Abstract The surface adhesion mortar of recycled coarse aggregate (RCA) is the main factor leading to poor aggregate quality, and it also affects the internal structure and mechanical properties of recycled aggregate concrete (RAC). To improve the quality of RCA and mechanical properties of RAC, self-developed mortar removal equipment was used to strengthen the RCA. Then, the RCA was soaked in 1, 2, and 3% nano-silica solutions, and the vibration-mixing process was used to improve the quality of RAC. In addition, the microstructure of the RAC was examined via scanning electron microscopy to observe its improvement effect on the microstructure of the RAC. The results indicated that the quality of the RCA was improved by mechanical and physical strengthening, and the water-absorption rate and crushing value decreased by 32.9 and 23.9%, respectively. The improvement effect of nano-immersion on the RAC was obvious. The optimal condition was a combination of physical strengthening, 2 days of immersion in 2% NS solution, and vibration stirring. The 28 day compressive strength increased by 31.3%, the splitting tensile strength increased by 23%, and the flexural strength increased by 49%. The proposed strengthening method improves the mechanical properties and microstructure of RAC. The results of this study provided a technical reference for the mechanical strengthening of RAC and promotion of the application and popularization of RAC.

中文翻译：

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纳米增强再生骨料混凝土的力学性能和微观结构

摘要 再生粗骨料（RCA）表面粘结砂浆是导致骨料质量差的主要因素，同时也影响再生骨料混凝土（RAC）的内部结构和力学性能。为提高RCA的质量和RAC的力学性能，采用自主研发的砂浆清除设备对RCA进行加固。然后，将RCA浸泡在1%、2%和3%的纳米二氧化硅溶液中，并采用振动混合工艺来提高RAC的质量。此外，通过扫描电子显微镜检查RAC的微观结构，观察其对RAC微观结构的改善作用。结果表明，RCA的质量通过机械和物理强化得到了提高，吸水率和破碎值分别下降了32.9%和23.9%，分别。纳米浸没对RAC的改善效果明显。最佳条件是物理强化、在 2% NS 溶液中浸泡 2 天和振动搅拌的组合。28天抗压强度提高31.3%，劈裂抗拉强度提高23%，抗弯强度提高49%。所提出的强化方法改善了 RAC 的机械性能和微观结构。本研究结果为RAC的机械强化和RAC的推广应用和推广提供了技术参考。28天抗压强度提高31.3%，劈裂抗拉强度提高23%，抗弯强度提高49%。所提出的强化方法改善了 RAC 的机械性能和微观结构。本研究结果为RAC的机械强化和RAC的推广应用和推广提供了技术参考。28天抗压强度提高31.3%，劈裂抗拉强度提高23%，抗弯强度提高49%。所提出的强化方法改善了 RAC 的机械性能和微观结构。本研究结果为RAC的机械强化和RAC的推广应用和推广提供了技术参考。