modified Bitumen Based on Waste Molecular Sieves

Warm-mix foamed polyurethane modified bitumen (WPB) has been widely promoted due to its significant warm-mix effect and high viscosity. However, it still has problems such as too fast foam dissipation and unstable performance. Waste molecular sieves have an extremely fine pore structure that can absorb moisture. The porous characteristics of waste molecular sieves are used to adsorb water and let it slowly release water in bitumen. If the foam dissipation time can be prolonged and the bitumen expansion speed can be reduced, it will help to stabilize the performance of foamed bitumen. This paper conducts a study on the foaming characteristics and rheological properties of WPB based on waste molecular sieves. First, the bitumen foaming test is used to analyze the foaming characteristics of WPB with waste molecular sieves. Second, the basic properties of warm-mix foamed polymer-modified bitumen, including penetration, softening point, ductility, and viscosity, are investigated. Finally, a dynamic shear rheometer (DSR) is employed to study the high-temperature rutting resistance and high-temperature permanent deformation resistance of warm-mix foamed polymer-modified bitumen. The research results show that the amount of foaming water is the primary factor influencing bitumen foaming. The addition of waste molecular sieves has a significant impact on the intensity and duration of the bitumen foaming reaction. WPB with waste molecular sieves has a greater consistency and better high-temperature performance, but its low-temperature performance is somewhat weakened. The high-temperature deformation resistance of WPB with waste molecular sieves is superior to that of ordinary WPB and is affected by the amount of foaming water. An appropriate amount of foaming water can enable WPB with waste molecular sieves to exhibit excellent high-temperature deformation resistance.