This paper presents a micromechanics model aimed at understanding the mechanisms that influence the nonlinear basic creep of concrete when subjected to uniaxial compression. The model builds upon the affinity concept related to nonlinear creep, proposing that each microcrack contributes incrementally to the damage within the concrete, resulting in a gradual increase in its compliance. The research draws on experimental data from existing literature, utilizing strain and acoustic emission measurements obtained during a multi-stage creep test to inform the model's development. This process includes identifying the laws governing microcrack evolution for both short-term and sustained loading conditions. Additionally, strain measurements from four single-stage creep tests are employed to validate the model. The findings suggest that the nonlinear creep behavior of concrete is driven by two primary mechanisms: first, the stress-induced stick–slip transition of viscous interfaces at the nanoscale within the cement paste, which is captured phenomenologically by the affinity concept; and second, damage caused by microcracking, which becomes particularly significant when the applied stress exceeds approximately 70% of the material's strength.