Alexey Nikolaevich Beskopylny

Creating low-density composite materials that can handle significant temperature changes and bending stress is a promising approach for building floating platforms. This study creates a numerical model and conducts an experimental analysis of foam concrete containing polymer spheres with different diameters and properties. Laboratory bending tests were performed on manufactured foam concrete samples containing 10 mm, 12 mm, 15 mm, 19.05 mm, and 20 mm diameter polypropylene spheres. To predict the thermophysical properties of a composite featuring structural foam concrete with embedded polymer spheres, a numerical model was developed in the Material Designer module as the first step. The resulting density, thermal conductivity, and specific heat dependences were used as input for subsequent numerical analysis in ANSYS under nonuniform temperature and bending loading, based on the nonlinear Menetrey–Willam model. By comparing load–displacement curves for different sphere sizes, the accuracy of the model in forecasting strength and deformation properties was established. The study revealed that the maximum equivalent von Mises stress was 3.3 MPa, indicating that the material operates in the elastic zone, but close to crack formation. The maximum displacement due to temperature differences was 0.087 mm, and the tensile stress in the longitudinal direction was σ_X = 0.18 MPa. This indicates that the composite performs satisfactorily under temperature differences from +4 °C to −60 °C. Patterns of failure of structural foam concrete specimens with polymer spheres under bending were analyzed, demonstrating that cracking starts in the lower chord of the tensile zone, weakened by the presence of the spheres.

This research aims to develop new types of polymer concrete composites. The main objective of the work was to investigate the influence of various types of mineral fillers (ground granulated blast-furnace slag (GGBFS), quartz flour (QF), micro-calcite (MC)) and their combinations on the properties of polymer concrete (PC) and to develop new effective PC compositions. An optimal PC composition was developed and seven series of experimental PC samples with different types of mineral fillers were manufactured: 1PC (GGBFS); 2PC (QF); 3PC (MC); 4PC (GGBFS + QF); 5PC (GGBFS + MC); 6PC (QF + MC); 7PC (GGBFS + QF + MC). The following parameters were measured: density, compressive strength, water absorption, and thermal conductivity. Scanning electron microscopy was used to assess the PC microstructure. To quantitatively evaluate the significance and influence of the mineral filler type on the PC properties, an analysis of variance was performed. The experimental results showed that the mineral fillers GGBFS, QF and MC and their combinations affect the properties of PC, especially its strength. The composition of 5PC turned out to be optimal: epoxy resin 15%; hardener 1.5%; plasticizer 1.5%; quartz sand 30%; crushed granite 30%; GGBFS 11%; MC 11%. Polymer concrete of composition 5PC had a density of 2263 kg/m³, a maximum compressive strength of 103.8 MPa, a minimum water absorption of 0.25% and a thermal conductivity coefficient of 0.466 W/m·K. The PC of all compositions had similar morphology, with a uniform structure and a randomly distributed pore size ranging from 81.27 µm to 384.9 µm. Microcracks were predominantly concentrated at the phase boundaries and propagated through the polymer matrix, enveloping the filler grains. The study yielded effective composite materials that could potentially be used in mechanical engineering as well as in industrial and civil construction, following durability testing and the determination of the full range of required properties.

This study focuses on the influence of chemically pure nanodiamonds produced by cavitation synthesis on structure formation and physical and mechanical properties of self-compacting concrete (SCC) using an analytical approach. The objective of this research was to develop a high-performance, self-compacting concrete with enhanced properties suitable for the construction sector. Chemically pure nanodiamonds produced by cavitation synthesis (KHA-HC) were added to SCC at weight percentages of 0%, 0.15%, 0.3%, 0.45%, 0.6%, and 0.75% of the binder mass. Fresh SCC modified with nanodiamonds was evaluated for density and cone spread diameter. Hardened SCC with KHA-HC was tested for density, water absorption, compressive strength, and axial compressive strength. The most effective KHA-HC content was established at 0.3%, correlating with 13.5% greater compressive strength, 15.1% higher axial compressive strength, and 19.6% lower water absorption. Incorporating KHA-HC into SCC resulted in a wider spread cone as the additive content was raised. The microstructure of SCC containing KHA-HC was found to be more homogeneous with a decrease in void content within the cement matrix. Polynomial relationships for changes in SCC properties as a function of nanodiamond content were proposed. The effectiveness of nanodiamond additives for modifying SCC was demonstrated. Highly effective self-compacting concretes with improved performance properties have been developed, which are suitable for construction.

The potential of clay as a replacement for Portland cement in the manufacture of injection cement–clay mortars (ICCMs) for soil stabilization is examined in this investigation. The objective of this study is to produce environmentally friendly injection-molded mortars for soil stabilization based on Portland cement (PC) and clay (C). Experimental ICCMs with C contents ranging from 0% to 50% without the addition of microsilica (MS) and ICCMs with C contents ranging from 0% to 50% and 2% MS were produced. The evaluation included the density, water segregation, and cone spread diameter of fresh ICCMs, alongside the density, flexural strength, and compressive strength of hardened ICCMs. The findings indicated that as C content rose from 0% to 50%, fresh mortars experienced a decrease in density, flowability, and water segregation. Hardened mortars exhibited reduced density, compressive strength, and flexural strength as C content increased. Modifying mortars with MS has a positive effect on their strength properties. The reduction in flexural and compressive strength for mortars with 50% C was 54.2% and 60.1%, respectively, while for similar mortars with 2% MS, the reduction in strength was 47.9% and 51.8%, respectively. ICCM soil stabilization compositions modified with MS are the most effective in comparison with similar compositions without MS and have a homogeneous structure with pores, microcracks, and hydration reaction product zones. The optimal ratios of raw components for the production of ICCMs for soil stabilization were determined: a water–solid ratio of 0.6, PC content from 90% to 50%, C content from 10% to 50%, and an MS content of 2% of the dry component weight. This research contributes to sustainable development by reducing CO₂ emissions per 1 m³ of mixture production by up to 47.8% and by using raw materials rationally.

This study investigates the shear behavior and failure mechanisms of innovative hybrid structural beams fabricated by filling pultruded glass fiber-reinforced polymer (GFRP) box sections with waste rubber-reinforced concrete (RuC). Environmentally friendly concrete was produced by replacing natural aggregate with recycled tire-rubber fibers at proportions of 0%, 5%, 10%, and 15%. Twelve hybrid beam specimens were tested to evaluate the synergistic effects of rubber content and stirrup spacings of 16, 20, and 27 cm on shear capacity, ductility, and crack propagation. The experimental results revealed that the reference specimen (S16-0%) exhibited the maximum shear capacity of 154.41 kN and a brittle failure mode, while an increase in rubber content to 15%, combined with wider stirrup spacing, significantly reduced this capacity to a minimum of 96.89 kN (S27-15%). However, the 5% rubber replacement ratio achieved an optimal performance balance by preserving sufficient load-carrying capacity while enhancing flexural deformation and ductility, particularly in specimens with 16 cm stirrup spacing. Damage analysis demonstrated that longitudinal splitting cracks initiated in the mid-span tension zone at the bottom of the pultruded profiles, with final localized damage concentrated at the geometric corners of the box section. Crucially, the outer pultruded GFRP profiles provided substantial structural confinement, effectively mitigating the strength loss associated with high rubber incorporation and controlling the progression of sudden brittle failure. These findings highlight that combining pultruded GFRP profiles and optimized RuC offers a structurally viable and sustainable solution for modern infrastructure applications.

The paradigm of sustainable development, coupled with contemporary inclinations towards green construction, exerts a considerable effect on the evolution of environmentally benign building composites. The main aim of this study is to create geopolymer composites with improved physical and mechanical properties. An examination of the properties of a geopolymer composite (GS), using ground granulated blast furnace slag (GGBFS) and plant fibers, is presented in this paper. Sisal (SF) and flax (FF) fibers, along with their combination (SF + FF), were integrated into the slag at concentrations of 0%, 0.5%, 1.0%, 1.5%, and 2% by weight. Before use, plant fibers were treated with a 5% NaOH solution. The geopolymer composites (GC) underwent evaluation for their density, compressive and flexural strengths, and water absorption characteristics. Scanning electron microscopy was employed to examine the fracture characteristics of the GC. The compressive and flexural strengths of GC were improved by including 1% SF, FF, and their combination, 0.5% SF + 0.5% FF. Compressive strength increases were 11.5%, 8.6%, and 14.5%, while flexural strength increases were 17.4%, 13%, and 19.6%, respectively. Water absorption of GC with 1% SF, FF, and SF + FF decreased by 14.6%, 10.8%, and 20.4%, respectively. The apparent synergistic performance of hybrid sisal-flax reinforcement at a total fiber content of 1% was revealed. GCs at the fracture have a homogeneous rough structure with microcracks and accumulations of geopolymer reaction products. The matrix-plant fiber interface in GC is identified by a rounded region with elongated fibers, indicating the fiber’s performance under mechanical stress. The findings of this investigation suggest the feasibility of utilizing plant fibers in environmentally sound geopolymer construction composites.

In this study, the effect of the epoxy resin and mineral filler ratio on the density, compressive strength, flexural strength, water absorption, and structure of polymer matrices was investigated. The combined effect of Portland cement and microsilica on the structure–property relationship of epoxy matrices remains insufficiently understood. The control mixture was made from 100% epoxy resin with a hardener. Various types of mineral fillers, Portland cement (PC), microsilica (MS) and their mixtures were introduced by volume from 0 to 50% in increments of 10%. Experimental findings indicate that an optimal resin addition to a polymer matrix enhances strength and, consequently, decreases expenses. Epoxy–polymer matrices with an optimal mineral filler content of up to 30% demonstrate the highest durability. The increases in compressive and flexural strength for the matrix with 30% PC were 7.3% and 11.5%, for the matrix with 30% MS they were 4.1% and 4.4%, and the increases were 11.2% and 13.2% for the matrix with 15%PC+15%MS. Introducing a mineral filler increases the density of epoxy–polymer matrices up to 50%. Water absorption of polymer matrices increases as the amount of mineral filler in the matrix increases. The microstructure of polymer matrices with mineral fillers is dense and homogeneous, with a small number of pores. In optimal quantities, the mineral filler is evenly distributed in the polymer binder, improves the particle packing density, and creates additional stress redistribution centers. The polymer matrix of 70% epoxy resin, 15% PC and 15% MS is the most optimal in terms of the properties obtained: a density of 1282 kg/m3; compressive strength of 54.7 MPa; flexural strength of 20.6 MPa; and water absorption of 0.94%. In the future, it is planned to use this epoxy–polymer matrix composition in the development of high-performance concrete intended for manufacturing machine tool beds.

In recent years, the incorporation of voids with different geometrical configurations has emerged as one of the most effective strategies for reducing concrete consumption in structural systems. This article is devoted to the numerical analysis and experimental study of lightweight concrete using polymer spheres of various diameters and properties as voids. Lightweight concrete specimens with polypropylene spheres of 10 mm, 12 mm, 15 mm, 19.05 mm, and 20 mm diameters were manufactured. The experimental specimens were subjected to compression tests, and the results were compared with the numerical model. A numerical model employing the Menetrey–Willam constitutive model was established using spheres with comparable diameters and various types of polymers: polypropylene, polyamide 66, and polyester. The thermal properties of polymer-composite lightweight concrete (PCLC) were determined for various wall thicknesses using different polymers. The results demonstrated a 1% to 2% lower thermal conductivity coefficient for PCLC with polypropylene compared to polyethylene. Verification of the compressive strength results by comparing the data with the experiment demonstrated good accuracy in predicting the strength and deformation properties. The calculated stress and strain field distributions enabled the identification of the cracking patterns and failure mechanisms of the specimens containing polymer spheres. It has been proven that smaller radius spheres manufactured from higher modulus polymer materials have better deformation resistance and provide good, consistent strength in lightweight polymer concrete. The observed strength reduction in PCLC regarding the control composition (R_b = 21.4 MPa) without spheres is within 11% for 10 mm (R_b = 19.1 MPa) and 12 mm spheres (18.2 MPa). For larger-diameter spheres, the strength reduction reaches 25% (R_b = 16 MPa).