粗骨料与钢纤维对超高性能混凝土单轴拉伸性能的影响

为了提高含粗骨料超高性能混凝土(Ultra-high performance concrete,UHPC)的单轴拉伸性能,采用单轴拉伸试验和图像分析技术分别研究了粗骨料掺量、颗粒粒径对含粗骨料UHPC单轴拉伸性能和钢纤维在UHPC体系中分散性能的影响规律。结果表明,随着粗骨料掺量及颗粒粒径的增大,钢纤维在UHPC体系中的分散系数和取向系数显著降低,含粗骨料UHPC的单轴拉伸初裂强度、裂后强度和耗能也随之减小。根据粗骨料颗粒最大粒径与钢纤维体积分数、直径间的匹配关系式(Dmax=3df/(Vf)0.5),采用纤维混杂可以充分发挥多尺度纤维与具有不同粒径分布的骨料间的分级匹配关系;粗骨料体积分数和颗粒最大粒径分别为10%和10mm时,采用平直钢纤维(直径0.12mm、长度10mm、体积掺量1.2%)和端钩钢纤维(直径0.35 mm、长度20mm、体积掺量1.8%)混杂实现了含粗骨料UHPC的单轴拉伸性能的提升,其裂后强度和耗能分别为8.69 MPa和11.10J。

Effects of Coarse Aggregate and Steel Fiber on Uniaxial Tensile Property of Ultra-high Performance Concrete

In order to improve the uniaxial tensile property of ultra-high performance concrete (UHPC) with coarse aggregate,uniaxial tensile test and image analysis were employed to investigate the effects of dosage,maximum particle size of coarse aggregate on the tensile property of UHPC and steel fiber dispersion in the UHPC system,respectively.The experimental results showed that with the increase of dosage and particle size of coarse aggregate,the distribution coefficient and orientation coefficient of steel fiber in the UHPC systems were significantly decreased,resulting in the declines of tensile first cracking strength,post-cracking strength and energy absorption capacity of UHPC with coarse aggregate.Based on the matching relationship between maximum particle size of coarse aggregate and volume fraction and diameter of steel fiber (Dmax =3df/(Vf)0.5),the introduction of hybrid steel fibers can make full use of the hierarchical matching relationship between the multi-scale steel fibers and aggregates with different particle size distribution.The uniaxial tensile property of UHPC with coarse aggregate could be improved by the hybridization of straight steel fiber with 0.12 mm diameter,10 mm length and 1.2％ volume fraction and hooked-end steel fiber with 0.35 mm diameter,20 mm length and 1.8％ volume fraction when the volume fraction and maximum particle size of coarse aggregate were 10％ and 10 mm,respectively.And the UHPC's tensile post-cracking strength and energy absorption capacity were 8.69 MPa and 11.10 J,respectively.