The study aimed to assess how the chemical composition of slag concrete affects its resistance to chloride erosion. Two types of slag (A and B) with distinct mineralogical compositions, along with four types of cement (W, X, Y, and Z), were utilized as raw materials. A fixed cement substitution rate of 60% was employed to prepare slag concrete specimens. These specimens underwent testing for chloride ion adsorption and diffusive transport, involving various cement-slag combinations. The analysis included XRD analyses, thermomechanical modeling, and piezometric mercury testing. Evaluation included assessing the adsorption capacity and diffusive transport of concrete across different cement-slag combinations. Test results indicated that incorporating slag enhances both the chloride adsorption capacity and reduces the chloride diffusion rate in concrete. Concrete containing slag with high aluminum content exhibited greater chloride adsorption capacity compared to that with low aluminum content slag. Among the cements tested, Cement W demonstrated the highest chloride adsorption capacity, whereas Cement Z exhibited the lowest. Additionally, C3A and C3S significantly influenced the chloride adsorption capacity, whereas higher pH levels reduced physical chloride adsorption. The formation of carbon-aluminum salts, the filling effect of limestone, and pore size reduction contributed to increased chloride adsorption, while pore aperture reduction decreased chloride ion permeability.