This study focuses on loess in the Lanzhou region and employs a self-developed LM-1 ionic cementitious curing agent (mainly sodium silicate) combined with cement for loess improvement. Through mechanical tests, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) analysis, the mechanical properties, microstructure, and mineralogical evolution of composite-improved loess were systematically investigated, with emphasis on revealing the reinforcement mechanism. The results show that combining LM-1 and cement significantly enhances the unconfined compressive strength (UCS) of loess. The optimal proportion of 1.5% LM-1 + 10% cement achieves 7-day and 28-day UCS values of 3.43 MPa and 4.12 MPa, representing increases of 69.0% and 54.7% over 10% cement alone, and outperforming 12% cement-only specimens. This formulation develops a uniform, dense C-S-H gel network with optimized pore structure and reduced microcracks. LM-1 generates hydrated silicate products through alkali-activated reactions, which together with cement hydration C-S-H gel form a dual-gel cementation system, while effectively accelerating cement hydration. This provides a theoretical basis and technical support for balancing cement reduction and performance enhancement in subgrade reinforcement and slope protection in loess regions.

To investigate the engineering performance and microstructural evolution of magnesium chloride–cement composite-stabilized loess, laboratory tests were conducted on loess treated with different cement contents and MgCl₂ dosages. Compaction tests, unconfined compressive strength (UCS) tests after 7 and 28 days of curing, X-ray diffraction (XRD), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) analyses were performed to establish the relationship among hydration products, pore evolution, and strength development. The results showed that MgCl₂ increased the maximum dry density and reduced the optimum moisture content, thereby improving the compactability of cement-stabilized loess. The UCS exhibited a non-monotonic response to increasing MgCl₂ dosage, with an initial decrease followed by an increase and a subsequent decline. The optimal MgCl₂ content was 1.7% for 8% cement and 1.8% for both 10% and 12% cement. Integrated XRD, SEM, and NMR analyses revealed that an appropriate MgCl₂ dosage regulates the hydration and microstructural evolution of cement-stabilized loess through the formation of Mg-bearing reaction products, enhanced interparticle bonding, and refinement of the pore structure. The resulting reductions in total porosity and the proportion of medium and large pores were closely associated with the observed strength enhancement, establishing a clear hydration–pore structure–strength relationship. Although the 12% cement–1.8% MgCl₂ mixture achieved the highest strength, the 10% cement–1.8% MgCl₂ mixture provided a more favorable balance between mechanical performance and cement consumption. These findings provide mechanistic insight into MgCl₂-regulated hydration and pore-structure evolution and support the optimized use of MgCl₂ as an auxiliary modifier for cement-stabilized loess.