This study proposes a novel saturation-based compaction quality control approach for surplus soils treated with paper sludge ash and rice husk ash. Conventional dry density (ρd) and the water content methods are limited by the significant influence of compaction energy (EC) and soil type on the ρd-w relationship, particularly in challenging materials like surplus soils, which exhibit mud-like properties due to their high water content. A series of compaction and cone index tests investigated the effects of target initial water content (w/wL), compaction energy (EC), and water absorption capacity (Wab(t)) on compaction properties and strength development of PSA- and RHA-treated surplus soils. Results indicate that the cone index strength (qc)–degree of saturation (Sr) relationship remains independent of w/wL and EC at lower qc values. However, the strength is significantly influenced by stabilizer addition ratio (A), Wab(t), and w/wL, but remains independent of compaction energy. Parameter β(t), which is the product of Wab(t) and A, was used to investigate its cumulative effect on the strength development of the treated clay. The impacts of Wab(t) on the water content of the treated clay were examined, and the modified water content (w*), which accounts for absorbed water as a solid, was found to correlate more strongly with qc than the measured water content (w). Finally, the proposed saturation-based approach offers advantages over traditional methods, including independence from w/wL and EC, improving the accuracy and reliability of the compacted soil stability and performance.