scholarly journals Study on the Influence of Silica Fume (SF) on the Rheology, Fluidity, Stability, Time-Varying Characteristics, and Mechanism of Cement Paste

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 90
Author(s):  
Hengrui Liu ◽  
Xiao Sun ◽  
Yao Wang ◽  
Xueying Lu ◽  
Hui Du ◽  
...  
Keyword(s):  
Silica Fume ◽  
Cement Paste ◽  
Water Film ◽  
Dilution Effect ◽  
Plastic Viscosity ◽  
Initial Time ◽  
Rheological Parameters ◽  
Time Varying ◽  
Nucleation Effect ◽  
Stability Time

In this study, the rheology, fluidity, stability, and time-varying properties of cement paste with different substitute contents of silica fume (SF) were investigated. The result showed that the effects of SF on macro-fluidity and micro-rheological properties were different under different water–cement ratios. The addition of SF increased the yield stress and plastic viscosity in the range of 2.61–18.44% and 6.66–24.66%, respectively, and reduced the flow expansion in the range of 4.15–18.91%. The effect of SF on cement paste gradually lost its regularity as the w/c ratio increased. The SF can effectively improve the stability of cement paste, and the reduction range of bleeding rate was 0.25–4.3% under different water–cement ratios. The mathematical models of rheological parameters, flow expansion, and time followed the following equations: τ(t) = τ0 + k0t, η(t) = η0eat, and L(t) = L0 − k1t, L(t) = L0 − k1t − a1t2. The SF slowly increased the rheological parameters in the initial time period and reduced the degree of fluidity attenuation, but the effect was significantly enhanced after entering the accelerated hydration period. The mechanism of the above results was that SF mainly affected the fluidity and rheology of the paste through the effect of water film thickness. The small density of SF particles resulted in a low sedimentation rate in the initial suspended paste, which effectively alleviated the internal particle agglomeration effect and enhanced stability. The SF had a dilution effect and nucleation effect during hydration acceleration, and the increase of hydration products effectively increased the plastic viscosity.

Influence of Ground Slag on the Rheology of Mortar

2013 ◽  
Vol 438-439 ◽  
pp. 67-71
Author(s):  
Qian Qian Zhang ◽  
Jian Zhong Liu ◽  
Jia Ping Liu
Keyword(s):  
Film Thickness ◽  
Specific Surface ◽  
Yield Stress ◽  
Surface Area ◽  
Specific Surface Area ◽  
Water Film ◽  
Plastic Viscosity ◽  
Rheological Parameters ◽  
Water Film Thickness ◽  
Binder Ratio

The effects of ground slag with different specific surface area on the rheology of mortar at water-binder ratio of 0.25, 0.28 and 0.30 were investigated, and the combined effects of packing density and solid surface area on the rheology of mortar were evaluated in terms of the water film thickness. The results show that with the increasing of specific surface area of slag (220 m2/kg-784 m2/kg), plastic viscosity and yield stress decrease. The correlations of yield stress and plastic viscosity to the water film thickness are basically linear with high correlation R2 values. The action of the ground slag on the rheology of mortar can be characterized by water film thickness, and with the increasing of water film thickness the rheological parameters decrease.

Triple Blending with Superfine Natural Zeolite and Condensed Silica Fume to Improve Performance of Cement Paste

2017 ◽  
Author(s):  
P.L. Ng ◽  
J.J. Chen ◽  
A.K.H. Kwan
Keyword(s):  
Silica Fume ◽  
Cement Paste ◽  
Packing Density ◽  
Natural Zeolite ◽  
Water Film ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Concrete Production ◽  
Fine Size ◽  
Condensed Silica Fume

Superfine natural zeolite (SNZ) is obtained by grinding natural zeolite to micro-fine size, whereas condensed silica fume (CSF) is by-product of ferrosilicon industry. Both SNZ and CSF are environmentally-friendly supplementary cementitious materials for mortar and concrete production. Owing to the high fineness and favourable grading of SNZ and CSF (the median particle sizes were 4 μm and 0.4 μm, respectively), the addition of SNZ and CSF could successively fill the voids between ordinary Portland cement (OPC) grains and increase the packing density of the binder, so as to reduce the volume of voids to be filled with water. Therefore, triple blending of OPC+SNZ+CSF can benefit the overall performance of cement paste by releasing more water for flowability improvement at the same water/binder (W/B) ratio, or adopting a lower W/B ratio for strength improvement at the same flowability requirement. This study evaluated the effects of adding SNZ and CSF on the packing density and water film thickness of binder. The experimental results proved that triple blending with SNZ and CSF could increase the packing density and improve the flowability and cohesiveness of cementitious paste.

scholarly journals A Study on the Relationships between Water Film Thickness, Fresh Properties, and Mechanical Properties of Cement Paste Containing Superfine Basalt Powder (SB)

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7592
Author(s):  
Hengrui Liu ◽  
Zhenghong Tian ◽  
Haoyue Fan
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Film Thickness ◽  
Cement Paste ◽  
Water Film ◽  
Mineral Admixtures ◽  
Rheological Parameters ◽  
Fresh Properties ◽  
Bleeding Rate ◽  
Water Film Thickness

In this paper, the effect of a newly developed superfine basalt powder (SB) on the fresh and mechanical properties of cement paste was studied. The concept of water film thickness (WFT) was cited to explain the influence of SB on fresh and mechanical properties and related mathematical model formulas were established. In addition, the relationship between the fresh properties and mechanical properties of paste was also explored. The results indicated that SB can improve the segregation resistance and cohesiveness. The maximum improvement rate relative to the control cement paste was 75.4% and 50.4%, respectively. The 5% SB and 10% SB reduced the fluidity in the range of 4.1–68.7% but increased the early and late compressive strength in the range of 1.2–25.7% compared to control cement paste under different water/cementitious materials (W/CM) ratios. However, the influence of 20% SB on fluidity and compressive strength was opposite to the above behavior, and the increase rate and decrease rate were 1.8–11.8% and 1.1–13.9% respectively. The WFT was the most important factor that determined the compressive strength, rheological parameters, and flow parameters of paste containing SB, while the substitute content of SB and WFT together determined the bleeding rate and cohesiveness. Among them, the correlation between bleeding rate and WFT increased with time. The empirical mathematical models between WFT, fresh properties, and compressive strength were established and verified by other mineral admixtures, which were successfully extended and applied to the entire field of cement-based materials

scholarly journals Effect of Silica Fume on the Rheological Properties of Cement Paste with Ultra-Low Water Binder Ratio

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 554
Author(s):  
Juan He ◽  
Congmi Cheng ◽  
Xiaofen Zhu ◽  
Xiaosen Li
Keyword(s):  
Hysteresis Loop ◽  
Rheological Properties ◽  
Yield Stress ◽  
Silica Fume ◽  
Plastic Viscosity ◽  
Rheological Parameters ◽  
Loop Area ◽  
Binder Ratio ◽  
Hysteresis Loop Area ◽  
Water Binder Ratio

The effect of silica fume on the rheological properties of a cement–silica fume–high range water reducer–water mixture with ultra-low water binder ratio (CSHWM) was studied. The results indicate that the W/B ratio and silica fume content have different effects on the rheological parameters, including the yield stress, plastic viscosity, and hysteresis loop area. The shear-thickening influence of CSHWM decreased with the increased silica fume content. When the silica fume content increased from 0% to 35%, the mixture with W/B ratio of 0.19 and 0.23 changed from a dilatant fluid to a Newtonian fluid, and then to a pseudoplastic fluid. When the silica fume content was less than 15%, the yield stress was close to 0. With the increase of silica fume content, the yield stress increased rapidly. The plastic viscosity and hysteresis loop area decreased slightly with the addition of a small amount of silica fume, but increased significantly with the continuous increase of silica fume. Compared with the Bingham and modified Bingham models, the Herschel–Buckley model is more applicable for this CSHWM.

Effects of Condensed Silica Fume and Superfine Cement on Flowability of Cement Paste

2011 ◽  
Vol 121-126 ◽  
pp. 2695-2700 ◽  
Author(s):  
A. K. H. Kwan ◽  
Jia Jian Chen ◽  
L. G. Li
Keyword(s):  
Experimental Study ◽  
Silica Fume ◽  
Cement Paste ◽  
Water Film ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Definite Effect ◽  
Wide Range ◽  
Depth Analysis ◽  
Condensed Silica Fume

Addition of supplementary cementitious materials (SCM) has been contradictorily reported to be beneficial or detrimental to the flowability of concrete and no general conclusion can be drawn up to now. In order to comprehensively disclose the effects of SCM on the flowability, an experimental study had been carried out to measure the flowability of a total of 100 cement paste samples with different condensed silica fume (CSF) and superfine cement (SFC) contents at a wide range of water/cementitious materials (W/CM) ratios. The results showed that the addition of CSF would decrease the flowability at a relatively high W/CM ratio but increase the flowability at a low W/CM ratio, while the addition of SFC could generally improve the flowability of cement paste. Joint addition of SFC and CSF would not exert any definite effect on flowability at a relatively high W/CM ratio but could improve the flowability at a low W/CM ratio. In-depth analysis showed that these results could be well explained by the theory of water film thickness.

scholarly journals The VIT Transform Approach to Discrete-Time Signals and Linear Time-Varying Systems

Eng ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 99-125
Author(s):  
Edward W. Kamen
Keyword(s):  
Discrete Time ◽  
Initial Conditions ◽  
Linear Time ◽  
Order Term ◽  
Initial Time ◽  
Time Varying ◽  
Varying Coefficients ◽  
Time Signals ◽  
Time Varying Systems ◽  
Time Varying Coefficients

A transform approach based on a variable initial time (VIT) formulation is developed for discrete-time signals and linear time-varying discrete-time systems or digital filters. The VIT transform is a formal power series in z−1, which converts functions given by linear time-varying difference equations into left polynomial fractions with variable coefficients, and with initial conditions incorporated into the framework. It is shown that the transform satisfies a number of properties that are analogous to those of the ordinary z-transform, and that it is possible to do scaling of z−i by time functions, which results in left-fraction forms for the transform of a large class of functions including sinusoids with general time-varying amplitudes and frequencies. Using the extended right Euclidean algorithm in a skew polynomial ring with time-varying coefficients, it is shown that a sum of left polynomial fractions can be written as a single fraction, which results in linear time-varying recursions for the inverse transform of the combined fraction. The extraction of a first-order term from a given polynomial fraction is carried out in terms of the evaluation of zi at time functions. In the application to linear time-varying systems, it is proved that the VIT transform of the system output is equal to the product of the VIT transform of the input and the VIT transform of the unit-pulse response function. For systems given by a time-varying moving average or an autoregressive model, the transform framework is used to determine the steady-state output response resulting from various signal inputs such as the step and cosine functions.

Effect of incorporating iron‐filing waste on the properties of silica fume blended cement paste

2020 ◽  
Author(s):  
Moruf O. Yusuf ◽  
Sami I. Shamsah ◽  
Khaled A. Al‐Sodani ◽  
Salihu Lukman
Keyword(s):  
Silica Fume ◽  
Cement Paste ◽  
Blended Cement ◽  
Iron Filing ◽  
Blended Cement Paste

Interaction Between Naphthalene Sulfonate and Silica Fume in Portland Cement Pastes

1987 ◽  
Vol 114 ◽  
Author(s):  
Sidney Diamond ◽  
Leslie J. Struble
Keyword(s):  
Portland Cement ◽  
Silica Fume ◽  
Cement Paste ◽  
Uv Spectrophotometry ◽  
Residual Concentration ◽  
Cement Pastes ◽  
High Ph ◽  
Substantial Concentration ◽  
Low Dosage

ABSTRACTPortland cement pastes were mixed with predissolved naphthalene sulfonate superplasticizer at normal water:cement ratios. Solutions were separated from the fresh pastes at intervals and the residual concentration of the superplasticizer determined by UV spectrophotometry. At low dosage levels essentially all of the superplasticizer was found to be removed from solution within a few minutes; at high dosage levels a substantial concentration was maintained in solution at least to approximately the time of set. In pastes in which silica fume replaced 10% by weight of the cement, it was found that the incorporation of silica fume significantly increased the uptake of superplasticizer. In separate trials it was found that the silica fume by itself adsorbed little superplasticizer, even from high pH solution simulating that of cement paste.

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