Aging Viscoelastic Damage–Plasticity Constitutive Model for Concrete

Near or at initial setting, concrete becomes a solid-like, shape-stable, viscoelastic, deformable material that over time evolves to a stiff, strong, damage-prone solid. Binder reactions, temperature, and humidity drive and control this evolution. Conventional damage–plasticity constitutive models effectively describe the mechanical response of hardened concrete but fail to capture its gradual transition from the early-age to hardened state, which is critical for applications such as additive construction. This study presents an aging viscoelastic damage–plasticity (AVDP) constitutive model that extends conventional damage–plasticity formulations to capture the aging process from the early solid-like state (near or at the initial setting) to the hardened state obtained after hours, days, or weeks, depending on the material composition and environmental conditions. The presented model (1) is expressed in rate form to account for the evolution of mechanical properties while ensuring spatio-temporal continuity, which is often not guaranteed in the presence of varying mechanical properties; (2) introduces new cohesion functions to accurately reproduce stress–strain curves at various ages, both qualitatively and quantitatively; and (3) expresses major mechanical properties and model parameters in terms of an aging degree, which accounts for the extent/degree and kinetics of binder reactions and their dependence on environmental conditions such as temperature and humidity. Calibration with experimental data for normal concrete yielded a normalized root mean squared error below 3.5% and a coefficient of determination near unity across all ages. Regression-based parameter estimation revealed key model variables that evolve with aging, enabling efficient prediction of time-dependent behavior. Numerical analyses demonstrate the AVDP model’s capability to simulate the constitutive response of aging concrete under compression and environmental effects. The AVDP constitutive model provides a robust framework for simulating age-dependent response in additively constructed concrete structures following placement of initially stable layers.