超高性能混凝土紧密堆积体系中的纤维等效研究

Equivalent diameter of steel fibers incorporated into Ultra-High Performance Concrete(UHPC)

超高性能混凝土基于紧密堆积原理实现了优异的性能,且通过掺入钢纤维增强了其机械性能,但同时钢纤维的掺入也对其堆积体系造成了扰乱与破坏。为减少钢纤维对紧密堆积体系的扰乱,采用不同粒径范围的细砂替代钢纤维,以湿堆积密度法为依据,通过研究两者对堆积密实度的影响程度来寻找钢纤维的等效替代颗粒。结果表明:随着用水量的增加,浆体的密实度呈现出先增大后减小的趋势,各粒径尺寸替代颗粒均对应一个密实度峰值,即湿堆积密实度,将同一掺量下的钢纤维和不同粒径尺寸替代颗粒的湿堆积密实度进行对比后,可初步推测钢纤维的等效堆积粒径为5~6 mm;不同掺量下钢纤维和5~6 mm粒径颗粒在密实度上仍具有较好匹配度;根据骨料等效粒径公式并结合等效颗粒的累积曲线可得钢纤维的实际等效堆积粒径为5.65 mm;通过人工神经网络验证钢纤维的等效代替粒径为5.65 mm。

Ultra-high performance concrete achieves excellent performance by using the compact packing principle, and its mechanical properties are enhanced by the incorporation of steel fibers. But at the same time, the incorporation of steel fibers also disturbs and destroys its stacking system. In order to reduce the disturbance of steel fiber to tightly packed system, fine sand with different particle size range is used to replace steel fiber. Based on the wet packing method, the equivalent substitution of steel fiber is found by studying the influence degree of these two parameters on the packing density. The results show that with an increase of water consumption, the packing density of the paste firstly increases and then decreases. Every size range of alternative particle corresponds to a peak of the packing density, which is a wet packing density. Comparing the packing density of the steel fiber and the alternative particle in the same dosage, it can be presumed that the equivalent particle diameter of the steel fiber is 5~6 mm. The steel fiber and the particle size of 5~6 mm particle size have good matching degree under the different dosages. According to the equivalent particle size formula of aggregate and the cumulative curve of the effective particles can obtain the actual equivalent particle diameter of the steel fiber is 5.65 mm. The equivalent alternative particle size of the steel fiber is also verified by artificial neural network to be 5.65 mm.