Dimensions and quantity of specimens.

To investigate the influence of hybrid steel fibers on the mechanical properties of self-compacting concrete, this study systematically compared the mechanical performance of ordinary self-compacting concrete, single steel fiber-reinforced self-compacting concrete, and three types of hybrid steel fiber-reinforced self-compacting concrete through cube compression tests, four-point bending tests, and elastic modulus tests. The digital image correlation (DIC) method was employed to accurately measure the surface displacement and strain of the specimens. The results indicate that the self-compacting hybrid steel fiber concrete specimens exhibited excellent flexural-tensile performance. The incorporation of steel fibers significantly inhibited the development of macroscopic cracks, enhanced the crack resistance of the concrete, and effectively improved its brittleness. Particularly, when the fiber content was 1% 6mm + 1% 13mm + 1% 25mm, the compressive strength increased by 41.15%, the flexural strength increased by 266.41%, and the elastic modulus reached 40.82 MPa. Using the DIC method, this study successfully captured the full-field strain evolution during the failure process of the specimens. Based on the evolution of the maximum principal strain, the dynamic evolution characteristics of macroscopic and microscopic cracks on the specimen surface were thoroughly analyzed. The study found that the enhancement effect of hybrid steel fibers (HF) on concrete is primarily manifested in hindering the propagation of macroscopic cracks. This research provides important theoretical foundations and practical guidance for the engineering application of self-compacting concrete.

为探究混杂钢纤维对自密实混凝土（self-compacting concrete）力学性能的影响，本研究通过立方体抗压试验、四点弯曲试验及弹性模量试验，系统对比了普通自密实混凝土、单掺钢纤维增强自密实混凝土以及三类混杂钢纤维增强自密实混凝土的力学性能。本研究采用数字图像相关（DIC）法精准测定试件的表面位移与应变。试验结果表明，混杂钢纤维自密实混凝土试件展现出优异的抗弯抗拉性能。钢纤维的掺入可显著抑制宏观裂缝的扩展，提升混凝土的抗裂性能，并有效改善其脆性缺陷。尤其当纤维掺配方案为1%6mm+1%13mm+1%25mm时，试件抗压强度提升41.15%，抗弯强度提升266.41%，弹性模量可达40.82MPa。本研究借助DIC法成功捕捉到试件破坏过程中的全场应变演化规律。基于最大主应变的演化过程，本研究深入分析了试件表面宏观与微观裂缝的动态演化特征。研究表明，混杂钢纤维（HF）对混凝土的增强效应主要体现为阻滞宏观裂缝的扩展。本研究为自密实混凝土的工程应用提供了重要的理论依据与实践指导。