Nanotechnologies in Construction: A Scientific Internet-Journal @nanobuild-en
Статьи журнала - Nanotechnologies in Construction: A Scientific Internet-Journal
Все статьи: 606
Статья научная
Introduction. The issue of enhancing the long-term performance of asphalt concrete pavement on highways is not entirely addressed by conventional solutions, such as improving the choice of material composition and refining the production process for bitumen binders and mineral filler compounds. One of the most promising ways to improve the performance and durability of asphalt concrete is the complementary modification of bitumen and road-concrete nanocompositions with thermoplastic and elastic polymers. Methods and materials. Bitumen binders are assessed employing suitable methodologies to determine the following technological parameters: extensibility, softening temperature, brittleness, elasticity, and so forth. Asphaltenes of bitumen binders are the most important structure-forming component and form associated nanoclusters with sizes of 15–200 nm. Thermoplastic block copolymers are introduced into the composition of bitumen binders in granular form (chips) or melted form. Additionally, compatibilizers are used to improve the compatibility of complementary copolymers in bitumen binders. The quality of the finished asphalt concrete composition is significantly affected by the characteristics of the main components: mineral powder, sand, crushed stone, bitumen binder and macromolecular nano-additives, as well as by optimal process modes: mixing temperature, etc. Results. The complementary interaction of supramolecular associations of asphaltenes and fragments of macromolecules of polymer nanocomposites ensures the formation of Van der Waals bonds due to spatial mutual correspondence. The introduction of polymer nanomodifiers leads to an increase in the softening temperature and a decrease in the brittleness temperature of bitumen binders due to the formation of sufficiently stable supramolecular complexes. Discussion. Synergistic nanoadditives of complementary macromolecules into the bitumen binder provides a fewfold increase in the adhesion of the bitumen composition and the mineral components, as well as a noticeable increase of the temperature range for plasticity and deformability. Asphalt concrete coatings with polymer-bitumen binders increase the operability of the roadway and resistance to the formation of plastic flow deformations (shifts, ruts) at high and low temperatures. Conclusion. Bitumen binders of asphalt road concrete, which have been modified with polymer nanocomposites, have higher adhesion, an extended range of thermoplasticity and water resistance.
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Complex mechanical-thermal synthesis of nanostructured calcium hydrosilicates for cement composites
Статья научная
Introduction. The use of nanosized calcium hydrosilicates as additives accelerating the structure formation of cement compositions is becoming increasingly popular. The reason for this lies in their high efficiency as accelerators in the absence of a negative effect on the long-term strength and durability of cement composites. An additional advantage of nanoscale calcium hydrosilicates is the variety of existing methods for their synthesis, among which the mechanochemical method stands out due to the availability of raw materials and the simplicity of the technical design of the synthesis. Article body. The review considers a new method for the synthesis of nanostructured calcium hydrosilicates – complex mechanical-thermal synthesis, which is a combination of mechanochemical synthesis of carbohydrate-modified calcium hydrosilicates with their subsequent thermal decomposition. Modified calcium hydrosilicates , in the interlayer space of which the carbohydrate is intercalated , are capable of decomposition under conditions of low-temperature thermolysis (<150 oC ) with the formation of hydrosilicate nanoparticles, the coagulation of which leads to the formation of a nanostructured phase of calcium hydrosilicates – xerogel. A mixture of xerogel with residues of raw materials, hydrated phases that have not decomposed during thermolysis is a calcium silicate dispersion (CSD). The technological features of CSD synthesis and some properties of CSD are described. In particular, a moderate (up to 60%) acceleration of daily strength gain of CSD-modified cement mortars with a parallel increase in grade strength (17%) is revealed. A significant effect of CSD on the rheological properties of cement mixtures is noted. Conclusion. Complex mechanical-thermal synthesis is a new synthetic direction for obtaining nanosized calcium hydrosilicates. The development of this direction is far from complete and is closely related to the development of the theoretical base, in particular, the concept of non-classical nucleation as applied to hydrosilicate phases. The development of the method can be aimed at searching for new organic modifiers with the acquisition of new properties of modified hydrosilicates and products of their thermal decomposition, at improving synthesis modes in order to regulate the quantitative and qualitative parameters of the nanostructured phase, consumer properties of the CSD, and expanding the scope of its application.
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Composite building materials based on nanomodified cement systems
Статья научная
Introduction. This research work investigates the combined influence of nano-sized silicon dioxide (nano-SiO2), carbon nanotubes and surfactants on the structural and technological characteristics of cement compositions. Materials and research methods. The paper reveals the findings of a study on the effects of various dispersion techniques of carbon nanotubes (CNT) in surfactants, such as mechanical dispersion, ultrasonic treatment, and a combined method. It considers the uniformity of CNT distribution within the plasticizer and within the cement system, along with their impacts on the physical and mechanical properties of cement stone and concrete. Differential thermal and electron microscopic analysis of aqueous dispersions of carbon nanotubes and hardened activated nanomodified cement stone was carried out. Results and discussion. It has been experimentally proven that mixing nanotubes in dry cement does not allow them to be evenly distributed throughout the volume of the mixture. When using carbon nanotubes, the maximum effect is achieved when they are introduced into aqueous dispersions of plasticizers. The percentage of plasticizer was 1%, CNT 0,1% per 1 liter of water. The most effective method of dispersing carbon nanotubes in a plasticizer is a combined one. The results obtained were used in the preparation of cement stone and concrete compositions. Conclusion. The results show that complex additives consisting of nano-SiO2 and aqueous dispersions of carbon nanotubes have a positive effect on the physical-mechanical and structural-technological properties of cement stone and concrete. Graphic dependencies are shown indicating the effectiveness of using complex additives in the production of cement composites.
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Статья научная
Introduction. The aim of the research is to study the compressibility of composite materials obtained by varying the degree of impregnation of a non-woven needle-punched cloth with an aqueous dispersion of polyurethane. Materials and research methods. Non-woven needle-punched cloth made of polyethylene terephthalate fibers (TU 6-13-0204077-95-91) with a linear density of 0.33 tex (diameter 20–25 microns) was used as objects of research. For impregnation, an aqueous dispersion of anionic stabilized aliphatic polyethiruretane of the brand IMPRANIL DL 1380 (PRC) with a dry residue of 40% was used. The compressibility of canvases and composite materials was established using the ICH indicator according to GOST 577-68 with an accuracy of measuring the thickness of ± 0.001 mm. Results and discussion. An approach is proposed to establish the relationship between the degree of compressibility of composite materials and the load and to obtain an equation for predicting the degree of compressibility of composite materials from the degree of impregnation and load. Optimal loading conditions of the composite material with a minimum degree of compressibility has been established. Conclusion. The optimal degree of impregnation of a non-woven needlepunched fabric made of polyethylene terephthalate fibers with a diameter of 20–25 microns with polyurethane dispersion is 0.5.
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Статья научная
Introduction. Reducing the density, increasing the strength and other physical-technical characteristics of lightweight concretes are urgent tasks of modern building materials science. To solve them, it is necessary to consider new approaches to the development of compositions of cement systems using effective porous aggregates, binders, chemical and mineral additives, including different nanomodifiers (carbon nanotubes, fullerenes, nanoparticles of SiO2, Al2O3, Fe2O3, etc.). The complexity of designing modified cement concretes is largely due to their multicomponent nature and a large number of parameters affecting the key characteristics of material. The qualitative solution of such multicriteria problems is possible with the complex implementation of rational physical and computational experiments using mathematical modeling and computer technology. New opportunities for modeling of structure formation processes and predicting properties of multicomponent building materials are emerging with the development of machine learning methods. The purpose of this study is to develop machine learning algorithms that can efficiently establish quantitative dependences for the compressive strength of modified lightweight concretes on their composition, as well as to identify the optimal variation ranges of prescription parameters based on the obtained multifactor models to achieve the required level of controlled mechanical characteristic. Methods and materials. The processing and analysis of experimental research results were carried out using modern methods of machine learning with a teacher used in the problems of regression recovery, knowledge extraction and forecasting. To implement the developed machine learning algorithms, libraries in the Python programming language, in particular NumPy, Pandas, Scikit-learn, Matplotlib, Seaborn, were used. Results and discussion. It is established that the gradient boosting model is the most accurate type among the obtained machine learning models. It is characterized by the following quality metrics: R2 = 0.9557; MAE = 2.4847; MSE = 12.7704; RMSE=3.5736; MAPE = 11.1813%. According to the analysis of this multifactor model, the optimal dosages of pozzolanic and expanding modifiers amounted to 4.5–6.0% and 6.0–7.5% of the binder weight (Portland cement + modifier), respectively, which ensured achievement of the required level of compressive strength (40–70 MPa) of lightweight concretes at the age of 28 days at material density reduced by 3–10% (the range under consideration is 1200–1900 kg/m3). Conclusions. Thus, the study results show the prospects of using machine learning methods for design compositions and predicting properties of multicomponent cement systems.
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Concrete with fillers of various dispersion and their nanomodification
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The author is the first to propose the filling and nanostructuring of coarse materials such as concrete. Existing grinding methods in construction materials provide particle sizes of 10–50 microns (microns), including cement particles. It is preferable to use cavitation technology in suspensions when producing smaller particles. The article discusses the nanostructuring of cement systems by introducing ultra- and nanodispersed mineral additives. At the same time, additional grinding of mineral additives is carried out at cavitation plants. Nanostructuring provides compaction of concrete structures and increase the strength characteristics of concrete up to 2.5 times.
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Concretes with nanoadditive of fired recycled concrete
Статья научная
The practice of using recycled concrete from the broken concrete of substandard reinforced concrete products can become widespread in practice. The undoubted relevance of this topic is explained by the program for the renovation of the housing stock in the city of Moscow, which provides for the demolition of 5-storey residential buildings until 2032. The problem of recycling and reuse of construction waste becomes obvious to improve the environmental situation, as well as to reduce the cost of materials in construction and preserve natural resources. The article deals with the nanostructuring of cement systems by means of introduction of ultra- and nanodispersed mineral additives. In this case, additional grinding of mineral additives is carried out in cavitation units. Nanostructuring provides the compaction of concrete structures and an increase in the strength properties of concrete.
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Construction heat and sound insulating composite materials with high tensile strength
Статья научная
Introduction. The objective of this study is to examine the impact of the impregnation (with the aliphatic polyurethane water dispersion) degree on the deformation properties of the polyacetal, polyethylene terephthalate and polypropylene fibers based nonwoven needle-punched composite fabrics. Materials and methods. We investigated the deformation properties of the nonwoven fabrics manufactured from the 0.33 tex linear density fibers of: polyethyleneterephthalate (diameter 20–25 microns, according to TU 6-13- 0204077-95-91), polypropylene (diameter 27–30 microns, according to TU 2272-007-5766624-93) and the original polyacetal ones (diameter 18–22 microns). The nonwoven fabrics were obtained by the mechanical formation technique. The needlepunching surface density was 180 cm–2. The water dispersion of anionic stabilized aliphatic polyethyruretane (IMPRANIL DL 1380 (China)) with a dry residue of 40% was used for the impregnation. The experimental samples’ linear dimensions were determined in accordance with the requirements of GOST 15902.2-2003. The sample’s thickness was determined by a thickness gauge with a pressure of 10 kPa and an instrumental error ~ 0.01 mm according to GOST 11358-70. The samples’ mechanical properties were determined in accordance with the requirements of GOST 15902.3-79. Results and discussion. The fiber filler composition influence on the ob-tained (by the impregnation of polyethyleneterephthalate, polypropylene and polyacetal fibers based non-woven needle-punched fabrics with polyurethane aqueous dispersion) composite materials tensile resistance has been established. We found the impregnation degree (depending on the chemical nature of the fibers and on the direction of nonwoven fabrics formation) at which the tensile resistance of the composite materials reaches the maximum value. It is demonstrated that, in the construction of buildings and structures, it is advisable to utilize materials based on composite polyacetal fibers. These materials exhibit higher tensile resistance compared to those based on polypropylene and polyethylene terephthalate at equivalent impregnation levels. Conclusion. The obtained optimal impregnation degree (at which the maximum tensile resistance of polyacetal fiber based composite materials was achieved) depends on the direction of the non-woven fabric formation. The maximum tensile resistance was observed: in the transverse direction – at 0.44 and in the longitudinal direction – at 0.35 impregnation degree values.
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