Research On Flexural Behavior Of Steel Fiber Alkali-activated Concrete Beams

Alkali-activated concrete is a new type of building material with similar properties to cement concrete,but its tensile-compression strength ratio is very low,which makes it exhibit brittle failure characteristics under stress.Incorporating steel fibers that can transmit stress across cracks can improve the toughness and ductility of alkali-activated concrete,limit the development of cracks and deformations of reinforced alkali-activated concrete beams,and improve the energy dissipation capacity and ductility of beams.Further replace the reinforcement with BFRP reinforcement,it can solve the problem of steel bar corrosion in reinforced alkali-activated concrete structures.Therefore,it is necessary to study the influence of steel fibers and BFRP bars on the mechanical properties of alkali-activated concrete structures.The main research contents and conclusions of this paper are as follows:1.Axial compressive strength and split tensile strength tests were carried out on alkali-activated concrete specimens with different steel fiber contents.Studies have shown that adding steel fibers can improve the axial compression deformation properties of alkali-activated concrete,and effectively increase the split tensile strength.2.Through the four-point bending test of reinforced steel fiber alkali-activated concrete beam and BFRP reinforced steel fiber alkali-activated concrete beam,the changing laws of steel fiber content and longitudinal reinforcement ratio on the flexural bearing capacity,deflection,ductility,mid-span section strain and cracks of alkali-activated concrete beams were studied.The study shows that the failure mode of alkali-activated concrete beams is similar to that of ordinary cement concrete beams;adding steel fibers and increasing the longitudinal reinforcement ratio can improve the crack morphology,reduce the deflection and section strain,and increase the flexural bearing capacity and ductility of the beam.3.The domestic design specification for fiber cement concrete beams also applies to reinforced steel fiber alkali-activated concrete beams,which can accurately predict the flexural bearing capacity,the maximum mid-span deflection and the maximum crack width during normal use.The theoretical calculated values are in good agreement with the experimental values.4.For BFRP reinforced steel fiber alkali-activated concrete beams,according to the characteristics of different failure modes,the tensile effect of steel fiber reinforced concrete in the tension zone is considered,and the calculation method of flexural bearing capacity and equilibrium reinforcement ratio is proposed.The calculated values are in good agreement with the experimental values.5.The flexural performance of 10 steel fiber alkali-activated concrete beams is simulated and analyzed by ABAQUS software,and compared with the experimental values.The results show that the finite element simulation results are in good agreement with the actual experimental values,and the established finite element numerical model can reasonably simulate the flexural behavior of steel fiber alkali-activated concrete beams.