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Savremena uloga Instituta IMS u izgradnji, rekonstrukciji, sanaciji i održavanju građevinskih konstrukcija i objekata
Get PDFCentar za konstrukcije i prednaprezanje obuhvata delat-nosti zahvaljujući kojima je Institut IMS stekao veliki ugled u zemlji i inostranstvu. Kroz rad na širokom spektru aktiv-nosti vezanih za izgradnju ili sanaciju i rekonstrukciju razli-čitih građevinskih objekata i konstrukcija, posebno kroz primenu tehnoloških rešenja zasnovanih na prednapreza-nju, saradnici Centra nastavljaju bogatu tradiciju Instituta IMS. Savremena oprema i visokospecijalizovani kadar omogu-ćavaju izvođenje radova prednaprezanja, realizaciju ispiti-vanja u laboratoriji i na terenu, projektovanje i razvoj. U poslovima Centra za konstrukcije i prednaprezanje na kapi-talnim infrastrukturnim objektima i u obnovi graditeljskog nasleđa aktivno učestvuju skoro sve ostale organizacione celine Instituta IMS, kako bi se obezbedio integralni multidis-ciplinarni pristup, koji rezultira održivim rešenjima
Centar za metale i energetiku Instituta za ispitivanje materijala IMS (istorijat - sadašnjost - budućnost)
Get PDFCentar za metale i energetiku, u okviru Instituta IMS, je od početka osnivanja i kroz celu njegovu istoriju kroz svoje multidisciplinarne delatnosti neizostavni deo poslovanja. Sam centar za metale predstavlja lidera u oblastima ispiti-vanja metala, sa i bez razaranja. Takođe, kroz delatnosti koje obavljaju akreditovane celine kontrolnog tela i sertifikacio-nog tela za sertifikaciju zavarivača široka lepeza poslova-nja ogleda se i kroz akreditovane laboratorije na poljima metrologije. Učešće u privredi uz učešća u naučnoistraži-vačkim aktivnostima i primeni savremenih tehnologija ispi-tivanja visoko pozicionira centar za metale u Republici Srbiji i regionu
The influence of steel fibers obtained by recycling waste tires on the properties of concrete
No full textThe paper shows the influence of steel fibers obtained from steel wire separated in the recycling process of waste car tires on the properties of concrete. The reference concrete was prepared, as well as concretes with the addition of steel fibers, which were varied in contents at 20 kg/m3 and 40 kg/m3. The slump test of fresh concrete was performed using the Webe method, where it was established that with an increase in the amount of fibers, concretes with a stiffer consistency are obtained. Concrete beams were tested for strength during flexure tension (limit of proportionality (LOP) and residual flexural strength).
Can be concluded that the residual flexure strength greater than 1.5 MPa at a CMOD of 0.5 mm is already achieved with the addition of 20 kg of fibers per m3 of concrete, while both conditions for the residual bending strengths are satisfied with the addition of 40 kg of fibers per m3 of concrete and that they amount to 2.4 MPa at a CMOD of 0.5 mm and 1.4 MPa at a CMOD of 3.5 mm
The paleokarst origin of the carbonate "Ropočevo breccia" and a closing Neotethys: Regional Geological constraints on the Vardar Zone s.s. (Belgrade area, Central Serbia).
No full textAn extremely rare carbonate breccia in the Ropočevo area (southern outskirts of Belgrade, near Avala Mt., Central Serbia), provides a clue on the probable mechanism of both its paleokarstification and a tectonic relationship with lithospheric-scale compressional events which have occurred along the latest Jurassic Neotethyan Vardar Ocean margin. Outcropping as a well-lithified block, “Ropočevo breccia” exposes an abundance of large angular, boulder-size clasts composed of recrystallized limestone. It has been used for decorative purposes in the near past. The famous decorative stone “Ropočevo breccia” represents an isolated olistolith-like carbonate block engulfed by the Upper Cretaceous Vardar Zone s.s. turbidites. In the Ropočevo area, two penecontemporaneous turbidite systems are separated by the Alpine west-vergent thrust. However, the “Ropočevo breccia” is related to neither the underlying Lower Cretaceous- nor overlaying Upper Cretaceous turbidites. Such a regional-geological relationship indicates a presence of a pre-Upper Cretaceous tectonic exhumation event, followed by the rather short subaerial paleokarst episode. The suggested paleokarst episode is characterized by the absence of progressive abrasion and of visible roundness of the considerably larger carbonate clasts. The regional geological constraints on the investigated “Ropočevo breccia” show that the isolated “olistolith” is a breccia formed by the end of Berriasian from the clasts formed in a collapsed cave within the primary carbonate sequence of the (latest Tithonian-)Berriasian age. The proposed interpretation is in line with the “Basal unit” of the Lower Cretaceous “Paraflysch” belonging to the well-hidden basal sequence of the East Vardar Zone of Central Serbia. Moreover, the available aeromagnetic data of the Avala Mt./Ripanj-Ropočevo-Kosmaj Mt. sector, corroborate a deep-settled suture underneath the investigated segment of the Vardar Ocean. The results further show that a short tectonic uplift and karstification episode occurred in connection with the compressional interruption, affecting the lithospheric-scale contact between formerly descending and overriding plates. Thus, the short regional-scale lowermost Cretaceous uplift and karstification episode was likely induced by the closure of the Neotethyan Vardar Ocean. This latest Jurassic-earliest Cretaceous collisional event produced a short compressional episode, lifting up the investigated segment of the overriding East Vardar Zone
Karakteristike kompozitnih materijala na bazi polilaktidne kiseline (PLA)
Get PDFPolylactic acid (PLA) is aliphatic thermoplastic polyester. Composites based on PLA are biocompatible,
biodegradable and non-toxic, which are the main advantages of using such composites. Based on the
research results described in this paper, it was concluded that by adding natural fibers to the composite,
certain characteristics can be significantly improved. This paper describes some of composite material
characteristics based on PLA, modification of PLA, advantages and disadvantages of using PLA in
composite materials, composition and methods of obtaining PLA-based composites, as well as the
advantages of using wood plastic composites (WPC) based on PLA.Polilaktidna kiselina (PLA) je alifatični termoplastični poliester. Kompoziti na bazi PLA su biokompatibilni, biorazgradivi i netoksični, što čini glavne prednosti upotrebe ovakvih kompozita. Na osnovu rezultata istraživanja opisanih u ovom radu, došlo se do zaključka da se dodavanjem prirodnih vlakana kompozitu mogu znatno poboljšati pojedine karakteristike kompozita. U radu su opisana neke karakteristike kompozitnih materijala na bazi PLA, modifikacija PLA, prednosti i nedostaci upotrebe PLA u kompozitnim materijalima, sastav i metode dobijanja kompozita na bazi PLA, kao i prednosti upotrebe WPC kompozita na bazi PLA
Recycling and Reuse of Building Materials in a Historical Landscape—Viminacium Natural Brick (Serbia)
Get PDFDuring the MoDeCo2000 scientific and research project on mortars used in the territory of the Roman Danube Limes in Serbia, the biggest challenge was the quest for the provenance of raw materials. The area where Viminacium, the largest city in the province of Moesia Superior developed, with millennial continuity of land use and settlement, was selected as research case study and is presented in this research. People throughout history have always used what they had at hand, and the building remains were not only reused but also recycled for new constructions. Thus, the building material of Roman Viminacium has survived in the landscape through the in situ preserved remains of Roman buildings, as well as in the structures from the later periods, up to today. To the best of our knowledge, the use of natural sediments baked during the self-combustion or combustion of underneath layers (coal in our case) for the purpose of construction was extremely rare in the Roman Empire. In this study, we follow the presence of this type of material precisely in Viminacium construction, naming it natural brick, while focusing on its potential use in lime mortars whose production was perfected in the Roman period and has never been surpassed afterward. Archaeological contexts in which this material was found have been studied, along with simultaneous work in the laboratory and in the field during the research and experimental use of the natural brick in lime mortars. We sought to determine whether this material could have been recognised by Romans in Viminacium as a potential valuable pozzolanic component of mortar, along with or instead of fired brick, being locally available and recyclable. The final confirmation of its pozzolanic features and later discussion open completely new directions for the future research of Viminacium lime mortars
Vacuum Deposited Wide Bandgap Perovskite Solar Cells
No full textOver the last century the world population increased from 2 billion to approximately 8 billion, accompanied by an equally large rise in demand for energy. Nowadays the main energy sources are fossil fuels such as oil, natural gas and coal, that are finite and upon combustion release substantial amounts of CO2 in the atmosphere.[1] This gas is a major contributor to the greenhouse effect, leading to global warming and hence to climate change. Therefore, there is a need to implement renewable energy sources such as solar and wind, which are cleaner and more sustainable. The use of renewable energy sources has increased significantly, however, they still represent only a small percentage (approximately 15%) of the global energy generation. Hence, more efforts need to be undertaken in order to replace the use of fossil fuels and reduce their impacts on climate. The challenge is to continue to explore and develop new technologies that are more efficient, cost-effective and sustainable, helping to reduce greenhouse gas emissions and the use of finite resources. Among all renewable reserves, solar energy presents by far the planet’s largest energy source accessible
Assessing technological properties and environmental impact of fired bricks made by partially adding bottom ash from an industrial approach
Get PDFOver the past few decades, the fired clay brick industry has searched for industrial wastes to substitute raw clay deposits and lessen their impact on the environment. Despite several investigations showing positive results, industrial applicability is still scarce, mainly due to differences between industrial and laboratory procedures and the usage of certain wastes that already have added value in other circular economy chains. In addition, the assessment of such proposals commonly misses the environmental impact issue which is merely assumed to be positive. For these reasons this study, for the first time, has assessed together technological properties and the environmental impact of bricks made by strictly following industrial procedures. Hence, biomass bottom ash (BBA) was added at 9 replacement ratios, ranging from 2.5 to wt. 20.0% for making extruded bricks subjected to industrial drying and firing curves. Physical, thermal and mechanical properties of fired products were properly assessed and compared with the requirements set forth by Chilean standards. In addition, a life cycle impact assessment was developed to compare the ecological footprint among series. Although mechanical and water-proof requirements may limit the replacement ratio for exposed bricks, the feasibility of using BBA at industrial scale has been successfully demonstrated. Regarding the environmental impact, the raw clay may be replaced without adversely causing toxicity levels to exceed mandatory limits. However, this study demonstrated that the incorporation of BBA increases CO2 emissions due to the decomposition of contained carbonates during the firing process which compromise the results in terms of global warming potential and water consumption which highly impact on human health and ecosystems quality
The influence of the 2020 crisis on the demand for traditional and novel construction and building materials in Serbia
Get PDFEven though the specific COVID-19 consequences for sales have been extensively
discussed, no academic research has been done on how the pandemic has affected
consumer choice and purchases of construction and building products by private
individuals. This research was conducted to fill in the gaps in the body of knowledge
and advance understanding of how the crisis has impacted wages, market prices,
and material usage in the construction industry in a developing country. The data
are collected through the use of a questionnaire survey. The respondents shared
their experiences between the period before 2020 and after the beginning of the
crisis up until the end of 2022 and showed that purchases of these products
decreased during the lockdown and afterward. The obtained results were analyzed
using statistical tools, namely frequencies, descriptive statistics, and constructs.
This study reveals a high interest in using novel materials but also a desire to be
more informed on the details and their potential benefits. The results present a first of-
a-kind approach that will help further development in this branch of the industry
by following the needs of potential private customers in a developing country.
Further studies would need to include not only contextual but also personal factors
that influence environmentally friendly choices
Influence of Temperature on Impact Toughness of HSLA Steels
Get PDFThe aim of this paper is to present the influence of differ-ent temperatures on the impact toughness of welded joint of high strength low-alloy steel. The results of impact tests for all three constituents of the manual arc welded joint of NN-70 steel at temperatures range from 20 °C to -100 °C are presented. It has been shown that impact tests of high-strength low-alloy (HSLA) steels at room and lower tem-peratures indicate that temperature significantly affects the toughness of high-strength low-alloy steels in the context that lowering the test temperature leads to creation of brittle fracture in the form of a successive decrease in total impact energy. This indicator is very important in the further design and exploitation of welded steel structures