Ultra-high performance concrete (UHPC) is gaining popularity for large-scale applications due to its superior mechanical performance and durability. However, the extent of large applications remains limited because of the high cost and carbon footprint of UHPC components like steel fibers. This study aims to incorporate different types of recycled steel fibers (RSF) from landfill tires as an alternative to manufactured steel fibers (MSF), specifically in semi- or non-proprietary UHPC mixtures, to realize and validate an ultra-economical UHPC solution. An average compressive strength of 18.9 ksi was developed for UHPC RSF, a 9–13 % decrease compared to UHPC MSF. However, fiber aspect ratio and volume play a significant role in tensile and flexural performance, and the recommended fiber volume should be around 6.3 % and 1.6 % for Type I and II RSF, respectively. The truck mixing confirms the application of reduced RSF volume in large-scale mixing, which demonstrated acceptable mechanical performance. Overall, the study outlines the opportunities and challenges of using RSF in scalable UHPC but also demonstrates, for the first time, the validity of RSF with a high aspect ratio and recommends the proper RSF dosage for comparable mechanical behavior as using high-end MSF.

中文翻译：

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再生轮胎钢纤维特性对可扩展超经济型 UHPC 裂纹行为和力学性能的影响


超高性能混凝土 （UHPC） 因其卓越的机械性能和耐用性而在大规模应用中越来越受欢迎。然而，由于钢纤维等 UHPC 组件的成本和碳足迹高，大型应用的范围仍然有限。本研究旨在从垃圾填埋场轮胎中加入不同类型的再生钢纤维 （RSF） 作为人造钢纤维 （MSF） 的替代品，特别是在半专有或非专有 UHPC 混合物中，以实现和验证超经济的 UHPC 解决方案。UHPC RSF 的平均抗压强度为 18.9 ksi，与 UHPC MSF 相比降低了 9-13%。然而，纤维纵横比和体积在拉伸和弯曲性能中起着重要作用，I 型和 II 型 RSF 的推荐纤维体积应分别约为 6.3 % 和 1.6 %。卡车混合证实了减少 RSF 体积在大规模混合中的应用，这证明了可接受的机械性能。总体而言，该研究概述了在可扩展的 UHPC 中使用 RSF 的机遇和挑战，但也首次证明了具有高纵横比的 RSF 的有效性，并为与使用高端 MSF 相当的机械行为推荐了适当的 RSF 剂量。