Molecular investigation of freshly made cement-paste rheology for 3D-printing application

Cement is a key building material whose rheological behavior critically impacts emerging applications, such as 3D-printed concrete. Precise flow control and setting is essential for layer-by-layer construction; yet, the early-stage rheology of fresh cement paste remains poorly understood. This work addresses that gap using a multiscale modeling framework that integrates atomistic and coarse-grained simulations to investigate molecular mechanisms behind shear thinning. Atomistic simulations focus on tricalcium silicate (C3S), modeling the interactions between hydrated C3S layers using the INTERFACE forcefield. Interaction energies are parameterized into Morse potentials and used to inform an effective coarse-grained model, where cement particles and water are simplified into bead-based systems. Sensitivity analysis is used to identify a stable mesoscale cement–cement Morse interaction for dissipative particle dynamics (DPD) simulations. Using DPD and reverse nonequilibrium molecular dynamics, we compute viscosity across varying shear rates and water-to-cement ratios. Results show an increase in viscosity at lower water contents and shear rates, which agrees with experimental observations. Microstructural analysis further shows that shear accelerates cement–cement contact renewal without requiring complete network breakup. This study offers physical insights and an atomistically informed framework for interpreting viscosity-related flowability trends in 3D-printed cement composites.