Incorporation of glass fibre powder derived from wind turbine blades in OPC–alkali-activated hybrid binders

Reusing glass fiber powder (GFP) recovered from waste wind turbine blades (WTB) through alkali activation in Portland cement–alkali-activated hybrid binders (OPC–AAHB) offers a promising pathway for sustainable material reuse. This study systematically evaluates the feasibility of incorporating GFP into OPC–AAHB systems. GFP replacement levels ranging from 30% to 60% were investigated. Two alkaline activators were examined: NaOH solution and solid Ca(OH)₂, each applied at dosages of 3% and 6% by binder mass. The results show that NaOH activation leads to a pronounced reduction in compressive strength. This behaviour is primarily attributed to the high alkalinity of NaOH, which severely suppresses cement hydration, the dominant contributor to strength development in GFP-based OPC–AAHB systems. In contrast, when Ca(OH)₂ is introduced as a solid alkali activator, GFP can function effectively as a reactive SCM or precursor. Owing to its moderate alkalinity and controlled activation behaviour, Ca(OH)₂ does not significantly hinder cement hydration and promotes the formation of C–A–S–H, which is denser than conventional C–S–H.Among all investigated mixtures, the paste containing 30% GFP replacement and 3% Ca(OH)₂ exhibits the best compressive strength performance. These findings demonstrate the potential of Ca(OH)₂-activated GFP derived from WTB for the development of viable OPC–AAHB systems.