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Influence of cement replacement with limestone filler on the properties of concrete
No full textThis paper presents an experimental research of one type of green concrete in which Portland cement was replaced with two types of limestone filler of the same origin and mineralogical composition, but with a different fineness of particles. Ten concrete mixtures were designed in which 0%, 15%, 30% and 45% (by mass) of cement were replaced with filler. The water to cement ratio for each mixture was constant (w/c=0.54), and the water to powder ratio was decreasing with increasing cement replacement. Particle size distribution was selected using Funk and Dinger, as well as using Fuller's model. The results showed that it is possible to increase the compressive strength of concrete by reducing 45% of cement, but further research should be focused on improving the workability
Strength of the Welded Joint with Improved Mechanical Properties of Weld Metal and Heat Affected Zone
Get PDFSelection of steel, dimensions and fabrication technology for the welded structure are all parts of the design
process, because they are in close connection with the function of the structural whole under certain conditions of
exploitation for the predicted service life. Quality of welded joints in the process of production of the welded structure is
being defined by properties that the structure has to possess in order to fulfill certain requirements, which is being
accomplished by the selection of the adequate welding procedure and welding parameters, implementation of inspection
programs for all technological operations, as well as by performing mechanical and technological tests in order to
determine the magnitude of strength and deformation of base material and welded joints. Constituent parts of a welded
joint are base material, heat affected zone and weld metal. Heat affected zone of structural steels is being characterized by
the fusion zone, overheating zone, zone of complete normalization and zone of incomplete normalization.
In this paper the effect of change in hardness of weld metal and heat-affected zone on mechanical properties of
welded joints when base material is quenched and tempered steel C45 is being considered. Test results showed that the
application of welded structures made of quenched and tempered steels with hardness HV10 > 400 and tensile strength
UTS > 600 MPa is useful only when the stress concentration is low (αs ≤ 2) and when there are no residual stresses due to
welding
Improvement of at-welding technology of railway rails with different cross sections
Get PDFU radu je prikazana nova tehnologija aluminotermijskog zavarivanja (AT) prelaznih šina 49E1 na 60E1(EN 13674-1:2005.), oslonjena na potpuno nove materijale. Ona se odnosi na pešćane kalupe kod kojih su oblik i dimenzije ulivnog sistema projektovani tako da mogu odgovoriti svim zahtevima za postizanje zavarenih spojeva zadatog kvaliteta. Da bi ovaj zahtev bio u potpunosti ispunjen, projektovana je, takođe, AT smeša, čijom se aktivacijom dobija termitni čelik za ispunu, sa temperaturom izlivanja koja obezbeđuje optimalnu livkost metala, kao i viskoznost troske. U radu su zatim prikazani rezultati ispitivanja probnih prelaznih zavarenih spojeva, shodno standardima JŽS.Z2.610 i EN 14730-1:2012, a odnose se na utvrđivanje mehaničkih svojstava zavarenih spojeva, makrostruktirnih i mikrostrukturnih karakteristika, homogenosti i hemijskog sastava termitnog čelika za ispunu. Dobijeni rezultati pokazuju da je primenjena tehnologija optimalna, jer obezbeđuje upotrebu ove tehnologije u industrijskim uslovima na železnici.The paper presents a new aluminothermic (AT) welding technology of 49E1 transition rails on 60E1 (EN 13674-1: 2005), based on entirely new materials. It refers to sand molds in which the shape and dimensions of the inflow system are designed to meet all requirements for achieving welded joints of a given quality. The AT mixture was also designed to fulfill those requests; resulting liquid steel has a casting temperature that ensures optimal castability of the metal and slag viscosity. The paper presents the test results of the transients welded joints, following the standards JŽS.Z2.610 and EN 14730-1: 2012, and relates to the determination of mechanical properties of welded joints macrostructural and microstructural characteristics, homogeneity, and chemical composition of thermite steel. The obtained results show that the applied technology is optimal because it ensures the use of this technology in industrial conditions on the railway
Lamellar Tearing of Parent Material and Degradation of Welded Joints at Vital Welded Structures
Get PDFVertical Kaplan turbines, manufactured in Russia, are
installed in 6 hydroelectric generating units at ‘Djerdap 1’, with
nominal power of 176 MW each. Because of the structural
solution and inability of performing periodic inspections and
state analyses, 40 years long service life of the turbine and upper
ring of guide vane apparatus was predicted. Welded structures of
the turbine cover and upper ring of guide vane apparatus consist
of 4 segments made of steel St 3, in accordance with GOST 380-
94. Flux-cored arc welding was used in order to merge the
segments.
Non-destructive and destructive tests were performed on parent
material and welded joints during the rehabilitation of the
hydroelectric generating set A4, in order to carry out the
condition analysis and assessment of the level and cause of
eventual degradation of structures of the turbine cover and upper
ring of guide vane apparatus at hydro power plant ‘Djerdap 1‘.
In this paper the analyses that refer to determination of the cause
of lamellar tearing of parent material in the area of welded joints
based on results of magnetic particle testing and ultrasonic
testing are presented
Određivanje otpornosti na proklizavanje podnih obloga i pešačkih staza – metode vrednovanja
No full textModifikacija i unapređenje energetsko-disperzivne rendgensko fluorescentne metode za određivanje sadržaja deset elemenata u eluatima cementnih veziva
No full textVerifikacija tehničkog rešenja (Naučno-nastavni veće): Institut za ispitivanje materijala IMS, Bulevar vojvode Mišića 43, Beograd, Srbija
Korisnik/naručilac: Institut za ispitivanje materijala IMS, Bulevar vojvode Mišića 43, Beograd, Srbija (Centar za materijale; Laboratorija za veziva, hemiju i maltere)
Napomena: TR je softversko rešenje koja zadovoljava kriterijum otvorenog izvora, umesto ugovora o prodaji, kao dokaz se prihvata opis tehničkog rešenja u časopisu adekvatne kategorije (M21a) (Pravilnik "Sl. glasnik RS", br 24/2016, 21/2017, 38/2017 i 159/2020). godina izrade: 2021. godina prihvatanja TR od strane: TR je verifikovano na MNO za Materijale i hemijske tehnologije 2021. god. (sednica MNO 29.11.2021, potvrda 13.12.2021
Comparison of cover meter and ground penetrating radar performance in structural health assessment: case studies
No full textAn essential step in the condition assessment of reinforced concrete structures and evaluation of the residual capacity is the determination of the arrangement and quantity of reinforcement as well as the geometry of the structural elements. The objective of this paper is to present the fundamentals in the application of two non-destructive methods, cover meter and ground penetrating radar, in the determination of the above structural features. A comparison of the two methods is presented and their capabilities, advantages and disadvantages are shown through nine case studies
Uticaj zamene cementa krečnjačkim filerom na svojstva betona
No full textU radu su prikazana eksperimentalna ispitivanja jedne vrste zelenih betona kod kojih je Portland cement zamenjen sa dve vrste krečnjačkog filera istog porekla i mineraloškog sastava, a različite finoće mliva. Projektovano je deset mešavina kod kojih je 0%, 15%, 30% i 45% (maseno) cementa zamenjeno filerom. Vodocementni faktor bio je konstantan (w/c=0.54), dok je vodopraškasti opadao sa povećanjem procenta zamene. Izbor granulometrijskog sastava čestica izvršen je pomoću Fankovog i Dingerovog, kao i pomoću Fulerovog modela. Rezultati su pokazali da je moguće povećanje čvrstoće betona pri pritisku uz smanjenje 45% cementa, ali da buduća istraživanja treba usmeriti ka poboljšanju obradljivosti
Influence of corrosion-induced damage in reinforced concrete on GPR signal parameters
No full textGround penetrating radar (GPR) is a non-destructive technique (NDT) that is mainly used to locate
reinforcement in structures. Even though several studies have shown promising results in
characterizing corrosion with GPR, more research should be conducted on the effects of corrosion
on GPR signal parameters. This paper presents experimental work aimed at observing the
effects of water, water contaminated with chlorides, and corrosion-induced cracks in reinforced
concrete, on the ground penetrating radar signal strength. Two reinforced concrete specimens
with two reinforcing bars were cast; one to observe the influence of water and the other to observe
the influence of water contaminated with chlorides and ccorrosion-induced cracks on GPR
signal. The results show that, with the presented experimental setup, the changes due to these
effects are small. Immersion in water for 11 days caused a decrease in amplitude of 3.7 %, 11.2 %
for immersion in water contaminated with chlorides, and 12.69 % for a 0.8 mm crack
