The paper presents a robust approach for concrete stress blocks to evaluate accumulated internal damage during the post-heating phase of the fire. In this study, computational efforts have been made to get insight into the phenomena that occur during gradual cooling by predicting heat propagation, thermal response, material constitutive behavior, and transformation in stress blocks of concrete at different time intervals of a fire. The methodology includes heat transfer analysis to anticipate temperature profile at various time intervals, followed by stress analysis for the predicted thermal profile using a simplified mechanics-based sectional analysis method. The average layer temperature distribution is used in the stress analysis. The heating and post-heating analyses used the Euro code 4 theoretical stress-strain model as an input parameter. The modelled stress analysis tool is then employed to conduct a parametric study incorporating different strain profile and neutral axis depth combinations. The stress capacity of individual concrete fibers is presented by non-dimentionalising with the corresponding strength value. The findings of the study include a thermal evolution and stress block behavior in different fire time intervals. Even after the fire is extinguished, the surface concrete layers cool while the inner concrete layers heat, resulting in a differential thermal gradient occurred over the depth. Concrete fibers exhibit significant stress loss in the post-heating phase of fire due to the very high fire temperature encountered during the heating stage. Despite the recovery, the stress reduction becomes stable over the post-heating phase.