The effectiveness of the stabilisation/solidification process depends upon a number of factors, the most significant of which are the type of binder, contaminants, and soil undergoing treatment. In accordance with the principles of sustainable construction, alternatives to cement are sought after, with the objective of achieving the lowest environmental impact while maintaining a high level of strength and effective binding of the contaminant. In the study of the stabilisation/solidification of zinc-contaminated loess, incinerated sewage sludge fly ash with reactive magnesia was selected as the binder, and the UCS of the mixtures and microstructure was verified after 28 days of treatment. The values obtained were related to the strength of a reference sample and exhibited by S/S products using Portland cement. The findings verified the effectiveness of the selected materials in the S/S process. Following a 28-day treatment with 30 and 45% IFA and MgO in a 2:1 ratio, the samples were classified as a hard subgrade, suitable for civil engineering purposes, due to the UCS values achieved, ranging from 0.52 to 0.9 MPa. Furthermore, a correlation between the UCS values and the water content was identified, and the mineralogical composition of S/S products was determined with the use of the XRD technique.

Guided by the solidification of loess contaminated with heavy metal ions (HMs), a natural inorganic diatomite (NID) was developed as curing agent under an alkaline activator (AA). The curing time, NID content and AA type on the mechanical properties of contaminated soil and solidification effect of HMs were investigated. The solidification source was analysed by microstructure measurement. As curing time increased, the solidification effect increased, with an optimum curing time of 28 days. The higher the content of NID, the stronger the solidification ability. Nevertheless, the strength showed a tendency of initial increase and subsequent decrease. The strength was maximum when NID content reached 10%. The AA created an alkaline environment to promote solidification. In comparison to Na2SiO3 solution, NaOH solution is more effective in the adsorption of HMs. The larger ionic radius of Pb2+ relative to Cu2+, limited HMs migration ability, thereby facilitating solidification.

Due to climatic factors and rapid urbanization, the soil in the Loess Plateau, China, experiences the coupled effects of dry-wet cycles and chemical contamination. Understanding the mechanical behavior and corresponding microstructural evolution of contaminated loess subjected to dry-wet cycles is essential to elucidate the soil degradation mechanism. Therefore, direct shear and consolidation tests were performed to investigate the variations in mechanical properties of compacted loess contaminated with acetic acid, sodium hydroxide, and sodium sulfate during dry-wet cycles. The mechanical response mechanisms were investigated using zeta potential, mineral chemical composition, and scanning electron microscopy (SEM) tests. The results indicate that the mechanical deterioration of sodium hydroxide- contaminated loess during dry-wet cycles decreases with increasing contaminant concentration, which is mainly attributed to the thickening of the electrical double layer (EDL) by Na & thorn; and the precipitation of calcite, as well as the formation of colloidal flocs induced by OH-, thus inhibiting the development of large pores during the dry-wet process. In contrast, the attenuation of mechanical properties of both acetic acid- and sodium sulfate-contaminated loess becomes more severe with increasing contaminant concentration, with the latter being more particularly significant. This is primarily due to the reduction of the EDL thickness and the erosion of cement in the acidic environment, which facilitates the connectivity of pores during dry-wet cycles. Furthermore, the salt expansion generated by the drying process of saline loess further intensifies the structural disturbance. Consequently, the mechanical performance of compacted loess is sensitive to both pollutant type and concentration, exhibiting different response patterns in the dry-wet cycling condition.