In this study, the effects of steel fibers on the mechanical properties of the geopolymer concrete – compressive, splitting tensile, and flexural strength; compressive elastic modulus; and fracture properties – were evaluated. Milling steel fibers were incorporated into the geopolymer concrete, and the volume fraction of the steel fibers was varied from 0 to 2.5%. Fly ash and metakaolin were chosen as the geopolymer precursors. Fracture parameters – critical effective crack length, initial fracture toughness, and unstable fracture toughness – were measured by a three-point bending test. The results indicated that all the mechanical properties of the geopolymer concrete are remarkably improved by the steel fibers with the optimum dosage. When the steel fiber content was under 2%, the cubic and axial compressive strength and the compressive elastic modulus increased. The inclusion of 2% steel fibers enhanced the cubic and axial compressive strength and the compressive elastic modulus by 27.6, 23.7, and 47.7%, respectively. When the steel fiber content exceeded 2%, the cubic and axial compressive strength and the compressive elastic modulus decreased, having values still higher than those of the geopolymer concrete without steel fibers. The splitting tensile strength and flexural strength of the concrete were enhanced with increasing steel fiber content. When the steel fiber content was 2.5%, the increment of the splitting tensile strength was 39.8%, whereas that of the flexural strength was 134.6%. The addition of steel fibers effectively improved the fracture toughness of the geopolymer concrete. With 2.5% steel fibers, the initial fracture toughness had an increase of 27.8%, and the unstable fracture toughness increased by 12.74 times compared to that of the geopolymer concrete without the steel fibers.

中文翻译：

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钢纤维地聚合物混凝土的力学性能和断裂性能

在本研究中，钢纤维对地聚合物混凝土力学性能的影响——抗压、劈裂抗拉和抗弯强度；压缩弹性模量；和断裂特性 - 进行了评估。将铣削钢纤维掺入地质聚合物混凝土中，钢纤维的体积分数从 0 到 2.5% 不等。粉煤灰和偏高岭土被选为地质聚合物前体。断裂参数——临界有效裂纹长度、初始断裂韧性和不稳定断裂韧性——通过三点弯曲试验测量。结果表明，最佳掺量的钢纤维显着提高了地聚合物混凝土的各项力学性能。当钢纤维含量低于2%时，立方和轴向压缩强度和压缩弹性模量增加。加入2%的钢纤维使立方和轴向压缩强度和压缩弹性模量分别提高了27.6%、23.7%和47.7%。当钢纤维含量超过2%时，立方和轴向抗压强度和压缩弹性模量下降，仍高于不含钢纤维的地聚合物混凝土。混凝土的劈裂抗拉强度和抗弯强度随着钢纤维含量的增加而提高。当钢纤维含量为2.5%时，劈裂抗拉强度增幅为39.8%，而抗弯强度增幅为134.6%。钢纤维的加入有效地提高了地聚合物混凝土的断裂韧性。含 2.5% 钢纤维，