Experimental study on durability of steel-basalt fiber reinforced concrete under multiple factors coupling

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A series of durability tests were conducted using varying composite salt solutions (5% Na2SO4 + 3.5% NaCl, 10% Na2SO4 + 3.5% NaCl, and 3.5% NaCl) and stress levels (F-0.3, F-0.6) to investigate the durability of concrete reinforced with steel and basalt fibers. Specimens were extracted after 0, 25, 50, 75, 100, 125, and 150 wet-dry cycles to explore the changes in the appearance, mass loss, relative dynamic modulus of elasticity, and compressive strength with the number of wet-dry cycles and different coupling effects. Mathematical models correlating mass and compressive strength with wet-dry cycles and stress levels were separately established. The concrete microstructure under coupling effects was observed using Environmental Scanning Electron Microscopy (ESEM). The results indicated that the inhibitory effect on the increase in concrete mass was higher in the F-0.6 group than in the F-0.3 group, showing that concrete under F-0.3 exhibited faster mass growth. As the axial compressive stress ratio increased, steel-basalt fiber reinforced concrete's relative dynamic modulus of elasticity changed less. Concrete degradation was more pronounced in the 10% Na2SO4 + 3.5% NaCl solution and F-0.6 loading environment. The calculated results from the established models agreed with the experimental results, demonstrating a certain degree of feasibility.