Abstract: In response to the problem of poor sealing of existing grouting materials and fire prevention and extinguishing materials in the goaf of Yaoqiao Coal Mine,through nitrogen adsorption and scanning electron microscopy experimental methods,the evolution of hydration products and micro pore size of materials cured for 7 days in different steel slag cement ratios under CO₂ curing condition is studied.The research results indicate that under CO₂ curing condition and steel slag dosage,the hydration process of cement can be improved,which in turn affects the development of pore structures of cement-based materials.The isotherm adsorption curves of the materials are all of type IV;With the increase of steel slag dosage,there is a decrease phenonmenon occures in their nitrogen adsorption amount,pore volume,and specific surface area;In SEM,it is also observed that with the addition of steel slag,hydration products of cement increased,further filling pore structures,reducing the number of pores,and improving the compactness of steel slag cement-based materials.This provides theoretical basis for using CO₂ curing technology to improve the performance of steel slag cement-based materials and provides reference for its application in filling and air leakage blocking engineering practice.