The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Wanguo Hou - One of the best experts on this subject based on the ideXlab platform.
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Effect of Electrolytes and Polymers on the Thixotropy of Mg-Al-Layered Double Hydroxides/Kaolinite Dispersions
Chinese Journal of Chemistry, 2011Co-Authors: Xiaonan Dai, Wanguo Hou, Hongdong DuanAbstract:The effect of electrolytes (NaCl and CaCl2) and polymers (CPAM and HPAM) on the Thixotropy of Mg-Al-layered double hydroxide (LDHs)/kaolinite dispersions has been investigated. It was observed that the type of Thixotropy in LDH/kaolinite dispersions may be affected by NaCl, but not by CaCl2 in range of concentration of interest. The type of Thixotropy in LDH/kaolinite dispersion with R=0 transformed from positive Thixotropy to complex Thixotropy and at last positive Thixotropy again with the concentration of NaCl in range of 0.00–0.10 mol·L−1; the type of Thixotropy in LDHs/kaolinite dispersions with R=0.25 transformed from complex Thixotropy to positive Thixotropy and then complex Thixotropy again with the concentration of NaCl in range of 0.00–0.10 mol·L−1. The type of Thixotropy in LDH/kaolinite dispersion with R=0 may be not affected by cationic polyacrylamide (CPAM) and hydrolyzed polyacrylamide (HPAM); but the LDHs/kaolinite dispersions with R=0.25 transformed from complex Thixotropy to positive Thixotropy with the both polymers concentration in range of interest, which indicated that the microstructure of the dispersion changed from weak folc sediments structure to steric network structure.
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Thixotropy of Mg–Al-layered double hydroxides/kaolinite dispersion
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2006Co-Authors: X.n. Dai, Wanguo Hou, H.d. DuanAbstract:Abstract The rheological characteristics of Mg–Al-layered double hydroxide (LDHs)/kaolinite dispersions were investigated as a function of pH and mass ratio of LDHs to kaolinite (R). The stress ramp and stress sweep experiments were used to measure the yield stress of the dispersions. In both experiments, a critical shear stress (τc) was obtained at which the viscosity decreased by 3–4 orders of magnitude. The τc value decreased first and then increased with the increase of the R, showing a minimum at R = 0.05. The linear oscillatory shear experiments and the thixotropic loops experiments were performed to investigate the thixotropic behavior of the dispersions. The complex Thixotropy was observed with the linear oscillatory shear experiments, and it was found that the thixotropic type of the LDHs/kaolinite dispersions may be affected by R in the range of 0–0.35 and pH value in the range of 3–12. With the increase of R or pH value, the thixotropic type of LDHs/kaolinite dispersions transformed from positive Thixotropy to complex Thixotropy. By comparing the results of the thixotropic loops experiments with those of the linear oscillatory shear experiments, it was demonstrated that thixotropic loop of complex Thixotropy had a crossover point that divided the loop into two sections.
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influence of measuring conditions on the Thixotropy of hydrotalcite like montmorillonite suspension
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2003Co-Authors: Wanguo Hou, J.c XiaoAbstract:Abstract The influence of the measuring conditions on the Thixotropy of suspensions, which were made up of hydrotalcite-like compounds (HTlc) and Na-montmorillonite (MT), was studied. Usually, the structure recovery at rest after preshear is considered the fundamental thixotropic process. And the recovery process was performed under the steady shear experiments, then the thixotropic type can be judged according to the recovery process. In this paper, the influence of rest time (ts) and the shear rate ( γ ) on the recovery process was studied. Three kinds of HTlc/MT suspension were studied, their mass ratios of HTlc to MT, which were signed as R (e.g. R=WHTlc/WMT), were 0.013, 0.051, 0.091, respectively. It is found the HTlc/MT suspension with R=0.013 showed positive Thixotropy at ts=0, but it changed to negative one with the increase of ts. The suspension with R=0.051 transformed from complex Thixotropy at low γ or positive Thixotropy at high γ into negative one with the increase of ts. The suspension with R=0.091 behaved as complex Thixotropy when γ is 1022 s−1, and it behaved as negative Thixotropy when γ is 10 s−1. Whereas, the suspension transformed from negative Thixotropy to the weak complex one as the increase of ts when γ is 170 or 341 s−1. For all the systems, the equilibrium viscosity decreased gradually with ts at the low γ , but the equilibrium viscosity increased with ts at high γ because of the memory effect. The mechanism has been discussed.
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Influence of measuring conditions on the Thixotropy of hydrotalcite-like/montmorillonite suspension
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2003Co-Authors: Wanguo Hou, J.c XiaoAbstract:Abstract The influence of the measuring conditions on the Thixotropy of suspensions, which were made up of hydrotalcite-like compounds (HTlc) and Na-montmorillonite (MT), was studied. Usually, the structure recovery at rest after preshear is considered the fundamental thixotropic process. And the recovery process was performed under the steady shear experiments, then the thixotropic type can be judged according to the recovery process. In this paper, the influence of rest time (ts) and the shear rate ( γ ) on the recovery process was studied. Three kinds of HTlc/MT suspension were studied, their mass ratios of HTlc to MT, which were signed as R (e.g. R=WHTlc/WMT), were 0.013, 0.051, 0.091, respectively. It is found the HTlc/MT suspension with R=0.013 showed positive Thixotropy at ts=0, but it changed to negative one with the increase of ts. The suspension with R=0.051 transformed from complex Thixotropy at low γ or positive Thixotropy at high γ into negative one with the increase of ts. The suspension with R=0.091 behaved as complex Thixotropy when γ is 1022 s−1, and it behaved as negative Thixotropy when γ is 10 s−1. Whereas, the suspension transformed from negative Thixotropy to the weak complex one as the increase of ts when γ is 170 or 341 s−1. For all the systems, the equilibrium viscosity decreased gradually with ts at the low γ , but the equilibrium viscosity increased with ts at high γ because of the memory effect. The mechanism has been discussed.
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Influence of pH on the Thixotropy of magnesium aluminum hydroxide-kaolinite suspension
Science in China Series B: Chemistry, 2001Co-Authors: Xiaonan Dai, Wanguo Hou, Shangying LiuAbstract:The influence of pH on the Thixotropy of pure kaolinite suspension and magnesium aluminum hydroxide (Mg-Al-MMH)-kaolinite suspension was studied. The results show that the thixotropic type of pure kaolinite suspension was not affected by pH studied in the range of 3.60– 12.00. The thixotropic type of Mg-Al-MMH-kaolinite suspension with mass ratio (R) value of MMH to kaolinite 0.029 transformed from complex Thixotropy into positive Thixotropy with increasing of pH in the range of pH 3.83–12.00, and the type of Thixotropy of Mg-Al-MMH-kaolinite suspension withR = 0.129 transformed from positive Thixotropy into complex Thixotropy with increasing of pH in the range of pH 3.70–11.96.
Xin Cheng - One of the best experts on this subject based on the ideXlab platform.
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Mechanisms dominating Thixotropy in limestone calcined clay cement (LC3)
Cement and Concrete Research, 2021Co-Authors: Pengkun Hou, Tafadzwa Ronald Muzenda, Li Qinfei, Heng Chen, Shiho Kawashima, Tongbo Sui, Haiyan Yong, Ning Xie, Xin ChengAbstract:Abstract Limestone calcined clay cement (LC3) is a green binder with great practical importance for the cement industry. Growing application has increased the need to understand the mechanisms governing its Thixotropy for better control of workability. While formation of C-S-H bridges is understood to dominate the Thixotropy of ordinary Portland cement, LC3 paste displayed unique Thixotropy properties. In this study, focused beam reflectance measurement, zeta potential, 1H nuclear magnetic resonance relaxometry and micro X-ray computed tomography were used to track the colloidal interaction and hydration extent within LC3 paste. Results showed that flocculation due to the negative surface charge and water affinity of calcined clay appears to be the dominating factor. This leads to a reduction of water available to contribute to fluidity of the paste and, in turn, governing the development of Thixotropy over time. In addition, the dilution effect due to high clinker substitution diminishes Thixotropy growth with time.
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yield stress and Thixotropy control of 3d printed calcium sulfoaluminate cement composites with metakaolin related to structural build up
Construction and Building Materials, 2020Co-Authors: Mingxu Chen, Lei Yang, Yongbo Huang, Shoude Wang, Piqi Zhao, Yan Zheng, Xin ChengAbstract:Abstract The three-dimensional (3D) structural build-up with the precision has proposed new requirements related to yield stress and Thixotropy in the 3D-printed cementitious materials. In this study, the static and dynamic yielding behaviours of 3D-printed calcium sulfoaluminate (CSA) cement composites with metakaolin were studied to understand the relationship between Thixotropy and structural build-up through the powder-based extrusion system. Experimental results show that the static yield stress implemented by the constant shear-rate-controlled protocol in the 3D-printed CSA cement paste increased significantly with rest time. Dynamic rheological behaviours were investigated by the Bingham and Herschel-Bulkley model. Given the change of flocculation structure and shear-thinning behaviour during the shear period, Herschel-Bulkley model is more suitable for studying the dynamic rheological properties of 3D-printed CSA cement paste. Moreover, the Thixotropy can be well improved by the addition of metakaolin, and the correlation between the structure deformation and Thixotropy of 3D-printed CSA cement paste further proved that the improved Thixotropy is beneficial to 3D-printed structural build-up. In conclusion, developing a 3D-printed CSA cement composites with the controllable yield stress and Thixotropy is significant for structural build-up in the 3D-printed construction materials.
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Rheological parameters, Thixotropy and creep of 3D-printed calcium sulfoaluminate cement composites modified by bentonite
Composites Part B: Engineering, 2020Co-Authors: Chen Mingxu, Bo Liu, Lidong Cao, Yongbo Huang, Shoude Wang, Piqi Zhao, Xin ChengAbstract:Abstract The structural instability and poor Thixotropy of three-dimensional (3D) printing of calcium sulfoaluminate (CSA) cement composites hinder their applicability in the construction field. In this study, the rheological parameters, Thixotropy and creep of 3D-printed CSA cement composites containing bentonite are investigated based on shear-rate- and shear-stress-controlled protocols to achieve a stable three-dimensional structure and excellent Thixotropy. Experimental results show that a stable 3D structure with excellent Thixotropy can be achieved when the content of bentonite is 2%. In this case, the plastic viscosity and dynamic yield stress are lower than 2.50 Pa s and 645.54 Pa, respectively. The correlation between the rheological parameters and Thixotropy of 3D-printed CSA cement composites suggests that the actual Thixotropy can be predicted by the yield stress. Furthermore, the shear-stress-controlled protocol was implemented to simulate the effect of gravity and test different creep periods of 3D-printed CSA cement composites with bentonite. The improved static yield stress exhibited better effectiveness in resisting structural deformation over time.
Geert De Schutter - One of the best experts on this subject based on the ideXlab platform.
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enhancing Thixotropy of fresh cement pastes with nanoclay in presence of polycarboxylate ether superplasticizer pce
Cement and Concrete Research, 2018Co-Authors: Ye Qian, Geert De SchutterAbstract:Abstract Nanoclay, a thermal treated, purified attapulgite clay, has been used to increase Thixotropy. However, the effect of nanoclay in presence of water reducing agent, such as PCE, on rheology, and the compatibility between nanoclay and PCE have not been well studied. The dynamic yield stress, thixotropic index, characteristic time, and microstructure of fresh cement pastes with combination of nanoclay and PCE addition are measured. It is found that nanoclay has a good compatibility with PCE. Nanoclay increases the dynamic yield stress and enhances the Thixotropy of fresh cement pastes with and without PCE addition. The nanoclay addition agglomerates the microstructure at high PCE addition and increases the thixotropic index from bottom value to a high value. This study gives insight of achieving low dynamic yield stress yet high static yield stress and Thixotropy mixtures.
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effect of polycarboxylate ether superplasticizer pce on dynamic yield stress Thixotropy and flocculation state of fresh cement pastes in consideration of the critical micelle concentration cmc
Cement and Concrete Research, 2018Co-Authors: Ye Qian, Karel Lesage, Khadija El Cheikh, Geert De SchutterAbstract:Abstract Polycarboxylate ether surperplasticizer (PCE) has been commonly used and studied to enhance flowability of cementitious materials. However, the effect of PCE addition on Thixotropy and flocculation state has not gained enough attention. In this study, Focused Beam Reflectance Measurement (FBRM)-rheometer is coupled. The coupled setup could simultaneously measure both flocculation states in terms of chord length distribution of cement particles/agglomerates and rheological properties including dynamic yield stress and Thixotropy. The effect of various PCE additions is explored, firstly by measuring the adsorption of PCE surfactants and the concentration of PCE surfactants in cement pore solution. It is found that the effect of PCE addition on dynamic yield stress, Thixotropy and chord length distribution of paste particles/agglomerates are all bi-fold. The turning point is the Critical Micelle Concentration in cement pore solution. Results of more agglomerated flocculation states at low PCE addition are measured for the first time and further discussed.
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Influence of Thixotropy on the pumping of (self compacting) concrete
2008Co-Authors: Dimitri Feys, Geert De Schutter, Ronny VerhoevenAbstract:During full scale pumping tests with self compacting concrete (SCC) a decrease of pressure loss with time has been observed, which can only be explained by means of Thixotropy. In this paper, the modified Hattori - Izumi theory is presented to give a qualitative description of the effect occurring during pumping. Due to Thixotropy : a non-segregating SCC can become segregating during pumping. Also other consequences have been reported.
Dilson E. Rassier - One of the best experts on this subject based on the ideXlab platform.
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Thixotropy and rheopexy of muscle fibers probed using sinusoidal oscillations.
PLOS ONE, 2015Co-Authors: David Altman, Fabio C. Minozzo, Dilson E. RassierAbstract:Length changes of muscle fibers have previously been shown to result in a temporary reduction in fiber stiffness that is referred to as Thixotropy. Understanding the mechanism of this Thixotropy is important to our understanding of muscle function since there are many instances in which muscle is subjected to repeated patterns of lengthening and shortening. By applying sinusoidal length changes to one end of single permeabilized muscle fibers and measuring the force response at the opposite end, we studied the history-dependent stiffness of both relaxed and activated muscle fibers. For length change oscillations greater than 1 Hz, we observed thixotropic behavior of activated fibers. Treatment of these fibers with EDTA and blebbistatin, which inhibits myosin-actin interactions, quashed this effect, suggesting that the mechanism of muscle fiber Thixotropy is cross-bridge dependent. We modeled a half-sarcomere experiencing sinusoidal length changes, and our simulations suggest that Thixotropy could arise from force-dependent cross-bridge kinetics. Surprisingly, we also observed that, for length change oscillations less than 1 Hz, the muscle fiber exhibited rheopexy. In other words, the stiffness of the fiber increased in response to the length changes. Blebbistatin and EDTA did not disrupt the rheopectic behavior, suggesting that a non-cross-bridge mechanism contributes to this phenomenon.
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Thixotropy of Muscle Fibers Probed with Sinusoidal Oscillations
Biophysical Journal, 2014Co-Authors: David Altman, Fabio C. Minozzo, Dilson E. RassierAbstract:Mechanical properties of individual muscle fibers from rabbit psoas were probed by applying sinusoidal length changes at one end of the fiber and measuring the resulting force at the other end. At frequencies above 1 Hz, this oscillation resulted in a history-dependent reduction in muscle fiber stiffness in activated muscle fibers. Such a reduction in muscle stiffness in response to force is referred to as Thixotropy. Perturbing the actin-myosin interaction by treatment with EDTA and blebbistatin caused this effect to disappear, suggesting that this Thixotropy results from cross-bridge interactions. At frequencies less than 1 Hz, oscillation resulted in a history-dependent increase in muscle fiber stiffness in activated fibers. Disruption of actin-myosin interactions has no effect on this negative Thixotropy, suggesting a different mechanism is at play.
Ye Qian - One of the best experts on this subject based on the ideXlab platform.
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enhancing Thixotropy of fresh cement pastes with nanoclay in presence of polycarboxylate ether superplasticizer pce
Cement and Concrete Research, 2018Co-Authors: Ye Qian, Geert De SchutterAbstract:Abstract Nanoclay, a thermal treated, purified attapulgite clay, has been used to increase Thixotropy. However, the effect of nanoclay in presence of water reducing agent, such as PCE, on rheology, and the compatibility between nanoclay and PCE have not been well studied. The dynamic yield stress, thixotropic index, characteristic time, and microstructure of fresh cement pastes with combination of nanoclay and PCE addition are measured. It is found that nanoclay has a good compatibility with PCE. Nanoclay increases the dynamic yield stress and enhances the Thixotropy of fresh cement pastes with and without PCE addition. The nanoclay addition agglomerates the microstructure at high PCE addition and increases the thixotropic index from bottom value to a high value. This study gives insight of achieving low dynamic yield stress yet high static yield stress and Thixotropy mixtures.
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effect of polycarboxylate ether superplasticizer pce on dynamic yield stress Thixotropy and flocculation state of fresh cement pastes in consideration of the critical micelle concentration cmc
Cement and Concrete Research, 2018Co-Authors: Ye Qian, Karel Lesage, Khadija El Cheikh, Geert De SchutterAbstract:Abstract Polycarboxylate ether surperplasticizer (PCE) has been commonly used and studied to enhance flowability of cementitious materials. However, the effect of PCE addition on Thixotropy and flocculation state has not gained enough attention. In this study, Focused Beam Reflectance Measurement (FBRM)-rheometer is coupled. The coupled setup could simultaneously measure both flocculation states in terms of chord length distribution of cement particles/agglomerates and rheological properties including dynamic yield stress and Thixotropy. The effect of various PCE additions is explored, firstly by measuring the adsorption of PCE surfactants and the concentration of PCE surfactants in cement pore solution. It is found that the effect of PCE addition on dynamic yield stress, Thixotropy and chord length distribution of paste particles/agglomerates are all bi-fold. The turning point is the Critical Micelle Concentration in cement pore solution. Results of more agglomerated flocculation states at low PCE addition are measured for the first time and further discussed.