合成结构纤维对混凝土力学性能的影响

Effect of Synthetic Fibers on Mechanical Proportion of Fiber Reinforced Concrete

摘要:

采用长度分别为4.7，5.6和6.5 cm的合成结构纤维，均以5 kg?m-3的掺量配制C40混凝土，通过维勃稠度、抗压强度、方板和圆板弯曲韧性、混凝土梁和切口梁弯曲韧性等试验，分析了其对混凝土工作性能和力学性能的作用规律与特征，同时与素混凝土以及同体积掺量（40 kg?m-3）的钢纤维混凝土进行对比.结果显示，合成纤维的加入降低了混凝土的流动性、抗压强度和混凝土梁的抗弯强度，其长度越长则降低抗压强度及抗弯强度的程度越高；合成纤维对混凝土方板或圆板的初始断裂强度影响不大，但可明显提高断裂能，其作用高于同体积掺量的钢纤维，并且中等长度（5.6 cm）的合成纤维增加混凝土断裂能的作用最大；合成结构纤维混凝土的应力挠度曲线在其下降过程中呈现一个“平台段”，虽然平台高度不及钢纤维混凝土的，但其长度明显更长，这是由合成结构纤维的材质特征决定的.

关键词:纤维增强混凝土; 韧性; 合成纤维; 断裂能

Abstract:

The synthetic fibers, with three lengths of 4.7,5.6 and 6.5cm respectively and each dosage of them was 5 kg?m-3, were used for the preparation of grade C40 concrete. Weber consistency, compressive strength and the toughness of concrete samples, including square boards, circular plates, beams and coped beams, were tested to analyses the effect of synthetic fibers on the mechanical proportion of fiber reinforced concrete, comparing with that of concrete with the equal volume (40 kg?m-3) of steel fibers. The results indicated that the addition of synthetic fibers lead to both decreases of flowability and compressive strength, and reduced the bending strength of concrete beam, and the longer the length of synthetic fibers, the lower the compressive strength of concrete. The synthetic fibers affected little initial rupture strength of concrete square boards or circular plate. The synthetic fibers can enhance fracture energy of concrete obviously and this action is higher than the same volume content of steel fibers. The synthetic fiber with length of 5.6 cm impressed the most of fracture energy of concrete. The stress and the deflection curve of synthetic fiber reinforced concrete displayed a “platform” structure in the process of its decline. Although the platform height was less than that of the steel fiber reinforced concrete, its length was longer obviously. It is due to the material characteristics of the structure of synthetic fibers.

Key words:fiber reinforced concrete; toughness; synthetic fiber; fracture energy