With the increasing utilization of underground space, engineering muck has become a potential urban risk. This study employed a waste-to-waste strategy to promote its low-carbon recycling by using rice husk ash (RHA) as a stabilizer, with a focus on elucidating the stabilization mechanisms through multi-scale analysis. The results showed that RHA synergized with cement, enhancing unconfined compressive strength and water stability, while reducing the specific surface area and swelling potential of the engineering muck. The optimal RHA dosage was found to be between 4 % and 6 %, with cement content ranging from 3 % to 9 %. The multi-scale analysis demonstrated that the stabilization mechanisms of RHA-cement stabilized soil were governed by two main factors: structural enhancement and surface modification, both of which were driven by the promotion of novel hydration products through the incorporation of RHA. Specifically, the needle-like and columnar minerals effectively filled soil pores, forming a dense, robust skeletal structure that enhanced the mechanical properties of the stabilized soil. Meanwhile, the honeycomb-like C-S-H gel adhered to soil particle surfaces, repairing cracks and reinforcing interparticle bonding, thus improving the overall structural integrity. AFM analysis further revealed that the honeycomb-like C-S-H gel consisted of rod-like nanoparticles that were regularly arranged on the soil surface. This feature increased surface roughness, reduced fractal dimensions, and created a multi-scale structure of micro-papillae and nano-hairs with a lotus leaf effect, significantly enhancing the hydrophobic properties of the soil.