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Modern materials science encompasses a range of interdisciplinary issues and goes beyond the conventional curricula of universities and technical courses [...].
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The purpose of this article is to determine the effect of granite powder grain size and grinding time on the properties of cement paste. A series of cement pastes modified by the addition of granite powder were made and the properties of the fresh mixtures and the mechanical properties of hardened pastes were studied. Based on the study, the best results, from the point of view of the application of granite powder in cementitious composites, were obtained for a sample with granite powder ground for 3 h, in which 50% of the particles were smaller than 4 µm, and 90% were below 20 µm. Compressive strength of 55 MPa and flexural strength of 6.8 MPa were obtained on this sample after aging for 28 days. To confirm the validity of using granite powder as substitute materials, additional tests such as scanning microscopy with elemental analysis (SEM, EDS) and infrared (FTIR) studies were performed.
ABSTRACT
Increasing incidents of oil spills and dynamic development of civilization are driving the demand for sorbents. The production of the overwhelming majority of mineral sorbents involves the highly energy-consuming calcination process with CO2 emissions impacting the environment. Taking into account the environmental issues related to greenhouse gas emissions, we are in urgent need of green products and green technologies. The aim of this study was to investigate the possibility of using natural zeolite dust waste to produce oil sorbents in non-calcination technology. The main advantage of the proposed solution is reduction of greenhouse gas emissions and transformation of the waste material into green, useful product. The scope of the research covered the experimental tests for compaction of the zeolite material from Ukraine and Slovakia in a roller press with different type of binding agent and the performance tests for assessing the suitability of the produced agglomerates as a petroleum sorbent. In order to evaluate the agglomerates' properties, textural-structural analysis (optical microscopy, SEM microscopy, and low-temperature N2 sorption), petroleum sorption (Westinghouse method), and physical-mechanical tests (resistance to gravitational drop, abrasion resistance) were carried out. Properties of the manufactured agglomerates were studied in comparison to commercial sorbent DAMSORB, commonly used in Poland. The test results showed that it is doable to produce the effective surface oil-spill sorbent from zeolite waste dust in a roller press by applying the relevant binding agent. The main finding of this study was that optimum feed composition for dry granulation that provides the granular sorbent with the best properties was established: 6% of C binder and moisture content within a narrow range of 20-20.6%. The C-1 sorbent achieved the highest and closely comparable to commercial sorbent parameters of petroleum sorption and drop strength, which are key points of this study. The absorption efficiency of petroleum substances for C-1 sorbent is 8% lower than that of a commercial sorbent, and resistance to gravitational drop is lower by only 3%. However, commercial sorbent exhibited better abrasion resistance compared to produced agglomerates, which is a compelling reason to continue the research in order to enhance the abrasion performance of the manufactured granules. The effectiveness of the dust consolidation method carried out was proved by textural parameters of the obtained zeolite-based sorbents. Specific surface area (SBET) of B-2 (SBET = 28.1 m2/g) and C-2 (SBET = 28.3 m2/g) sorbents was very similar to the commercial sorbent (SBET = 28.1 m2/g). Interestingly, all granules produced from clinoptilolite dust from Slovakia (A-2, B-2, C-2) achieved an increase of 19%, 33%, and 35%, respectively, in volume of mesopores, compared to the commercial sorbent. Moreover, the presented granulation technology favorably affected the size of the specific surface area as well as volume and surface area of mesopores in the case of obtained zeolite-based sorbent A-1 and B-1, compared with the starting raw material. Zeolite-based sorbent A-1 and B-1 achieved an increase of 17% and 18%, respectively, in specific area surface and an increase of 35% and 12%, respectively, in mesopores volume, compared with the raw material. Finally, the results of this investigation proved that it is possible to produce the efficient oil sorbent in a much more eco-friendly and green way, compared with that of the commercial sorbent.
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In this study, nanofibers of poly (acrylic acid) (PAAc), polyacrylamide (PAAm) and poly (vinyl alcohol) (PVOH) were prepared using the electrospinning technique. Based on the Taguchi DOE (design of experiment) method, the effects of electrospinning parameters, i.e., needle tip to collector distance, polymer solution concentration, applied voltage, polymer solution feed rate and polymer type, on the diameter and morphology of polymer nanofibers were evaluated. Analyses of the experiments for the diameters of the polymer nanofibers showed that the type of polymer was the most significant factor. The optimal combination to obtain the smallest diameters with minimum deviations for electrospun polymer nanofibers was also determined. For this purpose, the appropriate factor levels were determined as follows: polymer PAAm, applied voltage 10 kV, delivery rate 0.1 mL/h, needle tip to collector distance 10 cm, and polymer solution concentration 8%, to obtain the thinnest nanofibers. This combination was further validated by conducting a confirmation experiment, and the average diameter of the polymer nanofibers was found to be close to the optimal conditions estimated by the Taguchi DOE method.
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This article presents an analysis of separation results in a specially designed and activated light fraction separator used to remove impurities from mineral aggregates. Laboratory tests conducted on a quarter-technical scale involved performing experiments to ascertain the scope for adjusting the variable settings of the separator operating parameters. These include the frequency and amplitude of pulsation, the height of the heavy-product reception threshold, the size of water flow and variations in the grain size and shape of the feed. During the experiments, the degrees of chalcedonite and dolomite grain purification were studied within the range of grain size for the feed: (2.0-4.0 mm for small grains, 8.0-16.0 for coarse grains and 2.0-16.0 mm for a wide range of grain sizes). The effects of the separator were assessed based on the amount of organic impurities in each heavy product. In all experiments, very good results were obtained, because the percentage of impurities in the product after separation was below 1% in accordance with the assumed technological standard assumption. Regarding the obtained content of light impurities with the separator set to optimal operating parameters, the percentage of light impurities in the product content was reduced to below 0.1%, which meets the guidelines described according to applicable standards. Multi-variant analysis allowed the optimal operating ranges of the separator to be determined, producing refined aggregate in terms of grain size and shape. The final results were also linked to the performance of the device, and its model dependencies were also determined.
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This work presents a summary of research on concrete fireplace materials made of various mineral aggregates and enriched with steel and organic fibers. To determine the optimal applications of such concretes, their ability to accumulate heat and their other physicochemical parameters were tested and analyzed. Studies on the behavior of concrete materials during cooling are reported, and the ability of such materials to accumulate heat is evaluated using calculations. In addition, tests were performed on the loss of mass during heating, as well as on the mechanical bending strength and microstructures of these materials. Studies have shown that the behavior of concrete materials at high temperatures can be modified and adapted for specific purposes. The addition of fibers to concrete improves both the mechanical properties of mortars and the heat flow in concrete materials.
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The article shows investigations on the behavior of preplaced aggregate concrete with regular and irregular coarse aggregates. The thermal properties, compressive strength, and internal structure were analyzed based on computed tomography images. The regular and irregular shapes of aggregates were obtained according to patented technology, which is possible to produce in both laboratory and industrial conditions. Based on the conducted calculations, heat storage capacity was assessed. The influence of grain shape on the material strength, porosity, and hydration gaps was determined. Debonded porosity, as a result of aggregate impurities, was shown using computer tomography analysis. It was shown that the arrangement and shape of the grains has a significant impact on the performance properties of hardened preplaced concrete.
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Hybrid polyacrylate-silicate hydrogels were obtained in the presence of N,N'-methylenebisacrylamide (NNMBA) as the cross-linking monomer and sodium thiosulphate/potassium persulphate (NTS/KPS) as the redox initiators. The results of the tests allowed us to conclude that a hybrid structure with a polyacrylate scaffolding and a silicate matrix had been obtained. The results of the rheological analysis revealed that the hydrogel sample with a 1:7 mass ratio of sodium water glass to the sodium polyacrylate is characterized by the highest complex viscosity. Thermal analysis (Thermogravimetry/Differential Scanning Calorimetry (TG/DSC)) showed that water begins to evaporate at higher temperatures, from 120 °C to even 180 °C. These results were confirmed by mid-infrared spectroscopy (MIR) and nuclear magnetic resonance spectroscopy (NMR) analysis. Differences in the intensity of the peaks derived from water in the MIR spectra indicate that most of the water is bounded. In turn, NMR results showed that the mobility of water molecules decreases as the amount of sodium water glass in the mixture increases.
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When understanding the effect of the morphology of coarse aggregate on the properties of a fresh concrete mixture, the strength and deformability of self-compacting high-performance fibre-reinforced concrete (SCHPFRC) can be seen to be critical for its performance. In this research, regular and irregular grains were separated from granite coarse aggregate. The morphology of these grains was described while using digital image analysis. As a result, the aspect ratio, roundness and area ratio were determined in order to better understand this phenomenon. Then, the principal rheological, physical, and mechanical properties of SCHPFRC were determined. The obtained results indicated that the morphology of the grains of coarse aggregate has an impact on the strength and stiffness properties of SCHPFRC. Moreover, significant differences in the transverse strain of concretes were observed. The morphology of the coarse aggregate also has an impact on the rheological parameters of a fresh concrete mixture. To better understand this phenomenon, the hypothesized mechanism of the formation of SCHPFRC caused by different morphology of coarse aggregate was proposed at the end of the article.
