The Influences of Cement Hydration and Temperature on the Thixotropy of Cement Paste

Abstract

The rheological properties of fresh cement paste are highly influenced by a large number of parameters, among which the most important factors are the applied shear stress, and the shear history, the age of the sample and the temperature. The effects of these parameters on the yield stress (designated as structural limit stress in this work), the viscosity and the structural recovery rate (i.e., the change in dynamic viscosity with time at rest) were studied. In parallel, the changes in ion composition of the carrier liquid, mineral phase content and granulometry were investigated. The results reveal that all investigated rheological parameters exhibit an approximated bi-linear trend with respect to the degree of hydration, with a period of quasi-constant properties until a degree of hydration of approximately 0.07, followed by a non-linear increase. This increase could be attributed to the formation of calcium hydroxide (CH) and calcium-silicate-hydrate (C-S-H) via calorimetry results. With regard to the effect of the shear history of the sample on the rheological properties, the structural limit stress showed a minor dependency on the shear history immediately after the end of shearing, which, however, vanished within the first minute at rest. The same is true for the structural recovery rate. The presented results give detailed insights into the influences of hydration and shear on the rheological properties-especially the thixotropy-of fresh cement pastes.

Mechanisms of thixotropy in cement suspensions considering influences from shear history and hydration

“…The investigated cement suspensions were prepared with an ordinary Portland cement CEM I 42.5 R. The cement was characterized in detail in an interlaboratory study (see [20]). The essential parameters are its density of 3.12 g/cm³, specific surface area of 3600 cm²/g determined by the Blaine method, and particle size distribution with a d50-value of 14.8 µm [16]. The cement suspensions for rheological testing were prepared with 1778.9 g of dry cement, stored at 20°C, and 728.0 g of demineralised water, pre-tempered at 10°C.…”

Mathematical Modeling of Initial Exothermic Behavior and Thixotropic Properties in Nanoclay-Enhanced Cementitious Materials

“…These requirements are significantly influenced by the rheological properties and can also be gauged by heat release behavior [7]. The rheological properties of fresh mortar are influenced by various factors, including the concrete's age, shear history, and temperature [8]. Understanding and regulating these factors is vital to ensure the quality and stability of the final product, especially during the placement at the job site [9].…”

Image‐based analysis of fresh concrete flow ‐ determining the correlation between flow behavior and rheological properties

“…During casting, unsuitable rheological properties may lead to serious problems like segregation, flow blockage or substantial voids in the structure to be cast [1]. The rheology of fresh concrete can be simplified by the Bingham parameters yield stress and plastic viscosity μ, as well as thixotropy (e.g., the change in dynamic viscosity η as a function of time and shear history), which can be determined by rheometer tests [1,4]. More specifically, by applying the Bingham model, values for the yield stress and the plastic viscosity µ can be determined with…”