The present study investigated the effect of the addition of steel fibres (SFs) and the synergy of SFs and carbon nanotubes (CNTs) on the mechanical properties of high-strength concrete (HSC). The addition of CNTs prevents the growth of micro cracks during loading, creates a denser composite and enhances the bond between SFs and cement paste. Three samples of HSC with a compressive strength of 68 MPa as a control sample, HSC with 1% volume fraction of SFs (HSC + SF1), HSC with 1% volume fraction of SFs and 0.8% cement weight of CNTs (HSC + SF1 + CNT) were prepared. The mechanical properties of samples including compressive strength, tensile strength, modulus of rupture, stress–strain curves and water absorption were investigated. The CNTs were mixed using an ultrasonic device in superplasticiser and water for 50 min to disperse homogenously. The results showed that adding 1% SFs to concrete improved the properties of concrete. The combined usage of SFs and CNTs in concrete increased the compressive strength, tensile strength and modulus of rupture up to 13.1, 39.7 and 49.3%, respectively, compared to HSC, and 6, 12 and 14.6%, respectively, compared to HSC + SF1. Furthermore, the combined use of steel fibres and CNTs improved the toughness of HSC by 35% compared to HSC + SF1 and reduced water absorption of HSC by about 15%.

中文翻译：

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钢纤维和高程碳纳米管对高强混凝土性能的综合影响

本研究调查了添加钢纤维 (SFs) 以及 SFs 和碳纳米管 (CNTs) 的协同作用对高强混凝土 (HSC) 力学性能的影响。添加 CNT 可防止加载过程中微裂纹的生长，形成更致密的复合材料并增强 SF 与水泥浆之间的结合。三个抗压强度为 68 MPa 的 HSC 样品作为对照样品，1% SFs 体积分数的 HSC (HSC + SF1)，1% SFs 体积分数和 0.8% CNTs 水泥重量的 HSC (HSC + SF1 + CNT) 被制备。研究了样品的力学性能，包括抗压强度、抗拉强度、断裂模量、应力-应变曲线和吸水率。使用超声波装置将碳纳米管在超增塑剂和水中混合 50 分钟以均匀分散。结果表明，在混凝土中添加 1% SFs 可以改善混凝土的性能。与 HSC 相比，SFs 和 CNTs 在混凝土中的组合使用分别使抗压强度、抗拉强度和断裂模量分别提高了 13.1%、39.7% 和 49.3%，与 HSC + SF1 相比分别提高了 6%、12% 和 14.6% . 此外，与 HSC + SF1 相比，钢纤维和 CNT 的组合使用使 HSC 的韧性提高了 35%，并使 HSC 的吸水率降低了约 15%。