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<p>Environmental pollution caused by construction waste has become increasingly severe. To effectively mitigate the environmental pressure exerted by construction waste, the preparation of recycled concrete has garnered widespread attention. However, recycled concrete exhibits low compressive strength and poor durability. Therefore, the incorporation of Nano-SiO<sub>2</sub>, basalt fibers, and CaCl<sub>2</sub> was employed to improve the performance of recycled concrete. A systematic orthogonal experimental study was conducted to investigate the effects of the combined dosages of these four materials on the mechanical and durability properties of recycled concrete. The order of influence effects on compressive strength is:CaCl<sub>2</sub> &gt; coarse recycled aggregate &gt; basalt fibers &gt; Nano-SiO<sub>2</sub>. The order of influence effects on flexural strength is: coarse recycled aggregate &gt; basalt fibers &gt; CaCl<sub>2</sub> &gt; Nano-SiO<sub>2</sub>. The optimal factor level combination, determined via comprehensive balanced optimization, was A<sub>2</sub>B<sub>2</sub>C<sub>2</sub>D<sub>1</sub>, corresponding to Nano-SiO<sub>2</sub> at 1.8%, CaCl<sub>2</sub> at 1.2%, basalt fiber volume content at 0.3%, and recycled aggregate at 20%. SEM analysis was performed to assess the compactness and elucidate the modification mechanism. Results indicated that, with the optimal additive proportions, the compressive strength of recycled concrete increased by 45%, and the flexural strength improved by 21.96%. After 300 freeze-thaw cycles, the mass loss rate was 3.02%; the chloride ion migration coefficient was 1.83 × 10<sup>−12</sup> m<sup>2</sup>/s, the carbonation depth at 28&#xa0;days was 7.26&#xa0;mm. The appropriate addition of Nano-SiO<sub>2</sub> triggered a pozzolanic effect, consuming part of the calcium hydroxide (Ca(OH)<sub>2</sub>) and forming C-S-H gel. The incorporation of CaCl<sub>2</sub> facilitated the formation of a “bridging” structure, accelerating cement hydration and promoting more complete C-S-H growth. The addition of basalt fibers hindered crack propagation and reduced internal porosity within the specimens.</p>

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Research on the Development, Mechanical Properties, and Durability of Nano-SiO2-Basalt Fiber-CaCl2 Recycled Concrete

  • 期刊论文

  • 发表日期：

    2026年7月9日

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  • Qianyu Chen,
  • Huaguo Gao,
  • Xinxin Shi,
  • Kuo Dong,
  • Zhida Zhang,
  • Jingke Qian

摘要

Environmental pollution caused by construction waste has become increasingly severe. To effectively mitigate the environmental pressure exerted by construction waste, the preparation of recycled concrete has garnered widespread attention. However, recycled concrete exhibits low compressive strength and poor durability. Therefore, the incorporation of Nano-SiO2, basalt fibers, and CaCl2 was employed to improve the performance of recycled concrete. A systematic orthogonal experimental study was conducted to investigate the effects of the combined dosages of these four materials on the mechanical and durability properties of recycled concrete. The order of influence effects on compressive strength is:CaCl2 > coarse recycled aggregate > basalt fibers > Nano-SiO2. The order of influence effects on flexural strength is: coarse recycled aggregate > basalt fibers > CaCl2 > Nano-SiO2. The optimal factor level combination, determined via comprehensive balanced optimization, was A2B2C2D1, corresponding to Nano-SiO2 at 1.8%, CaCl2 at 1.2%, basalt fiber volume content at 0.3%, and recycled aggregate at 20%. SEM analysis was performed to assess the compactness and elucidate the modification mechanism. Results indicated that, with the optimal additive proportions, the compressive strength of recycled concrete increased by 45%, and the flexural strength improved by 21.96%. After 300 freeze-thaw cycles, the mass loss rate was 3.02%; the chloride ion migration coefficient was 1.83 × 10−12 m2/s, the carbonation depth at 28 days was 7.26 mm. The appropriate addition of Nano-SiO2 triggered a pozzolanic effect, consuming part of the calcium hydroxide (Ca(OH)2) and forming C-S-H gel. The incorporation of CaCl2 facilitated the formation of a “bridging” structure, accelerating cement hydration and promoting more complete C-S-H growth. The addition of basalt fibers hindered crack propagation and reduced internal porosity within the specimens.