Mechanical Properties of Paste Slurry under Constant Shear Rate in Initial Structure Failure Process

Chaoqun Dai,Bin Li,Zhiqiang Chen,Yan Qi,Aixiang Wu

doi:10.1155/2019/2971563

Abstract

At constant shear rate, the process of deformation of the paste slurry is divided into two stages: one is the initial structural failure process with increasing shear stress; the other is the thixotropic process with decreasing shear stress after yielding. Based on experiments, the mechanical response characteristics of the paste slurry in the initial structural failure process under different shear rate conditions were studied in this paper. At the same time, according to the Maxwell model, the stress-time model equation describing the initial structure failure stage of the paste was deduced and the constant shearing test was carried out on the paste slurry at different mass concentrations; the model equation was used to fit the test data of the initial stress increment stage. The results showed that the model equation had higher prediction accuracy and better popularity. In the initial structural failure stage, the paste had a nonlinear stress-time relationship. At different shear rates (0.05, 0.5, and 1 s−1), the lower the rotation speed, the smoother the curve, and the slurry at various stages in the yielding process could be more clearly reflected; in the range of low constant shear rate (0.03, 0.05, and 0.07 s−1), the initial stress and yield stress of the paste increased with the increase of shear rate at the same mass concentration, and the time to yield was shorter. The yield stress increased exponentially with mass concentration.

Highlights

The process of deformation of the paste slurry is divided into two stages: one is the initial structural failure process with increasing shear stress; the other is the thixotropic process with decreasing shear stress after yielding
The mechanical response characteristics of the paste slurry in the initial structural failure process under different shear rate conditions were studied in this paper
When the paste slurry is at rest, the hydration hardening effect of the cement is gradually enhanced and the internal floc structure is gradually developed. e hydration product closely connects the inert tailings particles to form a spatial network structure with a certain strength; the system resists external disturbance is gradually enhanced, causing the paste slurry to lose fluidity as a whole, exhibiting a solid-like character [3]. e pressure required to restart the pipeline transportation is bound to be higher than the normal pipeline delivery pressure and even a pipe burst accident. erefore, studying the mechanical response characteristics of structural failure during the initial startup of paste slurry can provide theoretical guidance for pipeline design and is very beneficial for ensuring pipeline safety and economic operation

Summary

D Figure 1

It applies the fundamental concept of the yield stress as a true material property associated with the strength of a continuous network structure found in flocculated suspensions [15]. When an external shear rate c was imposed on a soft solid at time t 0 and was kept constant thereafter, the stress σt first increased with the strain c c_ · t. Such behavior may be attributed to the mere stretching of the “network bonds” interconnecting the structural elements (particles or aggregates or both). Equation (8) was an equation according to the Maxwell model to describe the stress-time relationship of the paste slurry in the initial structural failure process

Experiment

Conclusion