SYNERGISTIC OR ADVERSARIAL A CRITICAL REVIEW OF BIO-BASED FIBER AND RECYCLED AGGREGATE CONCRETE SYSTEMS FOR RESILIENT AND SUSTAINABLE INFRASTRUCTURE

The two concurrent challenges for the construction sector are (1) decarbonization of the construction material supply chains, and (2) increasing the resilience of the aging construction sector stock. To meet these pressures, two independent material strategies have emerged: the first is use of recycled concrete aggregate (RCA) to replace virgin mineral resources and the second is the addition of bio-based fibers, particularly hemp fiber, for their ability to improve tensile toughness and crack control. This review critically discusses the combined effects of these two strategies: hemp fiber-reinforced recycled aggregate concrete (HFRAC). Each of the constituent technologies is well documented but the combination of these is less studied and poorly understood. This review is motivated by the central question of whether the combination is a synergistic one involving fibre bridging that overcomes the weakness of the interface between the RCA and the fibre or whether it is an additive one where both the materials are imperfect. Based on limited available literature, it can be concluded that hemp fiber has a positive effect on the post-peak performance and fracture energy of RAC systems, with reported increases of +17.9% and +14.4% for shear and bond fracture energy, respectively, compared to control specimens (Ghosn et al., 2023). Peak load improvements are still relatively small (about 4% or less), however, and may be compensative rather than improving. Importantly, there are three competing interface phenomena that are essentially unstudied: water competition, crack bridging vs weakening at the interface and chemical incompatibility. This review describes the current state of knowledge and highlights the gaps that are systematic and identifies a research agenda based on multi-scale interface characterization and life cycle-resilience co-assessment.