Flexural performance of hybrid fiber reinforced alkali-activated coral concrete

With the continued development of sustainable island reef infrastructure, there is a growing demand for coral concrete that is low-carbon, environmentally friendly, and exhibits excellent mechanical performance. This study replaced cement with alkali-activated binders prepared from waste marble powder and ground granulated blast furnace slag as precursors to reduce carbon emissions. Stainless steel fibers (SSFs) and polyethylene fibers (PEs) were incorporated into the mixture to enhance the strength and toughness of the coral concrete. The flexural performance of hybrid fiber-reinforced alkali-activated coral concrete (HFRAACC) was assessed using four-point flexural tests and digital image correlation (DIC) technology. The results revealed that HFRAACC experienced flexural failure in three distinct stages: microcrack initiation, macrocrack propagation, and main crack development. The inclusion of SSFs significantly improved crack resistance, flexural strength, and deflection in the initial stages, while PEs mainly contributed to toughening effect in the later stages. When the SSF-to-PE ratio was 2:1, with a total fiber content of approximately 2 %, HFRAACC exhibited optimal flexural performance, achieving the best fiber synergy and the lowest damage evolution rate. Under these conditions, the equivalent flexural strength was 18 times greater than that of the fiber-free group. A model was developed to predict the equivalent flexural strength of HFRAACC, demonstrating good accuracy in its predictions. • Replaced cement with alkali-activated binders using waste marble powder & slag, reducing carbon emissions for coral concrete production. • Added stainless steel & polyethylene fibers to the alkali-activated coral concrete, reducing its brittleness. • Used four-point bending test with DIC to assess flexural performance & find optimal fiber dosage of hybrid fiber-reinforced coral concrete. • Established an equivalent flexural strength model with high precision for hybrid fiber-reinforced coral concrete.