Research On Flexural Properties Of The Basalt Fiber Reinforced Concrete Beams

Ordinary concrete has shortcomings such as poor tensile property,easy cracking,and self-heavy weight,limiting its application in civil engineering.Fiber reinforced concrete is a new type of cement-based composite material formed by adding disorderly distributed fibers into the common concrete matrix.It not only maintains the excellent properties of ordinary concrete,but also improves the tensile and flexural properties of the existing concrete and impacts resistance,making it have good deformation and crack control ability.Compared with the other types of fibers,basalt fiber has many advantages such as green environmental protection and high strength.At present,the research on basalt fiber reinforced concrete mainly focuses on the basic mechanical properties,durability and impact resistance of the material,but little of them are concentrated on the mechanical properties of basalt fiber reinforced concrete components.Therefore,in this paper,the flexural performance of basalt fiber reinforced concrete beams is studied,and three parts are mainly completed as follows:（1）The effects of longitudinal reinforcement ratio,basalt fiber volume content,and thickness of basalt fiber reinforced concrete layer on the flexural performance of basalt fiber reinforced concrete beams were studied experimentally,including,bending capacity,deflection,and crack width.The research results show that the assumption of plane section is still applicable to basalt fiber reinforced concrete beams and concrete-basalt fiber reinforced concrete composite beams;adding basalt fiber can increase the cracking load and ultimate bearing capacity of concrete beams,as well as improve the deformation capacity and crack width control ability of concrete beams.Basalt fiber content has littles effect on the loaddeflection curves of concrete beams.Under the same basalt fiber content,the load-deflection curves of basalt fiber reinforced concrete beams and concrete-basalt fiber reinforced concrete composite beams have little discrepancy before the specimen yields.However,the ultimate deflection of the composite beam is slightly smaller than that of the basalt fiber reinforced concrete beam.（2）Based on the assumption of plane section,material constitutive relationship and internal force balance equation,the whole stress process of basalt fiber reinforced concrete beam was analyzed,and the theoretical calculation formulas of cracking moment,yield moment,ultimate moment and deflection were deduced.Meanwhile,based on the calculation theory of flexural bearing capacity and short-term deflection of ordinary concrete beams,a simplified formula was proposed to calculate the ultimate bending moment and short-term deflection of the basalt fiber reinforced concrete beams.The calculated results obtained by the proposed formula were in good agreement with the experimental ones.（3）Based on the assumption of plane section,material constitutive relationship and internal force balance equation,the whole process of stress of concrete-basalt fiber reinforced concrete composite beams was analyzed,and theories of cracking moment,yield moment,ultimate moment and deflection were deduced.At the same time,based on the calculation formula of flexural bearing capacity and short-term deflection of ordinary concrete beams,a simplified formula was proposed to calculate the ultimate bending moment and short-term deflection of the this type of composite beam is proposed.The calculated results obtained by the proposed formula were in good agreement with the experimental ones.