scholarly journals Increase of aggregative and sedimentation stability of slag suspensions by ultrasound

2019 ◽  
Vol 110 ◽  
pp. 01061
Author(s):  
Svetlana Samchenko ◽  
Irina Kozlova ◽  
Оlga Zemskova ◽  
Ekaterina Baskakova
Keyword(s):  
Building Materials ◽  
Aqueous Dispersion ◽  
Micelle Formation ◽  
Cement Matrix ◽  
Aggregative Stability ◽  
Mechanical Mixing ◽  
Dispersion Parameters ◽  
Ultrasonic Dispersion ◽  
Sedimentation Stability ◽  
Object A

The paper discusses the relevance of the use of metallurgical wastes crushed to a fine state in the production of building materials. Domain granulated slag (DGS) was used as a research object. A method for introducing fine ground slag (FGS) into the cement composition in the form of a slag suspension instead of mixing water has been developed. To establish the uniform distribution of FGS particles in the cement matrix, the behavior of slag particles in an aqueous dispersion medium was previously studied. The optimal parameters of ultrasonic dispersion of slag suspensions are established: the frequency of ultrasonic vibrations is 44 kHz; temperature of dispersion - 25±2°C; dispersion time - 15 min. It has been established that the application of UST to slag suspensions with the observance of optimal dispersion parameters can increase the aggregative and sedimentation stability of the FGS suspension by 2–3 times as compared with mechanical mixing, accelerate the micelle formation process, and enhance the electrostatic factor of aggregative stability.

scholarly journals Influence of optimal conditions of ultrasonic dispersion on the stability of suspensions of finely ground slags

2019 ◽  
Vol 265 ◽  
pp. 01017 ◽  
Author(s):  
Svetlana Samchenko ◽  
Irina Kozlova ◽  
Оlga Zemskova ◽  
Ekaterina Baskakova
Keyword(s):  
Aqueous Dispersion ◽  
Cement Composite ◽  
Cement Stone ◽  
Mechanical Mixing ◽  
Dispersion Parameters ◽  
Ultrasonic Dispersion ◽  
Sedimentation Stability ◽  
Granulated Blast Furnace Slag ◽  
The Stability ◽  
Furnace Slag

The preparation in the jet mill of finely ground slag (FGS) from the waste of metallurgical production granulated blast-furnace slag, the obtaining of slag suspensions, and the behavior of FGS particles in an aqueous dispersion medium are considered in the paper. It was found that FGS particles in the suspension form micelles of two types with negative (micelle 1) and positive (micelle 2) charges of FGS surface. To increase the aggregative and sedimentation stability of FGS particles in suspensions, studies were carried out using ultrasonic dispersion. The results of investigations on the detection of optimal dispersion parameters for slag suspensions are presented. It was found that in the absence of temperature control, the process of coagulation of slag particles is accelerated and aggregative and sedimentation stability of suspensions of FGS is reduced. The slag particles in the suspension form aggregates that lead to a deterioration of the strength characteristics of the cement stone using suspensions of FGS. Optimal parameters of ultrasonic dispersion of slag suspensions are established: the frequency of ultrasonic vibrations is equal to 44 kHz; the dispersion temperature is 25 ± 2 °C; the dispersion time is 15 min. It was found that the application of ultrasonic dispersion to slag suspensions with the observance of dispersion conditions can increase the aggregative and sedimentation stability of FGS suspension by 2-3 times in comparison with the mechanical mixing of suspensions. The strength of samples with suspensions of FGS prepared using UST under the recommended dispersing conditions increased by 19 to 39% in the first day; for 28 days of hardening - by 19 - 36%, which allows using slag suspensions in the production of cement composite materials and concretes based on them.

scholarly journals Efficiency of stabilization of slag suspensions by polycarboxylate

2019 ◽  
Vol 91 ◽  
pp. 02039 ◽  
Author(s):  
Svetlana Samchenko ◽  
Irina Kozlova ◽  
Olga Zemskova ◽  
Denis Potaev ◽  
Dana Tsakhilova
Keyword(s):  
Aqueous Dispersion ◽  
Optimal Concentration ◽  
Aggregative Stability ◽  
Surface Charges ◽  
Mechanical Factor ◽  
Particle Sedimentation ◽  
Sedimentation Stability ◽  
The Third ◽  
Mechanical Factors ◽  
Second Period

The paper describes the method of stabilization of slag suspensions prepared on the basis of finely ground slag (FGS) with a predominant particle size of 1-7 μm, a plasticizer based on polycarboxylate (polycarboxylate). In suspension, FGS particles form two types of micelles with negative and positive surface charges. It has been established that stabilization with polycarboxylate, which is an anionic long-chain surfactant, affects slag particles with a positive surface charge. The formation of strong and elastic gel-like films on the surface of FGS leads to an increase in the structural and mechanical factor of aggregative stability of slag suspensions. Thus, the stabilization of slag particles by polycarboxylate is ensured by electrostatic, structural and mechanical factors of aggregative stability. It was established experimentally that the introduction of polycarboxylate into the aqueous dispersion medium increases the aggregative and sedimentation stability of slag suspensions. In the first period of particle sedimentation, on average, stability of slag suspensions is increased by 36 times, in the second period - 19 times, in the third period - 4 times. To ensure stability of slag suspensions, the protective number and the optimal concentration of the polycarboxylate are determined. The protective number of the suspension was 0,016 g/l; the optimal concentration of polycarboxylate - 4 g/l.

Improvements on Mechanical Property and Microstructure of Cementitious Composite Incorporated with Silica Fume and Carbon Nanotube

2019 ◽  
Vol 298 ◽  
pp. 167-171
Author(s):  
Gu Yue Han ◽  
Jian Lin Luo
Keyword(s):  
Compressive Strength ◽  
Carbon Nanotube ◽  
Silica Fume ◽  
Cementitious Materials ◽  
Filler Loading ◽  
Cement Matrix ◽  
Ultrasonic Dispersion ◽  
Integrated Network ◽  
Positive Effects ◽  
Ultrafine Silica

Nano-size fillers (ultrafine silica fume (USF) or/and multi-walled carbon nanotube (MWCT)) were incorporated into cement matrix to fabricate nano-fillers reinforced cementitious materials (NFRCs) with surfactant ultrasonic dispersion and subsequently mix cast process. The flexural and compressive strengths of four groups NFRCs with varied nano-filler loading were comprehensively investigated. Results show, there are positive effects on the flexural and compressive strength of NFRCs with nano-fillers loading, especially when USF and MWCT are incorporated simultaneously, and the correspondent maximal flexural and compressive strength can increase by above 17%, 28% with respect to the baseline, respectively. The pozzolan infilling effect of USF and the crack-bridging effect of dispersed MWCT result in the dense and integrated network microstructures of cured NFRC.

Einfluss der elektrochemischen Doppelschicht auf die Sorption und den Transport von Chlorionen im Zementstein / Influence of the electrochemical double layer on sorption and transport of chlorides in hardened cement paste

2000 ◽  
Vol 6 (4) ◽  
pp. 415-428
Author(s):  
O. Wowra ◽  
M.J. Setzer
Keyword(s):  
Double Layer ◽  
Cement Paste ◽  
Building Materials ◽  
Pore Solution ◽  
Chloride Ions ◽  
Transport Processes ◽  
Cement Matrix ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Electrochemical Double Layer

Abstract Besides the formation of Friedel salt the transport and binding of chlorides in concrete is mainly defined by the electrochemical double layer at the interface between cement matrix and pore solution. Due to the alkaline pore solution the surface of hardened cement paste is negatively charged which may change to positive values by the potential regulating calcium ions. Inverting of the surface charge leads to an attraction of anions and therefore, to an adsorption of chloride ions in the diffuse part of the electrochemical double layer. Influence from outside like sulphates and carbon dioxide may lead to a decomposition of Friedel salt. Apart from these effect temperature, pH-value and certain environmental conditions affects the electrochemical double layer as well. The chloride equilibrium is mainly controlled by adsorbed ions in the electrochemical double layer. The model presented here is relevant for the assessment of ion transport processes in mineral building materials. Continuing investigations may lead to optimize transport models and a better evaluation of the critical chloride threshold value in reinforced concrete.

Properties of Cement Composites Containing Coir Pith

2014 ◽  
Vol 982 ◽  
pp. 136-140 ◽  
Author(s):  
Eva Vejmelková ◽  
Dana Koňáková ◽  
Anna Krojidlová ◽  
Veronika Hovorková ◽  
Monika Čáchová ◽  
...  
Keyword(s):  
Moisture Transport ◽  
Building Materials ◽  
Agricultural Waste ◽  
Cement Matrix ◽  
Cement Composites ◽  
Coir Fiber ◽  
Transport Parameters ◽  
Coir Pith ◽  
Adhesion Ability ◽  
Mechanical Strengths

Application of agricultural waste materials as building materials not just provides solutions of environmental problems related to the waste management, but it also decreases the use of limited available natural resources and energy. The research in this work is focused on using coconut waste, in the form of natural and chemically treated coir pith, as admixture partially replacing cement in cement composites. The coir pith is the residue acquired during the extraction coir fiber from the outer protective husk of the coconut. Basic physical properties, mechanical, thermal and hygric parameters of several mixtures were studied. The results of measurements showed the influence of amount of coconut addition primarily on parameters such as the bulk density, open porosity, mechanical strengths, moisture transport parameters and thermal parameters. Restrictions for utilization of this waste material relate primarily with its low adhesion ability to the cement matrix.

scholarly journals A research into the distribution of silicium dioxide nanoparticles in the mixing water

Vestnik MGSU ◽  
2020 ◽  
pp. 678-687
Author(s):  
Dmitry A. Nemuschenko ◽  
Vladimir V. Larichkin ◽  
Anastasiya P. Onipchenko ◽  
Vasilij S. Subbotin
Keyword(s):  
Building Materials ◽  
Ultrasonic Method ◽  
Matrix Material ◽  
Solid Particles ◽  
Chemical Compositions ◽  
Ultrasonic Dispersion ◽  
Nanoparticle Distribution ◽  
The Matrix ◽  
Silicium Dioxide ◽  
The Impact

Introduction. The co-authors studied suspensions of silicium dioxide nanoparticles in the water. The application of suspensions helps to most effectively add nanoparticles to slip ceramic mixtures and mixtures that contain concrete. A review of publications has proven that Russian and foreign researchers are willing to learn more about nanoparticles used to modify various materials. Particles having different chemical properties are applied depending on the types of problems to be solved. The method of ultrasonic dispersion of fillers in the matrix material is widely used; surfactants stabilize suspensions and mortars. Silicon dioxide, being one of the cheapest ultra-dispersed powders, has been proven as an active filler designated for building materials. Materials and methods. A method of ultrasonic dispersion was used to uniformly distribute nanoparticles in the water. A surfactant was added to the suspension to reduce the reaggregation of particles and to rise the stability of suspensions in the course of time. The turbidimetric method was employed to control the nanoparticle distribution efficiency in the suspension, and a spectrophotometer was used to identify the dimensions of solid particles by measuring the optical density. Results. The co-authors have proven the efficiency of the ultrasonic method in distributing nano-sized particles over the water. The suspensions, developed by the co-authors, were used to mold samples of ceramics; a scanning electron microscope and a nozzle, designated for the identification of chemical compositions, were used to identify dimensions of nanoparticle conglomerates in the matrix. The co-authors identified the concentration of OP-10 surfactant that was optimal for the destruction of conglomerates in the suspension; the impact of the ultrasonic treatment duration was assessed in respect of the suspension. Conclusions. The research findings can be contributed to ceramic production technologies for versatile nanoparticles to be employed to modify materials.

scholarly journals Physicomechanical and Antimicrobial Characteristics of Cement Composites with Selected Nano-Sized Oxides and Binary Oxide Systems

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 661
Author(s):  
Patryk Jędrzejczak ◽  
Łukasz Ławniczak ◽  
Agnieszka Ślosarczyk ◽  
Łukasz Klapiszewski
Keyword(s):  
Binary Systems ◽  
Building Materials ◽  
Inhibitory Effect ◽  
Physicochemical Analysis ◽  
Cement Matrix ◽  
Oxide Systems ◽  
Potential Measurement ◽  
Cement Mortars ◽  
Single And Binary Systems ◽  
Bacteria And Fungi

In recent years, increasing attention has been paid to the durability of building materials, including those based on cementitious binders. Important aspects of durability include the increase of the strength of the cement matrix and enhancement of material resistance to external factors. The use of nanoadditives may be a way to meet these expectations. In the present study, zinc, titanium and copper oxides, used in single and binary systems (to better the effect of their performance), were applied as additives in cement mortars. In the first part of this work, an extensive physicochemical analysis of oxides was carried out, and in the second, their application ranges in cement mortars were determined. The subsequent analyses were employed in determining the physicochemical properties of pristine oxides: Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray fluorescence (EDXRF), scanning electron microscopy (SEM), measurement of the particle size distribution, as well as zeta potential measurement depending on the pH values. Influence on selected physicomechanical parameters of the cement matrix and resistance to the action of selected Gram-positive and Gram-negative bacteria and fungi were also examined. Our work indicated that all nanoadditives worsened the mechanical parameters of mortars during the first 3 days of hardening, while after 28 days, an improvement was achieved for zinc and titanium(IV) oxides. Binary systems and copper(II) oxide deteriorated in strength parameters throughout the test period. In contrast, copper(II) oxide showed the best antibacterial activity among all the tested oxide systems. Based on the inhibitory effect of the studied compounds, the following order of microbial susceptibility to inhibition of growth on cement mortars was established (from the most susceptible, to the most resistant): E. coli < S. aureus < C. albicans < B. cereus = P. aeruginosa < P. putida.

scholarly journals Dependence of the fractality of the silica gel on the method of sol emulsification

2021 ◽  
pp. 88-90
Author(s):  
S. S. Tkachenko ◽  
V. O. Yemelyanov ◽  
K. V. Martynov
Keyword(s):  
Silica Gel ◽  
Silicic Acid ◽  
Active Substance ◽  
Sol Gel ◽  
Aqueous Dispersion ◽  
Ceramic Shell ◽  
Organic Polymers ◽  
Sedimentation Stability ◽  
Final Structure ◽  
Gel System

The article presents experimental data confirming the effect of capillary active substance (surfactants) and sedimentation stability on the final structure of the gel with stabilized silicic acid. Studies of the macrostructure of silica gel depending on the method of emulsifi ation of silicic acid sol and the effect of the resulting fractality on the strength of the mold are presented.The direction of modifying the binder for lost‑wax casting (LWC) with obtaining the specified properties of the ceramic shell is shown.The complex effect of organic polymers on the sol – gel system has been established. The conclusion is made about the possibility of using an aqueous dispersion of acrylic to form a given structure of a silica gel.

Modification of the interfacial layer of reinforced polymer composites with nanodispersed silicon dioxide

2021 ◽  
Vol 4 ◽  
pp. 37-55
Author(s):  
S. A. Koksharov ◽  
◽  
S. V. Aleeva ◽  
N. L. Kornilova ◽  
E. N. Kalinin ◽  
...  
Keyword(s):  
Silicon Dioxide ◽  
Mechanical Activation ◽  
Materials Science ◽  
Aqueous Dispersion ◽  
Shear Stresses ◽  
Chemical Transformations ◽  
Ultrasonic Dispersion ◽  
Rational Distribution ◽  
Deformation Properties ◽  
Wet Heat

The behavior of colloidal silicon dioxide in a composition with a styrene / butyl acrylate oligomer, grafted onto a thermoplastic polyamide adhesive to obtain a branched binder structure with penetration of branches into the capillary-pore system of the reinforcing fiber component, was studied. The variants of disaggregation of SiO2 using ultrasonic treatment and mechanical activation with exposure by high shear stresses, ultrasound and cavitation are compared. Methods of dynamic light scattering, IR spectroscopy, thermal analysis, and textile materials science were used to evaluate the elastic-deformation properties of duplicated packets. The set of complementary results confirms that the combined mechanical activation of an aqueous dispersion of oligoacrylate and silica causes the destruction of silica nanospheres and the formation of a hybrid oligolymer-inorganic adduct. In contrast to the short-term effects of ultrasonic dispersion of SiO2, joint mechanical activation of the components solves the problems of preventing aggregation of nanoparticles and uniform distribution of the reinforcing filler in the composite. The effectiveness of using the method for regulating the properties of forming units and parts of sewing products is shown. When selecting oligoacrylate, specific for sewing production separation of the stages of preliminary bonding of materials using thermoplastic adhesive, the creation of a finished product form and its fixing during wet-heat treatment, is taken into account. The preparation of a hybrid adduct of mechanical activation provides an optimal ratio of particle size for rational distribution of fractions in interfacial, interfiber, and intrafiber spaces of the textile web. The shift of the peaks of phase transitions and chemical transformations in a system with nanodispersed SiO2, controlled on DSC thermograms, is consistent with the temperature regimes of successive stages of the technological process. The possibilities of a controlled change in the properties of forming composite materials and a decrease in the material consumption of sewing products by grafting a modified oligoacrylate with a variable content of silicon dioxide are demonstrated.

scholarly journals Photocatalytic BiOX Mortars under Visible Light Irradiation: Compatibility, NOx Efficiency and Nitrate Selectivity

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 226 ◽  
Author(s):  
Magaly Y. Nava-Núñez ◽  
Eva Jimenez-Relinque ◽  
Maria Grande ◽  
Azael Martínez-de la Cruz ◽  
Marta Castellote
Keyword(s):  
Visible Light ◽  
Urban Areas ◽  
Building Materials ◽  
Oxidation Potential ◽  
Alkaline Media ◽  
Cement Matrix ◽  
Oxide Compound ◽  
Environmentally Sustainable ◽  
Visible Light Driven ◽  
Light Absorbance

The use of new photocatalysts active under visible light in cement-based building materials represents one interesting alternative to improve the air quality in the urban areas. This work undertakes the feasibility of using BiOX (X = Cl and I) as an addition on mortars for visible-light-driven NOx removal. The interaction between BiOX photocatalysts and cement matrix, and the influence of their addition on the inherent properties of the cement-based materials was studied. The NO removal by the samples ranking as follows BiOCl-cem > BiOI-cem > TiO2-cem. The higher efficiency under visible light of BiOCl-cem might be ascribed to the presence of oxygen vacancies together with a strong oxidation potential. BiOI-cem suffers a phase transformation of BiOI in alkaline media to an I-deficient bismuth oxide compound with poor visible light absorbance capability. However, BiOI-cem showed considerably higher nitrate selectivity that resulted in the highest NOx global removal efficiency. These results can make its use more environmentally sustainable than TiO2 and BiOCl cement composites.

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