Multi-scale analysis of 3D printable high-strength engineered cementitious composite with carbon and polyethylene fibres: rheology, printability and hydration kinetics in structural components

The issue which is always debated in the magnetorheological (MR) fluid is the dynamic and static yield stress values obtained from a flow curve. To evaluate these, a suitable constitutive equations are required. The aim of this article is to provide suitable rheological models for the prediction of static and dynamic yield stress from a single flow curve under wide shear rate and magnetic field ranges. The proposed model is well suited for isotropic and anisotropic particle-based MR fluids. The parameters, like yield stress, critical shear rate and viscosity at high shear rate obtained from the fit show systematic variation with applied magnetic field strength. These variations in the parameters can be related to the mesostructure formation and its influence on the MR suspension rheological properties. To further confirm the value of the static yield stress derived from the proposed model, the small-strain oscillatory shear flow experiment is carried out and the static yield stress values are obtained. These values agree well with that obtained from the proposed model. Similarly, to evaluate the dynamic yield stress from the flow curve, modified three parameter model applied to soft glassy materials is used. Here, the critical shear rate parameter obtained from the proposed model is used to deduce dynamic yield stress. It is identified that the values obtained are lower than the static yield stress. Furthermore, at low magnetic field, the static and dynamic yield stress follows the relationship defined by the square dependence of the magnetic field strength. The difference between the static and dynamic yield stress values at high field is greater for anisotropic particle based MR fluid than isotropic particle based MR fluid. This reflects the contribution of particle-particle and particle-carrier interaction in the value of the yield stress in anisotropic particle based MR fluid. Thus, the present model provides a clear idea of the dissipation process that occurs in a shear MR fluid.

A multi-method investigation into rheological properties, hydration, and early-age strength of cement composites with admixtures recovered from inorganic and bio-based waste streams

In this paper, shear rate-dependent rheological properties of mine tailings taken from abandoned mine deposits prone to mass movements are examined using a commercial ball-measuring rheological system. The yield stresses (i.e., dynamic and static yield stresses) and viscosity of sand-rich materials are examined by the shear rate-controlled flow curve and time-dependent stress growth methods. Before yielding, the shear stress reaches a peak value (i.e., yield stress) observed for all flow curves. In the steady-state condition, the materials have a minimum shear stress (i.e., dynamic yield stress). The static yield stress can be determined under a constant applied shear rate with different initial values ranging from 10−4 to 10−1 s−1. As a result, the Bingham yield stress and viscosity can be used as a first approximation for estimating the debris flow mobility of post-failure materials. However, the Bingham yield stress is competitive with the static yield stress measured from stress growth methods. Upon comparison of the dynamic and static yield stresses, the static yield stress is approximately 35–45 times greater than the dynamic yield stress, and may be strongly related to microstructural changes (i.e., thixotropy). In this context, special attention must be paid to the determination of yield stresses in debris flow mitigation programs.

Rheological properties of foams generated from egg albumin after pH treatment

Synergistic effect of shrinkage mitigating materials on rheological properties of flowable and thixotropic cement paste

A comprehensive review on fresh and rheological properties of 3D printable cementitious composites

Summary Cuttings transport, in connection with drilling fluid rheology, has been extensively studied in the literature. Despite this, contradictory results continue to be reported regarding the effect of yield stress on cuttings transport. This study uses the concepts of static and dynamic yield stresses to investigate the effects of yield stress on cuttings transport. A modified form of an existing rheological function is proposed to model static and dynamic yield stresses while incorporating flow history. Flow equations are based on the mixture approach and are numerically solved using computational fluid dynamics (CFD) methodology. Assuming that the liquid phase is homogenous and drill cuttings are noncolloidal, it is shown that the distinction between static and dynamic yield stresses diminishes as volumetric cuttings concentration increases. The Herschel-Bulkley function predicts infinite viscosity at the limit of zero shear rate and, hence, improved cuttings transport with increasing dynamic yield stress, whereas in line with the majority of experimental studies, the proposed rheological model shows that high dynamic yield stress is detrimental for cuttings transport. Comparing fluids with the same dynamic yield stress, the fluid with a larger difference between static and dynamic yield stresses has better cuttings carrying capacity. However, these results are only valid for simple yield stress fluids in which yield stress is dependent on shear rate only.

We studied particle size, shape, molecular weight and temperature dependencies of ER effect of poly(ethylene glycol) (PEG) suspensions. The particles were dispersed in low-viscosity silicon oil. We obtained flow curves and dynamic yield stresses by increasing shear rate and compared these with static yield stresses in our previous study (obtained by increasing shear stress). The yield stress under a dc electric field increased by decreasing molecular weight and increasing particle concentration, and did not change with particle size or shape. In addition, significant differences between static and dynamic yield stresses disappeared in absolute value and electric field intensity dependence. And the static yield stress increased with temperature and the dynamic yield stress showed a maximum value at near room temperature. We also measured transient behavior of a PEG suspension at various temperatures and found that it took about 30 seconds to reach the constant viscosity on the application or removal of electric fields. It can be thought that this relatively long response time to create chain structures causes sudden flowing by increasing shear stress gradually and different results between static and dynamic yield stresses.

Influence of hydroxypropyl methylcellulose and silica fume on stability, rheological properties, and printability of 3D printing foam concrete

Geopolymer mortar can be used as an environmentally friendly sustainable construction material for the repair and strengthening of already-existing structures with the utilization of various recycled materials, such as fly ash, slag powder, etc. With mature application of fibers and nanoparticles in construction materials, nano-SiO2 (NS) and polyvinyl alcohol (PVA) fibers have been utilized to enhance the properties of geopolymer mortar, which has a major impact on the rheological properties of geopolymer mortar. The rheological property tests of geopolymer mortar were carried out in this study, and three indices including dynamic yield stress, static yield stress, and plastic viscosity were studied as rheological parameters. The results of the study were used to establish the relationships between PVA fiber content as well as NS content and rheological parameters. The results showed that a tendency of first decreasing and then increasing was observed in the rheological parameters with the addition of NS content from 0 to 2.5%. Compared with the geopolymer mortar without NS addition, the dynamic yield stress, static yield stress, and the plastic viscosity increased by 22.6, 12.4, and 22.9%, respectively, when NS content was 2.5%. The results showed that the rheological parameters of geopolymer mortar increased linearly with the increment in PVA fiber content which was less than 1.2%. In comparison to the geopolymer mortar without PVA fibers, the dynamic yield stress, static yield stress, and plastic viscosity increased by 65, 56, and 161%, respectively, as the PVA fiber content was 1.2%.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation R. T. Bonnecaze, J. F. Brady; Yield stresses in electrorheological fluids. Journal of Rheology 1 January 1992; 36 (1): 73–115. https://doi.org/10.1122/1.550343 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentThe Society of RheologyJournal of Rheology Search Advanced Search |Citation Search

An experimental study of the rheological behaviour of three natural pyroclastic soils with different depositional processes remixed with water was carried out with the help of a rotational rheometer and inclined plane tests. A homogeneous fluid-like behaviour is obtained only within a very narrow range of concentrations, typically not more than 10%. Below this range the material sedimentates rapidly; above this range it behaves like a solid. In the fluid-like range the typical rheological behaviour of these suspensions is that of a yield stress fluid exhibiting a static yield stress larger than its dynamic yield stress. This effect probably finds its origin in a ‘local' sedimentation effect: that is, the particles sedimentate just as necessary to form a structure more jammed than the structure during flow. As a result the flow of such materials is usually unstable: they will start to flow beyond a critical stress, but just beyond this value will reach a high shear rate associated with a high flowing velocity. The static and dynamic yield stresses of these materials increase widely from very low to very large values (several orders of magnitude). Inclined-plane tests were shown to provide reasonable although still approximate values for the static and dynamic yield stresses. These results suggest that in the field a small change in solid fraction will cause a slight decrease of the static yield stress, readily inducing a rapid flow that will stop only when the dynamic yield stress is reached, namely on a much smoother slope. This can explain the in situ observed post-failure behaviour of pyroclastic debris flows, which are able to flow over very long distances, even on smooth slopes.

Evaluation of rheological properties of sustainable self-compacting recycled aggregate concrete produced by two-stage mixing approach

3D printing hybrid-fiber reinforced engineered cementitious composites (3DP-HECC): Feasibility in long-open-time applications

Yield stress and rheological characteristics of activated sludge in an airlift membrane bioreactor