含粗骨料超高性能混凝土力学性能研究及机理分析

An Experimental Study and a Mechanism Analysis on Mechanical Properties of Ultra-high Performance Concrete with Coarse Aggregate

为探索含粗骨料超高性能混凝土的各项力学性能,研究了粗骨料体积掺量(0kg/m^3、280kg/m^3、400kg/m^3、480kg/m^3、560kg/m^3)、纤维掺量(2%、2.5%)以及纤维形态(平直型、端钩型)对超高性能混凝土抗压强度、弹性模量以及四点弯曲强度的影响,并引入纤维取向系数和纤维有效长度,探索粗骨料掺量对弯曲强度影响的微观机理。结果表明,粗骨料体积掺量对含粗骨料超高性能混凝土抗压强度的影响不大(0.4%~4.5%);对弹性模量的提高效果显著,最高可提高7.8%;对抗弯强度具有不利影响,并且随着粗骨料掺量增大,纤维取向系数下降,纤维有效长度减小,负面影响扩大。当粗骨料体积掺量为560kg/m^3时,弯曲强度下降了21.2%。增加纤维掺量或者掺入端钩型纤维可提高弯曲强度,掺入端钩型钢纤维可显著增大纤维有效长度,从而大幅度提高弯曲强度。

In order to explore the mechanical properties of ultra-high performance concrete(UHPC)with coarse aggregate,the effects of coarse aggregate volume contents(0 kg/m 3,280 kg/m 3,400 kg/m 3,480 kg/m 3,560 kg/m 3),fiber contents(2%,2.5%)and fiber shape(flat type,hooked-end type)on compressive strength,elastic modulus and flexural strength of UHPC have been studied in the present work.Fiber orientation coefficient and effective length of fiber were introduced to explore microscopic mechanism for the influence of coarse aggregate content on flexural strength.The results demonstrated that coarse aggregate volume content affects little on the compressive strength(0.4%-4.5%);applies significant enhancement on the elastic modulus(maximum increment 7.8%);causes negative effect to flexural strength whose decrement will be fostered due to the declined orientation coefficient and effective length induced by coarse aggregate.Increasing fiber content or adding hooked-end fiber will benefit the flexural strength,in which hooked-end fiber reinforcement has greater effect in this experiment because of the substantial increment of fiber effective length.