State-of-the-art review on high-temperature performance of plant-based fiber reinforced concrete

Using plant-based fibers in concrete composites has significantly contributed to the eco-friendliness and sustainability of the construction sector. However, the vulnerability of natural-fiber reinforced concrete (NFRC) to elevated temperatures is a critical concern as its global usage continues to increase. It is crucial to recognize the residual characteristics of NFRC to establish safe design standards and ensure its suitability for various applications. While studies have extensively reviewed the behavior of manufactured and steel-fiber concrete subjected to fire, there is a notable absence of research systematically addressing the performance of NFRC under high-temperature conditions. This review bridges that gap by synthesizing findings from over 120 studies, providing the first comprehensive evaluation of NFRC degradation patterns, thermal cracking behavior, spalling mitigation mechanisms, and the influence of fiber type, treatment, and hybridization on fire performance. The work offers a comparative framework with synthetic and steel fiber-reinforced concretes, delivering actionable insights for fire safety design and material selection. The findings indicate that the critical temperature range for NFRC is between 350 °C and 450 °C, beyond which spalling can lead to catastrophic damage to surrounding structures. Notably, including 15 mm long jute fibers effectively mitigated thermal spalling. Exposing steel rebars to fire can reduce concrete density, strength, and permeability while increasing stiffness and contributing to spalling. However, incorporating hybrid fibers (steel or synthetic + natural fibers) into high-strength concrete reduced thermal spalling by 43% compared to individual additions of steel or synthetic fibers and natural fibers. Additionally, the review highlights that coconut fibers exhibited the most improved compressive strength among all-natural fibers under heating conditions. Lignocellulosic fibers (such as sisal, hemp, coconut, and jute) were observed to effectively mitigate micro-cracking and violent spalling in ultra-high-performance, high-strength, and high-performance concrete, in contrast to concrete without natural fibers.