Ivan Gabrijel - Academia.edu (original) (raw)
Papers by Ivan Gabrijel
Applied Sciences
Wood biomass is widely used in the European Union as a fuel for the production of heat and electr... more Wood biomass is widely used in the European Union as a fuel for the production of heat and electrical energy, generating a considerable amount of ash. The disposal of ash, especially its finest fraction, requires proper engineering solutions, since these particles contain heavy metals and caneasily pollute soil, groundwater, or air. In this work, wood fly ash with a high amount of pozzolanic oxides and one with a high CaO content were used in concrete as a 15% and 30% cement replacement. Incorporation of wood ash in concrete reduced the 28-day compressive strength of concrete by up to 37%, which was attributed to the low stiffness of the wood ash particles, while the 2-year compressive strength indicated very low pozzolanic reactivity. The capillary absorption of concrete increased with the increase in the ash content, but almost no influence on the gas permeability was observed. Wood fly ash with high CaO content reduced the drying shrinkage of concrete by up to 65% after 1 year. I...
Kvalitetom do poslovne izvrsnosti, 2011
Proceedings of the International Conference in Ljubljana, 10-11 June, 2021 in edition of Application of Structural Fire Engineering, 2021
Materials, 2022
This paper presents an experimental investigation of the compressive behavior of high-strength se... more This paper presents an experimental investigation of the compressive behavior of high-strength self-compacting concrete exposed to temperatures up to 600 °C. Ten different concrete compositions were tested, in which part of the cement (by weight) was replaced by three different mineral additives (5–15% metakaolin, 20–40% fly ash and 5–15% limestone). The stress–strain curves, compressive strength, modulus of elasticity and strain at peak stress were evaluated from uniaxial compression tests. Scanning electron microscope micrographs were also taken to evaluate the damage caused by the high temperatures. A sharp decrease in mechanical properties and an increase in peak strain were observed already after 200 °C for all mixes tested. The different mineral additives used in this study affected the variations of residual compressive strength by 24% and peak strain by 38%, while the variations of residual modulus elasticity were 14%. Comparing the obtained results with the recommendations ...
Interdisciplinary Approaches for Cement-based Materials and Structural Concrete: Synergizing Expertise and Bridging Scales of Space and Time, 2018
Journal of Civil Engineering and Architecture, 2011
Concrete setting and hardening processes are the most critical phases during construction works, ... more Concrete setting and hardening processes are the most critical phases during construction works, influencing properties of a concrete structure. The initial set is important as it provides an estimate when concrete has reached a point that it can no longer be vibrated without damaging concrete. The point at which final set occurs is important since it provides an estimate when the development of concrete strength and stiffness starts. In this study, experimental work is performed under laboratory conditions to indentify the setting time of cement paste using ultrasonic waves. Correlation between the ultrasonic wave parameters (speed, amplitude and energy) passing through the fresh cement paste and setting time determined using the Vicat test method is analyzed. A method of acoustic emission is also used and acoustic signals recorded in cement paste during hydration are presented.
Advanced Techniques for Testing of Cement-Based Materials, 2020
Ultrasonic techniques have been developed worldwide aimed to determine and monitor various import... more Ultrasonic techniques have been developed worldwide aimed to determine and monitor various important properties of cement-based materials. In recent years, advances in computer and experimental equipment have allowed the development of advanced ultrasonic systems. This chapter describes principles of determination of various properties of cement-based materials using ultrasonic techniques. Advantages and limitations of these techniques are briefly presented and discussed. State-of-the-art form of the chapter gives other researchers a comprehensive overview of the developed ultrasonic procedures. Due to their clear physical basis, accuracy, and ease of use, ultrasonic techniques have a great potential to soon become standard testing techniques for determination of setting and other properties of fresh and early-age cement-based materials. The first steps in this direction have already been performed.
Tok procesa temperaturnih promjena složeno je predvidjeti racunski jer obuhvaca istovremeni poras... more Tok procesa temperaturnih promjena složeno je predvidjeti racunski jer obuhvaca istovremeni porast temperature u betonu uslijed oslobađanja topline hidratacije i međudjelovanje sa okolisem. Prilikom izrade Posebnih tehnickih uvjeta za betonske radove na Maslenickom mostu izrađena je i analiza temperaturnog toka u betonu. Rjesavanje ovog problema je provedeno na racunalu Schmidtovom numerickom metodom. Isti problem rjesavan je programskim paketom Cosmos/m metodom konacnih elemenata. U ovom radu je prikazan princip proracuna po obje metode i uspoređeni su dobiveni rezultati.
U radu se upozorava da u slucaju naglog hlađenja masivnih betonskih blokova nastaju vlacna naprez... more U radu se upozorava da u slucaju naglog hlađenja masivnih betonskih blokova nastaju vlacna naprezanja veca od vlacne cvrstoce betona pa zbog toga nastaju pukotine u betonu. Istica se da je ta pojava kriticna u vrijeme ocvrscivanja betona. Razvoj temperature uzrokovan hidratacijom cementa modeliran je metodom konacnih elemenata koje je provedeno na primjeru jednodimenzionalnog konacnog elementa. Dobiveni su rezultati analizirani i uspoređeni s rezultatima terenskih ispitivanja.
The mechanism of compressive failure is still in progress to be clarified ; this has been tried w... more The mechanism of compressive failure is still in progress to be clarified ; this has been tried with acquisition and analysis of acoustic emission parameters. The processing of the AE data is often not trivial and because of that, simple tests on the concrete samples were made. This paper deals with the relations between load and acoustic emission activities in concrete under different loading conditions. The compressive strength loading test was done with decreasing the friction between the specimen and the loading plates by means of rubber backing and by that decreasing the shear stresses. During testing, the acoustic emission activity was acquired. The three-point bending strength testing was also done. Cyclic loading was applied in both uniaxial compression strength testing and three-point bending strength testing in order to observe the Kaiser effect and Felicity ratio. Presented paper includes the differences in reading the acoustic emission signal and its behavior during the ...
Following the needs of the hydro power plant (HPP) Lesce construction on the river Dobra in Croat... more Following the needs of the hydro power plant (HPP) Lesce construction on the river Dobra in Croatia, the development of maximum temperatures in mass concrete blocks of the power-plant’ s gravity dam is analysed. Hardening of early age concrete is connected to chemical processes which go along with a severe temperature and dimensional changes depending on the quantity of cement, heat of hydration, initial temperature of concrete and temperature changes of the environment. When constructing mass concrete elements two conditions are set connected to temperature changes in concrete. One is the maximum temperature that concrete is allowed to achieve because of hydration process. The other condition is much more complex and it refers to the temperature gradient which is forming from the inside out to the surface and it is a consequence of the heat transfer from concrete block to the environment and of the small thermal conductivity of concrete. The problem is mathematically solved using t...
Knowledge of mechanical properties of concrete, i.e. its developement from a moment of concreting... more Knowledge of mechanical properties of concrete, i.e. its developement from a moment of concreting to the moment of taking load, is of great importance to designers and constructors because it can significantly contribute to the quick and safe construction. Relationships between the strength and modulus of elasticity are well known for the hardened concrete, where a process of hydration is mostly finished, and they can be considered as constant. However properties of concrete just after concreting and all the way until approximately 7 days of age, are unknown. In that early stage, concrete is transforming from liquid to a solid state and a hardening begins. Deformation of concrete due to shrinkage, and also ability of the concrete creep and relaxation are the greatest. At the same time, concrete is expanding due to the heating resulting from the release of the cement's hydratation heat. Also, because of a non-uniform temperature in the concrete element, the degree of hydration is...
In civil engineering practice there is often the need for estimation of compressive strength of c... more In civil engineering practice there is often the need for estimation of compressive strength of concrete during construction process and for that purpose different testing methods have been proposed. This paper deals with application of acousto-ultrasonic (AU) measurement method for monitoring of strength development process in concrete and presents outcomes of an experimental investigation conducted in Laboratory for materials testing at Civil Engineering Faculty in Zagreb.
Beton je po svojoj prirodi porozan materijal. Pore u betonu se mogu podijeliti u cetiri grupe: ge... more Beton je po svojoj prirodi porozan materijal. Pore u betonu se mogu podijeliti u cetiri grupe: gel pore, kapilarne pore, uvuceni i zahvaceni zrak. Karakteristike pora uvucenog i zahvacenog zraka – velicina i distribucija pora mogu se određivati u svježem i ocvrsnulom betonu. U ovom radu prikazani su rezultati ispitivanja sest vrsta betona s velikom kolicinom pora. Ispitivanja su provedena na betonu u svježem i ocvrsnulom stanju. Karakteristike zracnih pora, ukupna kolicina, faktor razmaka i specificna povrsina ispitane su tlacnom metodom (HRN EN 12350– 7:2000), analizom zracnih pora u svježem betonu (air void analyzer) i linijskom mikroskopskom analizom (HRN EN 480– 11: 2005) u ocvrsnulom stanju. Opisane su metode ispitivanja te uspoređeni dobiveni rezultati.
Reinforced concrete is one of the most widely used structural materials, because it offers good d... more Reinforced concrete is one of the most widely used structural materials, because it offers good durability properties, a range of engineering solutions and a variety of aesthetic opportunities. To obtain required properties of concrete as a structural material in the laboratory and on site is not the same. Real properties of material which is placed and cured on site in different environmental conditions stay unknown. Therefore it is obvious that there is a strong need for the application of the non-destructive methods in testing of concrete structures on site. When using NDT methods the main goal is to obtain reliable results but for a method to be “good” also some other requirements should be satisfied, i.e. method must be simple and truly non destructive. In this paper two non-destructive methods for measuring permeability properties of in-situ concrete are presented. Methods include measuring of initial surface absorption and air permeability. Testing was performed with the two ...
Prediction of compressive strength of concrete at a certain age requires understanding of hydrati... more Prediction of compressive strength of concrete at a certain age requires understanding of hydration process and a means of monitoring it. In the research presented in this paper an acousto-ultrasonic (AU) method was studied for monitoring of strength development of concrete. Changes in the waveform of the ultrasonic signal transmitted through the concrete during the first days of hydration are recorded and different stress wave factors extracted from the signal have been analysed. It was found that amplitude of the signal and the energy contained in the waveform transmitted showed almost linear correlation with compressive strength development.
Upotreba mortova pri sanaciji ostecenih armiranobetonakih konstrukcija sve je veca. Jedno od rije... more Upotreba mortova pri sanaciji ostecenih armiranobetonakih konstrukcija sve je veca. Jedno od rijesenja može biti i polimerom modificirani mort. Sanacijski mort se nanosi na prethodno pripremljenu i ociscenu povrsinu betona u jednom ili vise slojeva. Mehanicka i termicka svojstva betona i sanacijskog morta su vrlo cesto razlicita i zbog toga , kao posljedice, nastaju pukotine na povrsini sanacijskog morta. U ovom radu provedena je teorijska analiza s ciljem određivanja raspodjele naprezanja u kompozitnom elementu koji se sastoji od betonske podloge i sloja sanacijskog morta. Element je podvrgnut temperaturnom opterecenju. Varirana je debljina sloja sanacijskog morta. Analiza je provedena na 2D modelu, u Cosmos/m programu, metodom konacnih elemenata.
U radu su prikazani i analizirani rezultati ispitivanja karakteristika zracnih pora u svježem i o... more U radu su prikazani i analizirani rezultati ispitivanja karakteristika zracnih pora u svježem i ocvrsnulom betonu. U svježem betonu ispitivanja su provedena tlacnom metodom pomocu porometra i analizatorom zracnih pora uređajem Air void analyzer. Na ocvrsnulom betonu pore su analizirane mikroskopskom analizom, uređajem pod nazivom RapidAir 457. Mjerene karakteristike zracnih pora su: ukupna kolicina, faktor razmaka i specificna povrsina. Uspoređeni su rezultati iz dva laboratorija.
Applied Sciences
Wood biomass is widely used in the European Union as a fuel for the production of heat and electr... more Wood biomass is widely used in the European Union as a fuel for the production of heat and electrical energy, generating a considerable amount of ash. The disposal of ash, especially its finest fraction, requires proper engineering solutions, since these particles contain heavy metals and caneasily pollute soil, groundwater, or air. In this work, wood fly ash with a high amount of pozzolanic oxides and one with a high CaO content were used in concrete as a 15% and 30% cement replacement. Incorporation of wood ash in concrete reduced the 28-day compressive strength of concrete by up to 37%, which was attributed to the low stiffness of the wood ash particles, while the 2-year compressive strength indicated very low pozzolanic reactivity. The capillary absorption of concrete increased with the increase in the ash content, but almost no influence on the gas permeability was observed. Wood fly ash with high CaO content reduced the drying shrinkage of concrete by up to 65% after 1 year. I...
Kvalitetom do poslovne izvrsnosti, 2011
Proceedings of the International Conference in Ljubljana, 10-11 June, 2021 in edition of Application of Structural Fire Engineering, 2021
Materials, 2022
This paper presents an experimental investigation of the compressive behavior of high-strength se... more This paper presents an experimental investigation of the compressive behavior of high-strength self-compacting concrete exposed to temperatures up to 600 °C. Ten different concrete compositions were tested, in which part of the cement (by weight) was replaced by three different mineral additives (5–15% metakaolin, 20–40% fly ash and 5–15% limestone). The stress–strain curves, compressive strength, modulus of elasticity and strain at peak stress were evaluated from uniaxial compression tests. Scanning electron microscope micrographs were also taken to evaluate the damage caused by the high temperatures. A sharp decrease in mechanical properties and an increase in peak strain were observed already after 200 °C for all mixes tested. The different mineral additives used in this study affected the variations of residual compressive strength by 24% and peak strain by 38%, while the variations of residual modulus elasticity were 14%. Comparing the obtained results with the recommendations ...
Interdisciplinary Approaches for Cement-based Materials and Structural Concrete: Synergizing Expertise and Bridging Scales of Space and Time, 2018
Journal of Civil Engineering and Architecture, 2011
Concrete setting and hardening processes are the most critical phases during construction works, ... more Concrete setting and hardening processes are the most critical phases during construction works, influencing properties of a concrete structure. The initial set is important as it provides an estimate when concrete has reached a point that it can no longer be vibrated without damaging concrete. The point at which final set occurs is important since it provides an estimate when the development of concrete strength and stiffness starts. In this study, experimental work is performed under laboratory conditions to indentify the setting time of cement paste using ultrasonic waves. Correlation between the ultrasonic wave parameters (speed, amplitude and energy) passing through the fresh cement paste and setting time determined using the Vicat test method is analyzed. A method of acoustic emission is also used and acoustic signals recorded in cement paste during hydration are presented.
Advanced Techniques for Testing of Cement-Based Materials, 2020
Ultrasonic techniques have been developed worldwide aimed to determine and monitor various import... more Ultrasonic techniques have been developed worldwide aimed to determine and monitor various important properties of cement-based materials. In recent years, advances in computer and experimental equipment have allowed the development of advanced ultrasonic systems. This chapter describes principles of determination of various properties of cement-based materials using ultrasonic techniques. Advantages and limitations of these techniques are briefly presented and discussed. State-of-the-art form of the chapter gives other researchers a comprehensive overview of the developed ultrasonic procedures. Due to their clear physical basis, accuracy, and ease of use, ultrasonic techniques have a great potential to soon become standard testing techniques for determination of setting and other properties of fresh and early-age cement-based materials. The first steps in this direction have already been performed.
Tok procesa temperaturnih promjena složeno je predvidjeti racunski jer obuhvaca istovremeni poras... more Tok procesa temperaturnih promjena složeno je predvidjeti racunski jer obuhvaca istovremeni porast temperature u betonu uslijed oslobađanja topline hidratacije i međudjelovanje sa okolisem. Prilikom izrade Posebnih tehnickih uvjeta za betonske radove na Maslenickom mostu izrađena je i analiza temperaturnog toka u betonu. Rjesavanje ovog problema je provedeno na racunalu Schmidtovom numerickom metodom. Isti problem rjesavan je programskim paketom Cosmos/m metodom konacnih elemenata. U ovom radu je prikazan princip proracuna po obje metode i uspoređeni su dobiveni rezultati.
U radu se upozorava da u slucaju naglog hlađenja masivnih betonskih blokova nastaju vlacna naprez... more U radu se upozorava da u slucaju naglog hlađenja masivnih betonskih blokova nastaju vlacna naprezanja veca od vlacne cvrstoce betona pa zbog toga nastaju pukotine u betonu. Istica se da je ta pojava kriticna u vrijeme ocvrscivanja betona. Razvoj temperature uzrokovan hidratacijom cementa modeliran je metodom konacnih elemenata koje je provedeno na primjeru jednodimenzionalnog konacnog elementa. Dobiveni su rezultati analizirani i uspoređeni s rezultatima terenskih ispitivanja.
The mechanism of compressive failure is still in progress to be clarified ; this has been tried w... more The mechanism of compressive failure is still in progress to be clarified ; this has been tried with acquisition and analysis of acoustic emission parameters. The processing of the AE data is often not trivial and because of that, simple tests on the concrete samples were made. This paper deals with the relations between load and acoustic emission activities in concrete under different loading conditions. The compressive strength loading test was done with decreasing the friction between the specimen and the loading plates by means of rubber backing and by that decreasing the shear stresses. During testing, the acoustic emission activity was acquired. The three-point bending strength testing was also done. Cyclic loading was applied in both uniaxial compression strength testing and three-point bending strength testing in order to observe the Kaiser effect and Felicity ratio. Presented paper includes the differences in reading the acoustic emission signal and its behavior during the ...
Following the needs of the hydro power plant (HPP) Lesce construction on the river Dobra in Croat... more Following the needs of the hydro power plant (HPP) Lesce construction on the river Dobra in Croatia, the development of maximum temperatures in mass concrete blocks of the power-plant’ s gravity dam is analysed. Hardening of early age concrete is connected to chemical processes which go along with a severe temperature and dimensional changes depending on the quantity of cement, heat of hydration, initial temperature of concrete and temperature changes of the environment. When constructing mass concrete elements two conditions are set connected to temperature changes in concrete. One is the maximum temperature that concrete is allowed to achieve because of hydration process. The other condition is much more complex and it refers to the temperature gradient which is forming from the inside out to the surface and it is a consequence of the heat transfer from concrete block to the environment and of the small thermal conductivity of concrete. The problem is mathematically solved using t...
Knowledge of mechanical properties of concrete, i.e. its developement from a moment of concreting... more Knowledge of mechanical properties of concrete, i.e. its developement from a moment of concreting to the moment of taking load, is of great importance to designers and constructors because it can significantly contribute to the quick and safe construction. Relationships between the strength and modulus of elasticity are well known for the hardened concrete, where a process of hydration is mostly finished, and they can be considered as constant. However properties of concrete just after concreting and all the way until approximately 7 days of age, are unknown. In that early stage, concrete is transforming from liquid to a solid state and a hardening begins. Deformation of concrete due to shrinkage, and also ability of the concrete creep and relaxation are the greatest. At the same time, concrete is expanding due to the heating resulting from the release of the cement's hydratation heat. Also, because of a non-uniform temperature in the concrete element, the degree of hydration is...
In civil engineering practice there is often the need for estimation of compressive strength of c... more In civil engineering practice there is often the need for estimation of compressive strength of concrete during construction process and for that purpose different testing methods have been proposed. This paper deals with application of acousto-ultrasonic (AU) measurement method for monitoring of strength development process in concrete and presents outcomes of an experimental investigation conducted in Laboratory for materials testing at Civil Engineering Faculty in Zagreb.
Beton je po svojoj prirodi porozan materijal. Pore u betonu se mogu podijeliti u cetiri grupe: ge... more Beton je po svojoj prirodi porozan materijal. Pore u betonu se mogu podijeliti u cetiri grupe: gel pore, kapilarne pore, uvuceni i zahvaceni zrak. Karakteristike pora uvucenog i zahvacenog zraka – velicina i distribucija pora mogu se određivati u svježem i ocvrsnulom betonu. U ovom radu prikazani su rezultati ispitivanja sest vrsta betona s velikom kolicinom pora. Ispitivanja su provedena na betonu u svježem i ocvrsnulom stanju. Karakteristike zracnih pora, ukupna kolicina, faktor razmaka i specificna povrsina ispitane su tlacnom metodom (HRN EN 12350– 7:2000), analizom zracnih pora u svježem betonu (air void analyzer) i linijskom mikroskopskom analizom (HRN EN 480– 11: 2005) u ocvrsnulom stanju. Opisane su metode ispitivanja te uspoređeni dobiveni rezultati.
Reinforced concrete is one of the most widely used structural materials, because it offers good d... more Reinforced concrete is one of the most widely used structural materials, because it offers good durability properties, a range of engineering solutions and a variety of aesthetic opportunities. To obtain required properties of concrete as a structural material in the laboratory and on site is not the same. Real properties of material which is placed and cured on site in different environmental conditions stay unknown. Therefore it is obvious that there is a strong need for the application of the non-destructive methods in testing of concrete structures on site. When using NDT methods the main goal is to obtain reliable results but for a method to be “good” also some other requirements should be satisfied, i.e. method must be simple and truly non destructive. In this paper two non-destructive methods for measuring permeability properties of in-situ concrete are presented. Methods include measuring of initial surface absorption and air permeability. Testing was performed with the two ...
Prediction of compressive strength of concrete at a certain age requires understanding of hydrati... more Prediction of compressive strength of concrete at a certain age requires understanding of hydration process and a means of monitoring it. In the research presented in this paper an acousto-ultrasonic (AU) method was studied for monitoring of strength development of concrete. Changes in the waveform of the ultrasonic signal transmitted through the concrete during the first days of hydration are recorded and different stress wave factors extracted from the signal have been analysed. It was found that amplitude of the signal and the energy contained in the waveform transmitted showed almost linear correlation with compressive strength development.
Upotreba mortova pri sanaciji ostecenih armiranobetonakih konstrukcija sve je veca. Jedno od rije... more Upotreba mortova pri sanaciji ostecenih armiranobetonakih konstrukcija sve je veca. Jedno od rijesenja može biti i polimerom modificirani mort. Sanacijski mort se nanosi na prethodno pripremljenu i ociscenu povrsinu betona u jednom ili vise slojeva. Mehanicka i termicka svojstva betona i sanacijskog morta su vrlo cesto razlicita i zbog toga , kao posljedice, nastaju pukotine na povrsini sanacijskog morta. U ovom radu provedena je teorijska analiza s ciljem određivanja raspodjele naprezanja u kompozitnom elementu koji se sastoji od betonske podloge i sloja sanacijskog morta. Element je podvrgnut temperaturnom opterecenju. Varirana je debljina sloja sanacijskog morta. Analiza je provedena na 2D modelu, u Cosmos/m programu, metodom konacnih elemenata.
U radu su prikazani i analizirani rezultati ispitivanja karakteristika zracnih pora u svježem i o... more U radu su prikazani i analizirani rezultati ispitivanja karakteristika zracnih pora u svježem i ocvrsnulom betonu. U svježem betonu ispitivanja su provedena tlacnom metodom pomocu porometra i analizatorom zracnih pora uređajem Air void analyzer. Na ocvrsnulom betonu pore su analizirane mikroskopskom analizom, uređajem pod nazivom RapidAir 457. Mjerene karakteristike zracnih pora su: ukupna kolicina, faktor razmaka i specificna povrsina. Uspoređeni su rezultati iz dva laboratorija.