端钩型钢纤维UHPC抗压强度的试验研究

Experimental Study on Compressive Strength of Ultra-High Performance Concrete with Hooked Steel Fiber

本文对5组超高性能混凝土(UHPC)立方体试件进行了轴心受压试验,观察不同纤维掺量及不同尺寸UHPC试件的破坏过程及破坏形态,研究了端钩型钢纤维及不同尺寸对UHPC受压性能的影响,比较各纤维体积掺量立方体试块的荷载-位移曲线,给出了纤维约束系数,分析了其对UHPC立方体抗压强度及压缩耗能的影响,建立了UHPC立方体抗压强度的预测模型。结果表明:与未掺纤维UHPC试件相比,掺入端钩型钢纤维的试件,在载荷达到极限荷载的40%左右时,试件开始发生损伤,在载荷接近极限荷载时,试件内部发生持续的快速断裂声响;掺入端钩型钢纤维的UHPC试件最终破坏呈多条斜向裂缝,且最终破坏时试件仍能保持完整形态,呈现"裂而不碎"的状态;随着端钩型钢纤维体积掺量的增加,试件的受压峰值荷载增加,且伴随着试件的变形增大;与未掺纤维UHPC试件相比,随着纤维掺量的增大,尺寸效应对UHPC的受压性能的影响逐渐减小。基于纤维约束指数,建立了UHPC立方体抗压强度的预测模型,预测结果与试验结果吻合度较高。

In order to study the influence of the content of hooked steel fibers on the compression performance of ultra-high performance concrete(UHPC), five groups UHPC cube specimens were tested under axial compression. The failure process and failure modes of UHPC specimens with different fiber volume fraction were recorded, and the load-displacement curves of them were compared. Then the fiber constraint coefficient and the influence of the constraint coefficient of end-hooked steel fiber on the compressive strength and compression energy consumption of UHPC cube specimens were analyzed. Based on the experimental data in this paper, a prediction model of UHPC cube specimens compressive strength was established. The results show that compared with the normal UHPC, when the hooked steel fiber is added to the test piece, the specimen starts to be damaged when the load is about 40% of the ultimate load. A continuous rapid fracture sound occurs inside the specimen when the load is close to the ultimate load. The UHPC specimens with end-hook type steel fibers finally failed and showed multiple diagonal cracks, and they can still remain as complete shape in the final failure, showing the phenomenon of "cracked but not broken". With the increase of the volume content of the hooked steel fiber, the compressive strength and the deformation of the specimen increase. Compared with the prime UHPC specimen, with the increase of fiber content, the influence of size effect on UHPC gradually decreases. Considering the fiber constraint index, a prediction model of UHPC cube compressive strength is established, which match well with the test results.