The purpose of this study was to assess the performance of high water content clayey sediments at different liquid limits as the clays are treated with cement-based solidifying materials. Three clay samples are obtained from different locations in the Kumamoto Reservoir. Two types of cement-based solidifying agents, namely, ordinary Portland cement and a cement–fly ash binder, were used. Using the initial water content of clay and the mixing amount of the solidifying agent as experimental variables, a cone penetration test was performed on the solidifying agent-stabilized clays to obtain the cone index (q_c). The results showed that when the water content to cementitious content ratio (w/A_W) was used as a parameter for evaluating the improvement of solidifying agent-stabilized clay, different forms of improvements were observed when different water and solidifying agent contents were used. This implied that the parameter w/A_W was not suitable for evaluating the improvement of such clay. A new parameter, K, representing the content of solidifying agent, was introduced to account for the water content. For all sampled clays, the correlation coefficients for the K–ln q_c relationship exceeded 0.9. Considering the effect of the liquid limit of the samples, the modified content of the solidifying agent (K_L) was introduced to evaluate the cone index of the stabilized soils. It was discovered that the proposed equation unified the assessment of the improvement of the three samples of Kumamoto clayey sediments owing to the new parameter, K_L.

The effective and sustainable treatment of high-water-content waste dredged clay (WDC) remains a significant challenge in water conservancy engineering. In this study, we focused on the treatment of WDC produced by Kumamoto Ohkirihata Reservoir. The study examined the effect of two types of cement-based solidifiers, namely, ordinary Portland cement (OPC) and cement–fly ash agent (DF), on three clay samples collected from different locations. The cone index test was used to assess the samples’ properties. The dosage of cement required for effective improvement with DF was significantly reduced (by about 47–55%), compared to OPC. Moreover, the dewatering efficiency of WDC improved by the simple dewatering method of vertically placing environmental protection materials. Within seven days, the average water content of the WDC decreased to below the liquid limit compared with natural air drying. Finally, the dosage of DF required to stabilize the WDC under effective improvement conditions was reduced by 37–58%, which is higher than the dosage of OPC reduction (22–50%). The reduction in water content reduced the pore space of the soil particles, benefiting the internal bonding of DF-stabilized clay. Dewatering methods facilitate the use of DF solidifiers, facilitating sustainable and environmentally friendly improvement in WDC.

This review examines recent advances in hydrated lime-activated systems using hydrated lime (HL) as the sole alkaline activator, with particular emphasis on the effects of reactive precursors and auxiliary materials on mechanical properties and carbonation behavior. Compared with conventional strong alkali activators, HL provides a milder alkaline environment and an additional Ca source, promoting precursor reactions and the formation of C–S–H, C–(A)–S–H, and other calcium-containing hydration products. Precursor characteristics, multicomponent mixture design, water-to-binder ratio, and curing conditions strongly influence reaction kinetics, strength development, hydration products, and microstructure. Carbonation is a key process that distinguishes hydrated lime-activated systems from conventional strong alkali-activated systems and plays an important role in their microstructural and mechanical development. It has a dual effect on material performance, as it can contribute to matrix densification but may also lead to the degradation of calcium-containing binding phases as carbonation progresses. Therefore, material composition and curing conditions should be considered together to balance mechanical performance and carbonation behavior. From a sustainability perspective, hydrated lime-activated systems show promise in by-product utilization, reduced use of conventional strong alkalis, substitution of OPC, and CO₂ uptake through mineral carbonation. Further systematic studies are needed to evaluate these potential sustainability benefits.