Periodica Polytechnica (Budapest University of Technology and Economics)
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Sustainable Concrete: Exploring Fresh, Mechanical, Durability, and Microstructural Properties with Recycled Fine Aggregates
Get PDFThe growing construction industry and global population have led to increased demand for concrete, resulting in increased waste production. Recycling construction and demolition (C&D) waste as recycled fine aggregates (RFA) in concrete could help reduce waste and conserve natural resources. This research delves into the meticulous examination of particle packing density within specific cylindrical volumes under standard compacting efforts, elucidating an order of compressive strength. The study comprehensively explores various concrete properties, including workability, compressive strength, flexural strength, split tensile strength, drying shrinkage, electrical resistivity, rapid chloride penetration, and microstructural characteristics (analyzed through XRD, SEM, and EDAX). RFA particles, ranging from 0.15 to 4.75 mm, were employed as partial replacements for fine aggregates, with replacement percentages varying from 0% to 100% in increments of 25%. The empirical findings underscore that the incorporation of RFA significantly enhances concrete properties. However, it was observed that surpassing the optimum replacement percentage of 25% (RFA 25) adversely impacts the concrete’s strength and microstructure. Specifically, RFA 25 exhibited remarkable improvements, with a 14.75% increase in compressive strength, a 6.61% boost in flexural strength, and a 13.14% enhancement in split tensile strength compared to conventional concrete (RC). Furthermore, RFA 25 demonstrated a 4.16% increment in drying shrinkage, 17.65% higher electrical resistivity, and an 18.83% superior resistance to chloride penetration compared to RC. The analysis of XRD, SEM, and EDAX results elucidated that at lower replacement percentages, the pozzolanic reaction enhances strength by forming additional hydration products. Conversely, at higher replacement levels, strength diminishes
A Comprehensive Investigation of Performance Characteristics, Mechanical Properties and Durability Parameters of Self-compacting Concrete Containing Iron Slag as Coarse Aggregate
Get PDFIn this paper, iron slag is used as partial coarse aggregate substitution in Self-compacting concrete (SCC). The SCC samples tests were conducted after 28 days of water curing for samples with 0%, 10%, 20%, 30%, 40%, 50%, and 60% iron slag as coarse aggregate substitutes. This paper evaluates slump flow, V-funnel, L-box, compressive strength, flexural strength, splitting tensile strength, surface water absorption, capillary water absorption, electrical resistance, acid resistance, and ultrasonic pulse velocity (UPV) of concrete samples. Furthermore, scanning electron microscopy (SEM) of samples was investigated for evaluating cement paste microstructure. Samples containing 20%, 60%, and 60% iron slag as coarse aggregate substitute have higher compressive, flexural, and splitting tensile strength than control samples (about 18.4%, 28.6%, and 16.9% higher, respectively). In addition, using 10%, 20%, 30%, and 40% iron slag as coarse aggregate increased the compressive strength. Moreover, incorporating iron slag as a coarse aggregate decreased the mass loss of samples which were exposed to the acid environment compared to control specimens. Using iron slag as partial coarse aggregate substitution reduced the porosity of the cement matrix compared to control samples (based on SEM images)
Financing and Investing in Women-led Businesses: Understanding Strategic Profits and Entrepreneurial Expectations by Analysing the Factors that Determine Their Company Success
Get PDFThis paper examines the strategic profits and entrepreneurial expectations that accompany financing and investing in women-led businesses in Kosovo, India, and United Kingdom. Its main goal was to observe what the strategic profits and entrepreneurial expectations were for these businesses, based on consideration of three factors: Factor 1 (Strategic profits and entrepreneurial expectations), Factor 2 (Financing and investing expectations), and Factor 3 (Strategic profits). Were these factors associated with one another when making financing and investment decisions, and which variables should be considered more carefully by businesses to improve performance, survive as a business and stay ahead of competitors, meet stakeholder expectations and achieve strategic profit forecasts? Through data processing (SPSS program for Windows 16) using tests and econometric analysis (descriptive, factorial, reliability, and multiple regression) the model shows that all three factors play a significant role in determining strategic profits and entrepreneurial expectations. However, it is suggested that if staff cannot quickly adapt to changes in the environment, and the managerial skills and correct leadership are not in place to execute ideas that increase profit, ensure the regular repayment of debts and loans, deploy innovative strategies, maintain a company's legal status and evaluate the work of employees, then businesses will struggle to increase their strategic profit and guarantee their market survival when compared to their competitors
Synthesis and Studies of 9-Activated 4,5-Dimethoxyacridine Multifunctionalizable Building Blocks
Get PDF9-Substituted-4,5-bifunctionalized acridines are common subunits of numerous drugs and fluorescent dyes, thus studies were carried out on a series of their potential precursors from the aspect of preparation, reactivity, chemical stability and potential applications. The syntheses of the new 9-fluoro-, 9-triflate and 9-lithiated derivatives of 4,5-dimethoxyacridine were reported. All the new intermediates supplemented with the recently synthetized 9-haloacridine analogues were compared and their applicability was discussed. The reactivity of the studied acridino-precursors was tested by using them as starting materials in Suzuki-Miyaura and Kharasch type cross-couplings as well as in Li-organic reactions
Recent Advances on Impedimetric Electroanalysis with Non-commercial Portable Instruments: A Mini Review
Get PDFElectrochemical impedance spectroscopy (EIS) is one of the most important methods for studying the electrochemical interface. The instrumentation for its implementation consists of an electrochemical cell and a potentiostat with a frequency analyzer. Several authors have demonstrated the feasibility of designing and constructing low-cost, in-lab portable potentiostats for EIS. This type of electrochemical instrument reduces research costs, allows in-field analysis, enables adaptation to specific experimental conditions, as well as modern capabilities such as machine learning (ML) techniques or Internet of Things (IoT) integration. The use of portable EIS devices for substance identification and quantification, i.e., electroanalysis, has been reported. Although these applications are more limited than for interface characterization, some progress has been made in recent years. This paper presents a mini-review of EIS electroanalysis performed with in-lab portable instruments. The aim is to show different options for the implementation of EIS as investigation technique when portability is needed for in-field impedimetric analysis or applications where available commercial instruments do not work
Microstructure and Corrosion Study on Friction Surfaced Aluminum Alloy Coatings over Mild Steel
Get PDFIn this study, the low-carbon steel (AISI 1018 mild steel) substrate is coated with the aluminum alloys AA6082-T6, Al-20Zn, and Al-2Si-15SiC to improve its corrosion resistance by the friction surfacing (FS) technique. To produce a high-quality coating, friction surfacing process variables including spin speed, speed of travel, and the rate of feed are crucial. This experiment examines twelve friction-surfaced plates with different parameter combinations. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) examinations were carried out in order to comprehend the microstructure and chemical composition of the coating deposits and the area in contact between the coated surface and the substrate. Microstructure investigation reveals that the intermetallic combination of Fe-Al at the coating interface region is an effect of the elemental diffusion of Fe to aluminum at the contact interface. Then a uniform and fine-grained coating deposit is observed as a result of the continuous recrystallization of the consumable rod under frictional stress and heat generation. According to the outcomes of the microhardness test, the coated surface is roughly 15–16% harder than the consumable rod. The coating bond strength was measured using a ram tensile test, and it ranged from 102 MPa to 135 MPa. Finally, evaluation of corrosion behavior through immersion testing and pitting corrosion testing reveals that the coatings made of Al-20Zn and Al-2Si-15SiC exhibit good corrosive resistance in an alkaline environment
Enhancing the Mechanical Performance of Concrete Slabs through the Incorporation of Nano-sized Iron Oxide Particles (Fe2O3): Non-local Bending Analysis
Get PDFThe utilization of recycled iron in durable concrete production has gained attention for enhancing sustainability and resource efficiency. Simultaneously, incorporating nanoparticles as supplementary cementitious materials (SCMs) offers significant benefits. Introducing nano-sized iron particles (Fe2O3) into the cement paste results in a compact microstructure, improving strength, and durability. In this study, we investigate the bending behavior of concrete slabs reinforced with Fe2O3 nanoparticles using the non-local quasi-3D shear deformation theory based on Eringen's non-local differential constitutive relations. To characterize the elastic material properties of the nanocomposite, we employ Eshelby's homogenization model. In order to extend the applicability of our findings, we assume that the concrete plate rests on Kerr's foundation, which includes a shear layer connected to upper and lower springs. By deriving the equations of motion using the principle of virtual work, we establish a comprehensive framework for analyzing the bending of the concrete plate. To solve the equilibrium equations for a simply supported concrete plate, we present Navier's analytical solutions. Our investigation considers various influential parameters, such as the concentration of Fe2O3 nanoparticles in the concrete matrix, the elastic constants of the soil medium, different types of bending loads, and size-dependent nonlocal parameters. One of the most captivating findings of this study is that the incorporation of 30 wt% of iron nanoparticles in concrete leads to a remarkable improvement of 60% in the elastic properties of the material. Additionally, this same amount of iron nanoparticles has shown the potential to reduce the deflection of thin plates by over 60%
Effect of Wrapping Thickness and Type on Reinforced Bridge Piers: A Numerical Study
Get PDFThis research paper investigates the impact of wrapping thickness and type on reinforced bridge piers through a numerical study. The Incesu bridge, located in the Ardanuç district of Artvin province, was selected as the case study, as it was completed with low concrete strength. Initially, the bridge was examined, revealing that the piers were inadequate against dynamic, dead, pedestrian, and covering loads. The study concentrated on employing carbon fiber reinforced polymer to reinforce the bridge piers. Various models were wrapped with carbon fiber reinforced polymer in full-length, half-length, and one-meter intervals. In the analysis, it is assumed that the wraps are linked to each other in both principal directions and not detached from one another. Along with the analyses conducted, stress and strain values are presented separately. It was observed that the wrapping effect obtained in small-sized elements in literature could not be obtained in large-sized elements. As the concrete quality improves, the influence of wrapping thickness diminishes. Moreover, the effects of full-length and half-length wrapping are very close to each other, suggesting that half-length wrapping of bridge piers is sufficient. The authors believe that the obtained analysis results will prove beneficial in achieving economic advantages in retrofitting projects within the construction sector
The Effect of Mineral Composition on the Correlation between Point Load Index with the Uniaxial Compressive Strength of Sulfate Rocks and their Point Loading Deformation
Get PDFPoint load test is a common, inexpensive and fast test for the indirect achievement of compressive or tensile strength of the rocks in the laboratory and the field. In this research, by conducting uniaxial compression test (UCT), axial (APLT), and diametral (DPLT) point load tests on gathered sulfate rock blocks from the Gachsaran Formation outcrops at the four under-construction reservoir dam sites in Iran, investigate the effect of mineral composition on the relationships between point load index, the uniaxial compressive strength (UCS) and their point load deformation. Regarding that, firstly by creating a correlation between axial (APLI) and diametral (DPLI) point load index and UCS, relationships for each specific mineral composition were provided. Secondly, by comparing the reliability of the APLT and DPLT results in predicting UCS, the conversion factors of the APLI and DPLI to the UCS were calculated. Thirdly, the effect of unique or multiple sampling locations in the analysis results was compared, and finally, for the first time, the deformation of loading points in point load tests was investigated. The results of this study confirmed that by variation of mineral composition of sulfate rocks, the relationships between APLI and DPLI, and UCS, conversion factors as well as loading points deformation patterns during point load tests are changed significantly, and the results of APLT and DPLT can be used to predict UCS with the same reliability in dry and saturated conditions