高性能纤维增强混凝土与筋材复合体系拉伸性能研究

Experimental Study of Tensile Properties of Composite System of High Performance Concrete and Reinforcements

超高性能混凝土(UHPC)具有优异的抗压强度,而超高延性水泥基复合材料(ECC)具有优良的拉伸应变强化能力,二者均属于高性能纤维增强基材。纤维增强复合材料筋(FRP bar)具有抗拉强度高、密度小、耐腐蚀性能好的优点。高性能基体与高强度筋材的结合使用,有望解决传统钢筋混凝土结构的耐久性问题,同时保证结构体系的承载能力。选取力学性能不同的3种基体(普通混凝土、ECC和UHPC)与2种筋材(钢筋、BFRP筋),在其材料性能试验基础上,对其组成的6种配筋复合体系进行了轴拉试验。试验结果表明,复合材料的拉伸性能受多种因素的影响。高性能基材可以有效地提升构件强度,但复合体系的变形能力由基材与筋材中应变能力较弱的一方决定;高性能基材所提供的抗拉贡献和应变软化会导致复合体系提前进入破坏状态,反而降低了体系的延性(拉伸变形能力)。初步证明,基于高性能材料的结构构件设计必须综合考虑材料各自的力学性能和材料间相互作用造成的综合影响。

Ultra-high-performance concrete(UHPC)is known for its ultra-high strength,engineered cementitious composites(ECC)possesses high tensile strain-hardening characteristic,and fiber reinforced polymer bar(FRP bar)has the advantages of high tensile strength,low density,and good corrosion resistance.It is expected that the combination of high-performance matrix and high-performance reinforcement can solve the durability issue long-existed in civil engineering and maintain high strength simultaneously.In this paper,three kinds of matrix materials(normal concrete,ECC,and UHPC)and two kinds of reinforcements(steel and BFRP bar)were selected for fabricating six different composite systems.Tensile tests were conducted to obtain the tension-strain behaviors of the composite system for comparison.The test results indicate that the tensile properties of the composite system are affected by various factors.High-performance matrix can effectively enhance the tensile strength of the system,but the sustained tensile contribution and the strain-softening behavior after peak strength of high-performance matrix may bring premature failure to the system,thus reducing the ductility eventually.It is preliminarily demonstrated that the ductility of the composite system is determined by the components with a weaker deformability.In the design of the composite structural member made of highperformance materials,it is recommended that the individual properties of materials and the interaction between materials be comprehensively considered.