Flexural Behavior of Lightweight Sandwich Panels with Rice Husk Bio-Aggregate Concrete Core and Sisal Fiber-Reinforced Foamed Cementitious Faces

The development of sustainable and energy-efficient construction materials is crucial for mitigating the growing environmental impact of the building sector. This study introduces a new lightweight sandwich panel, featuring a core made of lightweight concrete with rice husk bio-aggregate (RHB) and faces constructed from foamed cementitious composites. The innovative design aims to promote sustainability by utilizing agro-industrial waste while maintaining satisfactory mechanical performance. Composites were produced with 4% short sisal fibers and matrices containing 15%, 20%, and 30% foaming agent. These composites were evaluated for density, direct compression, and four-point bending. It was found that the mixture with 20% foam volume demonstrated the highest efficiency for use in the production of sandwich panels. Concrete mixtures containing 50%, 60%, and 70% rice husk bio-aggregates were tested for density and compressive strength and used in the production of lightweight sandwich panels with densities ranging from 670 to 1000 kg/m³. Mechanical evaluation under flexion and shear indicated that the presence of fibers inhibited crack propagation in the face, enabling the creation of lightweight sandwich panels with deflection-hardening behavior. On the other hand, the increase in RHB content led to a reduction in the ultimate stress on the face, the core shear ultimate stress, and the toughness of the sandwich panels.