Search Results (9)

Composite materials are characterized by multiple layers, which leads to a complexity in the design in order to ensure the effective operation of the constituent elements. This article provides information on the use of fractal dimension in assessing the quality of the appearance of paint coatings. The scientific originality of the article lies in the establishment of a correlation between the surface roughness of coatings, the quality grade of their appearance and fractal dimension. As a result, a model of the length of the coating surface profile, with the fractal dimension D, was proposed. The practical significance lies in the proposal to evaluate the quality of the surface of paint and varnish coatings in terms of fractal dimension. An increase in the surface roughness of the coating, a decrease in the appearance quality grade and an increase in the fractal dimension have been observed. Numerical values of the index of the fractal dimension of the coating surface profile, which depended on the porosity of the substrate, have been obtained. The influence of the filling of the paint composition on the quality of the appearance of the coatings has been estimated. It has been revealed that there was an increase in the surface tension of the paint composition, a decrease in the quality of the appearance of the resulting coating and an increase in the roughness and fractal dimension of the coating surface. The influence of the method of applying the paint composition and the preparation of the base surface on the quality of the appearance of the coatings are considered. The results obtained can be applied in various types of production to improve the quality of paint coatings. Full article

Due to renovation and fighting in the world, a huge accumulation of construction and demolition waste is formed. These materials are effectively used as aggregates, but there is very little information about the use of scrap concrete to create cementless binders. The purpose of the work is to be a comprehensive study of the composition and properties of concrete wastes of various fractions with the aim of their rational use as cementless binders. The scientific novelty lies in the fact that the nature of the processes of structure formation of a cementless binder based on sandy fractions of the screening of fragments of destroyed buildings and structures, as a complex polyfunctional system, has been theoretically substantiated and experimentally confirmed. Different percentages of non-hydrated clinker minerals in concrete scrap were determined. In the smallest fraction (less than 0.16 mm), more than 20% of alite and belite are present. Waste of the old cement paste is more susceptible to crushing compared to the large aggregate embedded in it, therefore, particles of the old cement paste and fine aggregate predominate in the finer fractions of the waste. Comprehensive microstructural studies have been carried out on the possibility of using concrete scrap as a completely cementless binder using scanning electron microscopy, X-ray diffraction analysis, and differential thermal analysis. It has been established that for cementless samples prepared from the smallest fractions (less than 0.315 mm), the compressive strength is 1.5–2 times higher than for samples from larger fractions. This is due to the increased content of clinker minerals in their composition. The compressive strength of the cementless binder after 28 days (7.8 MPa), as well as the early compressive strength at the age of 1 day after steaming (5.9 MPa), make it possible to effectively use these materials for enclosing building structures. Full article

Erection of buildings using 3D printing has great potential. However, its mass use for high-rise buildings is hampered by the lack of cement mortars with the required technical characteristics, the most important of which is high plastic strength (in the first minutes after pouring). The significance of the work (novelty) lies in the creation of a composite binder using a mineral modifier obtained by joint grinding up to 500 m²/kg of bentonite clay, chalk, and sand. A comprehensive study of the developed mortars was carried out from the standpoint of the necessary characteristics for volumetric concreting of high-rise thin-walled buildings. A composite binder for high-strength composites (compressive strength up to 70 MPa) has been obtained, which can provide effective mortars for 3D-additive high-rise construction technologies. The influence of the genetic characteristics of the modifier components on the properties of the composite binder has been established. The hydration process in this system of hardening concrete of the optimal composition proceeds more intensively due to the significantly larger specific surface of the mineral modifier components, which act as an active additive and activators of the crystallization of new growths. It has been proven that the features of mortars of high-strength fine-grained composites for 3D-additive technologies of high-rise buildings must meet special properties, such the rheotechnological index and the bearing capacity of the freshly formed layer (plastic strength or dimensional stability). Compared with a conventional mortar, the plastic strength of the developed one increases much faster (in 15 min, it is 762.2 kPa, in contrast to 133.0 kPa for the control composition). Thus, the strength remains sufficient for 3D printing of high-rise buildings and structures. Full article

Fibers of various origins are of great importance for the manufacture of new generation cement composites. The use of modified composite binders allows these highly efficient building materials to be used for 3D-printing of structures for various functional purposes. In this article, changes in building codes are proposed, in particular, the concept of the rheological technological index (RTI) mixtures is introduced, the hardware and method for determining which will reproduce the key features of real processes. An instrument was developed to determine a RTI value. The mixes based on composite binders and combined steel and polypropylene fibers were created. The optimally designed composition made it possible to obtain composites with a compressive strength of 93 MPa and a tensile strength of 11 MPa. At the same time, improved durability characteristics were achieved, such as water absorption of 2.5% and the F300 frost resistance grade. The obtained fine-grained fiber-reinforced concrete composite is characterized by high adhesion strength of the fiber with the cement paste. The microstructure of the developed composite, and especially the interfacial transition zone, has a denser structure compared to traditional concrete. The obtained materials, due to their high strength characteristics due to the use of a composite binder and combined fiber, can be recommended for use in high-rise construction. Full article

A person spends most of his life in rooms built from various building materials; therefore, the optimization of the human environment is an important and complex task that requires interdisciplinary approaches. Within the framework of the new theory of geomimetics in the building science of materials, the concepts of technogenic metasomatism, the affinity of microstructures, and the possibilities of creating composites that respond to operational loads and can self-heal defects have been created. The article aims to introduce the basic principles of the science of geomimetics in terms of the design and synthesis of building materials. The study’s novelty lies in the concept of technogenic metasomatism and the affinity of microstructures developed by the authors. Novel technologies have been proposed to produce a wide range of composite binders (including waterproof and frost-resistant gypsum binders) using novel forms of source materials with high free internal energy. The affinity microstructures for anisotropic materials have been formulated, which involves the design of multilayered composites and the repair of compounds at three levels (nano-, micro-, macro-). The proposed theory of technogenic metasomatism in the building science of materials represents an evolutionary stage for composites that are categorized by their adaptation to evolving circumstances in the operation of buildings and structures. Materials for three-dimensional additive technologies in construction are proposed, and examples of these can be found in nature. Different ways of applying our concept for the design of building materials in future works are proposed. Full article

It is necessary to solve the ecological problems of regions where there is large-tonnage storage of various finely dispersed materials, including technogenic ones. This article presents the results of an investigation into the possible use of substandard dispersed quartz sands to obtain effective granular aggregates, with the purpose of putting them to use in mortars and concrete. The study used standard and original experimental research methods related to the analysis and preparation of raw materials, technological tests, and the study of the properties of finished composites. Investigations were carried out to obtain composite binders in the component composition of which the use of different ratios of Portland cement and substandard quartz sands prepared in a vortex jet mill was envisaged. It was found that the obtained composite binders had high physical and mechanical characteristics, which was due to the high specific surface area and hydration activity. On the basis of composite binders and finely dispersed quartz sands (fineness from ≤0.16 mm to 1 mm), the granulation of mixtures of 36 types of component compositions was performed. The developed compositions of granular aggregates (GAs) showed the possibility of obtaining them with sufficiently high strength values in cement stone. The studies carried out make it possible to recommend finely dispersed substandard and technogenic materials for the production of GAs, which would ensure the economy of binding materials as well as contribute to the reuse of large-tonnage waste of ferrous and nonferrous metallurgy and the chemical and mining industries. Full article

Concrete is the most common building material; therefore, when designing structures, it is obligatory to consider all structural parameters and design characteristics such as acoustic properties. In particular, this is to ensure comfortable living conditions for people in residential premises, including acoustic comfort. Different types of concrete behave differently as a sound conductor; especially dense mixtures are superior sound reflectors, and light ones are sound absorbers. It is found that the level of sound reflection in modified concrete is highly dependent on the type of aggregates, size and distribution of pores, and changes in concrete mix design constituents. The sound absorption of acoustic insulation concrete (AIC) can be improved by forming open pores in concrete matrices by either using a porous aggregate or foam agent. To this end, this article reviews the noise and sound transmission in buildings, types of acoustic insulating materials, and the AIC properties. This literature study also provides a critical review on the type of concretes, the acoustic insulation of buildings and their components, the assessment of sound insulation of structures, as well as synopsizes the research development trends to generate comprehensive insights into the potential applications of AIC as applicable material to mitigate noise pollution for increase productivity, health, and well-being. Full article

Quartz sandstone (QS) is a mine waste; therefore, its use in construction allows for both reducing the cost of the concrete and contributing to the utilization of waste. The scientific originality of this study is the identification of models of the effect of QS aggregate on the physicomechanical, durability characteristics, and eco-safety of greener high-strength concrete. The study used an energy-efficient method of non-thermal effects of electromagnetic pulses on the destruction mechanisms of quartz-containing raw materials. The characteristics of quartzite sandstone aggregates, including the natural activity of radionuclides, were comprehensively studied. The features of concrete hardening, including the formation of an interfacial transition zone between the aggregate and the cement matrix, were studied, taking into account the chemical and morphological features of quartzite sandstone. In addition, the microstructural and morphological properties of concrete were determined after a 28 day curing. In this study, the behaviors of the concrete with QS aggregate were investigated, bearing in mind the provisions of geomimetics science on the affinity of structures. The results obtained showed that the QS aggregate had the activity of natural radionuclides 3–4 times lower compared to traditional aggregates. Efficient greener concrete with a 46.3 MPa compressive strength, water permeability grade W14, and freeze–thaw resistance of 300 cycles were also obtained, demonstrating that the performance of this greener concrete was comparable to that of traditional concrete with more expensive granite or gabbro diabase aggregates. Full article

The novelty of this paper lies in the identification of the scientific patterns of the influence of thermal power plant waste (TPPW) on the hydration mechanism and the structure of the gypsum-cement binder (GCB). The classification of raw materials for the production of GCB has been developed taking into account the genesis, which contributes to the prediction of the properties of composites. The features of the hydration phase formation and hardening of GCB have been studied taking into account the chemical, structural and morphological features of fly ash and slag. In addition, the microstructural, morphological, and thermal properties of the cured binders at a 28 day cure were determined. For the first time, scientific data on the properties of gypsum-cement fiber-reinforced composite using TPPW and microfiber have been obtained. The results show that the synergistic effect of gypsum-cement binder, TPPW, and polyamide or basalt microfiber improves the physicomechanical properties of a 28 day cured binder: compressive strength of 20 MPa, flexural strength of 8.9 MPa, and softening coefficient 0.87. Full article