Biomaterials as an Alternative to Steel Reinforcement in Concrete: A Comparative Analysis of Stiffness and Strength

Objective: To assess whether any biomaterial can match both the tensile strength and the elastic modulus of reinforcing steel, and to quantify the reinforcement area required when it cannot. Methodology: Eleven bio-based materials were compared with CA-50 steel and GFRP bars using published data, a strengthmodulus selection chart and equivalent-area calculations for a 20 50 cm C30 beam reinforced with four 16 mm bars. Results: Stiffness governed design in every case. The stiffest macroscopic candidates (cellulose nanofibril filament, flax fibre and densified wood) required 2.45.3 times the steel area, raw bamboo 10.5 times, and strength-based sizing delivered only 333% of the cracked stiffness of the steel-reinforced beam. Limitations: Representative literature values, a single beam geometry, perfect bond and no long-term effects were assumed. Originality: A simple stiffness-based screening criterion separates promising biomaterials from those that excel only in strength. Conclusions: Biomaterial reinforcement should follow the design path established for GFRP, governed by deflection, and is currently suited only to members in which deflection is not critical.