Thermodynamic modeling helps to reveal insights into the basic chemical kinetics of dissolution and precipitation in cementitious materials, but relevant applications to cement-stabilized soils have seldom been reported. Based on the thermodynamic database of Cemdata18 and the pore solution composition of cement-stabilized soils, this study formulated a specialized thermodynamic model, using essential thermodynamic constants for soil minerals that were calculated to ensure the model’s accuracy. Two commercial admixtures of alkaline activator and polynaphthalene sulfonate were selected for the different modification mechanisms and plain and modified cement-stabilized soils were prepared. Compressive strength was tested to determine the specimens for pore solution analysis and the influences of the admixture type and dose on dissolution and precipitation were investigated by modeling the ionic activity products and saturation indexes. An X-ray diffraction (XRD) analysis was performed to verify and complement the thermodynamic results. The major research findings were that (1) thermodynamic modeling can be reliably applied to cement-stabilized soils by providing the essential thermodynamic data and an appropriate product model, (2) the pozzolanic reaction is accelerated by increasing the OH⁻ concentration in the pore solution, while the cement hydration is highly dependent on the dissolution of Ca(OH)₂ and the relevant complexes and (3) the dissolution equilibrium of Ca(OH)₂ is directly affected by the alkaline activator dissolution and is indirectly affected by the polynaphthalene sulfonate adsorption of the reactants.

This study conducts quantitative analysis of the degree of mortar carbonation under the influence of a multi-dimensional interaction. The HABT method is used to determine the degree of mortar carbonation and is compared with the TGA method. The result shows that the determination result of the HABT method is only 3.86% higher than that of the TGA method. This method is suitable for determining the degree of carbonation. The study analyzes the influence of factors such as water-reducing agents on the degree of carbonation, demonstrates the relationship between pore structure and mortar carbonation, and explores the degree of carbonation of corner areas and general edges. It is found that as time prolongs, the degree of carbonation and carbonation depth will no longer show a linear relationship. Carbonation time also affects the direction of the carbonation front line and the effect of water-reducing agents on concrete carbonation. The degree of carbonation is linearly related to carbonation time and the number of exposed surfaces. The water~cement ratio and the number of exposed surfaces affect the porosity of concrete. There is interaction in the multi-dimensional area of mortar. The degree of carbonation at two-dimensional corners is 1.20~1.25 times that at general edges, and the degree of carbonation at three-dimensional corner areas is 2.03~2.11 times that at general edges. Accounting based on general edges will underestimate the carbon sink capacity of mortar structures.

To investigate the evolution of impermeability and pore structure in concrete under long-term service, systematic tests were conducted on submerged concrete from dam sections with over 75 years of service. Results show that the surface water permeation resistance index of concrete in the downstream section of the main dam is only 9.19 × 10⁻⁹, significantly lower than that of concrete from the upstream of the main dam (UMD), downstream of the main dam (DMD), upstream of the auxiliary dam (UAD), and upstream of the weir (UW). Moreover, its impermeability improves noticeably within the 0–100 mm depth range. Mercury intrusion porosimetry revealed that the median pore diameter, average pore diameter, pore content, and porosity in this region reach 306.7 nm, 55.4 nm, 35.64%, and 3.961 mm, respectively—all markedly higher than in other dam sections. Combined XRD and SEM/EDS analyses indicate that crystallization pressure from saline solutions in the coastal environment, together with long-term carbonation, leads to structural loosening and increased porosity in the downstream concrete of the main dam, ultimately degrading its impermeability performance.

In response to the urgent demand for ship lock structures for high durability and construction performance of concrete, this study carries out research on the mix proportion optimization of High-Performance Self-Compacting Concrete. The influence of laws of water-cement ratio (W/C) and dosage of expanding agent on the workability, mechanical properties, free shrinkage, restrained expansion rate, and impermeability performance of self-compacting concrete was systematically analyzed. The results show that the incorporation of an appropriate amount of expanding agent can effectively compensate for shrinkage, improve impermeability, and has no adverse effect on mechanical properties. The decrease of W/C significantly improves strength and impermeability, but increases shrinkage, reduces the tensile-compressive ratio of the material, and exerts an adverse effect on the crack resistance of concrete. Considering all properties comprehensively, it is recommended that the project adopt the mix proportion scheme with a unit water consumption of 183 L/m ³ , a W/C of 0.38, and an internal addition of 30 kg/m ³ expanding agent. This scheme not only ensures good construction performance and mechanical properties but also significantly improves the crack resistance and impermeability of concrete. It achieves the balance of properties under a low-cementitious material system, and provides key material and technical support for extending the service life of ship lock projects and reducing maintenance costs.