Abstract
Abstract Cemented paste backfill (CPB) is considered to be a concentrated suspension in which tailings are bonded together by the hydraulic binder and water, and it has a high solid volume concentration (≥50 vol.%). Although the shear thinning and thickening of CPB has been extensively reported in literature, the shear history effects have been ignored in previous studies. In this paper, by using rheometer and Focused Beam Reflectance Measurement, the relationship between the rheological properties and microstructure of the paste under different shear histories was studied. The results have shown that at a low shear rate, CPB revealed shear thinning, low yield stress and low index parameters; while exhibited shear thickening, high yield stress and high consistency index when at high shear rates of shear history. This agreed with the general trends shown in the FBRM analysis. It was proposed that the action of shear is beneficial to particle dispersion, whereas a high shear rate history tends to promote the aggregation of particles. It was revealed that both shear thinning and thickening of paste are related to the situation of particles (flocculation, dispersion and aggregation), and shear history effects play an important role in rheological properties of CPB.
Highlights
Utilizing concentrated suspensions for tailings disposal and other complex multiphase mixtures requires studying interesting rheological phenomena, such as shear thinning and thickening [1, 2]
The relationship between yield stress and shear rate as shown in Figures 6-9 was drawn according to the measurements of the experiment (The different groups in each graph are named according to the shear rate in Step-4)
A synergistic effect of shear history, solid content, and additives used appeared to control the rheological behavior of Cemented paste backfill (CPB), which has been proved in many researches [42, 43]
Summary
Utilizing concentrated suspensions for tailings disposal and other complex multiphase mixtures requires studying interesting rheological phenomena, such as shear thinning and thickening [1, 2]. Shear thinning and thickening are typical rheological behaviors associated with concentrated particulate suspensions [3, 4] They are two opposing phenomena that can often be observed with suspensions undergoing shear, and the two rheology phenomena of concentrated suspensions have been well studied for many years, and some progress has been made [5,6,7]. They have a common feature in that the material rheograms show a sharp change in flowcurves of concentrated suspensions under different shear histories, and were often referred to as nonlinear change in rheological behavior [8]. Several explanations have been frequently proposed for the change in rheological parameter when deemed as a function of shear rate, including the development of doublets, network structures and a variety of other shear-induced structures [9, 10]
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