Rheology Of Cement Research Articles

Effect of Air-Entraining Agent on Rheology of Cement- Based Magnetorheological Pastes

Effect of Air-Entraining Agent on Rheology of Cement- Based Magnetorheological Pastes

Rheology of cement pastes with calcium carbonate polymorphs

Naturally occurring limestone currently used for concrete production mainly consists of calcite, and the other two metastable forms of anhydrous calcium carbonate include aragonite and vaterite. In this research, all three calcium carbonate polymorphs were synthesized in laboratory conditions and their effects on cement rheology were investigated. After comprehensive characterization of the polymorphs, they were used as cement substitutes (20 wt%) to prepare pastes for rheological testing. Aragonite was found to increase the initial static yield stress, dynamic yield stress, and storage modulus of cement pastes, while calcite and vaterite did not. The rate of structural build-up was also enhanced by aragonite, as indicated by higher rates of static yield stress development and storage modulus increase over time. The underlying mechanisms of the rheological changes induced by the calcium carbonate polymorphs – geometric features, hydration kinetics, and surface charge – were discussed and supported with experimental evidence.

Rheology of cement–sodium silicate grout containing bentonite and cellulose ether at high temperatures

Cement–sodium silicate grout (CSG) is widely used to control water inrush disasters, and its apparent viscosity considerably impacts its water-plugging effect. However, traditional grouting materials and methods are inappropriate for high-temperature environments as high temperatures can affect the grout's viscosity. To thicken grout and increase its apparent viscosity, viscosity-modifying admixtures can be used. In this work, two types of bentonite (calcium bentonite (Ca-B) and sodium bentonite (Na-B)) and hydroxyethyl methyl cellulose (HEMC) were used to modify CSG and laboratory tests were performed to evaluate the fluidity, gelation time and rheology. The results showed that both bentonites and the HEMC decreased fluidity and prolonged the gelation time. HEMC, Ca-B and Na-B decreased the fluidity by 46.8–60.4%, 12.5–31.5% and 17.7–39.1%, respectively, at different temperatures. HEMC, Ca-B and Na-B increased the gelation time by 23.8–50.1%, 23.3–71.4% and 20%–57.1%, respectively. Bentonite can partially resist high temperatures and improve the apparent viscosity of grout owing to its water-absorption capacity. Conversely, HEMC has a negative effect on apparent viscosity, which is attributed to the formation of a complex microstructure resulting from intermolecular cross-linking between the cement particles and HEMC, preventing the connection of sodium silicate.

Effects of Sodium Tripolyphosphate Addition on the Dispersion and Hydration of Pure Calcium Aluminate Cement.

In this paper, the effect of a sodium tripolyphosphate (STPP) addition on the dispersion and hydration of pure calcium aluminate cement (PCAC) was investigated, and the corresponding mechanism of effect was studied. The effects of STPP on the dispersion, rheology, and hydration processes of PCAC and its adsorption capacity on the surface of cement particles were analysed by measuring the 𝜁-potential on the surface of cement particles, the changes in the concentrations of elemental P and Ca2+ ions in a solution at different STPP additions. The experimental results show that STPP easily complexes with Ca2+ ions to produce the complex [CaP3O10]3- adsorbed on the surface of cement particles, which changes the potential on the surface of cement particles and increases the electrostatic repulsive force between cement particles, thus improving the dispersion and rheology of cement. At the same time, the contact area between cement particles and water is reduced, which hinders the hydration process and makes the time of hydration process longer. A comprehensive analysis shows that the best effect of STPP on pure calcium aluminate cements is achieved when the addition of STPP is 0.2%. This study can provide a reference for the addition of water-reducing agents in refractory castables as well as improving the quality of refractory materials.

Effect of silica fume on cement rheology properties in presence of superplasticisers

The effect of silica fume (SF) at different mass concentrations (0, 2, 4, 6, 8 and 10%) on the ordinary Portland cement (C) paste rheology, in the presence of superplasticisers, has been studied. The shear stress versus shear rate was obtained by using the rheometer AR 2000. Two types of superplasticisers (PCEs) have been conducted which are acrylic copolymer (PA) and modified polycarboxylate (PC), and the saturation point of each one was 2% on the amount of cement. The water-cement ratio is equal to 0.35 (W/C = 0.35). The rheological properties of which have been defined applying a rotational viscometer with co-axial cylinders were yield stress, consistence, behavior index and thixotropy. The thixotropy was evaluated by hysteresis loop test which was performed on paste specimen with 6% of SF at 10, 40 and 70 min. The rheological behavior of cement and C-SF solutions was shear-thinning with yield stress. The flow curves were modelled by Hurshel-Bulkly (H-B) law (R2 > 0.99). Hence, it has been noted that the fluidizing effect of the organic additives on cement pastes is conditioned by the presence of silica fume addition. The yield stress and apparent viscosity of the mixtures were increased significantly by raising SF amount. In fact, the yield stress and consistency values were higher for samples added to with SF than for samples without SF. In addition, the results indicated that the PC-admixture effect on the C-SF paste fluidity is more than the PA-admixture one. In other hand, the C-6% SF mixture presented a slight thixotropy value in presence of PC-admixture in comparison with PA-admixture thixotropy especially at 70 min.

Effect of Packing Density According to CPM on the Rheology of Cement–Fly Ash–Slag Paste

AbstractParticle-packing theory has been widely applied in the field of composite particle materials, and packing density (Φ) is an important parameter to evaluate the compactness of particle packi...

Effect of polycarboxylate superplasticizer on fluidity and rheology of cement slurry containing silica fume

The effect of polycarboxylate superplasticizer on the fluidity and rheology of cement - silica fume - water paste was investigated. The changes of dispersion degree, yield stress and plastic viscosity of paste with different superplasticizer content were analyzed. The results show that the rheological properties of paste with different superplasticizer content conform to Herschel-Bulkley model. The shear thinning of the slurry is manifested as a typical yielding pseudoplastic fluid characteristic. When the content of superplasticizer is less than 1.0%, the plastic viscosity and yield stress decrease and the fluidity increase with the increase of plasticizer content. When the content of superplasticizer is more than 1.0%, the yield stress decreases slightly and the plastic viscosity increases with the increase of plasticizer content. The fluidity decreases with the increase of yield stress, and there is a good correlation between them.

Enhancing the cement quality using polypropylene fiber

Durability and long-term integrity of oil well cement are the most important parameters to be considered while designing the cement slurry, especially in the high-pressure and high-temperature (HPHT) environments. In this study, the effect of adding the polypropylene fiber (PPF) to Saudi Class G cement is evaluated under HPHT conditions. The effect of the PPF on the cement compressive and tensile strength, thickening time, density, free water, porosity, and permeability was studied. The effect of the PPF particles on the cement sheath microstructure was studied through powder X-ray diffraction (XRD) and scanning electron microscope. The results obtained showed that PPF did not affect the cement rheology, density, and free water. The addition of PPF considerably decreased the thickening time and improved the tensile and compressive strength of the cement. 0.75% by weight of cement (BWOC) of PPF reduced the thickening time by 75%, from 317 to 78 min. The compressive strength of the cement increased by 17.8% after adding 0.5% BWOC of PPF, while the tensile strength increased by 18% when 0.75% of PPF is used which is attributed to the formation of stable forms of calcium silicate hydrates because of the ability of PPF to accelerate cement hydration process as indicated by the XRD results. The ability of the PPF to decrease the cement thickening time along with its ability to improve the cement strength suggests the use of PPF as an alternative for silica floor in shallow wells where a reduction in thickening time will decrease the wait on cement time. Porosity and permeability of the base cement were also decreased by incorporating PPF because of the pores filling effect of PPF particles as indicated by the microstructure analysis.

An approach to enhance the durability and mechanical properties of Class G cement using nano materials

Maintaining the integrity of the cement used to seal off the injection intervals of sequestrations sites is crucial to confine CO2 for thousands of years. There have been many studies to resolve the issue of cement degradation induced in the presence of CO2, but a very limited success has been reported to the application of the approaches proposed so far. Nano materials have gained the attention of many researchers in the past decade and might be able to resolve the issue of cement degradation given their outstanding performance and proven applications in the civil and polymer industries. In this paper, attempts are made to improve the physical and mechanical characteristics of class G cement using nano glass flakes (NGFs) and multiple-walled carbon nanotubes (MWCNTs). To do this, different cement-nanocomposites were prepared using two mixing techniques and their physical and mechanical changes were evaluated under different curing conditions. Samples with cylindrical shape of were prepared and cured under the temperature of 50°C and atmospheric pressure for 1 days. The results obtained indicated both nanoparticles are neutrally stable and may have a very slight effect on the cement rheology but may significantly increase the strength of the cement. It was concluded that the cement with 0.05 wt.% MWCNTs can provide the best results in terms of rheology, compositional changes and compressive strength.

Effects of Additive Concentrations on Cement Rheology at Different Temperature Conditions

Effects of Additive Concentrations on Cement Rheology at Different Temperature Conditions

A model about dynamic parameters through magnetic fields during the alignment of steel fibres reinforcing cementitious composites

The aim of this paper is to perform a model to understand and to predict the dynamic behaviour of steel fibres immersed in fresh cementitious materials when exposed to Homogeneous Magnetic fields. Fibres behaviour is of especial interest to improve and develop a method to achieve the alignment of fibres in reinforced composites by means of magnetic fields. The torques and forces that a magnetic field summit a ferromagnetic fibre during its alignment find an opposition, in a fresh cementitious composite considered as a Bingham fluid: shear rate (γ̇) and yield stress (τo) and plastic viscosity (η). The torque necessary to rotate a single fibre is determined through a rotational rheometer and the relation between its geometry and the fresh cement rheology is determined. In this work, the alignment of fibres under magnetic fields within the range of 20 mT to 80 mT immersed in fresh mortars and fresh cements is studied. The orientation factor of the fibres after the magnetic field has been obtained. The probabilities of success depending on the initial angle of the fibres are also showed. The model to predict the alignment of fibres in cement-based materials presented here can be used also for different magnetic and rheological ranges.

The Improvement of the Pozzolanic Properties of Recycled Glass during the Production of Blended Portland Cements

The replacement of primary raw materials in cement production is a relevant topic today. One potentially usable raw material is recycled glass. The disadvantage of glass is its tendency towards aggregation. Due to this phenomenon fine glass incement composites work only physically and mechanically as filler rather than as an active pozzolan. The possibilities of improving the pozzolanic properties of recycled glass by means of new milling techniques were examined in this paper. Next to the pozzolanic activity of recycled glass, the advancement of the hydration process of the binder and the effect on the physical and mechanical properties were also monitored. A combination of a ball mill and a nontraditional high-speed pin mill DESI 11 was selected for sample preparation. Portland clinker and recycled glass mixed at a ratio of 80: 20wt. % were used for the preparation of the blended cement. The pozzolanic activity of the pure recycled glass was evaluated using a modified Chapelle test. The hydration process of glass grains in the cement composite was observed using an SEM with an EDX probe. The effect of the grinding technology on the cement rheology and on the compressive and flexural strength was also assessed. The results of the experiment show that the improvement of the pozzolanic properties of recycled glass by using it as the basis of blended cement is possible. The synergistic effect of the co-grinding of the components was observed. The glass particles were better distributed in the composite and could react with Portland cement hydration products. It positively influenced the values of the material's physical and mechanical parameters.

Inexpensive bone cement substitute for vertebral cement augmentation training.

Vertebral compression fractures are treated surgically for approximately 25 years. In percutaneous cement augmentation techniques bone cement is applied to a fractured vertebra under fluoroscopic evidence to stabilize the bone fragments. Complications due to leakage of the low viscosity bone cement are reported in 5 to 15% of all routine cases. During the intraoperative application of bone cement surgeons rely on visiohaptic feedback and hence need to be familiar with the cement's rheology properties. Therefore, training is necessary. A hybrid simulator for cement augmentation training was developed but the usage of expensive real cement limits its purpose as a training modality. Twentythree inexpensive bone substitutes were developed and tested with the objective to mimic real bone cement. Cement application measurements were conducted and a mathematical model of the measurement setup was created. Compared with real bone cement, a cement substitute based on Technovit 3040 in combination with radical catchers and additional additives was identified as an appropriate substitute for cement augmentation training.

A Review- State of Art on Hot Weather Concreting and Rheology of Cement-Based Materials

The objective of this paper is to explore the important mechanisms that control the rheology of cement based materials under hot weather conditions. The effect of hot weather on the fresh and mechanical properties of concrete was investigated. The paper presents some of the practices taken to alleviate the effects of hot weather on concreting. The rheological properties of Portland cement paste and concrete were discussed using both the conventional flow technique and the oscillatory shear technique.

Molecular architecture requirements for polymer-grafted lignin superplasticizers.

Superplasticizers are a class of anionic polymer dispersants used to inhibit aggregation in hydraulic cement, lowering the yield stress of cement pastes to improve workability and reduce water requirements. The plant-derived biopolymer lignin is commonly used as a low-cost/low-performance plasticizer, but attempts to improve its effects on cement rheology through copolymerization with synthetic monomers have not led to significant improvements. Here we demonstrate that kraft lignin can form the basis for high-performance superplasticizers in hydraulic cement, but the molecular architecture must be based on a lignin core with a synthetic-polymer corona that can be produced via controlled radical polymerization. Using slump tests of ordinary Portland cement pastes, we show that polyacrylamide-grafted lignin prepared via reversible addition-fragmentation chain transfer polymerization can reduce the yield stress of cement paste to similar levels as a leading commercial polycarboxylate ether superplasticizer at concentrations ten-fold lower, although the lignin material produced via controlled radical polymerization does not appear to reduce the dynamic viscosity of cement paste as effectively as the polycarboxylate superplasticizer, despite having a similar affinity for the individual mineral components of ordinary Portland cement. In contrast, polyacrylamide copolymerized with a methacrylated kraft lignin via conventional free radical polymerization having a similar overall composition did not reduce the yield stress or the viscosity of cement pastes. While further work is required to elucidate the mechanism of this effect, these results indicate that controlling the architecture of polymer-grafted lignin can significantly enhance its performance as a superplasticizer for cement.

Volumetric Variation and Rheology of Cement Based Mineral Additions (Blast Furnace Slag and Silica Fume)

The partial substitution of clinker by mineral additions offers very significant, both economical and environmental benefits. This adds value to industrial waste, and contributes also in the preservation of natural resources, like clay and limestone, as well as the reduction of greenhouse gas emissions (CO2). This study is interested in the simultaneous effect of BFS (blast furnace slag) and SF (silica fume) on setting time and water requirement of cement paste. The volumetric variations are tested in mortars, prepared in the same mixture of pastes, and the tests indicate that the addition of slag increase the fluidity, reduce the water demand, shrinkage and expansion, compared to the mortar, containing ten percent (10%) of Silica Fume only. The images of pastes obtained by SEM (scanning electron microscopy), are indicated an improvement of the microstructure of the paste with a large amount of slag, which leads to improve durability.

Aluminium-free glass polyalkenoate cements: ion release and in vitro antibacterial efficacy

Glass polyalkenoate cements (GPCs) have exhibited potential as bone cements. This study investigates the effect of substituting TiO₂ for SiO₂ in the glass phase and the subsequent effect on cement rheology, mechanical properties, ion release and antibacterial properties. Glass characterization revealed a reduction in glass transition temperature (T(g)) from 685 to 669 °C with the addition of 6 mol % TiO₂ (AT-2). Magic angle spinning nuclear magnetic resonance (MAS-NMR) revealed a shift from -81 ppm to -76 pmm when comparing a Control glass to AT-2, indicating de-polymerization of the Si network. The incorporation of TiO₂ also increased the working time (T(w)) from 19 to 61 s and setting time (T(s)) from 70 to 427 s. The maximum compressive strength (σ(c)) increased from 64 to 85 MPa. Ion release studies determined that the addition of Ti to the glass reduced the release of zinc, calcium and strontium ions, with low concentrations of titanium being released. Antibacterial testing in E. coli resulted in greater bactericidal effects when tested in aqueous broth for both titanium containing cements.

Rheological and calorimetric behaviour of cements blended with containing ceramic sanitary ware and construction/demolition waste

This research paper analyses the behaviour of new blended cements containing 10% and 20% ceramic sanitary ware (SW) and construction and demolition waste (C&DW) to determine their suitability as future supplementary cementitious materials for commercial cement manufacture. The effects of these recycled materials on cement rheology and heat conductivity were studied and an analysis of covariance was run to quantify the impact of each factor and co-variable involved on rheological properties. The addition of ceramic waste reduced shear yield stress and retarded the hydration reactions, whereas construction and demolition waste (C&DW) had the opposite effect, raising yield stress and accelerating hydration kinetics. These behavioural differences between the two types of industrial waste would have a direct effect on the final applications of the resulting blended cement.

Role of water film thickness in rheology of CSF mortar

In a recent study, the authors have demonstrated that the combined effects of water content, packing density and solid surface area on the rheology of cement–sand mortar may be evaluated in terms of the water film thickness (WFT). The present study aims to extend the concept of WFT to mortar containing condensed silica fume (CSF). For the study, mortar samples with various CSF and water contents were made for packing density, flowability and rheology measurements. It was found that although the effects of adding CSF are fairly complicated, the WFT is still the single most important parameter governing the rheology of CSF mortar. However, the rheological properties are dependent also on the CSF content. Correlations of the rheological properties to both the WFT and CSF content yielded R2 values of at least 0.896.

Water film thickness, flowability and rheology of cement–sand mortar

It is well known that the fresh properties of cement paste and cement–sand mortar are governed mainly by three parameters: water content, packing density and solid surface area. However, these parameters vary simultaneously upon any change in the mix composition and hence the evaluation of their individual and combined effects has been a difficult task. Recently, the authors have found that the effects of these parameters on the flowability and rheological properties of cement paste may be evaluated in terms of the water film thickness (WFT) of the solid–water mixture. Herein, this concept of WFT is extended to cement–sand mortar made of sand with a maximum size of 1·18 mm. A number of mortar samples proportioned with different water contents and different sand gradings were produced for packing density, flowability and rheological properties measurements. From the results, the WFT of each sample was determined and the effects of the WFT on the flowability and rheological properties of the mortar were investigated. The good correlations between the flowability and rheological properties with the WFT revealed that the concept of WFT is applicable also to cement–sand mortar.