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

TL;DR

This paper introduces an elasto-viscoplastic thixotropic model for fresh concrete that accurately captures flow-rest transitions and flow cessation, improving upon traditional models by incorporating rate-dependent yield stress and time-dependent thixotropic behavior.

Contribution

The study develops a novel continuum mechanics-based model that combines elasto-viscoplasticity with thixotropy, implemented within the Material Point Method for improved simulation of concrete flow.

Findings

Successfully predicts flow stoppage and transition behaviors.

Demonstrates robustness in large deformation flow simulations.

Provides a more physically consistent tool for construction process optimization.

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.