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<p>This study systematically investigated the preparation process, mechanical properties, and long-term durability of recycled permeable bricks using recycled aggregate from waste concrete and recycled micronized powder as primary raw materials. Synergistic ball milling (20&#xa0;min) and 3 wt% sodium silicate modification significantly enhanced the pozzolanic activity of RMP,&#xa0;resulting in&#xa0;a 23.4% higher 3-day compressive strength (19.5&#xa0;MPa) than the unmodified control group. An orthogonal experimental design determined the optimal mix proportion: 10% cement replacement by RMP, 25% natural aggregate substitution by RA, and a coarse-to-fine aggregate ratio of 7:3. Mechanical tests showed that the optimized formulation achieved a 28-day compressive strength of 50.53&#xa0;MPa, representing an 8.3% reduction from the pure-cement reference group while meeting the requirements of GB/T 25993–2023 (Sect.&#xa0;5.2.1). After 25 freeze–thaw cycles, the mass loss and strength loss rates were 1.6% and 8.4%, respectively, both&#xa0;significantly&#xa0;below the standard limits of 5% and 25%. The permeability coefficient reached 8.15&#xa0;mm/s.s, exceeding the minimum standard requirement (1.0&#xa0;mm/s) by over 700%. Microstructural analysis demonstrated that the pozzolanic reaction of RMP generated C-S–H gel and ettringite (AFt), which filled pore spaces and optimized the interfacial transition zone (ITZ) structure. This mechanism effectively compensated for the strength reduction caused by RA. Pore size distribution analysis showed: (i) surface pores predominantly ranging from 0.5–3&#xa0;mm (&gt; 70% concentration), and (ii) a cross-sectional bimodal distribution with a primary peak (0.5–2&#xa0;mm) ensuring permeability and a secondary peak (0.1–0.5&#xa0;mm) enhancing ITZ strength through microfilling effects. Life cycle assessment (cradle-to-gate system boundary)&#xa0;revealed&#xa0;that the global warming potential (GWP) was 28% lower and the resource depletion potential (RDP) was 22% lower than those of conventional cement permeable bricks. This study provides a high-value utilization approach for concrete waste in permeable infrastructure, promoting circular economy goals in sustainable construction.</p>

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Waste concrete recycled permeable bricks: mechanical properties, permeability mechanisms, frost resistance and carbon emission reduction

  • 期刊论文

  • 发表日期：

    2026年4月2日

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  • Zhong-jie Wang,
  • Chao-qiang Wang,
  • Yi-lian Dai,
  • Sheng-hui Gao

摘要

This study systematically investigated the preparation process, mechanical properties, and long-term durability of recycled permeable bricks using recycled aggregate from waste concrete and recycled micronized powder as primary raw materials. Synergistic ball milling (20 min) and 3 wt% sodium silicate modification significantly enhanced the pozzolanic activity of RMP, resulting in a 23.4% higher 3-day compressive strength (19.5 MPa) than the unmodified control group. An orthogonal experimental design determined the optimal mix proportion: 10% cement replacement by RMP, 25% natural aggregate substitution by RA, and a coarse-to-fine aggregate ratio of 7:3. Mechanical tests showed that the optimized formulation achieved a 28-day compressive strength of 50.53 MPa, representing an 8.3% reduction from the pure-cement reference group while meeting the requirements of GB/T 25993–2023 (Sect. 5.2.1). After 25 freeze–thaw cycles, the mass loss and strength loss rates were 1.6% and 8.4%, respectively, both significantly below the standard limits of 5% and 25%. The permeability coefficient reached 8.15 mm/s.s, exceeding the minimum standard requirement (1.0 mm/s) by over 700%. Microstructural analysis demonstrated that the pozzolanic reaction of RMP generated C-S–H gel and ettringite (AFt), which filled pore spaces and optimized the interfacial transition zone (ITZ) structure. This mechanism effectively compensated for the strength reduction caused by RA. Pore size distribution analysis showed: (i) surface pores predominantly ranging from 0.5–3 mm (> 70% concentration), and (ii) a cross-sectional bimodal distribution with a primary peak (0.5–2 mm) ensuring permeability and a secondary peak (0.1–0.5 mm) enhancing ITZ strength through microfilling effects. Life cycle assessment (cradle-to-gate system boundary) revealed that the global warming potential (GWP) was 28% lower and the resource depletion potential (RDP) was 22% lower than those of conventional cement permeable bricks. This study provides a high-value utilization approach for concrete waste in permeable infrastructure, promoting circular economy goals in sustainable construction.