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Netinger I.,Josip Juraj Strossmayer University of Osijek | Varevac D.,Josip Juraj Strossmayer University of Osijek | Bjegovic D.,University of Zagreb | Bjegovic D.,Civil Engineering Institute of Croatia | Moric D.,Josip Juraj Strossmayer University of Osijek
Fire Safety Journal | Year: 2013

The use of slag as a fire-resistant aggregate was investigated in concrete and in structural members. Three mixtures of three-fractional concrete with type CEM I 52.5 N cement were prepared: the reference mixture (dolomite fractions of 0-4 mm, 4-8 mm and 8-16 mm) and two mixtures with coarse slag fractions (4-8 mm and 8-16 mm) and a fine dolomite fraction (0-4 mm). At 56 days the specimens were exposed to high temperatures. Their residual mechanical properties (flexural strength, compressive strength and static modulus of elasticity) and residual mass were tested after cooling, and results were compared among specimens. To determine the fire resistance of a structural member with slag in the concrete mixture, fire resistance of reinforced-concrete beams with slag was compared with that of reinforced-concrete beams with dolomite. In these experiments, concrete beams were exposed to high temperature according to the ISO 834 temperature curve for 60 min. The temperature increase within the beams during their exposure to high temperature in the furnace was also observed. Bearing capacity was tested after fire exposure and compared with bearing capacity of the beams at room temperature. The results showed that slag in combination with Portland cement did not increase fire resistance of concrete and its structural members. In order to create a structural member with improved fire resistance, slag should be combined with a binder that can better adapt to slag expansion under high temperature or be used as a partial replacement for coarse aggregate in concrete. © 2013 Elsevier Ltd. Source


Jurak V.,University of Zagreb | Ortolan Z.,RNK Geomod d.o.o | Slovenec D.,University of Zagreb | Mihalinec Z.,Civil Engineering Institute of Croatia
Summa Phytopathologica | Year: 2011

The engineering-geological/geotechnical correlation column can be established in zones of limited extent using one or several characteristic layers, one of which is selected as the reference layer. The Reference Level of Correlation method, i.e. the RNK (Referentni nivo korelacije in Croatian) method, is a confirmed procedure enabling the establishment of such columns. In the engineering geological/geotechnical correlation column, the plasticity index is the most significant indicator of the peak friction angle, full-softening friction angle and residual friction angle for coherent soils and soft rock formations. As a rule, maximum plasticity index values correspond to the minimum values of such friction angles. This opens up the possibility of an exact engineering-geological/geotechnical model, with accurate differentiation of minimum shear strength zones, zones of different permeability, and zones of various degrees of natural compaction. This procedure was applied inter alia on the successfully improved Granice landslide located in the Zagreb area, where it was proven that elements for verification based on the RNK-method exist for all three areas of investigation: sliding body - drain trench section - detail in the central portion of the sliding zone. The procedure is recommended as a means for finding solutions to similar problems. Source


Bezjak M.,Civil Engineering Institute of Croatia | Zvizdic D.,University of Zagreb
International Journal of Thermophysics | Year: 2011

Measurements of the thermal conductivity of insulators that are commonly used in civil engineering are as a rule performed using Pönsgen's guarded hot-plate method under steady-state conditions. Achieving these steady-state conditions is a time consuming and relatively expensive procedure. Therefore, the application of a method that is less time consuming and less costly to common building insulating materials is of interest. The method should also have the accuracy and repeatability comparable to that of presently used methods. One such method is the transient hot-wire method (predominantly used for liquids, non-Newtonian fluids, plastics, semi-plastics, and similar materials), a dynamic method that uses a very thin pure platinum wire that functions as a thermal source in combination with a temperature sensor that detects temperature transients. This article describes the application of the transient hot-wire method to most commonly used building thermal insulating materials. The transient hot-wire measurements of the thermal conductivity were performed on many building material samples. For the sake of comparison, the thermal conductivity of samples made from the same materials was also tested using the stationary Pönsgen's guarded hot-plate method. This article describes the comparison and evaluation of the measurement results obtained from both methods as well as the estimation of pertinent measurement uncertainties. The results are presented in graphical and numerical form in tables and diagrams for each type of thermal insulator. © 2011 Springer Science+Business Media, LLC. Source


Arbanas Z.,University of Rijeka | Vivoda M.,University of Rijeka | Kursar P.,Civil Engineering Institute of Croatia
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses - Proceedings of EUROCK 2014, ISRM European Regional Symposium | Year: 2014

A business center's 4-story underground garage in the center of Rijeka, Croatia is under construction. The excavation of an open pit for the underground garage commenced during Spring 2012 and was completed in December 2013. The construction site is located very close to an old shallow railway tunnel constructed in 1870. The tunnel was constructed without any rock mass reinforcement. The excavation pit for the underground garage is located only 6.0m from the side of the existing railway tunnel. The pit excavation had a significant effect on the existing tunnel construction; thus, a reinforcement of the rock mass using rock bolts and multi-layered reinforced sprayed concrete was embedded. In this paper we present a design for pit construction including numerical models and geotechnical analyses. Based on these analyses, a required reinforcement of rock mass around the tunnel and an appropriate support system for the stabilization of pit walls was designed and executed. © 2014 Taylor & Francis Group, London. Source


Netinger I.,Josip Juraj Strossmayer University of Osijek | Bjegovic D.,University of Zagreb | Bjegovic D.,Civil Engineering Institute of Croatia | Vrhovac G.,Civil Engineering Institute of Croatia
Materials and Structures/Materiaux et Constructions | Year: 2011

This paper aims to investigate the possibility of utilizing steel slags produced in Croatian plants as a concrete aggregate. Aggregate properties were determined on coarse slag fractions (4-8, 8-16 mm) according to the relevant European Standards. Considering the obtained results, slags were specified in accordance with the classes as given in the main European standard for aggregates, whereupon these classes were compared to the Croatian regulation requirements. The obtained results proved that coarse slag fractions can be suitable for concrete application. Therefore, concrete mixtures were prepared with coarse slag fractions whose hardened state properties (compressive and flexural strength, static modulus of elasticity, volume changes and corrosion susceptibility) were then compared with the properties of reference concrete made of commonly used natural aggregate materials, namely dolomite. According to the obtained test results it can be concluded that the observed slags can be a good substitute for natural aggregate materials. © 2011 RILEM. Source

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