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<p>Urban sludge, characterized by its large volume and poor engineering properties, has become a significant environmental issue in the southeastern coastal regions of China. This research investigates a method for transforming urban sludge into a usable soil resource through the utilization of a low–carbon binder (CFS), providing a novel approach for sludge treatment and resource recycling. To achieve this, multi–scale experimental research and mechanistic analysis were conducted, focusing on the unit and microscopic experiments of industrial waste slag in collaboration with CFS solidification of engineering waste sludge. The materials used in CFS included Portland cement (PC), fly ash (FA), and steel slag (SS), with the incorporation of response surface methodology (RSM). The findings indicate that the singular addition of FA and SS exhibits a limited solidification effect on the sludge. However, significant synergistic interactions were observed between PC and FA, and between FA and SS. Based on the unconfined compressive strength test results of sludge cured for 7&#xa0;days, the optimal ratio of the CFS was determined to be PC: FA = 40.7%:40.7%:18.6%, demonstrating the most effective sludge enhancement. The falling head permeability test results showed that the stabilized sludge had permeability approximately two orders lower in magnitude than the untreated sludge. Characterization techniques, including X–ray diffraction (XRD), scanning electron microscopy (SEM), energy–dispersive spectroscopy (EDS), thermogravimetric analysis (TGA) and identified the primary products within the stabilized sludge matrix as ettringite (Aft), calcium–silicate–hydrate (C–S–H) gel, and calcite. Additionally, cured sludge had a lower pore volume than its raw counterpart, according to mercury intrusion porosimetry (MIP) data, which suggests a stronger microstructural structure after stabilization. The improvement in sludge properties attributed to CFS is primarily due to the hydration reaction, pozzolanic reaction, ion exchange, and carbonation. Compared to traditional Portland cement, the CFS curing agent offers comparable economic benefits and substantial environmental advantages.</p>

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Physico-mechanical performance and micro–mechanism analysis on urban sludge modified with a low carbon binder

  • 期刊论文

  • 发表日期：

    2025年7月28日

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  • J.-F. Zhu,
  • Y.-N. Xia,
  • L.-Y. Ju,
  • H. Yang,
  • Z.-Q. Wang,
  • J.-Y. Jin,
  • Y.-C. Zou,
  • Y.-C. Liao

摘要

Urban sludge, characterized by its large volume and poor engineering properties, has become a significant environmental issue in the southeastern coastal regions of China. This research investigates a method for transforming urban sludge into a usable soil resource through the utilization of a low–carbon binder (CFS), providing a novel approach for sludge treatment and resource recycling. To achieve this, multi–scale experimental research and mechanistic analysis were conducted, focusing on the unit and microscopic experiments of industrial waste slag in collaboration with CFS solidification of engineering waste sludge. The materials used in CFS included Portland cement (PC), fly ash (FA), and steel slag (SS), with the incorporation of response surface methodology (RSM). The findings indicate that the singular addition of FA and SS exhibits a limited solidification effect on the sludge. However, significant synergistic interactions were observed between PC and FA, and between FA and SS. Based on the unconfined compressive strength test results of sludge cured for 7 days, the optimal ratio of the CFS was determined to be PC: FA = 40.7%:40.7%:18.6%, demonstrating the most effective sludge enhancement. The falling head permeability test results showed that the stabilized sludge had permeability approximately two orders lower in magnitude than the untreated sludge. Characterization techniques, including X–ray diffraction (XRD), scanning electron microscopy (SEM), energy–dispersive spectroscopy (EDS), thermogravimetric analysis (TGA) and identified the primary products within the stabilized sludge matrix as ettringite (Aft), calcium–silicate–hydrate (C–S–H) gel, and calcite. Additionally, cured sludge had a lower pore volume than its raw counterpart, according to mercury intrusion porosimetry (MIP) data, which suggests a stronger microstructural structure after stabilization. The improvement in sludge properties attributed to CFS is primarily due to the hydration reaction, pozzolanic reaction, ion exchange, and carbonation. Compared to traditional Portland cement, the CFS curing agent offers comparable economic benefits and substantial environmental advantages.