L. Balazs

Budapest University of Technology and Economics, Department of Construction Materials and Technologies, Faculty Member

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Papers by L. Balazs

Bond of FRP bars in air-entrained concrete: Experimental and statistical study

Construction and Building Materials, 2021

The combined use of Fibre Reinforced Polymer (FRP) and Air-Entrained Concrete (AEC) can be an alt... more The combined use of Fibre Reinforced Polymer (FRP) and Air-Entrained Concrete (AEC) can be an alternative to traditional steel-reinforced concrete as this system is less affected by the corrosion of the reinforcement and by the freeze-thaw cycles induced concrete degradation. However, the viability of this system hinges on the bond performance of the reinforcing bars. A total of 236 pull-out specimens were prepared and tested to study the effect of air-entraining admixtures (AEA) on the bond behaviour of FRP bars to concrete with varying compressive strengths. Failure modes and bond stress-slip curves were reported and discussed. The bond energy, calculated as the area under the bond stress-slip diagram, was also analyzed. The experimental peak bond stresses (bond strength) were compared to the theoretical ones characterized by the formula proposed for steel bars by the Model Code 2010. In addition, the statistical significance of the effect of AEA on bond characteristics was determined, yielding a reduction factor to account for the effect of AEA on bond strength. The test results show that the bond strength of FRP bars in AEC was statistically significantly lower than in normal concrete. However, the decrease is sufficiently small that could be accounted for, during the design stage, by merely increasing the reinforcement development length.

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Improved Fire Resistance by Using Different Types of Cements

Lecture Notes in Civil Engineering, 2018

Composition and microstructure of hardened cement paste have important influences on the properti... more Composition and microstructure of hardened cement paste have important influences on the properties of concrete exposed to high temperatures. An extensive experimental study was carried out to analyse the post-heating characteristics of concretes subjected to temperatures up to 800 °C. Major parameters of our study were the content of supplementary materials (slag, fly ash, trass) of cement (0, 16 or 25 m%) and the value of maximum temperature. Our results indicated that (i) the number and size of surface cracks as well as compressive strength decreased by the increasing content of supplementary materials of cements due to elevated temperature; (ii) the most intensive surface cracking was observed by using Portland cement without addition of supplementary materials. The increasing content of the supplementary material of cement increased the relative post-heating compressive strength. Tendencies of surface cracking and reduction of compressive strength were in agreement, i.e. the more surface cracks, the more strength reduction.

Presentation of activities in fib TG 4.1 Serviceability Models

Cracking is almost unavoidable in concrete structur es. Formation of cracks may start at very ear... more Cracking is almost unavoidable in concrete structur es. Formation of cracks may start at very early ages of concrete and continues under loading. Cracks may significantly influence serviceability behaviour. Cracking in concrete is a very complex phenomenon, which is reflected in the many influencing parameters as we ll as available approaches and opinions.

fib Bulletin 72. Bond and anchorage of embedded reinforcement: Background to the fib Model Code for Concrete Structures 2010

fib Bulletins, 2014

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“Damage mechanics” — North-Holland series in applied mathematics and mechanics vol. 41

Cement and Concrete Research, 1997

Daß Manasses auch ein jambisches Gedicht geschrieben habe, das wahrscheinlich , (Itinerariurn) be... more Daß Manasses auch ein jambisches Gedicht geschrieben habe, das wahrscheinlich , (Itinerariurn) betitelt war und aus mindestens zwei Büchern bestand, wußten wir aus einem Zitat des Allatius, der in einer Anmerkung zu Georgios Akropolites (S. 201 ed. Paris. 1651 = S. 205 ed. Bonn. 1836) 6 Verse aus "Constantinus Manasses lib. 2 Odoeporici" anführt. (Es sind die Verse 153-158 des vollständigen Textes.) Eine Angabe über die Handschrift, der dieses Zitat entnommen ist, fehlt bei Allatius und man hat bisher auch keine weitere Spur des Werkes gefunden. Vgl. K. Krumbacher, Gesch. der byz. Lit. 2 S. 380 Anrn. 10. Vor kurzem hat L. Sternbach (Jahreshefte des österr. archäol. Instituts V (1902) Beiblatt S. <>5ff.) den Versuch gewagt, aus diesen ganz allgemein gehaltenen 6 Versen den Inhalt des verlorenen Gedichtes zu erschließen und die Behauptung aufgestellt, das Hodoiporikon habe eine enkomiastische Schilderung von Byzauz und dessen Herrlichkeiten enthalten. Es ist jetzt, nicht mehr Nötig, diese als "positive Gewißheit" vorgetragene Hypothese zu widerlegen, da es mir gelungen ist, zunächst ein umfangreiches Fragment und endlich das ganze Gedicht des Manasses aufzufinden. Schon in meinem Aufsätze: Die Epigramme des Theodore s Balsainon in den Wien. Stud. XXV (1903) S. 177 habe ich mitgeteilt, daß im Marcianus 524 (fol. 94 V -9f) r j nahezu 300 Verse aus dem Hodoiporikon des Manasses stehen. Allerdings fehlt hier Titel und Autorangabe vollständig. Aber der Inhalt des Bruchstückes zeigt, daß es aus einem Itinerar ist und daß der Verfasser mit Johannes Konto steplianos, an den die zwei von E. Kurt z im Viz. Vrem. VII edierten rhetorischen Stücke des Manasses gerichtet sind, befreundet ist. Die Vermutung, daß man es hier mit dem Hodoiporikon desselben Autors zu tun habe, lag also nahe und Kurt/, dem ich gelegentlich das Fragment Byzaut. Zeitschrift XIII 3 u. 4. 21

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Experimental pulmonary infarction in a pig model

Investigative …, 1992

RESULTS. A complete and permanent arterial occlusion was achieved, involving up to three orders o... more

Bond of NSM FRP-Strengthened Concrete: Round Robin Test Initiative

Journal of Composites for Construction, 2015

Although an extensive amount of research into the debonding behaviour of FRP strengthening system... more Although an extensive amount of research into the debonding behaviour of FRP strengthening systems has been conducted in literature, no standard methodology has been yet established that represent the actual behaviour. To asses the performance and reliability of small scale testing on NSM (near surface mounted) FRP strengthening systems an experimental program, in the framework of an international Round Robin Testing (RRT) has been carried out on a series of 9 NSM FRP strengthening systems. Eleven laboratories and seven manufacturers and suppliers participated in this extensive international exercise, which was initiated within the framework of the European funded Marie Curie Research Training Network, ENCORE , with the support of Task Group 9.3 of the International Federation for Structural Concrete (fib). Test results obtained by the participating laboratories are discussed and compared in this paper.

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Models for flexural cracking in concrete: the state of the art

Structural Concrete, 2005

Crack formation presents a complex mechanical and geometrical question to be modelled. The availa... more Crack formation presents a complex mechanical and geometrical question to be modelled. The available crack width formulations are often based on simplifications. A rigorous formulation of crack widths should be based on the integration of strain differences of reinforcement and concrete between cracks, due to the accumulated slips. In this paper an extensive literature review on crack widths and crack spacing is presented. The basic intention of the present paper is to summarise the development of flexural crack models and collect the most relevant formulae for crack spacing and crack width. It reports not only the possible improvement of design or research equations but also the appearance of new types of reinforcements with different characteristics from those of steel reinforcements. This state-of-the-art Report is a contribution to the work of fib TG 4.1 ‘Serviceability Models’.

3D nyomtatott hálóval erősített beton

Vasbetonépítés

A XX. század végei gyártástechnológiák gyors fejlődése új gépek és technológiák megjelenését is e... more A XX. század végei gyártástechnológiák gyors fejlődése új gépek és technológiák megjelenését is eredményezte. Ezek közé tartozik az 1980-as években megjelent 3D nyomtatás is. Néhány évvel ezelőttig ez a technológia csak prototípus előállására alkalmas gyártási folyamat volt. Azonban a 3D nyomtatók 2010-es évek elején szélesebb körű elterjedése lehetőséget adott a 3D nyomtatás új területekre történő beintegrálására és szerte ágazóbb ipari alkalmazására. Ebben a cikkben rövid betekintés adunk a 3D nyomtatás világába és a 2020. őszi félévében Kasik Tamás által készített betontechnológus szakmérnöki diplomamunkába, melyben 3D nyomtatott hálókkal és szövetekkel erősített lemez alakú beton próbatestekkel végeztünk kísérleteket (konzulensek voltak: dr. Sólyom Sándor és dr. Balázs György)

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Szerkesztőbizottság elnöke / President of Editing Committee

An effective method for degradation of Aflatoxin B 2 (AFB 2) in sunflower oil was developed, need... more An effective method for degradation of Aflatoxin B 2 (AFB 2) in sunflower oil was developed, needed for controlling this toxin. Contaminated sunflower oil samples was treated with UV light, AFB 2 content was extracted from samples, and was determinated by HPLC. The UV light was found able to decrease the AFB 2 concentration with 23% after 3 minutes, with 39% after 6 minutes and 52% after 9 minutes of treatment. REZUMAT Aflatoxina B 2 (AFB 2), una dintre cele mai vătămătoare micotoxine prezente în alimente, a fost studiată în scopul degradării sub acţiunea radiaţiilor ultraviolete (UV). Ulei de floarea-soarelui (UFS) artificial contaminat cu AFB 2 a fost expus la radiaţii UV şi s-a determinat scăderea de concentraţie a AFB 2 în timp. S-a observat scăderea concentraţiei de AFB 2 cu 23% după 3 minute, cu 39% după 6 minute şi cu 52% după 9 minute de tratament. ÖSSZEFOGLALÓ Aflatoxin B 2-vel (AFB 2) mesterségesen szennyezett napraforgó olajat ultaibolya sugárzással kezeltek, majd mintákat vettek a kezelés során, melyekből kivonták az AFB 2 tartalmat, és meghatározták az időben a koncentráció változását HPLC segítségével. Megállapították, hogy az UV kezelés időtartamának előrehaladtával az AFB 2 tartalom 3 perc után 23%-kal, 6 perc után 39%-kal, 9 perc után pedig 52%-kal csökkent.

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fib Bulletin 90. Externally applied FRP reinforcement for concrete structures

fib Bulletins, 2019

Potentials in Developing Lightweight Concrete Prestressed Bridge Girders

György L. Balázs 1 Rita Nemes 2 Éva Lublóy UDK: 691.328.2 : 624.21.036.5/.7 DOI:10.14415/konferen... more György L. Balázs 1 Rita Nemes 2 Éva Lublóy UDK: 691.328.2 : 624.21.036.5/.7 DOI:10.14415/konferencijaGFS 2016.036 Summary: Lightweight aggregate concrete is a challenge for developing bridge girders with reduced self-weight. Savings in transportation costs for precast girders can be considerable. An extensive research started in Hungary (within a cooperation with a design office and a precast plant) to develop possible concrete mixes and design rules for precast bridge girders of lightweight aggregate concrete. Particular aspects for our studies were: selection of type of lightweight aggregate, concrete mix design, adequate curing, relatively high final compressive strength and adaptation of the production process in the prefabrication plant. An additional request was the high early age strength. As part of the research project, a prototype girder has been cast with concrete strength class of LC50/55 and density class of D2.0. In the paper we concentrate on two main aspects as bond ...

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Bond and Development of Straight Reinforcing Bars in Tension ACI 408 R-03 Reported by ACI Committee 408

ACI Committee Reports, Guides, Standard Practices, and Commentaries are intended for guidance in ... more ACI Committee Reports, Guides, Standard Practices, and Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. This document is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains. The American Concrete Institute disclaims any and all responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom. Reference to this document shall not be made in contract documents. If items found in this document are desired by the Architect/Engineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer.

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Design criteria of serviceability limit states

fib Bulletins

fib Bulletin 57. Shear and punching shear in RC and FRC elements Technical report

3D betonnyomtatás - korszerű betonelemek anyagtudományi fejlesztése a BME-n

A 3D nyomtatás a megjelenésétől fogva az érdeklődés középpontjában van. A technológia fejlődésén ... more A 3D nyomtatás a megjelenésétől fogva az érdeklődés középpontjában van. A technológia fejlődésén és sikeres alkalmazásain keresztül életünk részévé vált a legkülönbözőbb területeken. A folyamatok összetettsége révén a betonnyomtatás van talán a többi területhez képest (műanyagnyomtatás és fémnyomtatás) leginkább lemaradva. Szándékunk ezért részletes beszámolók nyújtása egy cikksorozat formájában a 3D betonnyomtatás kihívásainak és eredményeinek bemutatásáról. A BME Építőmérnöki Kar, Építőanyagok és Magasépítés Tanszékén megkezdődtek az ország felsőoktatásában első 3D betonnyomtató beszerzésére vonatkozó előkészületek. A beszerzésre VKE 2018-1-3-1_0003 „Korszerű betonelemek anyagtudományi fejlesztése” című kutatás fejlesztési pályázaton keresztül kapott kutatási támogatás révén nyílik lehetőség. 3D betonnyomtató pályázaton keresztül történő beszerzésén túlmenően annak beüzemelése és lehetőségeinek megismerése a feladatunk. A jelen cikk elsődleges célja a figyelemfelkeltés és az irány...

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CT alkalmazási lehetőségei az építőanyagok vizsgálatánál = Possibility of Application of CT in case of Building Materials

Az epitőanyagok belső szerkezetenek ismerete szamunkra nagyon fontos, hiszen az anyagok tulajdons... more Az epitőanyagok belső szerkezetenek ismerete szamunkra nagyon fontos, hiszen az anyagok tulajdonsagait es tartossagat az nagymertekben befolyasolja. Az anyagok belső szerkezete sok kiegeszitő informaciot tartalmaz, melynek vizsgalata analitikai modszerekkel csak reszben lenne lehetseges. A komputertomografias (CT) felveteleken a vizsgalat targya szeletekre bontva lathato. Az adatmatrixbol előallitott kep tulajdonkeppen egy sűrűsegterkep az adott anyagokrol. Ezen sűrűsegkepen jol kirajzolodnak a vizsgalt targy kulonboző sűrűsegű elemei, ezaltal kulonboző sűrűsegű osszetevői is azonosithatoak. A szeletek egymas utani lejatszasaval gyakorlatilag bele lathatunk az anyag szerkezetebe, de harom dimenzioban is abrazolhatjuk a vizsgalt anyagot. A cikk keretein belul szeretnenk attekinteni, hogy a CT vizsgalatok hogyan lehetnek celszerűen hasznalhatoak az epitőanyagok vizsgalatai soran.

Synthetic fibres or fibre cocktail in terms of shear capacity of concrete after elevated temperatures

Mechanics of Materials

Elevated temperatures can substantially affect the shear capacity of concrete. Herein we examine ... more Elevated temperatures can substantially affect the shear capacity of concrete. Herein we examine the effect of using different types of fibres on the behaviour of concrete at different maximum temperatures in terms of shear failure. The experiments were carried out by testing thirty specimens using two types of fibres at the age of 28 days. The study has adopted the push-off model for testing, which has been widely used as a relatively small, inexpensive, easy to perform and no need for special equipment, using either synthetic fibres or fibre cocktail. In addition, both crack width and crack slip have been investigated using LVDTs in both directions. The shear tests have been carried out at cold state after exposure to different levels of elevated temperatures. Using a bicomponent synthetic fibre with 4 kg/m³ approved to enhance the concrete ductility and toughness. However, using cocktail fibres, containing both synthetic fibres of 2 kg/m³ and steel fibres of 40 kg/m³, showed higher values than using synthetic fibres in terms of shear. Finally, mixes containing fibre cocktail showed more ductile behaviour than mixes with synthetic fibres at low as well as high temperatures.

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Investigations of direct shear of one-year old SFRC after exposed to elevated temperatures

Construction and Building Materials

h i g h l i g h t s Significant improvements in shear strengths and shear toughness using steel f... more h i g h l i g h t s Significant improvements in shear strengths and shear toughness using steel fibres. Improvements of shear are reported at ambient and less degree at elevated temperatures. Crack deformations (slip and width) are developed in SFRC in terms of shear measurements. Both fibre content and elevated temperatures decrease the shear stiffness. Crack width has generally more stiffness than crack slip.

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Effect of steel fibres on concrete at different temperatures in terms of shear failure

Magazine of Concrete Research

The behaviour of concrete reinforced with steel fibres at elevated temperatures was investigated ... more

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