Molecular Adhesion Between Asphalt and Glass Fiber-Reinforced Composites from Recycled Wind Turbine Blades in Dry and Hydrated Conditions

A large number of wind turbine blades will be retired in the near future. Glass fiber-reinforced composites from retired blades, due to their extraordinary strength, toughness, and durability, are promising aggregate candidates in asphalt mixtures. This work studied the interfacial behavior between asphalt and glass fiber-reinforced composites through combined molecular modeling and experimental approaches. Predictions from molecular modeling were first verified through experimental findings using particle probe scanning force microscopy. Then, molecular simulations were conducted to examine the chemical adhesion between binders and aggregates made from minerals and wind turbine blades. The results showed that epoxy-binder adhesion was higher than calcite-binder and silica-binder adhesion but lower than alumina-binder adhesion, denoting that the glass fiber composite aggregates were comparable in chemical adhesion to mineral aggregates. The adhesion was primarily due to van der Waals forces (>80%). Furthermore, the dependence of epoxy-asphalt adhesion on loading rates was examined, during which the high-speed, transitions, and low-speed regions were identified. The impact of water on interfacial behavior was illustrated by examining how water molecules infiltrated interfaces between aggregates and binders at different speeds. The results showed that interfacial adhesion in a hydrated state at low speeds was 20-40% lower than that in a dry state, whereas at high speeds, interfacial adhesion in a hydrated state was 5-15% higher than that in dry conditions. These results could provide essential guidance for the application of retired wind turbine blades as asphalt aggregates.