An elasto-viscoplastic thixotropic model for fresh concrete capturing flow-rest transition

TL;DR

The paper addresses the challenge of predicting flow and stoppage in fresh concrete, a non-Newtonian material whose flow can cease due to thixotropy. It introduces an elasto-viscoplastic Bingham solid model with a thixotropy evolution law, implemented within the Material Point Method (MPM), to capture flow-rest transitions without artificial stabilization. A closed-form stress-update algorithm with return-mapping enforces yielding and handles the evolving yield stress $ ilde{ au}_0=(1+oldsymbol{ abla}) au_0$, driven by the thixotropy parameter $oldsymbol{ abla}$ evolving via $rac{ ext{d}oldsymbol{ abla}}{ ext{d}t} = rac{A_{ ext{thix}}}{ au_0} - oldsymbol{ abla}oldsymbol{oldsymbol{D}}$; this enables realistic cessation when $oldsymbol{D}^p o 0$. Numerical demonstrations across slump-flow, L-box, and V-funnel tests show the EV model matches experimental data for dynamic flow and final runout while avoiding the perpetual-flow artifacts seen in regularized Bingham fluids. The framework also supports thixotropy parameter transfer across test setups, and highlights the importance of boundary effects such as rebars on local flocculation. Overall, the approach provides a physically consistent, robust tool for optimizing concrete casting and additive manufacturing processes, with clear paths for extending to multi-physics couplings and more detailed microstructural models.

Abstract

The flow properties of fresh concrete are critical in the construction industry, as they directly affect casting quality and the durability of the final structure. Although non-Newtonian fluid models, such as the Bingham model, are widely used to model these flow properties, they often fail to capture key phenomena, including flow stoppage, and frequently rely on non-physical regularization or stabilization techniques to mitigate numerical instabilities at low shear rates. To address these limitations, this study proposes an elasto-viscoplastic constitutive model within the continuum mechanics framework, which treats fresh concrete as a solid-like material with a rate-dependent yield stress. The model inherently captures the transition from elastic response to viscous flow following Bingham rheology, and vice versa, enabling accurate prediction of flow cessation without ad-hoc criteria. Additionally, a thixotropy evolution law is incorporated to account for the time-dependent behavior resulting from physical flocculation and shear-induced deflocculation. The proposed model is implemented within the Material Point Method (MPM), whose Lagrangian formulation facilitates tracking of history-dependent variables and robust simulation of large deformation flows. Numerical examples demonstrate the model's effectiveness in reproducing a range of typical concrete flow scenarios, offering a more physically consistent numerical tool for optimizing concrete construction processes and minimizing defects.

Figures (27)

• Figure 1: Typical concrete defects and flaws caused by improper casting. In Figure (d), 3DCP refers to the 3D Concrete Printing. Figures (a)-(c) are obtained from civilengineerdk2023civilengineermag2025gharpedia2025elop2023martinello2018amir2019; Figure (d) is adapted from suiker2020elastic.
• Figure 2: Stress-strain-rate relationship of the regularized Bingham model.
• Figure 3: Schematic illustration of flocculation- and deflocculation-induced strengthening in fresh-concrete characterized through the evolution of $\lambda$ over time.
• Figure 4: MPM computational cycle at each time step. In the MPM, a continuum body is discretized into a set of material points that move spatially. A material point is not a real physical particle, but rather a control volume representing a homogenized portion of the material domain. At the beginning of each time step, the kinematic fields are mapped from the material points to a background grid (with active nodes highlighted in blue). The next step is to solve the mass and momentum balance equations, considering imposed boundary conditions. At the end of the step, the kinematic fields are transferred back to the material points, where they are then advected through space. After deformation, the background grid can be reset to its original shape.
• Figure 5: Schematic illustration of the proposed stress return mapping algorithm in $\tau$--$p$ space and $\tau$--$\dot{\gamma}^p$ space.

Theorems & Definitions (2)

• Remark 1
• Remark 2