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Feasible brittleness evaluation method and suggestion for brittleness reduction of cementitious materials based on stress–strain curve

Fu Qiang, Wang Zhenhua, Zhou Zhiming, Niu Ditao, Wang Yan

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e209, 2022

EN

In this study, a brittleness evaluation index B5 and brittleness–plasticity classification standard for cementitious materials were established, and a suggestion for brittleness reduction was proposed. The results showed that B5 established based on the principle of energy conversion can effectively characterize the variation in the brittleness of cementitious materials with the confining pressure, and the brittleness order of different cementitious materials. Based on the established brittleness–plasticity classification standard, the ranges of B5 corresponding to the weak, high and ideal brittleness are [0.3, 0.6), [0.6, 1) and 1, respectively; and those corresponding to the weak, high and ideal plasticity are [0.1, 0.3), (0, 0.1) and 0, respectively. Finally, a suggestion for brittleness reduction using prismatic aggregates and hybrid nanofibers, flexible and rigid fibers of different sizes was proposed, and the corresponding design process of cementitious materials with weak brittleness was given. The research results in this study provide a basis for the brittleness evaluation of cementitious materials and the design of cementitious materials with weak brittleness.

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Dynamic splitting tensile behaviour and statistical scaling law of hybrid basalt-polypropylene fibre-reinforced concrete

Fu Qiang, Zhao Xu, Zhang Zhaorui, Peng Gang, Zeng Xiaohui, Niu Ditao

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 4

123--144

EN

The dynamic splitting tensile behaviour of hybrid basalt‒polypropylene fibre-reinforced concrete (HBPRC) was investigated, and the reinforcing mechanism of the fibres was explored. The results indicate that the dynamic splitting tensile strength and dynamic energy dissipation capacity of HBPRC increased with strain rate. The effects of fibre type and content on the strain rate sensitivity of dynamic splitting tensile strength were consistent with that of dynamic dissipation energy. Furthermore, the dynamic splitting tensile strength of concrete was improved by adding appropriate content of basalt fibre (BF) and polypropylene fibre (PF), and the improving effect of hybrid BF and PF was the most significant. Excess fibres reduced the dynamic splitting tensile strength at low strain rates but improved it at high strain rates. The addition of fibres improved the dynamic dissipation energy and the impact resistance of concrete. With an increase in the strain rate, the pull-out lengths of BF and PF decreased gradually. When using hybrid BF and PF, the failure morphology of BF did not change considerably, although PF underwent more severe damage. Based on the weakest-link theory, a calculation model for the statistical scaling law of dynamic splitting tensile strength considering the strain rate effect was established.

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Dynamic non-linear Mohr-Coulomb strength criterion for hybrid basalt-polypropylene fibre-reinforced concrete under impact loading

Fu Qiang, Xu Wenrui, Huang Daguan, He Jiaqi, Zhang Lu, Kou Hailei, Niu Ditao

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 3

95--113

EN

Variations in the dynamic triaxial strength of hybrid basalt–polypropylene fibre-reinforced concrete (HBPRC) with strain rate and confining pressure were investigated, and a dynamic non-linear Mohr–Coulomb (M–C) strength criterion for HBPRC was established. The results showed that the dynamic strength of HBPRC increased non-linearly with the strain rate and confining pressure; however, the strain rate effect decreased with an increase in the confining pressure. The restraint effect of the basalt fibre and polypropylene fibre on the cracks enhanced the strain rate effect of the dynamic strength of concrete. The cohesion of HBPRC increased with the strain rate and confining pressure but decreased with an increase in the amount of fibre monofilaments. However, the internal friction angle showed a reverse trend. The established dynamic non-linear M–C strength criterion reflected the relationship of the dynamic strength of HBPRC with the confining pressure and strain rate, as well as the effect of fibre content on dynamic strength. The less average standard deviation and the tangential relationship between the strength envelope and the Mohr’s circle of stress demonstrated the applicability of the established dynamic non-linear M–C strength criterion.