Abstract This paper investigates for the first time the effect of blending hybrid steel-polypropylene fiber (SF-PF) and coarse aggregate (CA) on the stress–strain behavior of ultra-high performance concrete (UHPC) under uniaxial compression. The uniaxial compression tests of UHPC specimens were carried out for different SF-PF, CA dosages and PF aspect ratios. Results show that the addition of hybrid SF-PF not only helps build stronger interfaces in UHPC, but also alters the failure pattern. The single corporation of SF significantly enhances the toughness, while the compressive strength and elastic modulus are diminished due to the less strong and compact ‘skeleton’ structure composed of the cement unhydrated core and hydrated coating. The toughness can be further improved under larger PF aspect ratio for the higher PF utilization ratio in restraining micro-cracks’ growth. The inclusion of CA leads to an evident increase in both the strength and modulus attributed to the increasing packing density and stronger ‘skeleton’, but simultaneously reduces the deformability and toughness. PF could compensate for the adverse effects of CA on the toughness without sinking too much. Finally, a developed analytical model is presented for predicting the UHPC compressive stress–strain behavior considering the dosage of SF, PF and CA.

中文翻译：

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钢-聚丙烯混杂纤维和粗骨料夹杂对超高性能混凝土单轴受压应力应变行为的影响

摘要 本文首次研究了混合钢-聚丙烯纤维（SF-PF）和粗骨料（CA）对单轴压缩下超高性能混凝土（UHPC）应力应变行为的影响。对不同SF-PF、CA用量和PF纵横比的UHPC试样进行了单轴压缩试验。结果表明，添加混合 SF-PF 不仅有助于在 UHPC 中构建更强大的接口，而且还改变了故障模式。SF的单一组合显着提高了韧性，而由于水泥未水化芯和水化涂层组成的强度和致密的“骨架”结构不那么坚固，压缩强度和弹性模量降低。在较大的PF纵横比下，可以进一步提高韧性，以提高PF利用率以抑制微裂纹的生长。CA 的加入导致强度和模量的明显增加，这归因于堆积密度的增加和更强的“骨架”，但同时降低了可变形性和韧性。PF 可以补偿 CA 对韧性的不利影响而不会下沉太多。最后，提出了一个开发的分析模型，用于预测考虑 SF、PF 和 CA 剂量的 UHPC 压缩应力 - 应变行为。PF 可以补偿 CA 对韧性的不利影响而不会下沉太多。最后，提出了一个开发的分析模型，用于预测考虑 SF、PF 和 CA 剂量的 UHPC 压缩应力 - 应变行为。PF 可以补偿 CA 对韧性的不利影响而不会下沉太多。最后，提出了一种开发的分析模型，用于预测考虑 SF、PF 和 CA 剂量的 UHPC 压缩应力-应变行为。