Currently, traditional vertical barrier materials are associated with large carbon footprints and high costs (in some regions) due to the widespread use of Portland cement and sodium-based bentonite materials. In recent years, a new technology of Carbonized Reactive Magnesia Cement (CRMC) has gradually been developed to sequester CO2 using Eco-cement. The application prospects of CRMC in vertical barrier materials are explored in this study. The changes in flowability of Reactive Magnesia Cement (RMC) slurry and the unconfined compressive strengthen (UCS) and permeability characteristics of CRMC treated soils are investigated. The results show that the fluidity of RMC slurry decreases further with the increase of MgO substitute cement content. For RMC slurry meeting the fluidity requirements, UCS increased rapidly in the early period (3 h) after carbonization, reaching 348.33 kPa, and the hydraulic conductivity k decreased (k < 1 x10(- 7) cm/s) in the later period (14d), and the final hydraulic conductivity reached 6.13 x 10(- 8) cm/s (28d). The pores of the material are filled with a large number of hydration products and carbonates, which alters the pore size distribution structure of the material. This is the reason for the mechanical properties and permeability performance of CRMC treated soils. The overall results of this study well demonstrate that CRMC treated soils, as a new, environmentally friendly, and cost-effective material, have great potential in the construction of vertical barriers.

The ionic soil stabilizer (ISS) can synergistically enhance the mechanical properties and improve the engineering characteristics of iron tailings soil in conjunction with cementitious materials such as cement. In this paper, the influence of ISS on the cement hydration process and the charge repulsion between iron tailings soil particles was studied. By means of Isothermal calorimetry, X-ray diffraction (XRD), Scanning electron microscope (SEM), and Low-field nuclear magnetic resonance microscopic analysis methods such as (LF-NMR), X-ray photoelectron spectroscopy (XPS), Non-evaporable water content and Zeta potential were used to clarify the mechanism of ISS-enhanced cement stabilization of the mechanical properties of iron tailings soil. The results show that in the cement system, ISS weakens the mechanical properties of cement mortar. When ISS content is 1.67%, the 7 d compressive strength of cement mortar decreases by 59.8% compared with the reference group. This retardation arises due to carboxyl in ISS forming complexes with Ca2+, creating a barrier on cement particle surfaces, hindering the hydration reaction of the cement. In the cement-stabilized iron tailings soil system, ISS has a positive modification effect. At 0.33% ISS, compared with the reference group, the maximum dry density of the samples increased by 6.5%, the 7 d unconfined compressive strength increased by 35.3%, and the porosity decreased from 13.58% to 11.85%. This is because ISS reduces the double electric layer structure on the surface of iron tailings soil particles, reduces the electrostatic repulsion between particles, and increases the compactness of cement-stabilized iron tailings soil. In addition, the contact area between cement particles increases, the reaction energy barrier height decreases, the formation of Ca(COOH)2 reduces, and the retarding effect on hydration weakens. Consequently, ISS exerts a beneficial effect on augmenting the mechanical performance of cement-stabilized iron tailings soil.

During the improvement and reinforcement of peat foundation soils, cement hydration alters the pH of the subsurface water-soil ecosystem. This change negatively impacts humus acid, the main component of organic matter in peat soils, thereby deteriorating the engineering properties of peat foundations. Tests simulated the subsurface alkaline environment by using cement treat peat soils in actual projects. The objective is to understand the dynamic processes of cement hydration affecting peat environments and to investigate the dissolution properties of humus acid in peat soil under alkaline environment during cement hydration. Results indicate that peat soil environment transforms into an alkaline environment under cement hydration, where humus acid in peat soil exhibits dissolution properties under alkaline environment. Humus acid undergoes dissolution and reacts in alkaline environment. As the pH of the environment stabilizes, the dissolution of humus acid practically ceases. As humus dissolves, the pores inside peat soil expand, and the skeleton structure becomes less compact, reducing the soil's compactness connectedness, leading to significant strength loss. The dissolution of humus acid can significantly damage the peat soil structure. study provides valuable insights into engineering issues arising from humus acid dissolution in peat soil under alkaline environment induced by cement hydration.

The carbonation of cementitious materials with CO2 2 was utilised to prepare fluid solidified soil, and the characteristics of fluid solidified soil were investigated. Experimental tools such as flow extensibility, unconfined compressive strength, thermogravimetric analysis, and scanning electron microscopy were employed to explore the influence laws of different carbon dioxide pressures, cement dosages, and initial water contents on the strength properties and microstructural evolution of fluid consolidated soils. The results showed that with the increase of CO2 2 pressure, the flow characteristics of carbonated fluid solidified soil decreased and the unconfined compressive strength increased. This is due to the fact that after the carbonation process, the formation of carbonation products such as calcium carbonate and hydration products in the fluid solidified soil significantly improves the microstructure of the soil, which is the main reason for the increase in its strength. In addition, the carbonation test revealed that the ratio of the amount of COQ generated to the mass of cement was as high as 18.36 % under the condition of COQ pressure up to 0.20 MPa, which fully proved the high efficiency of the carbonation technology. Therefore, the carbonation technology has great potential and broad application prospects in optimising the performance of fluid solidified soil as well as achieving effective carbon sequestration.