基于紧密堆积理论优化超高性能混凝土钢纤维参数

基于改良的Andreasen & Andersen 颗粒堆积模型优化设计了超高性能混凝土(UHPC)的基础配合比,研究了钢纤维的形状、含量及混杂钢纤维对UHPC湿堆积密实度的影响。然后采用D-最优设计(DOD)方法,预测和评估混杂钢纤维对UHPC湿堆积密实度的影响,并基于DOD模型优化设计了UHPC的最佳钢纤维掺量。结果表明,长直纤维、短直纤维、端钩纤维的掺入会对UHPC堆积体系、密实度带来不同程度的影响,其中端钩纤维对UHPC密实度的降低程度最大。此外,钢纤维掺量与UHPC堆积体系也有一定关系,当纤维掺量超过2.0%(体积分数,下同)时,UHPC的密实度急剧下降,造成UHPC堆积体系的显著破坏;基于建立的DOD优化模型分析得出,0.9%的长直纤维与1.1%端钩纤维为最佳纤维混杂方式,可使得钢纤维对UHPC堆积体系的扰乱作用最小化。

Steel Fibre Parameter Optimization of Ultra-High Performance Concrete Based on Dense Particle Packing Theory

The basic mixture of ultra-high performance concrete (UHPC) was optimized by the modified Andreasen & Andersen particle packing model, and the effects of steel fibre shape, content and hybridization on the wet packing density of UHPC were evaluated. Moreover, the D-optimal design (DOD) method was employed for modelling of wet packing density of UHPC against hybrid steel fibres. The results reveal that the incorporation of long straight fibres, short straight fibres and hooked-end fibres have varying degrees of effects on UHPC packing system, among which the end hook fibre reduces the density of UHPC the most. In addition, the steel fibre content has obvious effects on wet packing density of UHPC, and especially as the steel fibre content exceeds 2.0% (volume fraction, below is the same), the packing density of UHPC drops dramatically, resulting in significant damage to UHPC packing system. Based on the analysis results of the DOD model, it is concluded that the hybridization of 0.9% long straight fibres and 1.1% hooked-end fibres is optimized mixture and disturbing effect of steel fibre on UHPC accumulation system is minimized.