Nanotechnologies in Construction: A Scientific Internet-Journal @nanobuild-en
Journal articles - Nanotechnologies in Construction: A Scientific Internet-Journal
All articles: 652
Scientific article
Introduction. The aim of the work is to determine the influence of the structure of the filter materials formed as a result of modification of the surface layer on their water permeability and the size of trapped solid particles. Materials and methods. The non-woven fabrics from a mixture of polyethylene-terephthalate (PET) (70 wt.%) and bicomponent fibers (BCF) of the coreshell structure were used as objects of the study. The non-woven fabrics were obtained by mechanically forming the canvas with its subsequent hardening by needle punching. The resulting materials were modified by heat treatment. The water transfer in the modified materials was determined by the permeability coefficient. The filtration efficiency was determined by the number of trapped particles of a certain size. Results and discussion. The needle-punched non-woven fabrics without additional heat treatment are not suitable for water filtration. The proposed method of thermal and deformation-thermal modification provides the production of gradient materials with a controlled thickness of the nanoscale surface layer. Although a decrease in water permeability is observed, the modified material traps solid particles with a smaller (compared to unmodified ~ 20 μm) equivalent diameter of 2–4 μm, which is sufficient to prepare water for use in steam generators and in the production of building materials. Conclusion. The optimal parameters of deformation-heat treatment for obtaining the high-effective filtration non-woven materials were established: the temperature – 180оC, the processing speed – 3.5 m/min.
Free
High-Performance Concretes for Machine Building with Nano- and Micro-Scale Raw Materials
Scientific article
Introduction. The unique combination of rheotechnological properties and mechanical performance opens up prospects for the application of self-compacting and high-strength concretes in the manufacturing of base elements for machines and industrial equipment. The processes of adsorption of modern plasticizers on various mineral and polymeric modifiers of concrete mixtures were investigated. The compatibility of nano- and micro-scale mineral additives in composite cementitious binders was determined using calorimetry with an improved semi-adiabatic setup. Materials and methods. The cementitious binders used were CEM 52.5N Portland cement (Asia Cement LLC, Russia) and Nanodur (Germany, Dyckerhoff GmbH); hyperplasticizers included Melflux 1641F, 2651F, 5581F (Germany), PCE TR-6088 (China), Sika ViscoCrete 240 HE Plus and 226-P (Russia); superabsorbent polymer; nano- and micro-scale mineral additives included microsilica MK-85, metacaolin VMK-45, microcalcite MM-315, marshalite Silverbond 15 EW, and ground silica-containing rocks. Selective dissolution, differential thermal analysis, laser granulometry, and semi-adiabatic calorimetry were employed. Results and discussion. The quality of ultrafine mineral additives determines their ability to chemically bind portlandite through pozzolanic activity. Among the investigated additives, microsilica and gaize demonstrated the highest pozzolanic activity. Thermal activation was effective for components consisting of crystalline silica (marshalite, ground quartz sand), resulting in a 25% increase in performance. There was no selective adsorption of hyper plasticizer molecules by superabsorbent modifiers based on sodium polyacrylate compositions. Metakaolin and tremolite exhibited high adsorption to hyper plasticizers among the mineral additives. The rapid evaluation of the influence of formulation factors on the setting of cementitious composites was tested on an improved version of the semi-adiabatic calorimeter. Conclusions. The presence of micro-scale mineral additives based on microsilica in composite cementitious binders enables the development of high-performance concretes adapted for machine building. The study of pozzolanic activity, adsorption capacity, and cumulative heat release curves has indicated the feasibility of replacing microsilica with metacaolin and the potential for its partial blending with finely ground natural gaize. Analysis of the thermal effects accompanying the hydration processes of the "cement-additive-water" system with calorimeters allows us to provide more efficient research on the compatibility of additives in high-performance concrete compositions.
Free
High-performance nano-modified concrete of increased strength and durability
Scientific article
Introduction. To create concrete with a set of physical and mechanical characteristics, a rational selection of the components of the concrete mix is required, including the use of finely dispersed fillers, including those based on recyclable materials, and a highly effective chemical additive of a certain nature and reactive action, which has a complex effect on concrete system. Methods and materials. The effectiveness of the components in used additive was assessed by changing the indicators of compressive strength, tensile strength in bending, the assessment of which was carried out according to GOST 10180-2012 “Concrete. Methods for determining the strength of control samples. For carrying out scientific and experimental studies, the following materials were used: Portland cement CEM I 42.5N; natural sand; fine microsilica; complex chemical additive with increased plasticizing and reactive effects. Results. The combination of polycarboxylate polymers and nanodispersions of silicon hydroxide enhances the effectiveness of each component, which is reflected in a significant increase in the coefficient of crack resistance of concrete at high compressive strength. It has been established that when using a complex nanopolymer chemical additive, the increase in tensile strength in bending is 67% and it exceeds the increase in compressive strength by more than 30%. Discussion. An increase in hydration activity in the presence of a nanopolymer additive has a positive effect on the compaction of the emerging concrete structure. Confirmation of the formation of a dense and strong structure during the hardening of nanomodified concrete is an increase in the water resistance of concrete by 2.5 times and its frost resistance by more than 2.5 times. Conclusion. The advantage of nanomodified concrete is its increased chemical resistance to carbon dioxide and magnesia corrosion and, in accordance with the index of chemical resistance coefficient, CCSт> 0.8, and GOST R 58895-2020, the developed nanomodified concrete belongs to chemically highly resistant concretes. It is advisable to recommend nanopolymer concrete with high physical and mechanical properties for the manufacture of structures for overhead power transmission lines (OPL).
Free
High-strength cement-based repair and grouting compositions modified with nanodispersed silica
Scientific article
Introduction. The development of high-strength repair and grouting compositions for restoring concrete structures is a relevant task. The aim of the research is to study the effect of long-term stored nanodispersed silica (NS) on cement stone properties. Methods and Materials. Portland cement CEM I 42.5 N and sol-gel NS (storage: 1 day – 1.5 years) were used. Surface acid-base properties – indicator method; hydration kinetics – non-isothermal calorimetry. Four compositions: control, NS, NS + PC type S, NS + PFM. Compressive strength – up to 28 days; SEM, XRD, DTA. Results. NS surface has a polyfunctional acid-base spectrum. Long-term storage does not degrade activity: strong acid centers (pKa = –4.4) increase from 7.42 to 260–265 mg eq/g; strong basic centers (pKa = 8.8) remain at 515–628 mg eq/g. NS stored for 1.5 years intensifies heat release (max ~25.5 °C). Compressive strength increase by day 28: NS – 14.5%; NS + PFM – 16.7%; NS + PC type S – 18% vs control. SEM, XRD, DTA confirm portlandite binding and dense low-basic C–S–H matrix formation (min. weight loss on heating – 9.1% for NS+PFM). Discussion. Bifunctional NS surface provides a synergistic effect: basic centers adsorb Ca²+ ions, initiating nucleation; Lewis acid centers coordinate OH– and H2O, activating them. Complex NS + surfactants improve nanoparticle distribution and intensifying pozzolanic reaction. Conclusion. NS activity remains after 1.5 years of storage. Complex NS+plasticizers provide a synergistic effect. Developed compositions are recommended as class R3 (B35) repair compounds and grouting mixtures for critical structures, including collector repair, equipment grouting and anchor bolt installation.
Free
High-strength wall ceramics based on phosphorus slag and bentonite clay
Scientific article
Introduction. One of the promising ways to get high-strength ceramics is the method of semi-dry pressing of the "coarsely dispersed component – finely ground binder" formula. This method suggests using crushed industrial waste as the core, and finely ground nanostructured fusible clay as the binder material. Methods and materials. In the research, bentonite clay of the Darbazinsky deposit of the Turkestan region was used as plastic material, and dense crystallized phosphorus slag which is a waste of phosphorus production was used as a non-plastic coarse material. The study of the prescription factors’ influence on the basic physical and mechanical properties of ceramic wall materials was carried out by the simplex method characterized as lattice planning of experiments. The nanostructure of the phosphorus slag and bentonite clay formula was studied by the electron microscopic analysis method. Results. The binder content in the amount of 25% guarantees the density of the packages, while the sintering effect becomes sufficient and the strength of the samples is 27.1 MPa. If the amount of binder increases from 25% to 40%, the sintering effect continues to grow and the strength of the samples reaches 54.3 MPa. Discussion. The results show that the most active sintering effect and the dense structures forming in coarse-grained formulas with high-calcium phosphorus slag occur at 40–60% binder content. The presence of flux around slag grains in an amount of less than 30% contributes to obtaining less dense samples, with a binder content of 40%, a density increase is observed, which corresponds to the mixed ceramic structures modeling. Conclusion. To get high-strength ceramic bricks, the content of coarsely dispersed components in the form of phosphorus slag with a fraction of less than 1.25 mm should amount to 60–70%, finely ground phosphorus slag should be 5–10%, and bentonite clay is to be 20–30%. Optimum technological indicators are: calcination temperature 1050–1100oC, pressing pressure 20–25 MPa, press powder moisture content 7–8%.
Free
High-viscosity nanoemulsions of petroleum products in a sand matrix: problems and solutions
Scientific article
Introduction. Oil spills on sandy shores lead to the formation of stable emulsions that are difficult to eliminate. The research is aimed at a comprehensive analysis of the physical and chemical properties of such an emulsion and the development of effective methods for its separation using modern chemical and technological approaches that have aspects of nanolevel interaction at the phase boundary. Methods and materials. The object of the study was a sample of contaminated soil. Visual inspection was performed; density and dynamic viscosity were determined in the range of 25–90 °C. The separation of the emulsion was tested by centrifugation (including the use of a demulgator) and water distillation (Dean-Stark method). The content of mechanical impurities was determined gravimetrically, and their composition was determined using Fourier transform IR spectrometry. For demulsification and viscosity reduction, dilution with diesel fuel and solvent was used, followed by centrifugation. Results and discussion. The sample was a highly viscous (105 379 MPa•s at 25 °C) emulsion that could not be separated by standard centrifugation. The content of water (33%) and mechanical impurities (23.8%) identified as sand (SiO2) was determined. The high stability of the emulsion is probably due to the formation of strong interfacial layers. Dilution of the sample with diesel fuel and Nefras-C280 in a 1:1 ratio significantly reduced the viscosity and achieved effective separation into the oil phase and mechanical impurities during subsequent centrifugation. Conclusion. It is shown that traditional methods of emulsion destruction are ineffective without preliminary modification of the system. The most effective strategy is chemical dilution followed by thermomechanical treatment, which disrupts the stable nanostructure of the emulsion and facilitates separation. The data obtained are important for developing practical recipes for oil spill response in coastal areas.
Free
How Nanocarbon Fillers Influence Properties of the Composite Materials
Scientific article
Introduction. Currently the most promising type of repair uses composite materials to fill in fractures or fracture-like defects. In order to be effective, the composite material must possess high fluidity in its liquid state to ensure it can fill the cavity of the defect, adhesion to steel to bond the edges of the crack, and plasticity to compensate for any deformation caused by regular and static loading of the structure. Methods and materials. Composite materials with nanocarbon fillers were studied, including fullerenes, nanotubes, and graphene. The solutions to the problems were obtained using both standard and independently developed methods, statistical data processing techniques, and modern software complexes. Results and discussion. The composite material with a fullerene filler demonstrates a sustainable fluidity in comparison to other studied composites. This allows to recommend such a material for fixing cracks with a slight opening. The composite with a carbon nano tube filler maintains the fluidity at the same level within 35 minutes on average. It can be used as a repair material in cases where the location of the defect does not allow for its sealing to be carried out in a short period of time. Conclusion. The conducted research allows to solve the direct and inverse problem: a) studying properties of a composite material and designing its structure allow to determine, if it fit to certain dimensions of the crack; b) a detected crack with a certain configuration of the cavity can be offered the most suitable properties of the composite by adjusting its content.
Free
How to properly test and apply BETOPRESS® lyophobic sols and sol-based modifiers in cement concrete
Scientific article
This article provides information in the accessible form about a completely different approach to the testing and application of lyophobic sols and sol modifiers in cement concrete, in contrast to any other chemical additives that are classified as true solutions in liquid form. The criteria outlined in clause 6.11 of GOST 27006-2019 for the selection of compositions produced in laboratory conditions cannot be extended to sols and sol modifiers, which are stabilized colloidal solutions. This specifically pertains to the preparation of concrete mixtures for subsequent testing. GOST 27006-86 was released during a period when all chemical additives used in concrete were solely available in the form of true solutions, comprising fully dissolved molecules and ions resulting from the complete dissolution of all components in water.
Free
