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Recent developments in pullout behaviors and tensile properties of ultra-high-performance concrete reinforced with steel fiber

Wu Hansong, Zang Zhishu, Deng Shiyi, Shen Aiqin, Cai Yanxia, Ren Guiping, Pan Hongmei

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 3

art. no. e216, 2023

EN

Ultra-high-performance concrete (UHPC) has gained significant attention as a construction material owing to its exceptional mechanical properties and durability. Steel fibers are widely utilized as a reinforcement material for UHPC. Achieving excellent bond and tensile performances is considered to be a predominant issue for the utilization of steel fiber reinforcement. This comprehensive review presents recent research progress on the bond and tensile properties of steel-fiber-reinforced UHPC. First, an overview of the experimental methods for evaluating pullout and tensile performance is provided. Subsequently, the factors influencing these properties are discussed in detail. The review then comprehensively examines several analytical models for steel-fiber-reinforced UHPC, ranging from traditional approaches to innovative methods such as artificial neural network models, genetic algorithms, deep learning methods, inverse analysis, and micromechanical damage models. Furthermore, the correlations between pullout behavior, tensile performance, and flexural strength are explored in detail. Finally, the review addresses essential considerations and summarizes various modification techniques for improving the pullout and tensile performances, including physical and chemical methods of modifying the steel fiber surface and UHPC matrix. This review serves as a valuable reference for researchers and engineers in relevant fields, promoting further research and application of steel fiber-reinforced UHPC.

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Effect of the addition of basalt fiber on life-cycle anti-cracking behavior of concrete

Li Yue, Shen Aiqin, Guo Yinchuan

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no. e92, 2023

EN

To evaluate the cracking resistance of basalt fiber reinforced concrete (BFRC) in different periods, including the curing period and the service period, restrained slab, restrained ring and three-point bending tests were conducted. In this investigation, various fiber lengths (i.e., 6 mm, 12 mm, and 18 mm) and fiber contents (ranging from 0.07% to 0.09%) were used to prepare BFRC. The plastic shrinkage behavior of BFRC was characterized by monitoring evaporation, bleeding, capillary pressure and plastic shrinkage strain, and the mechanism of the effect of the fibers in reducing plastic cracking was subsequently revealed. The restrained shrinkage strain in the steel ring was measured, and the cracking potential index (ΘCR) was assessed for all BFRC specimens. Furthermore, the fracture behavior, including the strain distribution and cracking process, was monitored by the digital image correlation (DIC) technique. The results showed that long basalt fibers (12 mm and 18 mm) effectively delayed the occurrence of the plastic settlement and reduced capillary pressure, resulting in a decreased crack width of concrete. The basalt fibers also led to a pronounced decrease in the ΘCR of the concrete, particularly at an early curing age (3 d). Moreover, the DIC test revealed that the crack occurrence was accompanied by a fuctuation in the strain field during the fracture process. Basalt fibers considerably slowed the formation and evolution of the strain stripes of the concrete under load, and consequently, the fracture energy and cracking resistance capacity of concrete can be improved by the addition of basalt fibers.

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A review on autogenous self‑healing behavior of ultra‑high performance fiber reinforced concrete (UHPFRC)

Yao Chao, Shen Aiqin, Guo Yinchuan, Lyu Zhenghua, He Ziming, Wu Hansong

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e145

EN

Ultra-high performance fiber reinforced concrete (UHPFRC) is well known for its superior workability, strength, ductility as well as durability, but its intrinsic self-healing ability is rarely valued and developed. This review focuses on the inherent potential or superiority, characterization, and mechanism of autogenous healing UHPFRC, aiming to obtain fundamental data for its mixture innovation, design, and application. High potentialities of autogenous self-healing UHPFRC depend on its excellent component requirements (fiber; abundant binding particles), mix design (high cementitious materials content, low water-binder ratio, moderate fiber content), rehydration capacity, and shrinkage or loading-initiated cracking features. Meantime, the generation of cracks makes the internal substances include active ingredients exposed to the external environment such as air, water, and temperature, which induces physical, chemical, and mechanical interaction between them at cracks. Intrinsic partial or entire sealing of the multiple cracks in UHPFRC has been proven to improve the safety and durability of UHPFRC infrastructures. A higher healing rate exists in cracks with a width of 75-175 μm, which is connected with crack healing kinetics, and the width of total healing cracks can reach up to 162 μm, which is mainly filled with calcium carbonate. Continuous accumulation of healing products at cracks can effectively improve the mechanical properties and suppress the decay of transport performance and steel fiber corrosion. Furthermore, mild fiber corrosion contributes to the partial restoration of flexural strength during the self-healing process.