Building Testing and Research Institute

Košice, Slovakia

Building Testing and Research Institute

Košice, Slovakia
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Paulik P.,Slovak University of Technology in Bratislava | Hudoba I.,Slovak University of Technology in Bratislava | Sevcik P.,Building Testing and Research Institute
Solid State Phenomena | Year: 2016

Gas permeability of concrete is a property, which is recognized as one of the basic indicators of its durability. Measuring of the air permeability is mostly carried out on samples, which are not exposed (before or during the tests) to any certain external loads, which could cause microcracks in hardened cement matrix. However, in the case of real structures there is always some stress level and thus the concrete permeability is usually affected by microcracks. To know both, permeability of sound concrete and the permeability of concrete containing certain amount of microcracks, is the basic assumption for correct evaluation of its durability. Our paper deals with the permeability of loaded specimens made of high performance fibre reinforced concrete (HPFRC). This type of concrete is in Slovakia used for the construction of containers for a low and medium level radioactive waste storage and thus their properties in loaded conditions are of primary concern. Permeability was measured with Torrent Permeability Tester on cube specimens at different loading levels and after unloading. Specimens were 10 years old and varied in the amount of fibre reinforcement. © 2016 Trans Tech Publications, Switzerland.

Krajci L.,Slovak Academy of Sciences | Moujmdar S.C.,University of New Brunswick | Kuliffayova M.,Slovak Academy of Sciences | Janotka I.,Building Testing and Research Institute
Journal of Thermal Analysis and Calorimetry | Year: 2010

Two types of raw materials, original kaolin sand OKS I and OKS II were used for experiment. They were transformed (1 h at 650 °C with 10 °C/min temperature increase) to burnt kaolin sand (BKS I and BKS II) with pozzolanic properties. Contents of decisive mineral-metakaolinite-in BKSs are as follows: BKS I (fraction below 0.06 mm) 20%; BKS II (fraction below 0.06 mm) 36% and BKS II (fraction below 0.1 mm) 31% by mass. Mortars with blends of Portland cement (PC) and BKS were prepared announced as: MK I (0.06) with 5 and 10% cement substitution by metakaolinite; MK II (0.06) with 5 and 10% cement substitution by metakaolinite and MK II (0.1) with 5, 10, 15 and 20% cement substitution by metakaolinite. The reference mortar with 100% of PC was made for comparison. All mortars were adjusted on the constant workability 180 ± 5 mm flow. Besides significant increase in compressive strengths-the refinement of pore structure in mortars with BKS connected with decreases in permeability and Ca(OH)2 content were revealed. The above facts confirm pozzolanic reaction of BKS in contact with hydrated PC and indicate perceptiveness of BKS for the use in cement-based systems as a pozzolanic addition. © Akadémiai Kiadó, Budapest, Hungary 2010.

Martauz P.,Cement Plant Povazska Cementaren | Janotka I.,Building Testing and Research Institute | Strigac J.,Cement Plant Povazska Cementaren | Bacuvcik M.,Building Testing and Research Institute
Materiales de Construccion | Year: 2016

Utility properties of novel hybrid cement (H-Cement) are influenced by pozzolanic reaction of fly ash, latent hydraulic reaction of metallurgical slag together with the alkali activation of inorganic geopolymer based on precipitated waste water coming from bauxite residues. Content of Portland cement clinker is at maximum of 20 mass %, the remaining portion consists of inorganic geopolymer. Up to 80% of CO2 emissions are saved by H-Cement manufacture compared to ordinary Portland cement (OPC). No heat treatment or autoclaving is needed at H-Cement production. The field application of H-Cement is performed by the same way than that of common cements listed in EN 197-1, and is also connected with highly efficient recovery and safe disposal of red mud waste. H-Cement is suitable for ready-mixed concretes up to C30/37 strength class and is specified by beneficial shrinkage-reducing property of the concrete kept in long dry-air cure opposite to common cements. Copyright: © 2016 CSIC.

Osacky M.,Comenius University | Osacky M.,Building Testing and Research Institute | Sucha V.,Comenius University | Czimerova A.,Slovak Academy of Sciences | Madejova J.,Slovak Academy of Sciences
Applied Clay Science | Year: 2010

The stability of seven dioctahedral smectites coming from bentonites of different origin was studied in the presence of iron to simulate the possible reactions between clay minerals and Fe canisters in a nuclear waste repository. The batch experiments were performed at 75°C for 35. days in a nitrogen atmosphere. The reaction products were examined by XRD, FTIR, HRTEM, BWA analysis and UV-Vis spectroscopy. Magnetite and 7-Å clay minerals (berthierine-like) were the main reaction products besides iron-smectite reaction. Bentonites reacted differently with iron. The quantitative XRD revealed that consumption of iron and formation of magnetite was significantly higher for Fe-rich smectites. Fe-rich smectites were the most affected by the reaction. This indicated that the octahedral iron ions may be largely responsible for smectite decomposition indicated by the decrease of the smectite content, partial dehydroxylation of its structure and alteration of octahedral and tetrahedral sheets. The layer charge and thickness of the smectites decreased during the reaction. Arrangement of the smectite layers was apparently changed, and rather large particles were split into thinner particles or even layers. © 2010 Elsevier B.V.

Janotka I.,Building Testing and Research Institute | Janotka I.,Slovak Academy of Sciences | Puertas F.,CSIC - Eduardo Torroja Institute for Construction Science | Palacios M.,CSIC - Eduardo Torroja Institute for Construction Science | And 2 more authors.
Construction and Building Materials | Year: 2010

In the present work, the use of three Slovak poor metakaolin sands with different metakaolin content (36.0% (MK-1), 31.5 (MK-2) and 40.0% (MK-3)) and specific surface has been deeply studied as mineral addition for Portland cement. The percentage of metakaolin sands in the blended cements was 10%, 20% and 40%. The pozzolanic tests confirm that the three metakaolin sands show a high pozzolanic activity, comparable to a commercial metakaolin and silica fume. With respect to the rheological behaviour, metakaolin sand-blended-cement pastes fit to Herchel-Bulkley model and their yield stress increases as the metakaolin content increases. MK-3 sand with the highest pozzolanic activity and highest specific surface induces the highest increase of the yield stress. From the calorimetric results it is concluded that the addition of MK-1 and MK-2 sands to Portland cement induces a delay up to 2 h of the precipitation of the main hydration products in the blended-cement pastes and decreases the maximum heat evolution rate. On the contrary, the incorporation of 40% of MK-3 sand shortens 6 h its apparition and increases significantly the maximum heat evolution rate. Additionally, the presence of the metakaolin sands reduces the heat released during the hydration process with respect to non-blended-cement pastes. The incorporation of metakaolin sand induces a decrease of the mechanical strength, being the decrease higher as the metakaolin sand content increases although they also produce a refinement in the pore structure and a decrease of the permeability. © 2009 Elsevier Ltd. All rights reserved.

Frankovska J.,Slovak University of Technology in Bratislava | Andrejkovicova S.,Slovak Academy of Sciences | Janotka I.,Building Testing and Research Institute | Janotka I.,Slovak Academy of Sciences
Geosynthetics International | Year: 2010

Sodium bentonite (Na-bentonite) is used as a sealing component in geosynthetic clay liners (GCL). Na-bentonite is very sensitive to chlorides, and flocculation occurs when it is exposed to saline environments. The purpose of this work is to investigate the properties of Na-bentonite and bentonite-palygorskite filler material for GCL in saline solutions in the range between 0.5% and 10% (0.09 and 1.8 M) NaCl concentration. The investigation has been carried out to evaluate and study the chemical and geotechnical properties of Na-bentonite and bentonite-palygorskite mixture. The observations suggest that the resistance of Na-bentonite to chlorides is increased by adding 40% palygorskite. The bentonite-palygorskite mixture is characterised by high liquid and plastic limits, and also by high water adsorption and free swell in water, crude oil and petrol. Hydraulic conductivity was determined for water and for 10% NaCl (1.80 M) solution. The results show that Na-bentonite palygorskite mixture serves as an effective absorber of both water and saline solutions up to a concentration of 10% (1.80 M) of NaCl without increasing the hydraulic conductivity. © 2010 Thomas Telford Ltd.

Sadovsky Z.,Slovak Academy of Sciences | Krivacek J.,Slovak Academy of Sciences | Ivanco V.,Technical University of Košice | Duricova A.,Building Testing and Research Institute
Journal of Constructional Steel Research | Year: 2012

Computational modelling of the buckling strength of cold-formed steel members as influenced by initial geometric imperfections is studied. The geometric imperfections are represented by the member eigenmode shapes. Along with the classical measure - the amplitude of imperfections, an energy measure defined by the square root of the elastic strain energy hypothetically required to distort the originally perfect structural element into the considered imperfect shape is used. Based on the measures, two approaches for the choice of the most unfavourable imperfections are suggested. Normalising imperfections by the amplitude, the energy measure is calculated as indicative parameter of imperfection significance. Vice versa, when adopting normalisation by the energy measure, the amplitude is used as a supporting parameter. The suggestions are illustrated on calculating the strength of an axially compressed steel lipped channel column with eigenmodes exhibiting local-distortional interactions. For eigenvalue and geometrically and materially non-linear strength calculations, the FEM codes MSC.NASTRAN and COSMOS/M are employed. © 2012 Elsevier Ltd. All rights reserved.

Krajci L.,Slovak Academy of Sciences | Kuliffayova M.,Slovak Academy of Sciences | Janotka I.,Slovak Academy of Sciences | Janotka I.,Building Testing and Research Institute
Procedia Engineering | Year: 2013

The advancement of cement composites with different pozzolana types represents needful domain in civil engineering. Utility properties of such composites are closely approaching the level of standard quality. The raw materials - kaolin sand thermally transformed at 650 °C/hour and clayey diatomite calcined at 900 °C/hour were used in the experiment. Cement ternary composites containing 5 and 10 wt.% of metakaolinite as well as 5 and 10 wt.% of calcined clayey diatomite (in varied proportions) with water to solid ratio of 0.5 were manufactured for this study. The physical-mechanical and physical-chemical behaviour of relevant ternary systems after 28-days water curing are presented in this paper. Thermal analysis disclosed calciumsilicate hydrate (CSH) and calciumaluminate hydrate (CAH) formation, portlandite dehydroxylation and calcite decarbonation. Portlandite content reduction was found as a result of respective pozzolanic reaction unlike reference composite without pozzolana. This statement was confirmed by X-ray diffraction analysis. The favourable standard mechanical properties (compressive strength) in this study of composites were documented as well. Results exhibit the effective pozzolanic reaction susceptible the attainment of valuable utility properties of cement composites. © 2013 The Authors. Published by Elsevier Ltd.

Kuliffayova M.,Slovak Academy of Sciences | Krajci L.,Slovak Academy of Sciences | Janotka I.,Slovak Academy of Sciences | Janotka I.,Building Testing and Research Institute | Smatko V.,Slovak Academy of Sciences
Journal of Thermal Analysis and Calorimetry | Year: 2012

The kaolin sand containing 36 wt% of kaolinite was thermally transformed at 650 °C/L h to the burnt kaolin sand (BKS) with relevant content of metakaolinite. Thermal behaviour of composites with substitution of Portland cement (PC) by the BKS containing 0, 5, 10 and 15 wt% of metakaolinite and water-to-solid ratio of 0.5 kept for 90 days in 20 ± 1 °C water was studied by thermal analysis. TG/DTA/DTG studies concerned calciumsilicate hydrate and calciumaluminate hydrate formation, portlandite dehydroxylation and calcite decarbonation. The influence of curing time and metakaolinite content were estimated. The reduction in portlandite content was observed in PC-BKS composites opposite to that found in the reference PC system. Compressive strength uptakes were observed in PC-BKS composites relative to that of reference PC system. BKS is characterized as effective pozzolanic material giving cement composites of high performance. The above findings were confirmed by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) results. © Akadémiai Kiadó, Budapest, Hungary 2011.

Ladomersky J.,Matej Bel University | Janotka I.,Building Testing and Research Institute | Hroncova E.,Matej Bel University | Najdena I.,Building Testing and Research Institute
Journal of Cleaner Production | Year: 2016

Cupola foundry slag has almost no utilisation. There has been no long term experience with the application of foundry slag in concrete production. This paper analyses the potential utilisation of cupola foundry slag. It also presents a proposal for processing and utilising granulated cupola slag from cast iron production in concrete products and the long term (one-year period) verification of its properties as a base for industrial scale application. The wt. 25.5% substitution of 0/4 mm fine natural aggregate by 0/4 mm cupola foundry slag in concrete (CFSC) declares the same or very similar main civil engineering properties when compared to control concrete (CC). The CC and CFSC concrete are not frost resistant according to STN EN 206/NA: 2015 requirement. This lack could be removed by increasing the entrapped air levels from the current 2.0-2.4 volume percent to around 5-6 volume percent in fresh concrete mixture. © 2016 Elsevier Ltd.

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