Recycled aggregate size effect on shear and tensile fracture toughness of SCB Eco-friendly cemented specimens

This study examines the innovative application of recycled glass powder as a partial substitute for natural fine aggregates in cementitious mortars, primarily focusing on its impact on pure shear (mode II) and tensile (mode I) fracture toughness, an area that remains crucial yet underexplored. While the sustainability benefits of using recycled glass are well-documented, the specific effects on fundamental fracture parameters under varying loading conditions are not adequately understood. This research introduces a significant advancement by systematically analyzing how the particle size of the glass aggregates (d₅₀ ranging from 0.134 mm to 0.533 mm) influences mechanical and fracture characteristics. An extensive experimental program, employing Semi-Circular Bending (SCB) tests, demonstrated that finer glass particles considerably enhance performance. The mortar incorporating the smallest glass particle size (d ~ 50 ~ = 0.134 mm) displayed the most pronounced improvements, yielding increases in compressive strength, tensile strength, and mode I fracture toughness by 34.6%, 58.4%, and 11.8%, respectively, in comparison to the control specimen. Additionally, a newly defined Ultrasonic Pulse Velocity (UPV) Quality Index, alongside microstructural evaluations, confirmed that finer particles facilitate matrix densification, reduce porosity by 24.2%, and enhance energy absorption, while avoiding any adverse alkali-silica reaction. The findings unequivocally establish that optimizing the particle size of recycled glass is a pivotal strategy for the development of high-performance, crack-resistant, and environmentally-friendly cementitious composites.