Impact of wind turbine blade waste fiber size on the properties of mortar: From material characteristics to performance

This study investigates the use of wind turbine blade (WTB) waste in mortar, with emphasis on how particle size affects hydration, mechanical performance, and alkali-silica reaction (ASR) expansion. Mechanically shredded WTB waste, composed mainly of glass fiber and epoxy resin, is used in mortar in different particle sizes: from 0.063 mm to larger than 8 mm. Experiments assessed the physical and chemical interactions of the different WTB waste fiber sizes with the cementitious matrix using isothermal calorimetry, X-ray diffraction, and scanning electron microscopy. Flexural and compressive strength, as well as ASR expansion of all the WTB waste-reinforced mortar were also determined. The results show that smaller WTB fractions (0.063–2 mm) contained more exposed glass surfaces, exhibited higher reactivity, and improved compressive strength while reducing porosity. However, these finer fractions also caused faster and greater ASR expansion. In contrast, larger WTB fractions (>8 mm), which more often retained epoxy resin on the fiber surface, showed lower early ASR expansion but introduced more defects and higher porosity, resulting in reduced compressive strength. The intermediate fraction (2–8 mm) displayed mixed powder-like and fiber-like behavior. WTB size strongly governs the balance between mechanical performance and ASR-related durability, showing that this waste stream can only be incorporated safely when its particle-size-dependent effects are carefully considered. • Increased pH leads to more dissolution of Ca 2 + , Mg 2+ , Si(OH) 4, and Al(OH) 4 ⁻ ions from WTB waste. • Smaller fibers (0.063–2 mm) suit SCM use; larger fibers (>8 mm) reinforce cement. • Epoxy resin around fibers enhances the alkaline resistance of fiberglass.