Discrete element simulation and theoretical calculation of flowability of cementitious suspensions containing attapulgite

The purpose of this paper is to clarify the mechanism of attapulgite affecting the macroscopic flowability of cementitious suspension, and to propose effective physical parameters that can characterize the flowability of attapulgite suspension. The discrete element method was used to simulate and analyze the evolution of microscopic parameters during dynamic and static flows of attapulgite suspension. The internal structural characteristics of the suspension were accurately represented using two essential parameters: Water film thickness (WFT) and bonding strength coefficient (ζ). A detailed analysis was undertaken to investigate the relationships between WFT, ζ and flow parameters. The results indicated that the adhesive rolling resistance linear model can well simulate the flowability of attapulgite suspension, the simulated and experimental results of flow expansion varied from 0.4% to 4.9%, and the flow velocity varied from 2.05% to 15.07%. The principal microscopic parameters significantly affecting the flowability of the suspension were the attractive range (D₀) and the maximum attractive force (F₀). Attapulgite influenced F₀ and D₀ by increasing the number of contact bonds and altering the distribution of contact normals, thereby resulting in subsequent adjustments to the flow parameters. The correlation coefficients of WFT and ζ with flow extension and flow velocity were 0.847, 0.864, 0.838 and 0.807, respectively, proving that WFT and ζ accurately reflected the F₀ and D₀ between particles of the suspension structure. WFT and ζ were the key indicators for determining the flow parameters of attapulgite suspensions.