Design of Nonbituminous Binders for Road Application Using Vegetable Resources

Abstract

This work proposes novel biobinders as a more sustainable alternative to traditional bituminous products. They should be able to fully replace petroleum bitumen as binders of aggregates in road asphalts. Colophony resin ester (R), waste cooking oil (O), and cellulosic pulp (CP) were used as the main components of biobinders. Furthermore, the addition of a small amount of a reactive isocyanate-terminated prepolymer (MDI) is required. Binder formulation and processing were assessed by a comprehensive rheological, microstructural, and technological characterization to understand the role of each component in the final material properties. Rosin was a structuring agent, oil acted as a plasticizer, and the cellulosic pulp increased the material's softening point. MDI played a key role as a compatibilizer via urethane/amide linkages between the isocyanate groups of MDI and the OH/COOH groups present in the other three components. As a result, a biobinder formulation was proposed to replace bituminous binders, which was composed of 27.22 wt % oil, 67.76 wt % rosin, 2.02 wt cellulosic pulp, and 3 wt % MDI. They should be added following the order R > O > MDI > CP and processed at 150 °C. Finally, its potential as an asphalt binder was evaluated according to European and American standards accepted for commercial bituminous products.