Experimental and analytical investigation of fracture behavior in GFRP reinforced seawater sea-sand HVFA-SCC beams

The high energy consumption and carbon emissions of cement, shortages of freshwater and river-sand resources, and steel reinforcement corrosion are major challenges in construction. To address these issues, the combination of seawater sea-sand (SWSS), high-volume fly ash self-compacting concrete (HVFA-SCC), and glass fiber reinforced polymer (GFRP) reinforcement has been introduced for engineering construction. However, the fracture behavior of GFRP reinforced seawater sea-sand HVFA-SCC (SWSS-HVFA-SCC) beams under three-point bending has rarely been studied. Therefore, this study conducts an experimental and analytical investigation on such beams to explore their fracture characteristics, fracture process, and failure mechanisms. The effects of reinforcement type, initial crack-depth ratio, concrete cover thickness, reinforcement diameter (reinforcement ratio), and concrete type on the fracture behavior of these beams are discussed. A four-stage fracture failure model, including the linear elastic, micro-crack propagation, macro-crack propagation, and unstability failure stages, for FRP reinforced concrete beams is established. The microscopic and macroscopic fracture toughness are introduced to characterize the crack propagation state of FRP reinforced concrete structures under the service limit state. A crack propagation criterion and a method for calculating fracture parameters are also proposed. The results indicate that for an initial crack-depth ratio of 0.4 or less, both the microscopic and macroscopic fracture toughness remain nearly constant. They can thus be regarded as material parameters for GFRP reinforced SWSS-HVFA-SCC specimens. Furthermore, the analytical methods for modeling the fracture process of GFRP reinforced SWSS-HVFA-SCC beams are proposed using both a tri-linear bond-slip model and a dual-$\alpha$ bond-slip model. The load-CMOD curves obtained from the proposed analytical methods for GFRP reinforced SWSS-HVFA-SCC beams show high consistency with the experimental results.