Browsing Ústav fyziky by Author "Topolář, Libor"
Now showing items 1-20 of 28
-
The Acoustic Emission Parameters Obtained during Three-point Bending Test on Thermal-stressed Concrete Specimens
Topolář, Libor; Kucharczyková, Barbara; Kocáb, Dalibor; Pazdera, Luboš (Elsevier, 2017-06-02)Fire response of concrete structural members depends on thermal, mechanical, and deformation properties of concrete. These properties vary significantly with temperature and also depend on the composition and characteristics ... -
Advanced Evaluation of the Freeze–Thaw Damage of Concrete Based on the Fracture Tests
Kucharczyková, Barbara; Šimonová, Hana; Kocáb, Dalibor; Topolář, Libor (MDPI, 2021-10-25)This paper presents the results of an experimental program aimed at the assessment of the freeze–thaw (F–T) resistance of concrete based on the evaluation of fracture tests accompanied by acoustic emission measurements. ... -
Analysis of Acoustic Emission Signals Recorded during Freeze-Thaw Cycling of Concrete
Topolář, Libor; Kocáb, Dalibor; Pazdera, Luboš; Vymazal, Tomáš (MDPI, 2021-03-05)This manuscript deals with a complex analysis of acoustic emission signals that were recorded during freeze-thaw cycles in test specimens produced from air-entrained concrete. An assessment of the resistance of concrete ... -
Analysis of temperature degraded concrete at high temperature by applying of non-linear characteristics
Pazdera, Luboš; Topolář, Libor; Hoduláková, Michaela; Dvořák, Richard; Mikulášek, Karel (IOP Publishing, 2018-07-12)Concrete structures are commonly exposed to thermal loads as a result of the structure, ambient conditions, the heat of hydration, or exposure to fire. Therefore, there has been a growing interest in the research of advanced ... -
The Application of Acoustic Emission Technique to Monitor the Early Setting Process of Cement Pastes
Hoduláková, Michaela; Topolář, Libor; Kucharczyková, Barbara (EDP Sciences, 2019-12-12)The obtained physico-mechanical properties (mainly flexural and compressive strength) of cement-based composite materials depend on various factors (type of mixture, its composition, standard hardening process, proper ... -
The Assessment of Cement Mortars after Thermal Degradation by Acoustic Non-destructive Methods
Topolář, Libor; Štefková, Daniela; Hoduláková, Michaela (IOP Publishing, 2017-10-25)Thanks, the terrorist attacks on the worldwide interest in the design of structures for fire greatly increased. One of the advantages of concrete over other building materials is its inherent fire-resistive properties. The ... -
Blastfurnace Hybrid Cement with Waste Water Glass Activator: Alkali-Silica Reaction Study
Kalina, Lukáš; Bílek, Vlastimil; Bradová, Lada; Topolář, Libor (MDPI, 2020-08-17)Hybrid systems represent a new sustainable type of cement combining the properties of ordinary Portland cement and alkali-activated materials. In this study, a hybrid system based on blast furnace slag and Portland clinker ... -
Comprehensive Testing Techniques for the Measurement of Shrinkage and Structural Changes of Fine-Grained Cement-Based Composites during Ageing
Kucharczyková, Barbara; Topolář, Libor; Daněk, Petr; Kocáb, Dalibor; Misák, Petr (Hindawi Publishing Corporation, 2017-01-15)The paper deals with an experimental analysis focusing on the utilization of a specific measurement technique for determining the development of shrinkage and for monitoring structural changes in fine-grained cement-based ... -
Decalcification resistance of various alkaliactivated materials
Hrubý, Petr; Bílek, Vlastimil; Topolář, Libor; Kalina, Lukáš; Marko, Michal; Šoukal, František; Dvořák, Richard; Herčík, Tomáš (IOP Publishing, 2021-09-29)The resistance of alkali-activated materials (AAMs) to degradation processes, particularly the decalcification, was studied in this paper. The ground granulated blast furnace slag was alkali-activated using various activators ... -
Efect of Chemical Aggressive Media on the Flexural Properties of Cured-In-Place Pipes Supported by Microstructure Observation and Acoustic Emission
Hodul, Jakub; Majerová, Jana; Drochytka, Rostislav; Dvořák, Richard; Topolář, Libor; Pazdera, Luboš (MDPI, 2020-07-08)The cured-in-place pipe (CIPP) method is currently the most frequently used approach for the renovation of piping without digging; this technology is suitable for pipes made from all types of material. The authors of this ... -
Effect of carbon nanotubes on the mechanical fracture properties of fly ash geopolymer
Rovnaník, Pavel; Šimonová, Hana; Topolář, Libor; Schmid, Pavel; Keršner, Zbyněk (Elsevier, 2016-06-01)Fly ash geopolymer is amorphous aluminosilicate material which is considered as alternative to Portland cement concrete. One of the limiting factors of its utilization is an increased shrinkage and related deterioration ... -
Effect of Hammer Type on Generated Mechanical Signals in Impact-Echo Testing
Dvořák, Richard; Topolář, Libor (MDPI, 2021-01-28)The impact-echo diagnostic method is a well-known nondestructive pulse compression test method, which can be relatively easily used for the testing of concrete and reinforced concrete elements. The evaluation of the ... -
The Effect of Specimen Size on Acoustic Emission Parameters and Approximate Position of Defects Obtained during Destructive Testing of Cementitious and Alkali-Activated Degraded Fine-Grained Materials
Topolář, Libor; Kocáb, Dalibor; Hrubý, Petr; Jakubka, Luboš; Hoduláková, Michaela; Halamová, Romana (MDPI, 2023-05-04)Two sizes of test samples were selected to investigate the effect of size on the level of degradation. The smaller test specimens had dimensions of 40 × 40 × 160 mm, and the larger ones had dimensions of 100 × 100 × 400 ... -
Effect of steel fibres dosage in alkali-activated slag mortars on acoustic emission obtained during three-point bending tests
Topolář, Libor; Šimonová, Hana; Schmid, Pavel; Rovnaník, Pavel (EDP Sciences – Web of Conferences, 2017-05-24)The acoustic emission phenomenon is directly associated with nucleation of cracks in structural materials during loading. This paper analyses acoustic emission signals captured during three-point bending fracture tests of ... -
Experimental Analysis of the Development of Elastic Properties and Strength under Different Ambient Temperature During the Hardening of Concrete
Kocáb, Dalibor; Daněk, Petr; Misák, Petr; Topolář, Libor; Pőssl, Petr (Elsevier, 2017-07-20)This paper focuses on the experimental assessment of the degree to which continued exposure to low ambient temperatures influences the concrete modulus of elasticity and compressive strength. The elastic modulus is not a ... -
Experimental assessment of steel fibre reinforced concretes with different concentrations of fibres
Komárková, Tereza; Láník, Jaromír; Topolář, Libor; Štoller, Jiří; Stoniš, Patrik (IOP Publishing, 2018-07-16)At present, steel fiber reinforced concrete can be classified as a composite material commonly used for load-bearing building structures. Adding steel fibers to fresh mixture improves its mechanical properties in comparison ... -
Experimental assessment of the influence of multiple cyclic loading on the dynamic modulus of elasticity of concrete
Misák, Petr; Kocáb, Dalibor; Daněk, Petr; Kucharczyková, Barbara; Topolář, Libor (EDP Sciences – Web of Conferences, 2017-05-24)The goal of the experiment was to determine the influence that cyclic loading has on concrete dynamic modulus of elasticity and compressive strength. Each test specimen was subjected to cyclic loading with the loading force ... -
The experimental comparison of parameters signals of acoustic emission during destructive test on composites based on cement
Hoduláková, Michaela; Kocáb, Dalibor; Topolář, Libor; Kucharczyková, Barbara (MATEC Web of Conferences, 2018-10-29)The paper reports the analysis of acoustic emission signals captured during compressive strength tests of fine-grained cement-based composites of various composition. Acoustic emission monitoring belongs to a non-invasive ... -
Experimental evaluation of the effect of carbon fibres on acoustic emission parameters obtained during compressive strength tests of alkaliactivated slag composites
Topolář, Libor; Rovnaník, Pavel; Schmid, Pavel (IOP Publishing, 2018-07-12)The generation of acoustic emission signals is directly associated with formation of cracks in materials during loading. This paper deals with possibilities of acoustic emission method application as the tool for the ... -
Flexure response of thermal loaded concrete specimens by acoustic emission method
Pazdera, Luboš; Topolář, Libor; Mikulášek, Karel; Smutný, Jaroslav; Hoduláková, Michaela; Chobola, Zdeněk; Seelmann, Herbert (EDP Sciences – Web of Conferences, 2017-05-24)The response to fire of concrete structural members depends on the thermal, mechanical, and deformation properties of concrete. These properties vary significantly with temperature depending on the composition and ...