Sand-free olive kernel aggregate mortars for sustainable building applications: Mechanical and hygrothermal characterization

This study explores the valorization of Olive Kernel Aggregate (OKA) as a total substitute for mineral sand in cementitious mortars, addressing the critical need for bio-based alternatives in the construction sector. While previous research on sand-free OKA mortars relied on high cement dosages ( > 600 kg / m 3 ) to ensure mechanical resistance, this approach often compromises the overall sustainability of the composite. To overcome this limitation, this work investigates the mechanical and hygrothermal performance of mortars produced with moderate binder contents ( 300 − 500 kg / m 3 ). The experimental campaign coupled standard mechanical testing and microstructural analysis (SEM, XRD) with an in-depth hygric characterization, including Water Vapor Permeability and Moisture Buffer Value (MBV) assessments. The results reveal that reducing the cement dosage significantly enhances the insulating properties and moisture buffering capacity, achieving an “Excellent” MBV classification according to the NORDTEST protocol. Conversely, increasing the binder content to 400 kg / m 3 yields a compressive strength of approximately 13 MPa , demonstrating that structural adequacy for specific building applications can be attained with significantly lower clinker content than current literature benchmarks. The discussion highlights a clear trade-off between mechanical strength and hygrothermal comfort, suggesting that these sand-free composites are viable for sustainable building applications ranging from lightweight insulating fillers to moderate load-bearing floor screeds. • Mortars were produced with crushed olive kernels as bio-aggregate. • Mechanical and hygrothermal performances were characterized. • Low-binder formulations showed excellent moisture-buffering capabilities. • Compatibility of bio-aggregate and binder was assessed by XRD and SEM.