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<p>MgO solidification carbonation of shield tunneling sludge clay is a low-carbon and efficient green modification method, but the carbon fixation rate of shield tunneling sludge clay during the solidification carbonation process has not been clearly defined, which deserves further exploration. This article is based on an improved device for quantitatively measuring the absorption of CO<sub>2</sub> during accelerated carbonation process. The variation laws of CO<sub>2</sub> absorption, soil mass, <i>UCS</i>, and carbon fixation rate of MgO solidification carbonation sludge clay were studied. The optimal solidification carbonation scheme was found from the perspective of CO<sub>2</sub> absorption, and carbon emissions were calculated based on engineering practice. The results show that MgO solidification carbonation of slurry shield sludge clay is an effective method for CO<sub>2</sub> fixation. Increasing carbonation time and carbonation pressure can improve the soil CO<sub>2</sub> absorption and carbon fixation rate. Although increasing MgO content can increase the absorption of CO<sub>2</sub>, with the increase of MgO content, the carbon fixation rate shows a decreasing trend, from 0.89 to 0.55. Under the curing age of 7&#xa0;days, a carbonation pressure of 200&#xa0;kPa, an MgO content of 7%, and a carbonation time of 4&#xa0;h can be recommended as the most environmentally friendly, cost-effective solution. The <i>UCS</i> reached 912.8&#xa0;kPa, meeting the strength requirements for expressways and first-class highways, with a carbon fixation rate of 0.54, thereby achieving a synergistic advantage of meeting strength targets and efficient carbon fixation. Using MgO as a curing agent offers superior energy-saving and emission reduction benefits: the net carbon emission of the MgO solidification carbonation process is 55.31&#xa0;kg/t, which corresponds to 68.25% and 60.05% of those of conventional curing agents such as cement and lime, respectively. This method provides a sustainable disposal pathway for the resource utilization of shield tunnel waste soil, achieving a synergy between carbon fixation and material value addition.</p>

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Carbon fixation and carbon emission analysis of MgO solidification carbonation shield tunneling sludge clay

  • 期刊论文

  • 发表日期：

    2026年6月15日

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  • Min Fanlu,
  • Li Bingzhi,
  • Zhang Nan,
  • Shen Zheng,
  • Li Yongbo,
  • Zhang Yazhou,
  • Qi Yujie

摘要

MgO solidification carbonation of shield tunneling sludge clay is a low-carbon and efficient green modification method, but the carbon fixation rate of shield tunneling sludge clay during the solidification carbonation process has not been clearly defined, which deserves further exploration. This article is based on an improved device for quantitatively measuring the absorption of CO2 during accelerated carbonation process. The variation laws of CO2 absorption, soil mass, UCS, and carbon fixation rate of MgO solidification carbonation sludge clay were studied. The optimal solidification carbonation scheme was found from the perspective of CO2 absorption, and carbon emissions were calculated based on engineering practice. The results show that MgO solidification carbonation of slurry shield sludge clay is an effective method for CO2 fixation. Increasing carbonation time and carbonation pressure can improve the soil CO2 absorption and carbon fixation rate. Although increasing MgO content can increase the absorption of CO2, with the increase of MgO content, the carbon fixation rate shows a decreasing trend, from 0.89 to 0.55. Under the curing age of 7 days, a carbonation pressure of 200 kPa, an MgO content of 7%, and a carbonation time of 4 h can be recommended as the most environmentally friendly, cost-effective solution. The UCS reached 912.8 kPa, meeting the strength requirements for expressways and first-class highways, with a carbon fixation rate of 0.54, thereby achieving a synergistic advantage of meeting strength targets and efficient carbon fixation. Using MgO as a curing agent offers superior energy-saving and emission reduction benefits: the net carbon emission of the MgO solidification carbonation process is 55.31 kg/t, which corresponds to 68.25% and 60.05% of those of conventional curing agents such as cement and lime, respectively. This method provides a sustainable disposal pathway for the resource utilization of shield tunnel waste soil, achieving a synergy between carbon fixation and material value addition.