The strength and deformation modulus of artificial cemented clay can be expressed as a function of an equivalent overconsolidation ratio related to the cementation effect. A model for predicting the undrained strength of cement-treated soil with statistical scatter due to mixing quality is presented, combining cementation effects into the critical state concept. The crux of the discussion is how the statistical scatter of the undrained compressive strength and the deformation modulus due to mixing quality should be considered. Further, the applicability of the model was verified by comparing the predicted results with the results from a series of undrained triaxial tests on cement-treated clay with differing cementation and initial water content.