Abstract
High-strength concrete (HSC) reinforced with steel fibre (SF) and carbon nanotube (HSCRSC) is a new type of high-strength composite concrete with good fluidity, high strength, toughness, durability and other remarkable advantages. HSCRSC can be widely used in underground structures, such as wellbores. In this study, HSCs ranging from 70 to 100 MPa were designed, and the effects of fibre on the performance of the HSCs were compared and analysed through single-doped and double-mixed SF and multi-walled carbon nanotubes. Results showed that the fibre effectively improved the uniaxial and multiaxial compressive strengths and durability of HSCs and changed the failure mode from brittle to ductile, especially in the case of multiaxial compression failure. HSCs remained intact, but the plain concrete specimens had fractured forms, such as flakes, columns and layers. Moreover, the ultimate strength of the biaxial compression was between 1.10 and 1.39 times higher than that of the uniaxial compression, satisfying the Kufer–Gerstle criterion. The ultimate strength of the triaxial compression was between 1.24 and 2.55 times higher than that of the uniaxial compression, adhering to the Willam–Warnke meridian criterion. The modified B3 model met the prediction accuracy of shrinkage and creep for HSC and surpassed the biaxial and triaxial compression ultimate strength models provided in this study. The absolute value of the relative error was less than 6%, indicating that the model and test data were reliable. All test results showed that HSCRSC exhibited satisfactory comprehensive performance.
Highlights
Underground structures, such as coal mine shafts up to 1000 m deep, and ground structures, such as super highrise buildings and super long-span bridges, have increasingly high requirements on the comprehensive performance of concrete
In accordance with the Chinese national standard GB/ T50081-2002 (2002), the mechanical property test specimens of concrete are in groups of three specimens which are in the same batch
To ensure that the loading head can be fine-tuned in real time during multiaxial loading, as well as the physical and geometric alignment, the wear reduction measures must be taken during the multiaxial compression tests
Summary
Underground structures, such as coal mine shafts up to 1000 m deep, and ground structures, such as super highrise buildings and super long-span bridges, have increasingly high requirements on the comprehensive performance of concrete. Adding steel fibre (SF), polypropylene fibre (PPF) and chopped basalt fibre (CBF) can resolve the brittleness of NWC and improve its toughness (Han et al 2019; Castoldi et al 2019; Caggiano et al 2016; Zhu et al 2019) Another type of fibre, namely multi-walled carbon nanotube (MWCN), has rarely been used in concrete because of its high price (Du et al 2017). HSC has high heat release due to its large amount of cementing material resulting from a hydration exothermic reaction (Pan and Meng 2016) This reaction leads to an increase in the temperature difference between internal and external concrete, early age shrinkage and long-term creep (Pan and Meng 2016). Experimental and theoretical bases for related research on and engineering application of high-strength, high-performance concrete are provided
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