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Thermo-mechanical resistance of additively manufactured carbon fiber-reinforced PLA
No full textIn this work, additively manufactured composite samples based on polylactic acid reinforced with carbon fibers, were studied from the aspect of their tensile strength, impact toughness, hardness, and thermal resistance, with respect to 3D printing orientation. In this technology, it is known that the printing parameters significantly impact the realization of the prototypes or the properties of the final products. The polylactic acid filament with incorporated carbon fibers reinforcement (PLA-CF) was used in additive manufacturing process of the composite samples. The samples for thermo-mechanical characterization were prepared using a BambuLab X1-Carbon 3D printer. In total, 27 tensile test samples and 27 impact test samples were examined according to the defined printing parameters: printed in 3 axes, 3 specimens for each testing, and tests were done at 3 temperatures (-30°C, +20°C and +50°C). During the realization of the samples, the layer height was 0.1 mm and the infill density was 90%. Differential scanning calorimetry was applied to determine the glass transition temperature of the material, and FTIR to examine interactions of PLA with CF. Due to the reinforcement with carbon fibers, PLA-CF has significantly better mechanical properties than the essential PLA filament. Solid parts produced by this technology are necessary nowadays for installation in places under substantial mechanical loads and require good heat resistance. The observed mechanical characteristics of the additively manufactured material provide good starting point for its potential use in the production of spare parts for automotive, nautical, sports industry as well as in lightweight aircrafts constructions and various protective materials
Assimilating nanographene into the pervious concrete - surface treatment for enhanced paving performance
No full textThis research aims to assess the impact of surface treatment with a nanographene solution on the properties of pervious concrete paving flags (PC paving flags). Four different methods of applying the nanographene solution were examined: spraying, submerging, double submerging, and brushing. The properties of the PC paving flags, as specified by EN 1339, were tested, including bending strength/breaking load, water absorption, abrasion resistance, unpolished slip resistance value (USRV) as well as porosity and permeability. To aid in the interpretation of the results, SEM analysis and optical microscopy were conducted. It is concluded that the surface treatment of PC paving flags with the nanographene solution resulted in a moderate increase in bending strength/breaking load and had a negligible impact on USRV and abrasion resistance values while reducing water absorption, total porosity, and permeability. Optical microscope images revealed that the nanographene treatment smoothed the surface of the PC paving flags sealing it and reducing open porosity. The sealed surface explained the observed reduction in water absorption while reduced open porosity clarified the reduction in total porosity and consequently, water absorption and permeability. The micrographics showed further evidence of the changes in mechanical strength and porosity introduced with nanographene and the presence of carbon on the surface. The elongated pores were present in all the samples, being largest in the sprayed sample
Nisko ciklične zamorne krive čelika: Metodologija konstruisanja i primena
No full textKORISNIK TEHNIČKOG REŠENJA:
Univerzitet u Beogradu, Mašinski fakultet, Laboratorija za dinamička ispitivanja;
TRCpro doo, Petrovaradin, Srbij
Effect of Use of Alkaline Waste Materials as a CO2 Sink on the Physical and Mechanical Performance of Eco-Blended Cement Mortars—Comparative Study
No full textThis research paper provides new insights into the impact of accelerated mineralization of
alkaline waste materials on the physical and mechanical behavior of low-carbon cementbased
mortars. Standardized eco-cement mortars were prepared by replacing Portland
cement with 7% and 20% proportions of three alkaline waste materials (white ladle furnace
slag, biomass ash, and fine concrete waste fraction) that had been previously carbonated
in a static reactor at predefined humidity and CO2 concentration. The mortars’ physical
(total/capillary water absorption, electrical resistivity) and mechanical properties (compressive
strength up to 90 d of curing) were analyzed, and their microstructures were
examined using mercury intrusion porosimetry and computed tomography. The results
reveal that carbonated waste materials generate a greater heat of hydration and have a
lower total and capillary water absorption capacity, while the electrical resistivity and
compressive strength tests generally indicate that they behave similarly to mortars not
containing carbonated minerals. Mercury intrusion porosimetry (microporosity) indicates
an increase in total porosity, with no clear refinement versus non-carbonated materials,
while computed tomography (macroporosity) reveals a refinement of the pore structure
with a significant reduction in the number of larger pores (>0.09 mm3) and intermediate
pores (0.001–0.09 mm3) when carbonated residues are incorporated that varies depending
on waste material. The construction and demolition waste (CCDW-C) introduced the
best physical and mechanical behavior. These studies confirm the possibility of recycling
carbonated waste materials as low-carbon supplementary cementitious materials (SCMs)
Autonomni modularni sistem za dinamičko ispitivanje šipova
No full textBroj prijave: MP-2023/0028
Link do baze patenata: https://reg.zis.gov.rs/patreg/?t=
Are volcaniclastics bad enough to make badlands?
No full textIn the past few decades, terrains of accentuated roughness with variety of topographical features and, due to the diversity of lithology and colors, known as badlands attract great attention not only from the scientist, but from people in general and contribute to the touristic popularization of geosites.
Badlands materials are mainly silty clays and clayey silts. However, they can be formed in volcaniclastics material too and one of the most prominent badlands developed in pyroclastic sediments is Cappadocia, Turkey. Less known are Kazar badlands, Hungary, developed in rhyolitic poorly-consolidated highly porous tuffs and Djavolja varos, Serbia developed in dacito-andesitic poorly-consolidated, poorly-sorted tuffs.
Volcaniclastic rock samples from Kazar badlands, Hungary and Djavolja varos, Serbia were analyzed with the purpose to broaden existing knowledge on materials in which badlands can form. Through analysis of eight unweathered volcaniclastic sediment samples that included petrographic characterization, content of macroelements, pH, electrical conductivity, sodium adsorption ratio and immersion test an attempt was made to answer the question whether volcaniclastics are “bad” enough to make badlands.
After all the analysis conducted, Kazar badlands and Djavolja varos materials have different properties, unique for each site, but are still more similar to each other than to, already known badlands materials. Similar bimodal grain size distribution of Kazar badlands and Djavolja varos reflects sediments erodibility and is making them similar to other badlands generally, while mineralogical composition and weathering processes are the main factors making these two sites a unique badlands group.
Conclusions brought in this study are opening new scientific topic and they imply that volcaniclastic material, even though site-specific, make unique badlands and that, through future research, could bring the possibility of a new badlands classification that will include only volcaniclastics and will bring up small sites like these to the existent geotouristic map
The Effects of Wind Velocity on the Binding Properties of Ash, Bottom Ash, and Additives: A Wind Tunnel Study
No full textThe more economically viable and environmentally sustainable approach for treating
the by-products of coal combustion from thermal power plants entails their collective disposal as
opposed to individual disposal methods. This aligns with pertinent EU directives and domestic
regulations, ensuring compliance with established standards while optimizing resource utilization
and minimizing environmental impact. This study evaluated the resistance to wind erosion of the
binding properties of a mixture (fly ash (FA), bottom ash (BA), and additives) using an indoor wind
tunnel under simulated ambient conditions. Investigations of the mutual impact of ash, bottom ash,
and additives (CaO and Ca(OH)2) with a certain percentage of water were carried out with eighteen
samples. The samples consisted of the water at six addition rates 5, 8, 10, 15, 20, and 25% (w/w),
and additive at three addition rates (1, 2, and 3% (w/w). Based on the obtained results, the optimal
ratios of additives (3% (w/w)) and water (15% (w/w)) were determined. Prior to the wind tunnel
experiments, and according to the different addition rates of additives and water, eight samples
were prepared with different addition rates of ash. The mass concentrations of suspended particles
(PM10) and total suspended particles (TSPs) in these samples were measured at three distinct wind
velocities: 1 m/s, 3 m/s, and 5 m/s, respectively. The results indicate that the samples containing
the optimal content of additives and water demonstrate a maximum increase in PM10 emission zero
values of no more than 1.9 times. This finding can be considered satisfactory from the standpoint of
environmental protection
Feasibility study on utilization of pulverized construction and demolition waste as alternative raw material for Portland cement clinker production
No full textA number of beneficial characteristics are displayed by ordinary Portland cement (OPC), including workability, appropriate setting and hardening behavior, superior mechanical performance, and good chemical resistance. OPC has been used as the major bonding agent in the building industry for more than 200 years due to these reasons. OPC is commercially produced by heating limestone, quartz, clay, and slag in a specially designed rotary kiln. The goal of this study is to use waste materials (construction and demolition waste) and alternative clayey materials to produce cement clinker. When it comes to the resources needed to make cement clinker, caution has been applied because substitute raw materials need to be accessible in adequate quantity and quality. Carbon dioxide is a byproduct of the chemical reactions in a rotary kiln. One kilogram of CO2 is released into the atmosphere during the cement-making process. Up to 9% of global human CO2 emissions are produced annually by the manufacture of cement and concrete. An attempt has been made to decrease the sintering temperature and the duration of thermal treatment in order to decrease the carbon emissions of the process. Therefore, in this study, cement clinker was synthesized at temperatures ranging from 1100°C to 1400°C upon mechanical activation of the raw material. Four cement clinkers were produced based on different raw materials: 1) recycled concrete, kaolinitic-illitic clay, Fe-slag, and limestone; 2) recycled concrete, zeolite, Fe-slag, and limestone; 3) recycled concrete, bentonite, Fe-slag, and limestone; and 4) recycled concrete, refined kaolinitic-illitic clay, Fe-slag, and limestone. The obtained clinkers were characterized by DTA/DCS/TG, XRD, FTIR, and SEM methods. The results indicated that the obtained clinkers exhibited four main cement clinker phases, namely C3S, C2S, C3A, and C4AF, identical to commercial ordinary Portland cement (OPC). The obtained results pointed out that the production of cement clinker based on recycled waste resources and alternative clayey materials is feasible.http://www.serbianceramicsociety.r
New Eco-Cements Made with Marabou Weed Biomass Ash
No full textBiomass ash is currently attracting the attention of science and industry as an inexhaustible
eco-friendly alternative to pozzolans traditionally used in commercial cement manufacture (fly ash,
silica fume, natural/calcined pozzolan). This paper explores a new line of research into Marabou
weed ash (MA), an alternative to better-known conventional agro-industry waste materials (rice husk,
bagasse cane, bamboo, forest waste, etc.) produced in Cuba from an invasive plant harvested as
biomass for bioenergy production. The study entailed full characterization of MA using a variety of
instrumental techniques, analysis of pozzolanic reactivity in the pozzolan/lime system, and, finally
its influence on the physical and mechanical properties of binary pastes and mortars containing 10%
and 20% MA replacement content. The results indicate that MA has a very low acid oxide content
and a high loss on ignition (30%) and K2O content (6.9%), which produces medium–low pozzolanic
activity. Despite an observed increase in the blended mortars’ total and capillary water absorption
capacity and electrical resistivity and a loss in mechanical strength approximately equivalent to
the replacement percentage, the 10% and 20% MA blended cements meet the regulatory chemical,
physical, and mechanical requirements specified. Marabou weed ash is therefore a viable future
supplementary cementitious material
Primena 8R strategije u realizaciji nosivih senzora
No full textU radu je prikazan algoritam primene 8R strategije u okviru cirkularne ekonomije u realizaciji nosivih senzora na tekstilu. Primena aditivne proizvodnje u realizaciji nosivih senzora u tekstilnoj industriji podrazumeva koncept održive proizvodnje kroz minimalno generisanje otpada, realizaciju složene geometrije, brzoj izradi prototipa. Takođe, aditivna proizvodnja se danas posmatra kao moćan alat u realizaciji kompletnog senzora primenom sirovih ili recikliranih materijala. U radu je dat algoritam za primenu i upotrebu nosivih senzora kroz primenu 8R strategije. Proizvodnja se odnosi na proces 3D štampe, realizaciju fleksibilne štampe, ugradnju elektronskih komponenti. Svi pomenuti delovi mogu brzo da se zamene, modifikuju, rastave i recikliraju, što je u osnovi bitno za cirkularnu ekonomiju