Tensile Bending Strength Research Articles

Increasing the Corrosion Resistance and Durability of Geopolymer Concrete Structures of Agricultural Buildings Operating in Specific Conditions of Aggressive Environments of Livestock Buildings

The problem of increasing the service life of buildings and structures for agricultural purposes operated in aggressive environments is relevant. The aim and scientific novelty of the work were to determine the relationship between the structure and properties of geopolymer concretes in aggressive environments. The properties of various concrete compositions under the influence of a solution of lactic, acetic, and oxalic acids were studied. With an exposure time of 90 days in an aggressive environment, samples of concrete based on a geopolymer binder had up to 6% less loss of strength and up to 10% less weight loss than concrete based on a cement binder. The effectiveness of the developed composition and technological solutions was confirmed, and it was quantitatively expressed in increased compressive strength and tensile strength in bending by 81.0% and 73.5%, respectively. It has been established that raising the heat treatment temperature to 80 °C leads to increased compressive strength for all compositions of geopolymer binders. The most favorable heat treatment conditions are created at 80 °C. The relations of the strength characteristics of geopolymer binders are revealed, which allow a detailed quantitative and qualitative assessment of the influence of the studied factors on the change in the system “composition—hardening conditions—properties” and can be used in the development of production compositions of binders and composites based on them, as well as their regulation—physical, mechanical, and operational characteristics.

High mechanical strength aluminum foam epoxy resin composite material with superhydrophobic, anticorrosive and wear-resistant surface

By combining organic materials with metal materials, it is easy to obtain new composite materials with excellent properties. Here, an excellent performance aluminum foam epoxy resin composite material (AFE) was prepared by heat-assisted vacuum infusion technology. Owing to the unique foam structure of aluminum foam (AF) and excellent physical and chemical properties of modified epoxy resin, the AFE with an interpenetrating network structure shows excellent wear resistance, bending resistance and corrosion resistance. The SEM images show that the filling efficiency of epoxy resin to AF is over 99%, and the epoxy resin was tightly combined with the metal foam. The surface and mechanical properties test results show that AFE has excellent mechanical properties and high wear resistance, the maximum bending σb and tensile strength σt can reach 74.33 MPa and 42.09 MPa, respectively, and the minimum wear rate Ws is 8.231 × 10−4 mm3/Nm. Tafel polarization curve and electrochemical impedance spectroscopy (EIS) results show that the AFE has excellent corrosion resistance, with corrosion current icorr as low as 1.399 × 10−9 A•cm−2 and Z0.01 Hz as high as 7.74 × 107 Ω•cm2 after superhydrophobic treatment process.

The Influence of Composition and Recipe Dosage on the Strength Characteristics of New Geopolymer Concrete with the Use of Stone Flour

Currently, considering global trends and challenges, as well as the UN sustainable development goals and the ESG plan, the development of geopolymer binders for the production of geopolymer concrete has become an urgent area of construction science. This study aimed to reveal the influence of the component composition and recipe dosage on the characteristics of fine-grained geopolymer concrete with the use of stone flour. Eleven compositions of geopolymer fine-grained concrete were made from which samples of the mixture were obtained for testing at the beginning and end of setting and models in the form of beams and cubes for testing the compressive strength tensile strength in bending. It was found that the considered types of stone flour can be successfully used as an additive in the manufacture of geopolymer concrete. An analysis of the setting time measurements showed that stone flour could accelerate the hardening of the geopolymer composite. It was found that the addition of stone waste significantly improves the compressive strength of geopolymers in comparison with a geopolymer composite containing only quartz sand. The maximum compressive strength of 52.2 MPa and the tensile strength in bending of 6.7 MPa provide the introduction of potassium feldspar in an amount of 15% of the binder mass. Microstructural analysis of the geopolymer composite was carried out, confirming the effectiveness of the recipe techniques implemented in this study.

Property Evaluation of Cement-Stabilized Macadam Modified via Phosphorus Slag Materials

Phosphorus slag, known as the waste product of the phosphate ore industry, is causing critical environmental issues due to its direct exposure to natural spaces. In this article, a partial replacement of the natural fine aggregate ordinarily used in cement-stabilized macadam (CSM) base by phosphorus slag was explored to be an effective solution for phosphorus slag waste. CSM specimens were fabricated by adding various dosages of phosphorus slag particle and fine powder, whereas the optimum moisture content and maximum dry density were analyzed through compaction tests. Compressive strength, bending tensile strength, fatigue life span, dry shrinkage, and temperature shrinkage performance at different curing durations were investigated to evaluate the properties of modified macadam. Results show that phosphorus slag reduced the early compressive strength of CSM to a small extent, but the compressive strength finally increased at 90 days’ curing. The modified slag particles and slag fine powder exhibited different behaviors to repeated loading, moisture loss, and temperature difference. Finally, according to the strength change, fatigue performance comparison, and shrinkage strain caused by the incorporation of phosphorous slag materials into the CSM, it was verified that 25% of the particles to 40% of the fine powder is the best replacement ratio.

ВЛИЯНИЕ КРУПНОГО ЗАПОЛНИТЕЛЯ НА ЭНЕРГЕТИЧЕСКИЕ И СИЛОВЫЕ ХАРАКТЕРИСТИКИ СТАЛЕФИБРОБЕТОНА

At present, composite materials are gaining more and more development in construction, including the use of dispersed reinforced concrete, which is due to its significantly improved physical, mechanical and operational characteristics compared to traditional concrete and reinforced concrete. The article presents the results of the influence of coarse filler in the composition of the composite on the energy and power characteristics of the crack resistance of fiber-reinforced concrete reinforced with steel anchor fibers. The process of deformation and the mechanism of destruction of steel fiber reinforced concrete have been studied. To do this, in accordance with the provisions of GOST 29167 "Methods for determining the characteristics of crack resistance (fracture toughness) under static loading", steel-fiber-reinforced concrete sample beams were tested with control of the applied load and the deflection caused by it. Based on the data obtained, diagrams of the dependence of the load on the deflection were constructed, after their processing and additional constructions, the energy costs for static destruction, tensile strength in bending, and the stress intensity factor were determined. It has been established that the value of the conditional specific effective energy consumption for static failure and tensile strength in bending of fiber-reinforced concrete samples with a matrix of heavy concrete with coarse aggregate turned out to be lower than that of fiber-reinforced concrete samples with a matrix of fine-grained concrete, which is explained by the lower adhesion of the steel anchor fiber to the matrix, and a corresponding decrease in their efficiency.

A method for calculating the uncertainty of the tensile strength during bending of concrete prisms used in the construction of transport infrastructure

In this research we provide the result of measurements, which is presented as a measured value of a quantity with an indication of the corresponding indicator of accuracy. If the accuracy indicators for the corresponding measurement are not specified in the normative documentation, it is necessary to calculate the measurement (test) uncertainty. This research presents the calculation of the measurement uncertainty using the example of determining the strength of concrete used in the construction of transport infrastructure. To do this, using the Ishikawa causal diagram, sources of uncertainty and the parameters on which they depend were identified. Uncertainties of Type B uncertainties for flexural tensile strength were determined and extended uncertainty for the strength of concrete used in the construction of transport infrastructure was calculated. The results of this study will allow taking into account the resulting uncertainty of the result in subsequent tests for tensile strength in bending.

ТЯЖЕЛЫЙ БЕТОН НА ОСНОВЕ ПОЛИДИСПЕРСНОГО ВЯЖУЩЕГО С КОМПЛЕКСНЫМ ПОЛИМЕРНЫМ МОДИФИКАТОРОМ С ПОВЫШЕННЫМИ ЭКСПЛУАТАЦИОННЫМИ ПОКАЗАТЕЛЯМИ

The main task of obtaining concrete, in particular for irrigation and drainage construction, with increased performance by modifying their structure and properties with complex additives is becoming more and more relevant every year. Within the framework of these studies, issues related to the modification of the composition of heavy concrete with the use of a complex chemical additive consisting of the superplasticizer Melflux 5581 F and the water-soluble polymer additive Polydon-A were considered. The aim of the study is to develop a scientifically based technological solution that provides the production of heavy concrete based on a polydisperse binder with a complex polymer modifier (Melflux + Polydon-A) for agricultural construction. The object of study is heavy concrete based on a polydisperse binder with a complex polymeric modifier for agricultural construction. Research results: The resulting modified concrete is characterized by an increase in compressive and tensile strength in bending, a conditional stress intensity factor, water absorption, water resistance and frost resistance, which makes it possible to recommend it for the production of building products and structures operating in harsh operating conditions, in particular, for trays irrigation systems.

ПОСТРОЕНИЕ И ПРОВЕРКА АДЕКВАТНОСТИ УРАВНЕНИЯ РЕГРЕССИИ ПРОЧНОСТИ НА РАСТЯЖЕНИЕ ПРИ ИЗГИБЕ ОТ СООТНОШЕНИЯ КОМПОНЕНТОВ КОМПОЗИТНОГО МАТЕРИАЛА

Nowadays, most of the materials used in the construction industry are composites. This is why it is necessary to select their optimal composition, which can be done using the mathematical planning of the experiment. In order to determine the most appropriate composition of the composite material based on gypsum binder with the addition of sawdust according to the criterion of the bending tensile strength, mathematical planning of the experiment was performed. The press was used to measure the bending tensile strength. The regression equation has been also obtained, the response surface has been constructed and the adequacy check of the obtained regression coefficients has been performed.

Effect of graphene oxide and nano silica on mechanical and durability properties of cement mortar

Nowadays, nano-technology has already influenced many fields, including civil engineering also. Cementitious composites contain various nanomaterials that have considered as novel materials with improved microstructure, mechanical and durability properties. Recently graphene oxide and nano silica have appeared as the most promising nano-materials for civil engineering applications. However, graphene oxide and nano silica addition in the cement mortar improves the compressive strength, split tensile strength and flexural strength. Ultra-high resolution field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) analysis are used to see the fracture surface of samples containing 0.07% GO and 4.5% of NS to the weight of cement indicated that GO and NS flakes were well dispersed in the cement mortar matrix and no aggregates were observed. The compressive, bending, and split tensile strength of cement mortar, which contains 0.07% GO and 4.5% of NS by weight of cement after 28 days of curing, is raised by 22.25%, 38.77%, and 10.25%, respectively, as compared to regular cement mortar. These durability studies, such as acid resistance and salt resistance, the weight loss was found in acid, and salt immersion addition of GO&NS shows good resistance in the cement matrix. In addition, SEM analysis has shown the growth of calcium silicate hydrates (C-S-H Gel) in GO and NS cement mortar has compared with normal cement mortar.

An alternative numerical model for fiber reinforced concrete strength evaluation

An alternative numerical model for fiber reinforced concrete (FRC) compressive and bending tensile strength determination is presented in this paper. Fibers are modeled explicitly by using the Extended Finite Element Method (XFEM). An alternative method for modeling the fiber-matrix interaction, without the need for additional subroutine definition, is proposed. The presented numerical model was evaluated by experimental tests and results are in good agreement. The model was developed for Simulia ABAQUS software, but the proposed modeling procedure is generally applicable. In the end, some possible model improvements and suggested applications are included.

Developing Environmentally Sustainable and Cost-Effective Geopolymer Concrete with Improved Characteristics

Improving the efficiency and quality of construction mainly depends on the cost of building materials, which is about 55–65% of total capital-construction costs. The study aimed to obtain geopolymer fine-grained concrete with improved quality characteristics that meet the construction field’s sustainable development criteria and that have environmental friendliness, economic efficiency, and advantages over competing analogues. The dependences of strength characteristics on various compositions of geopolymer concrete were obtained. It was found that the most effective activator is a composition of NaOH and Na2SiO3 with a ratio of 1:2. The increase in the indicators of the obtained geopolymer concrete from the developed composition (4A) in relation to the base control (1X) was 17% in terms of compressive strength and 24% in tensile strength in bending. Polynomial equations were obtained showing the dependence of the change in the strength characteristics of geopolymer concrete on the individual influence of each of the activators. A significant effect of the composition of the alkaline activator on the strength characteristics of geopolymer fine-grained concrete was noted. The optimal temperature range of heat treatment of geopolymer concrete samples, contributing to the positive kinetics of compressive strength gain at the age of 28 days, was determined. The main technological and recipe parameters for obtaining geopolymers with the desired properties, which meet the ecology requirements and are efficient from the point of view of economics, were determined.

Experimental investigations on the fracture strength of soda‐lime silica glass at elevated temperatures

The surface strength of glass plays a significant role when dimensioning glass components in structural facades. Commonly soda‐lime silica glass is used as material in architectural glass design. Different environmental conditions for example the load rate, relative humidity, surface flaws etc., but also the ambient temperature can have a strong influence on the resulting surface strength. The relationship between temperature, especially elevated temperatures, and surface strength of soda‐lime silica glass has so far been rarely investigated. Therefore, this paper methodically presents an experimental test setup for the determination of bending strength at elevated temperatures as well as first results. To determine the bending tensile strength of soda‐lime silica glass as float glass, the double ring bending test was conducted on specimens with small test surfaces according to EN 1288‐5. The double ring bending tests were performed using a tensile fatigue testing machine with furnace on circular glass plates of soda‐lime silica glass in a temperature range from room temperature to 550 °C. Before testing, the specimens were first pre‐damaged (inducing crack with diamond), stored and heat treated as the final pre‐treatment step. To determine the load rate for the experiments at elevated temperatures, the experiment was simulated in advance for the various temperatures using the finite element method with consideration of structural relaxation. To account for the structural relaxation, the Narayanaswamy model was utilized.

Nanomodification of Lightweight Fiber Reinforced Concrete with Micro Silica and Its Influence on the Constructive Quality Coefficient.

A hypothesis was put forward that a nano-modifying additive of micro silica, which had a beneficial effect on achieving a perfect structure of heavy concrete, can also be effectively used in lightweight fiber-reinforced concrete. The nano-modifying additives of micro silica application in manufacturing lightweight fiber reinforced concrete products and structures can significantly enchain their strength characteristics without increasing their mass and consequently improve their design characteristics. The purpose of the work was to increase the structural quality coefficients for all types of strengths of lightweight fiber-reinforced concrete due to its modification with micro silica. The effect of nano-modifying additives of micro silica on the strength characteristics of lightweight fiber reinforced concrete was studied. The optimal amount of micro silica addition was experimentally confirmed and established of 10% of the cement mass. The coefficients of constructive quality for all experimentally determined strength characteristics of lightweight fiber-reinforced concrete modified with micro silica additives were calculated. The coefficient of constructive quality for tensile strength in bending of lightweight fiber reinforced concrete with additives was two and a half times higher than that of heavy concrete without additives and up to 37% higher than that of lightweight fiber-reinforced concrete without additives.

Analysis of Fiber-Reinforced Concrete Slabs under Centric and Eccentric Load.

Research on the interaction between slabs and subsoil involves the field of materials engineering, concrete structures, and geotechnics. In the vast majority of cases, research focuses on only one of these areas, whereas for advanced study and computer simulations, detailed knowledge of the whole task is required. Among the new knowledge and information upon which this article focuses is the evaluation of subsoil stress using specialized pressure cells, along with detailed measurements of the deformation of a fiber-reinforced concrete slab. From a design point of view, this research is focused on the issue of the center of the cross section and the influence of eccentricity. Knowledge in this area is not yet comprehensively available for fiber-reinforced concrete slabs, where 2D deformation sections of the slab and 3D deformation surfaces of the slab are used in experiments. The experimental program includes a centrically and eccentrically loaded slab. These are structural elements that were tested on a specialized device. Both slabs had the same concrete recipe, with a dispersed reinforcement content of 25 kg/m3. The dimensions of the slab were 2000 × 2000 × 150 mm. Laboratory tests assessed compressive strength, the modulus of elasticity, splitting tensile strength, and bending tensile strength. Based on approximate data from the 3D deformation surfaces, an evaluation of the load-displacement diagrams for the center of the slab and for the center of eccentricity was performed. In conclusion, an overall evaluation and discussion of the results relies on experiments and the mechanical properties of fiber-reinforced concrete.

Consequence of silanee combination representative on the mechanical possessions of sugarcane bagasse and polypropylene amalgams

A composite material is created by combining at least two materials to create a unique combination of qualities, one of which comprises stiff, long strands and the other of filaments. And it is mainly concerned with improving ordinary fibre composites to explore the extra possibilities of use. Such typical fibre composites in the accommodation and building areas are suitable as wood alternatives. Many large loads of different yields are supplied, but much of their squandering has no practical use. Horticultural squandering incorporates a variety of dry natural resources and the influence of silanee coupling agents on mechanical characteristics like bending strength, tensile strength, and impact intensity in sugar cane baggage and PP (polypropylene) composites discussed in this Research. The reinforcing material was treated with a 0 percent coupling agent, 10 percent, and 20 percent. This substance was present for the production of composite boards via compression molding. The influence on mechanical parameters such as stress, bending, and impact strengths of the composites were analyzed by the silanee coupling agent.

Treatment and utilization of artificial aggregate in the production of cement composites

The aim of the work is to find a suitable way of treatment of steel ladle slag for subsequent use as a partial replacement of the binder component in cement composites. The goal is based on the raw materials policy of the Czech Republic. Within this work is solved the issue of possible use of steel slag as the largest by-product of steel production. The work is focused on a specific ladle slag from ladle furnaces, by which are equipped the modern steel plants. Ladle slag is similar in chemical composition to Portland cement. However, its mineralogical composition should be taken into account in relation to its expansion reactions and lower hydraulic activity. One of the goals is the research of effect of particle size in cement-slag mixtures. The slag was ground for research on two different specific surfaces - coarsely in a vibrating mill and finely in a ball mill. The research within the experimental part of the work verified the positive influence of ladle slag on the properties of fresh and hardened mortar mixtures. Tensile bending strengths and compressive strengths are for some mixtures with ladle slag even higher than the strengths of the reference mixtures.

Effect of fiber hybridization types on the mechanical properties of carbon/glass fiber reinforced polymer composite rod

In order to balance the cost performance of carbon and glass fibers, the unidirectional carbon/glass hybrid fiber reinforced polymer composite rods were developed through the pultrusion technology in the present paper. Two kinds of fiber hybridization types were proposed including intra-yarn hybrid (uniform dispersed hybrid, UDH) and inter-layer hybrid (core-shell hybrid, CSH). Furthermore, the effects of fiber hybridization types on the mechanical properties (interface/short beam shear strength, three-point bending strength and tensile strength) were investigated experimentally. The full-field strain was obtained through the digital image correlation method to reveal the hybrid mechanism. It was found that the effects of fiber hybridization types on mechanical properties were remarkable. Through uniformly dispersing the carbon fiber into the glass fiber, the maximum increase percentages of available strength were up to 10.9% for short beam shear, 60.3% for three-point bending and 58.7% for tensile strength, respectively. The results of full-field strain analysis revealed that the mechanical failure of CSH rods was dominant by the interface debonding of shell/core, which significantly decreased the mechanical properties. In comparison, UDH rods had the intact interface bonding of carbon/glass fiber/resin, the mechanical failure was derived from the fracture of carbon fiber. The tensile strength of carbon fiber was fully utilized, which contributed to the higher mechanical properties. The larger scale carbon fiber tow may form the weaker interface layer of carbon/glass fiber/resin, which led to uneven interface stress distribution under the external loading and the decrease of interface shear strength.

Nanolithography-induced exfoliation of layered materials

We present a comparative study of nanoexfoliation on bulk, layered materials (MoS2, WSe2, HOPG, and mica) conducted via atomic force microscopy (AFM). The samples were scratched by single crystal diamond probes with varying scan velocities and normal forces. Friction forces measured during the scratch tests and post-mortem topography images allow a detailed investigation of nanoexfoliation mechanisms. In particular, while MoS2, WSe2, and HOPG undergo nanoexfoliation that is characterized by the peeling of flakes from the surface and crack propagation off the main scratch direction, mica is devoid of such effects, instead forming well-defined wear tracks that involve layer-by-layer exfoliation of terraces separated by monoatomic steps. A comparison of material properties (bending stiffness, interlayer adhesion, and tensile strength) mechanistically explains the differences in nanoexfoliation behavior. Moreover, the velocity dependence of lateral contact stiffnesses is studied to infer the influence of capillary-adhesion-mediated contact aging on nanoexfoliation, revealing a connection to the degree of surface hydrophobicity. Our results contribute to the formation of a physical understanding of the elementary steps involved in wear of layered materials, and hint at the possibility of precise, controlled nanoexfoliation by a careful selection of operational and environmental parameters.

Impregnation modeling and preparation optimization of continuous glass fiber reinforced polylactic acid filament for 3D printing

AbstractContinuous glass fiber reinforced polylactic acid (CGF/PLA) composites were prepared by 3D printing technology in this study. The multi‐roll melt impregnation mold was manufactured according to the melt impregnation model. CGF/PLA filament was prepared by a melt impregnation device, and then used to prepare CGF/PLA composite materials by the self‐modified 3D printer device. The full impregnation of the fibers was achieved by the action of the coverage angle of the tension roller in the impregnation mold. The effects of the total coverage angle, traction speed, fiber content, and impregnation temperature on the fiber impregnation effect and 3D printed product performance were studied. The bending strength, tensile strength, impact strength, and interlayer shear strength of the printed sample reached 312, 220, 154, and 14 MPa, respectively. The strategy in this study can effectively improve the impregnation effect of PLA resin on CGFs and promote the development and application of 3D printing technology in the field of high‐performance composite manufacturing.

Optimization of Composition and Technological Factors for the Lightweight Fiber-Reinforced Concrete Production on a Combined Aggregate with an Increased Coefficient of Structural Quality

In recent years, developing lightweight concrete with both the necessary and sufficient strength characteristics is essential in the construction industry. This article studies the influence of the volumetric composition of lightweight fiber-reinforced concrete (LFRC) and the method of its distribution during the preparation of the fiber–concrete mixture on the strength and deformation characteristics of LFRC on a combined aggregate. The optimal grain size of the porous filler was calculated by the mathematical planning method of the experiment. Regression models of the strength and deformation characteristics on the volumetric content of fiber and its distribution method were obtained. The most effective combination of these factors has been determined. The model shows that the increase in compressive strength was 12%, the value of the prismatic strength increased by 25%, the bending tensile strength increased by 34%, and the axial tensile strength increased by 11%. The ultimate strains during axial compression decreased by 10%, axial tension decreased by 12%, and the elasticity modulus increased by 11% compared to the test results of the control composition samples without fiber and pumice. The coefficient of constructive quality (CCQ) of the LFRC on a combined aggregate compared to concrete with the control composition without fiber and pumice showed an increase of more than 32%. It was also found that fiber reinforcement with basalt fibers with a combination of heavy and porous aggregates achieves a synergistic effect together.