Evaluation of mechanical properties of 3D printed PLA-CF reinforced concrete under atlantic coastal conditions of Brazil

This study presents a novel hybrid reinforcement strategy for concrete beams exposed to marine environments by combining conventional steel rebars with geometrically optimized 3D-printed polymeric patterns. The mechanical performance of reinforced concrete elements integrating optimized 3D-printed carbon-fiber-reinforced PLA patterns with conventional steel rebars (10 mm and 18 mm diameters) was investigated under a simulated marine environment representative of Brazil’s Atlantic coast. Two infill geometries (honeycomb and triangular) were fabricated via Fused Deposition Modeling (FDM) and integrated with steel rebars. Beams were exposed to a 3.5% NaCl immersion solution simulating Atlantic coastal conditions. Results show that 3D-printed patterns enhanced flexural strength and ductility under conventional conditions (CC), with the honeycomb pattern improving load capacity by over 90% compared to unreinforced concrete. Under saline exposure, reductions of up to 30% in flexural strength were observed in 3D-reinforced beams, whereas the 10 mm steel-reinforced beams showed improved performance (+ 5.3%), indicating enhanced corrosion resilience. The findings demonstrate the potential of hybrid reinforcement combining additive manufacturing approaches to enhance structural durability in aggressive environments. The innovation of this study lies in the integration of traditional steel rebars with geometrically optimized 3D-printed PLA-CF reinforcement patterns, tested under accelerated corrosion conditions simulating the Brazilian Atlantic coast. Unlike previous works that typically address either fiber or bar reinforcement in controlled conditions, this research proposes and validates a hybrid reinforcement system under realistic saline exposure, highlighting a practical and sustainable contribution to the development of more durable coastal infrastructure.