Construction materials science. Рубрика в журнале - Nanotechnologies in Construction: A Scientific Internet-Journal
Study of the stability of zeolite suspensions for cement systems
Статья научная
Introduction. In Russia, the focus of scientific research in the construction industry is on the development of new materials with high functionality, durability, and strength. These materials also have various unique properties that make them suitable for a wide range of applications. Fine dispersed additives are used in the binder, for the construction of objects that require increased strength, or for repair work where early strength gain of the repair mixture is important. To improve the physical and mechanical properties of the hardened cement paste, which contains finely dispersed additives, it is necessary to consider the issue of uniform distribution of submicron particles in the volume of the cement composite. The study of this issue is one of the objectives of this study. Materials and methods. Fine dispersed zeolite, which has high ion-exchange, sorption, catalytic properties, was selected as the object of study, and the possibility of its introduction into the cement composition in the form of a stabilized suspension instead of mixing water was assessed/ Zeolite suspension with concentration of 10, 30, 50 g/l was prepared by mechanical stirring with a magnetic stirrer and ultrasonic dispersion under thermostatted conditions. The time of mechanical and ultrasonic treatment of suspensions was 20 min. Suspensions were prepared in two dispersion media – water and water-polymer (water + plasticizer). Physicomechanical tests of samples were carried out in accordance with current national and international standards and methods. Results. Studies of sedimentation stability of suspensions showed that the most stable suspension was stabilized by ultrasonic treatment and plasticizer. The sedimentation velocity of suspension particles in the first period was (3.43÷3.83)•10–6 m/s, in the second period – (0.98÷1.17)•10–6 m/s. The study of zeolite particle dispersion in suspensions showed that ultrasonic dispersion leads to a more significant shift in particle dispersion downwards from 25 μm to 3 μm, both in aqueous and aqueous-polymer suspensions with a concentration of 10–30 g/l. The conducted physical and mechanical tests of the samples showed that the introduction of an ultrasonic-stabilized aqueous-polymer zeolite suspension into the cement composition results in an increase in the initial and grade strength by 3.3 times and 51%, respectively. The analysis of the results for compressive strength showed the greatest efficiency when introducing a zeolite suspension into the cement composition instead of mixing water in an amount of 10–30 g/l. Conclusion. The studies conducted have shown the effectiveness of using ultrasonic treatment in combination with a plasticizer to stabilize the zeolite suspension. Stabilized zeolite particles, uniformly distributed in the volume of the cement matrix, act as a substrate for the nucleation and growth of crystal hydrate phases, thereby intensifying the process of hydration and formation of a crystal hydrate framework with a dense and strong structure of cement stone. Thus, the feasibility of considering zeolites as components of composite materials is a promising direction in solving multifaceted problems in the construction industry.
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Статья научная
Introduction. Nanomodification significantly enhances the performance characteristics of composite materials, particularly those based on polymers. A wide range of materials from natural to artificially created are being studied as nanoobjects. At the same time, carbon nanostructures, such as fullerenes, graphene and carbon nanotubes, are of great interest from the perspective of comprehensively improving material performance. The use of carbon nanotubes for the modification of building materials for various functional purposes, even at low (less than 1% by mass) and ultra-low (less than 0.1% by mass) concentrations, demonstrates a remarkable capability to enhance a multitude of parameters. At the same time, there are technological challenges associated with the need for compound homogenization, requiring the use of ultrasonic processing and other techniques. A new approach to applying nanomodifiers, including single-walled graphene nanotubes, emerged after the launch of a new synthesis facility by OCSiAl in 2020, as well as the introduction of these nanotubes into polymer compounds in the form of masterbatches, which are nanotube concentrates. Methods and materials. This research involved a masterbatch based on single-walled carbon nanotubes TUBALL MATRIX M201 manufactured by OCSiAl.ru LLC. The polymers were made on the basis of low-viscosity epoxy resin Etal–247 and two hardeners manufactured by ENPTs EPITAL JSC –Etal-45M and Etal-1472. Tensile testing was performed on briquet specimens according to GOST 11262-2017. The tests involved AGS-X series bursting machine with TRAPEZIUM X software at a temperature of 23±2 °C and a relative air humidity of 50±5%. The mechanical properties (tensile and deformation) of the polymers were measured in three different moisture conditions: equilibrium-moisture, dry, and moisture-saturated. Results and discussion. The research revealed variations in ultimate tensile strength, tensile elongation and elongation at break, tensile modulus as a function of SGNT concentration and the moisture content of the studied polymers (series “without conditioning”, “moisture-saturated”, and “dried”). Mathematical models were developed to assess the effect of the nanomodifier and moisture content on changes in the properties of the polymers under study. The research has identified the optimal concentrations of the nanomodifier injected for enhancing the elastic and strength characteristics of epoxy polymers. Conclusion. The research indicates that masterbatches based on TUBALL MATRIX M201 single-walled carbon nanotubes hold potential for enhancing the properties of epoxy polymers.
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The strength and deformability of cement stone and powder-activated concrete. Part I
Статья научная
Introduction. During the operation of buildings and structures, reinforced concrete structures are subject to various loads that can cause deformation and destruction. The strength and elastic-plastic properties, as well as the durability of modern concrete, are controlled using superplasticizers, nanoadditives, fillers, and aggregates. The potential of using nanohydrosilicate technologies is demonstrated. This article examines the physical and mechanical properties of cement stone and powder-activated concrete – one type of next-generation concrete. Materials and methods. The influence of the water/cement ratio, the presence of a carboxylate superplasticizer, and a modifying additive were considered as structure-forming factors for cement stone, and the influence of the water/cement ratio, modifying additive, superplasticizer, finely dispersed filler, rheological fillers and reactive fillers were considered for concrete. Results. The article presents the results of a study establishing the relationship between the density of cement stone and powder-activated concrete with the porosity and strength indicators under static and dynamic loads. The rational compositions of the developed composites are characterized by a set of improved physical and mechanical properties. It was found that an increase in the W/C ratio from 0.267 to 0.35 causes a decrease in the compressive and tensile strength of cement stone when splitting by 22–30%. The addition of the superplasticizer ”Melflux 1641F“ led to a significant decrease in the water-cement ratio – from 1.56 times compared to the composition of normal consistency and by 2.04 times – compared to the composition with an increased W/C ratio, as well as a corresponding increase in compressive strength properties – by 1.20 times and 1.72 times – in flexural tensile strength. Conclusion. It was found that the introduction of finely dispersed fillers into the composition of sand concrete led to an increase in compressive, flexural, and tensile strength when splitting by 1.62 to 2.55 times, which is explained by a denser packing of quartz filler, causing an increase in the density of such samples by 9.5%, the plasticizing effect of microquartz, and the high activity of microsilica. The impact strength of the cement composite was studied. It was found that plasticized highly filled compositions of the new generation demonstrated high values of the maximum contact force, contact duration, and impulse magnitude. The composite containing microquartz, quartz filler, fine aggregate, and Melflux 1641F superplasticizer has a maximum contact force of 4.530 N, compared to a similar value of 2.073 N for a cement stone composition made from normal consistency paste. Moreover, the contact duration and impact impulse magnitude are approximately twice as high. The addition of microsilica to the highly filled compositions caused even better results. The maximum contact force at which the samples failed was 4.530 N. This is more than twice that of cement paste based on normal consistency.
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Use of pulp and paper industry waste in binding and cementitious materials technology
Статья научная
Introduction. Utilization of chemical cellulose fillers in construction industry is one of the ways of processing unused wastes from pulp and paper industry. Decorative, finishing, and heat insulation materials are widely used as construction materials. This paper proposes various compositions and insulation materials characterized by compressive strength of not less than 10 MPa, water tightness of 0.8, and density of not over 600 kg/m3. The likely curing mechanism is studied for cement systems. The possible mechanism of hardening structures formation in the systems is discussed. Methodology. Corrugated fibreboard МS-5B waste is used as a filler, high-early strength cement М-500 (CEM 47.5) – as inorganic binder, and elemental sulfur, polyethylene terephthalate, cementmodified polyurethane (PU) with the addition of nanosized silicon oxide are used as a polymeric matrix. Infrared spectroscopy, terahertz time-domain spectroscopy (THz-TDS), and scanning electron microscopy are used for investigations. Cement samples undergo compressive strength, water tightness and water absorption testing. Results and discussion. Physical and mechanical properties obtained for composites with the paper filler and polymeric matrix based on cement-modified PU, are described, and testing results are compared with the experimental data obtained for materials based on other binders. It is found that the paper filler–cement-modified PU composition is consistent with the purposes of this research. The understanding is improved for the curing mechanism of the polymeric matrix–paper filler system. The THz-TDS data demonstrate a correlation between the spectral transmission and thermal conductivity and density of synthesized heat insulation materials. Conclusion. Synthesized is the effective heat insulation material with relatively high compressive strength, low density, and high tightness to water. Scientific understanding of the curing mechanism is improved.
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