Investigating the effects of fresh-state mechanics on early-age failure mechanisms in 3D concrete printing

A voxel-based finite element framework was employed to simulate fresh-state stability in extrusion-based 3D concrete printing. The model incorporated time-dependent material laws for Young’s modulus and cohesion and activated voxels according to the actual deposition sequence, enabling realistic layer-by-layer build-up under gravity. Experimentally characterized printable mortars reported in the literature were used to investigate how rheological evolution influences deformation behavior, failure mechanisms, and achievable build height. The simulations showed that mixtures exhibiting rapid early-age stiffening and strong cohesion development provided higher load-bearing capacity but failed abruptly through elastic-type buckling once a critical state was reached. Mixtures with more gradual rheological evolution displayed smoother deformation and enhanced ductility, accompanied by lower build height. The equivalent stress–plastic strain response captured these contrasting regimes, linking sharp peaks to stiffness-dominated, brittle behavior and extended plateaus to viscoplastic accommodation. The findings highlight that optimal printability depends not solely on maximizing early strength but on synchronizing material evolution with deposition timing. The voxel-based activation strategy proved effective for predicting instability onset, stress localization, and collapse morphology using literature-derived rheology, offering a validated and open-source approach for pre-printing assessment and data-informed mixture and process design.