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Incorporation of boron nitride nanoceramic as a functional additive in polyurethane coatings
No full textBoron nitride (BN), as a ceramic material with high hardness, thermal conductivity, chemical stability, and low density, offers promising multifunctional benefits in role of reinforcement incorporated into polymeric matrices. This study explores the possibility of addition of boron nitride nanoparticles into a polyurethane-based coating at concentrations of 1 wt.% and 2 wt.%, with the aim of enhancing mechanical durability and evaluating the resulting optical characteristics. Coatings were tested for impact resistance, abrasion resistance, and spectrophotometric properties within the visible and near-infrared (NIR) spectrum. The addition of nano-BN led to expected improvements in both impact and abrasion resistance, attributed to the ceramic’s inherent mechanical properties. Spectrophotometric analysis revealed minimal shifts in reflectance, indicating a slight brightening effect. These findings highlight the potential of nano-ceramic additives such as BN for multifunctional enhancements in advanced coating systems, regarding structural performance and optical properties
Ocena preostalog veka 1Cr-0.5Mo kotlovskog čelika posle dugotrajnog rada u uslovima puzanja
No full textRemaining life assessment (RLA) is an important tool in securing the operational safety of aged structures and plants. RLA can prevent unforeseen outages and failures that can have tragic and costly consequences. The key point in esti-mating the remaining life of a mechanical component is determining when structural integrity becomes critical due to progressive damage caused by the applicable damage mech-anism. The lifetime of mechanical components is often lim-ited due to creep damage mechanism occurring during ser-vice or periods of outage. In this paper, test results are dis-cussed for replication metallography performed for the high-temperature 1Cr-0.5Mo boiler steel. Replication for metal-lographic examination is carried out at different spots of the base and weld metal of boiler tubes. The estimated remain-ing life is calculated based on the classification of creep damage according to Wedel and Neubauer. The goal of the paper is to present the changes in microstructural properties of the 1Cr-0.5Mo low-alloyed boiler steel after long-term service in creep conditions. Thus, it will help the plant man-ager in real time condition monitoring the boiler steel.Procena preostalog veka (RLA) je važan alat u obezbeđi-vanju operativne bezbednosti starih objekata i postrojenja. RLA može sprečiti nepredviđene prekide rada i kvarove koji mogu imati tragične i skupe posledice. Ključna tačka u proceni preostalog veka mašinske komponente je određiva-nje kada integritet konstrukcije postaje kritičan usled progre-sivnog oštećenja izazvanog primenljivim mehanizmom ošte-ćenja. Vek trajanja mašinskih komponenata je često ograni-čen zbog mehanizma oštećenja usled puzanja tokom rada ili perioda prekida rada. U radu se razmatraju rezultati ispiti-vanja replikacione metalografije kotlovskog čelika 1Cr-0.5 Mo. Replike za metalografska ispitivanja su urađene na različitim mestima osnovnog i zavarenog metala kotlovskih cevi. Procena preostalog veka je izračunata na osnovu klasi-fikacije oštećenja od puzanja prema Vedelu i Nojbaueru. Svrha ovog rada je da prikaže promene mikrostrukturnih osobina niskolegiranog kotlovskog čelika 1Cr-0.5Mo nakon dugotrajnog rada u uslovima puzanja. To će pomoći mena-džeru postrojenja u praćenju stanja kotlovskog čelika u real-nom vremenu
Cirkularna ekonomija u službi održivog razvoja građevinskih proizvoda na bazi glina
No full textPred proizvodnjom tradicionalnih proizvoda na bazi gline postavljaju se brojni izazovi na
globalnom nivou. I pored toga, oni predstavljaju jedan od osnovnih materijala sa primenom u
građevinarstvu. U radu se predstavljaju moguća poboljšanja u proizvodnji: optimalno korišćenje
prirodnih mineralnih resursa, korišćenje otpadnih materijala, smanjenje potrošnje energije i
korišćenje zelene energije, smanjenje emisije opasne po zdravlje i životnu sredinu, smanjenje emisije
CO2, analiza uticaja proizvoda na životnu sredinu, rekultivacija ležišta i dr. Ključni parametri kod
kojih treba obratiti pažnju su vezani za značajan doprinos opekarske industrije globalnoj emisiji
CO2, uglavnom zbog energetski intenzivnih procesa proizvodnje i korišćenja neobnovljivih izvora
energije. Ključni pravci razvoja obuhvtaju prelazak na „zelenu“ energiju i korišćenje veštačke
inteligencije za praćenje i optimizaciju proizvodnje. Ovaj rad daje sveobuhvatan pregled trenutnog
stanja opekarske industrije i nudi preporuke za buduća istraživanja i inovacije za promovisanje
održivosti životne sredine
The influence of crumb rubber on the freeze-thaw resistance of concrete
No full textWaste tires are a persistent challenge in waste management. To reduce environmental
impact and utilize this material more effectively, its use in concrete mixtures has been studied. This
research aims to incorporate waste materials into concrete production while ensuring acceptable
performance. The study presents results where fine aggregate was partially replaced with crumb
rubber (2.5% and 5% by volume). All mixtures were designed with a w/c= 0.55 and compared with
a control and a mixture with a chemical air-entraining admixture. Fresh concrete properties were
monitored after 10, 30, and 60 minutes. After 60 minutes, rubber-modified mixtures showed
increased air content and decreased density. The hardened concrete with rubber had lower
compressive strength but better resistance after 200 freeze-thaw cycles compared to the control
Beton modifikovan grafen-oksidom
No full textS obzirom na to da je beton trenutno najrasprostranjeniji građevinski materijal, njegova
čvrstoća i izdržljivost su njegove bitne karakteristike. Nedavna dostignuća u vidu primene vlakna
nanodimenyije, kao što su ugljenične nanotube i grafen oksid, poboljšala su performanse betona.
Grafen oksid (GO) je dvodimenzionalni planarni list komprimovanih atoma ugljenika u
konfiguraciji saća debljine 0,335 nm. GO je obećavajući nanomaterijal zbog svojih jedinstvenih
svojstava, naime, dobio je međunarodnu pažnju zbog svojih izvanrednih mehaničkih, optičkih i
termičkih svojstava. Pored regulacije sekundarnog mehanizma hidratacije, dodavanjem GO betonu
poboljšavaju se njegove mehaničke performanse, izdržljivost, samozarastanje i druge
multifunkcionalne karakteristike. Ova studija predstavlja ispitivanje svojstava betona sa dodatkom
GO. Pripremljena su četiri različita projekta betonske mešavine. GO je dodat u količinama od
0,01, 0,02, 0,03 i 0,06 %. Hidratacija je analizirana diferencijalnom termičkom analizom. Praćene
su mehaničke čvrstoće u trajanju od 28 dana i otpornost na mraz sa solima za odleđivanje tokom
56 ciklusa
Fire Resistance of Crushed Brick-Based Alkali-Activated Mortars
No full textThis study investigates the fire resistance of alkali-activated mortar incorporating crushed brick as both a precursor and aggregate. The optimal alkaline activator was identified as a combination of KOH and Na₂SiO₃, with a curing period of 3 days at 70 °C. Two mortar series were produced, each exhibiting different workability: on series comprised cement mortar, while the other included three alkali-activated mortars, with variations in the molarity of the KOH solution. The mortar samples were subsequently heated to 600°C, and their mechanical properties and mass were measured to determine residual values/losses. The best-performing alkali-activated and cement mortars underwent visual assessments of cross-sections to evaluate the impact of mortar consistency on fire resistance. Additionally, changes in mineralogy and microstructure were followed by instrumental techniques to clarify the results before and after heating. While cement mortars had superior mechanical properties at room temperature, alkali-activated mortars retained a higher percentage of their mechanical properties post-heating, demonstrating better fire resistance. Mortars with plastic consistency showed better fire resistance than those with fluid consistency. These findings suggest that brick-based alkali-activated mortars could be developed into fire protection boards for structural member
Comparative analysis of concrete with Portland composite cements with reduced clinker content
No full textThe paper presents the results of experimental testing of concrete mixtures made with
Portland composite cements with reduced clinker content (PC 50M). The aim of the study was to
examine the justification for using this type of cement (defined by the document SDO 15 001:2021)
in concretes commonly used in construction practice. The compressive strength reached values
ranging from 48.0 to 55.8 MPa, while all other parameters: splitting tensile strength, water
impermeability, frost resistance, and thermogravimetric analysis, also showed very good
performance. The results support the use of this type of cement in the construction industry
Comparative analysis of different glass types during the standard fire test
No full textThe paper investigates the fire resistance of three types of glass samples exposed to
standard fire conditions. The tested samples were: thermal insulation glass (4 + 16 + 4 mm), single
glazing with 8 mm thickness, and single glazing with 6 mm thickness. All three samples were placed in
the standard furnace and tested simultaneously. The objective of this testing is to evaluate the
possibility of replacing single glazing with thermal insulation glass (double glazing: 4 + 16 + 4 mm)
in applications where single glazing is currently planned. The aim of the testing was to determine
when all three samples would lose their integrity, i.e., when the last piece of glass would break.
Installing thermal insulation glass in places where single-glazed windows are installed has higher
heat loss in winter, as well as better comfort inside the rooms in summer. Some buildings are
equipped with single-pane windows, which are installed with the intention of allowing rapid breakage
during a fire to facilitate the extraction of smoke and heat. The glazing type relevant in this case is one
that will lose its integrity within 15 minutes of testing. The results indicate that it is feasible to install
thermal insulation glass (4 + 16 + 4 mm double glazing) as a replacement for single-glazed windows
Smernice za tretiranje otpada od rušenja i građenja u cilju dobijanja recikliranog agregata, kvalitet dobijenog agregata na bazi izvršenih laboratorijskih ispitivanja
No full textReciklirani agregat, koji obuhvata otpad od rušenja, renoviranja i samog procesa
izgradnje, i u Srbiji polako počinje da dobija na značaju i da pronalazi svoje mesto na tržištu. O
tome svedoče sve češći zahtevi za ispitivanja i dokazivanje upotrebljivosti ovog materijala, kao i
uspostavljanje određenih zakonskih okvira, koji prepoznaju značaj ove vrste agregata. U radu su
dati osnovni preduslovi proizvodnje kvalitetnog recikliranog agregata i iskustva Instituta IMS
stečena kroz vršenje laboratorijskih ispitivanja
Application of acoustic emission in the brick and tile industry
No full textThe first part of this research focuses on characterising the raw material to assess its suitability for production. The second part explores the use of acoustic emission (AE) as a method for monitoring crack formation during the drying process. Numerous experiments are conducted on heavy clay tile samples to identify acoustic emissions related to physical changes in the material during drying. The impulsive nature of the expected acoustic events suggests broadband excitation, while the wet clay itself strongly attenuates higher frequencies. As a result, the main energy is expected to be concentrated in the lower part of the spectrum. The hypothesis that acoustic events associated with the formation of macro- and micro-cracks fall within the audio frequency range is confirmed. As the brick and tile industry is energy-intensive, this approach supports UN Goal 12 by promoting responsible production and reducing drying scrap rate