The mineralogical study on the cemented soil using conventional micro-analysis methods is inaccurate due to the compositional complexity. A method of thermogravimetry combined with the thermodynamic modelling， which calculated the mineral supersaturation index（SI） based on pore solution composition was proposed. The dry mass ratio of cement/soil of the referenced cemented soil specimen was 1/9， and the modified specimens were prepared by using the sintered limestone ash（SLA） from the steel-making industry to replace cement in fractions of 5%-100% of the referenced mass. The unconfined compressive strength of all specimens was tested and the representative specimens were then selected for quantitative analysis of the critical minerals using the proposed method within the timeframe of 5-672 h after the mixing. The results demonstrate that the thermodynamic modelling provides direct implications of the occurrence state of the minerals of the cemented soil， which complementes the defect of the endotherms overlapping of thermogravimetry. Meanwhile， the long-term unconfined compressive strength improvement is benefitted from the increased Ca（OH）₂ SI in the pore solution with appropriate SLA addition.