Construction sludge is generated from excavation works during tunnel constructions and pile constructions. The strength is very low because the sludge contains a lot of water. Thereby, the sludge cannot be used directly for construction of embankment, road subgrade, and back-filling. To overcome this issue, stabilizers can be used to improve the strength of the sludge. Meanwhile, paper sludge ash-based stabilizer (PSAS) has been recently developed in Japan. The paper sludge ash is a waste generated by the incineration of paper sludge discharged from paper mills. In this study, the PSAS and blast furnace cement class B (BFCB) were used as stabilizers to improve the strength of sludge. Then, the swelling potential of treated sludge with different initial water contents and per-compaction curing periods was investigated. CBR specimens were prepared in the laboratory to evaluate the swelling potential. The swelling potential of the treated sludge samples was compared with that of the untreated samples. Based on the test results, discussion was made on the effects of initial water content and per-compaction curing period on the swelling potential of treated and untreated samples. According to the result analysis, the lower the water content during compaction, the higher the swelling potential. However, a significant reduction of swelling potential was observed for the treated soil in comparison with the untreated samples. Furthermore, the difference in the swelling potential of treated samples due to differences in the number of per-compactions curing periods was insignificant.