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<p>The application of recycled concrete (RC) in the construction industry has yielded significant economic and social benefits in recent years. However, as RC structures reach the end of their service life, they themselves become a new source of demolition waste. To investigate the recyclability of secondary recycled aggregate (RRA) and to compare the performance of secondary recycled concrete (RRC) with that of RC, this study systematically examines the content influence of secondary recycled coarse aggregate (RRCA) on the overall performance of concrete. The analysis focuses on crack resistance, mechanical properties, and durability, with varying replacement ratios of recycled coarse aggregate (RCA) and RRCA as the main variables. Furthermore, the mechanisms underlying performance changes are explored in relation to microstructural characteristics. The results indicate that increasing the replacement ratio of both RCA and RRCA leads to a reduction in concrete strength. However, at equivalent replacement levels, the strength of RRC is comparable to that of RC. At a 100% replacement ratio, the 28-day splitting tensile strength and compressive strength of RRC are only 3.3% and 3.1% lower, respectively, than those of RC. Nevertheless, due to the higher water absorption and porosity of RRCA compared to RCA, concrete incorporating RRCA exhibits a higher cracking tendency and inferior crack resistance. In addition, its permeability resistance and frost resistance are significantly lower than those of RC. Overall, the crack resistance, impermeability, and frost resistance of RRC with a 50% RRCA replacement ratio (RRC50) are comparable to those of RC with 100% RCA replacement (RC100). Microstructural analysis reveals that, at the same recycled aggregate content, the number of transition pores in RRC is significantly greater than in RC, while the total area of gel pores and macro pores shows little difference. This suggests that transition pores have a limited effect on strength but play a critical role in reducing impermeability and frost resistance. Moreover, a greater number of micro cracks and loosely distributed hydration products are observed in RRC specimens, which further explains their inferior crack resistance, impermeability, and frost resistance compared to RC. In summary, although the application of RRC is feasible to a certain extent, it is recommended that the replacement ratio of RRCA should not exceed 50%.</p>

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Mechanical and durability investigation of concrete made with natural, recycled, and secondary recycled coarse aggregate

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月28日

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  • Mingming Zhang,
  • Xiaojia Ji,
  • Weifeng Zhu,
  • Tingting Lu

摘要

The application of recycled concrete (RC) in the construction industry has yielded significant economic and social benefits in recent years. However, as RC structures reach the end of their service life, they themselves become a new source of demolition waste. To investigate the recyclability of secondary recycled aggregate (RRA) and to compare the performance of secondary recycled concrete (RRC) with that of RC, this study systematically examines the content influence of secondary recycled coarse aggregate (RRCA) on the overall performance of concrete. The analysis focuses on crack resistance, mechanical properties, and durability, with varying replacement ratios of recycled coarse aggregate (RCA) and RRCA as the main variables. Furthermore, the mechanisms underlying performance changes are explored in relation to microstructural characteristics. The results indicate that increasing the replacement ratio of both RCA and RRCA leads to a reduction in concrete strength. However, at equivalent replacement levels, the strength of RRC is comparable to that of RC. At a 100% replacement ratio, the 28-day splitting tensile strength and compressive strength of RRC are only 3.3% and 3.1% lower, respectively, than those of RC. Nevertheless, due to the higher water absorption and porosity of RRCA compared to RCA, concrete incorporating RRCA exhibits a higher cracking tendency and inferior crack resistance. In addition, its permeability resistance and frost resistance are significantly lower than those of RC. Overall, the crack resistance, impermeability, and frost resistance of RRC with a 50% RRCA replacement ratio (RRC50) are comparable to those of RC with 100% RCA replacement (RC100). Microstructural analysis reveals that, at the same recycled aggregate content, the number of transition pores in RRC is significantly greater than in RC, while the total area of gel pores and macro pores shows little difference. This suggests that transition pores have a limited effect on strength but play a critical role in reducing impermeability and frost resistance. Moreover, a greater number of micro cracks and loosely distributed hydration products are observed in RRC specimens, which further explains their inferior crack resistance, impermeability, and frost resistance compared to RC. In summary, although the application of RRC is feasible to a certain extent, it is recommended that the replacement ratio of RRCA should not exceed 50%.