Application of CO2-induced carbonate minerals as novel grouting materials for soil improvement

This study evaluates CO 2 -induced carbonate minerals synthesised by direct CO 2 absorption, as novel injectable materials for permeation grouting, aiming to enhance the sustainability of ground improvement techniques. The investigation started with Scanning Electron Microscopy (SEM), and X-ray Diffraction (XRD) analyses that attested the formation of siderite (FeCO 3 ) and calcite (CaCO 3 ) carbonate minerals, which precipitated in the soil voids. Sand samples treated with siderite grout achieved the highest Unconfined Compressive Strength (UCS) of 70 kPa at 11 % siderite content; those treated with calcite grout reached 53 kPa at a calcite content of 16 %. Peat, of a 12 kPa UCS, reached a UCS of 36 kPa after grouting with 20 % siderite, and 23 kPa after grouting with 19 % calcite. Life Cycle Assessment (LCA) of carbonate grout mixtures against conventional cement-based grout showed an 85 %–87 % reduction in the global warming potential and improvements in 13–14 out of the 18 environmental impact categories respectively for calcite and siderite grout, with major reductions in fossil and mineral resource scarcity, ground level ozone and fine particle formation. The proposed carbonate-based grouts comply with green chemistry principles and SDGs and have the potential advantage of consuming captured CO 2 from industrial sources. Overall, carbonate minerals synthesised using CO 2 give promise for grouting applications, while providing a potential route for CO 2 utilisation. • CO 2 -induced carbonate minerals were studied as alternatives to cement-based grouts. • XRD and SEM analyses attested the formation of siderite (FeCO 3 ) and calcite (CaCO 3 ). • FeCO 3 grouts show finer crystals and higher unconfined compressive strengths. • Synthesised CaCO 3 and FeCO 3 grouts reduce GWP by ∼85–87 % vs cement. • Life cycle trade-offs include higher water use and stratospheric ozone depletion.