Repository of the Institute for Material Testing (RIMS)
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Svojstva teškog SCC sa letećim pepelom
No full textLeteći pepeo je visoko efikasan mineralni aditiv čija se uloga ogleda u poboljšanju mikrostrukture, čvrstoće i izdržljivosti kompozitnih građevinskih materijala kao što je samozbijajući beton (SCC). Referentni SCC je projktovan sa portland cementom, rečnim agregatom i krečnjačkim filerom. Eksperimentalni program obuhvatao je proizvodnju pet samozbijajućih betona sa različitim vrstama sitnog agregata, filera i specijalnog dodatka za povećanje otpornosti na dejstvo mraza. Ispitivani su i diskutovani efekti koje baritni pesak i dodaci imaju na svojstva svežeg SCC (sleganje rasprostiranjem, test V-levka i test L-kutije) i čvrstoću pri pritisku
Possibility of Using Other Additives as Replacement for Air Entraining Admixture in Concrete
No full textConcrete in which the air entraining admixture was used can exhibit behavior which alternate from the ‘standard’ concrete behavior when employed in the structural design. The origin of this problem can be found in the changeable properties of the componential materials, incompatibility of the utilized raw materials, influence of extreme conditions on the concrete curing (i.e., increased temperature), etc. The possibility of using other additives for the concrete exposed to various environmental influences was investigated. Sustainability of concrete production and resource efficiency urged the searching for an adequate waste material or an industrial byproduct which would improve freezing/thawing resistance of concrete. In this paper the possibility of Sika Aer Solid powdery additive and recycled rubber as a substitute for the air entraining admixture was investigated. Four mixtures were designed: referent concrete with no air entraining admixtures, concrete with Sika Aer Solid, concrete with recycled rubber, and concrete with air entraining admixture. The properties of fresh and hardened concrete were examined. The obtained results of compressive strength, resistance to freezing/thawing cycles and depth of water penetration under pressure for altered concretes indicate that it is possible to use alternative additives as substitutes for air entraining admixture
Contribution to geology and genetic pathway of the Ropočevo breccia – an "orphan" olistolithic body within the Upper Cretaceous flysch near Sopot (central Serbia)
No full textThe Ropočevo breccia, a dimension stone highly prized in 20th century, has been examined by numerous prominent geologists of the time. It is revisited by researchers still intrigued by its perplexing provenance. Its position as a rigid exotic block of hard and completely metamorphosed carbonate breccia within the moderately lithified Upper Cretaceous flysch sequence remains unsolved due to absence of its source. Large bodies of a monomictic breccia suggest a relatively monotonous protolith carbonate sequence of significant thickness, such as those being formed in a calm marine environment with gradually sinking bottom due to epeirogenic movements. Varicoloured laminations indicate slight variations in the feeding material due to the epeirogenic oscillation of the basin bottom level. There is no regularity in clast distribution regarding size, colour or roundedness degree. This, paired with the occurrence of the "in-place brecciation" suggests a sudden fall of brecciated material due to a "catastrophic" event, such as earth-quake, collapse brecciation due to karst dissolution and a large sinkhole formation, or a graben/trench formation as in onset of the extensional processes
Measurement and modeling of thermal conductivity of loess at the location of the Airport Nikola Tesla in Surcin
Get PDFThe thermal conductivity of a material is the parameter that is most reliably determined experimentally. The problem of determining the thermal conductivity in the soil is greater because the soil is heterogeneous, so for the same soil this parameter may be different depending on the their ohysical characteristics. Therefore, it is necessary to adopt an appropiate model for describing the thermal conductivity of the soil for a particular location after the necessary tests are performed. This paper is based on experimental measurements of soil thermal conductivity as a function of moisture content in the area of the ,Nikola Tesla Airport construction site in Surčin and the adoption of one of the existing theoretical models that would satisfactorily describe changes in thermal consuctivity. Based on the obtained results of experimental reasearche, a two- parameter fitting of the measured values of thermal conductivity of the soil was performed in Cote-Konrad model, which proves to be reliable and the simplest to describe the thermal properties of loess in the area of Belgrade
Fire resistance testing of fire doors
Get PDFFire-resistant doors are widely used as part of passive fire protection systems, preventing the spread of fire and smoke beyond the fire compartment. Fire resistance is usually determined through standard fire tests in accredited laboratories, such as the Laboratory for thermal technique and fire protection in Institute IMS, Serbia. Current regulations in Serbia allow testing of fire doors according to two standards: Serbian national SRPS U.J1.160 [1] and European SRPS EN 1634-1 [2].
In the past five years, 236 samples of different fire doors were tested. Most of them were single-leaf, steel doors. Although almost one third (31%) of all samples (tested on 15, 20, 30, 45, 60, 90, 120, 180, 240 and 380 minutes) provided fire resistance of 120 minutes, which should be sufficient for the safe evacuation of people, as well as the protection of expensive equipment (hospitals, rooms with electrical devices, etc.).Samples usually fail the test when sustained flaming occurs on the unexposed side in the upper corner of the specimen (lock side), or when the temperature measured by thermocouples exceeds the limitation given in the standard, usually at the top corner (lock side).In this paper, both currently valid standard testing procedures are analysed and compared
The role of drainage systems in the prevention of material degradation of bridge structures
Get PDFThe paper gives an illustrative presentation of damage to the material of bridge structures
due to failure to maintain the system for drainage of bridges. Damage is caused by mechanical
erosion and abrasion or by chemical means, corrosion or a combination of the above. The cause of
the damage is related to the retention of salted water on the road and other surfaces of the bridge
structure, as well as wetting of the side and ceiling surfaces by flooding due to the non-functionality
of the water drainage system from the bridge. The possibility of taking measures to prevent such
phenomena and reduce them to a minimum is also considered
Effect of temperature and specimen orientation on Charpy impact toughness
Get PDFSteel grade 14MoV6 3 is used for manufacturing of boilers and steam pipelines designed for steam temperatures up to 560°C. This paper presents the experimental analysis which included impact toughness test. The analysis resulted in impact energy values, and their respective components, crack initiation and crack propagation energy, and represents the initial stage of extensive research involving the behavior of 14MoV6 3 steel. The aim was to determine the effects of temperature (room vs. operated), as well as the effects of specimen orientation with regards to the rolling direction, on the impact toughness and the relation between its components
Ojačanje postojećeg AB zida radi zaštite puta od odrona
Get PDFU radu su prikazane sanacione mere zaštite od odrona na državnom putu IB-23, deonica puta broj 02332, Mijoska – Gostun. Odroni su česta pojava na strmim kosinama koje izgrađuju ispucale stenske mase nakon perioda velikih kiša ili usled otapanja snežnog pokrivača. U maju 2017. i februaru 2022. godine odigrala su se dva velika odrona što je onemogućilo dalje odvijanje saobraćaja na ugroženom putnom pravcu. Prvobitna sanaciona mera 2017 g. i najbrže rešenje u pogledu bezbednog odvijanja saobraćaja bilo je izvođenje armiranobetonskog zida. Trajnje rešenje za zaštitu puta od potencijalnih odrona bilo je izvođenje armiranobetonske galerije nakon odrona 2022. g. Rad se odnosi na povećanje kapaciteta nosivosti i stabilnosti postojećeg potpornog zida za prijem povećanih vertikalnih i horizontalnih uticaja za slučaj da se usvoji AB galerija kao trajnje rešenje zaštite od odrona
Neural network model for the condition assessment of hydro turbines
No full textDuring regular operation, hydro turbine elements have complex operating conditions. In order to prevent major failures, among other common preventive measures, it is necessary to make a useful model of hydro turbine. Development of this model was focused on real elements and data set of real operating history. To solve this, an integral diagnostic approach is used. Based on the real diagnostics data of the condition and data history of the hydro turbine shaft and the designed life expectancy, a multi-layer perceptron (MLP) based artificial neural network (ANN) is built. The idea with this model was to enable to life assessment of the turbine shaft in any particular moment during regular operation.
This paper describes a model for estimating the condition of the shafts of turbines of the current generator in Hydropower plant Derdap 2. The significance of this approach is that real experimental data support development of ML ANN (number of neurons and layers) topology, which is optimal for this model, training and testing. Results obtained from this model are used for decision-making about the planning time schedule of maintenance actions, as well as reducing overhaul time and direct losses
Testing of building materials - reaction to fire
Get PDFTo reduce occurrence of fires in buildings as efficiently as possible, it is necessary to take into account active and passive fire protection measures during construction of building. This paper will show more about passive fire protection measures related to the selection of adequate material to be used during construction, which contributes to the localization of fire and prevents it from spreading to other rooms and facilities.
All products, which are planned by project, must have adequate certificates not to contribute to the development of fire, as well as to meet the class of fire resistance. In the Republic of Serbia, only the Laboratory for Thermal Engineering and Fire Protection, within the IMS Institute, deals with this type of testing and issuing reports.
This paper will present test methods for obtaining a fire reaction class. After the tests, according to the standard SRPS EN 13501-1, a Classification Report is issued in which the final fire reaction class is given for the tested product whose validity lasts for 5 years