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<p>This study proposes a novel approach for recycling waste concrete fines, a by-product of concrete crushing, in a resource- and energy-efficient manner. Cement paste ground to 300&#xa0;μm or less was used as a substitute for waste concrete fines, compacted at low pressure (0.6&#xa0;MPa), and subjected to carbonation curing under controlled temperature (30–60&#xa0;°C) and CO₂ pressure (1 or 3&#xa0;MPa) to obtain hardened specimens. The compressive strength, CO₂ uptake, and porosity of the specimens after carbonation curing were evaluated. Powders ≤ 150&#xa0;μm achieved the highest performance, with compressive strength up to 42&#xa0;N/mm² and &gt; 90% of theoretical CO₂ uptake after 6&#xa0;h at 60&#xa0;°C and 3&#xa0;MPa. Scanning electron microscopy confirmed that calcium carbonate precipitation on particle surfaces filled interparticle voids and enhanced binding. This low-energy compaction and CO₂ curing technique offers a promising pathway to recycle waste concrete fines while simultaneously achieving CO₂ reduction in construction. By enabling effective reuse of waste concrete fines, the method also supports the transition toward a circular economy in concrete-based construction.</p>

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Carbonation of recycled cement paste specimen: influence of paste particle size, temperature, and pressure on physical properties

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年2月14日

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  • Mari Kobayashi,
  • Keisuke Takahashi

摘要

This study proposes a novel approach for recycling waste concrete fines, a by-product of concrete crushing, in a resource- and energy-efficient manner. Cement paste ground to 300 μm or less was used as a substitute for waste concrete fines, compacted at low pressure (0.6 MPa), and subjected to carbonation curing under controlled temperature (30–60 °C) and CO₂ pressure (1 or 3 MPa) to obtain hardened specimens. The compressive strength, CO₂ uptake, and porosity of the specimens after carbonation curing were evaluated. Powders ≤ 150 μm achieved the highest performance, with compressive strength up to 42 N/mm² and > 90% of theoretical CO₂ uptake after 6 h at 60 °C and 3 MPa. Scanning electron microscopy confirmed that calcium carbonate precipitation on particle surfaces filled interparticle voids and enhanced binding. This low-energy compaction and CO₂ curing technique offers a promising pathway to recycle waste concrete fines while simultaneously achieving CO₂ reduction in construction. By enabling effective reuse of waste concrete fines, the method also supports the transition toward a circular economy in concrete-based construction.