Characterization data of reference materials used for phase II of the priority program DFG SPP 2005 “Opus Fluidum Futurum – Rheology of reactive, multiscale, multiphase construction materials”

Studies have shown that in an aqueous suspension of inert glass beads, the yield stress is increased as a function of resting time. This study investigates this unexpected phenomenon, focusing on solid surface potentials, PCE size in ionic solutions, and their possible relations to rheological behaviour with resting time. Results indicated that PCE in artificial pore solution will result in a higher yield stress with time. PCE with lower anionic charges and molecular weight can significantly increase the yield stress after 2 h of resting. The absolute value of the zeta potential grows to a certain degree after resting phase. Dynamic light scattering (DLS) results showed that the size of PCE molecules in ionic solutions increases over time, suggesting an enhanced depletion force or bridging force among glass bead particles, which could be the reasons for the increase in yield stress over time. Furthermore, the possible impacts of the depletion force or bridging force resulting from the PCE size change on the rheological properties of cement suspension are discussed.

Section: Methodsmentioning

confidence: 99%

Resting time effect on the rheological behaviour of glass beads and cement suspension: The role of PCE size and ionic strength

Ji,

Mezhov,

Becker

et al. 2023

“…Für die Untersuchungen wurden Portlandzement CEM I 42,5 R (Deuna), ein calcinierter Ton [8] sowie Weißkalkhydrat (Ca(OH)2) verwendet. Die chemische Zusammensetzung ist in Tabelle 1 dargestellt.…”

Section: Materialienunclassified

Erhöhung des Carbonatisierungswiderstandes klinkerreduzierter Betone durch alkalische Puffer

Müller,

Sowoidnich,

Lieboldt

et al. 2023

Im Stahlbeton kann die Carbonatisierung der Betonrandzone dazu führen, dass die Passivierung des Betonstahls verloren geht, wodurch eine Stahlkorrosion eintreten kann. In Betonen mit puzzolanischen Stoffen, wie beispielsweise calcinierten Tonen, kann die Verringerung des Calciumhydroxidgehaltes im Beton infolge der puzzolanischen Reaktion zu einer Erhöhung der Carbonatisierungsneigung führen. Dies ist ein maßgeblicher begrenzender Faktor für die im Beton anwendbaren Einsatzmengen an calcinierten Tonen.Daher wurde an Mörteln untersucht, ob durch eine Erhöhung des Calciumhydroxidpuffers auch eine Verbesserung des Carbonatisierungswiderstandes möglich ist. Die grundsätzliche Eignung dieses Ansatzes konnte bestätigt werden. Dies sollte es ermöglichen, die Klinkeraustauschrate durch calcinierten Ton zu erhöhen, ohne zu einer gravierenden Beeinträchtigung der Betondauerhaftigkeit zu führen.

“…We used a low-clinker binder mix which has been characterized in the context of the DFG Priority Program 2005 [35]. The main constituents are summarized in Table 2 and additional analytical information can be found in the reference paper cited before.…”

Section: Cementmentioning

confidence: 99%

Rheology of low‐clinker suspensions: Multiscale comparison of the effect of PCE on thixotropy

Nicia,

Fobbe,

Jansen

et al. 2023

Addressing climate change requires reducing the carbon footprint of cement‐based building materials on a global scale. One promosing approach involves decreasing the clinker content by incorporating fine supplementary cementitious materials (SCM), which, however, can increase the stickiness of fresh concrete. Along with viscosity, thixotropic structural build‐up is a critical rheological parameter that impacts the stickiness of the SCM‐rich suspensions. Thus, it is essential to gain a precise understanding of how the molecular structure and mode of addition of polycarboxylate ethers (PCE) affect the thixotropic structural build‐up in low‐clinker suspensions. To address this issue, we investigate key parameters affecting thixotropy, specifically PCE adsorption and early hydration kinetics at the cement paste and mortar level, using a multiscale approach. In an application‐oriented concept, we maintain a constant yield stress by varying the PCE dosage to achieve constant workability. Our results demonstrate that higher thixotropy correlates with increased PCE charge density and direct addition in cement pastes and mortars. Moreover, it is indicated that increasing specific surface area and ettringite contents promote additional thixotropy‐enhancing mechanisms.