Spirulina based DFNS/Cellulose nano hybrid as a bioactive reinforcement for durable foamed concrete

This study investigates the mechanical performance and durability of foamed concrete reinforced with a newly engineered hybrid bio nanocomposite composed of cellulose supported Spirulina and dendritic fibrous nanosilica (DFNS). In the proposed system, cellulose functional groups were first anchored onto the DFNS framework, enabling them to act as pseudo chelators capable of stabilizing Spirulina derived nanoparticles and controlling their leaching under alkaline cementitious conditions. The DFNS/Cellulose/Spirulina (DCS) hybrid exhibited a hierarchical nano bio architecture with enhanced interfacial activity, as confirmed through SEM, FTIR, and TGA analyses. Incorporation of this hybrid reinforcement significantly improved energy absorption, crack resistance, and thermal stability of the foamed concrete, while effectively mitigating drying shrinkage induced damage. The synergistic interaction between the fibrous cellulose network, the bioactive Spirulina species, and the high surface area DFNS resulted in superior impact resistance and extended service life under both mechanical and environmental loading. These outcomes demonstrate the potential of DCS bio-nanocomposites as sustainable reinforcement systems capable of enhancing microstructural densification, mechanical integrity, and long-term durability in lightweight cementitious materials. Beyond performance gains, the hybrid system contributes to green construction by integrating renewable biomass (Spirulina), biodegradable cellulose, and low toxicity nanostructured silica, thus reducing embodied carbon and supporting environmentally responsible material design.