MÖGLICHKEIT DER ANWENDUNG DER EINHEIMISCHEN SCHLACKE ALS BETONZUSCHLAGSTOFF

Opisana su ispitivanja, provedena u skladu s hrvatskim normama, da bi se ustanovila mogućnost uporabe domaće zgure kao agregata u betonu. Agregat je specificiran prema razredbi danoj u HRN EN 12620/AC:2006 a dobiveni razredi po pojedinom svojstvu agregata uspoređeni su sa zahtjevima hrvatskih propisa. Rezultati pokazuju da se može domaća zgura rabiti kao agregat u betonu, što bi pridonijelo zbrinjavanju te vrste otpada i očuvanju uobičajeno rabljenih agregata iz prirode.Tests conducted in accordance with Croatian standards in order to define possibility of using domestic slag as concrete aggregate, are described. The aggregate is specified according to classification given in HRN EN 12620/AC:2006, and categories obtained for individual aggregate properties are compared with requirements contained in Croatian regulations. The results show that domestic slag can in fact be used as concrete aggregate. Such use would contribute to proper management of this type of waste and to preservation of aggregate normally taken from nature.Les essais faits en conformité avec les normes croates afin de définir la possibilité d'emploi de la scorie domestique comme agrégat de béton, sont décrits. L'agrégat est spécifié selon la classification présentée dans HR EN 12620/AC:2006, et les catégories obtenues pour propriétés individuelles des agrégats sont comparées avec les exigences contenues dans les règlements croates. Les résultats montrent que la scorie domestique peut en fait être utilisée comme agrégat de béton. Cet emploi contribuerait à la gestion appropriée de ce type de déchets et à la préservation des agrégats normalement pris de la nature.Приводится описание испытаний, проведенных в соответствии с хорватскими нормами, в целях установления возможности применения домашнего шлака в качестве агрегата для бетона. Агрегат специфицирован в соответствии с классификацией, предусмотренной HRN EN 12620/AC:2006. Проведено сравнение классов, полученных по отдельным свойствам агрегата, с требованиями, предусматриваемыми хорватскими правилами. Результаты показывают, что домашний шлак может использоваться в качестве агрегата в бетоне, что будет способствовать утилизации этого вида отходов и сохранению обычно используемых природных агрегатов.Man beschreibt die Untersuchungen, durchgeführt im Einklang mit kroatischen Normen, mit dem Ziel die Möglichkeit der Anwendung der einheimischen Schlacke als Betonzuschlagstoff festzustellen. Der Zuschlagstoff ist spezifiziert nach der Klassifizierung in HRN EN 12620/AC:2006 und die Klassen, erhalten nach einzelnen Eigenschaften, sind mit den Forderungen der kroatischen Vorschriften verglichen. Die Ergebnisse zeigen dass die einheimische Schlacke als Betonzuschlagstoff genutzt werden kann, was der Versorgung dieser Art Abfall und Bewahrung der üblich genutzten Zuschlagstoffe aus der Natur beitragen

Possibility of using domestic slag as concrete aggregate

Opisana su ispitivanja, provedena u skladu s hrvatskim normama, da bi se ustanovila mogućnost uporabe domaće zgure kao agregata u betonu. Agregat je specificiran prema razredbi danoj u HRN EN 12620/AC:2006 a dobiveni razredi po pojedinom svojstvu agregata uspoređeni su sa zahtjevima hrvatskih propisa. Rezultati pokazuju da se može domaća zgura rabiti kao agregat u betonu, što bi pridonijelo zbrinjavanju te vrste otpada i očuvanju uobičajeno rabljenih agregata iz prirode.Tests conducted in accordance with Croatian standards in order to define possibility of using domestic slag as concrete aggregate, are described. The aggregate is specified according to classification given in HRN EN 12620/AC:2006, and categories obtained for individual aggregate properties are compared with requirements contained in Croatian regulations. The results show that domestic slag can in fact be used as concrete aggregate. Such use would contribute to proper management of this type of waste and to preservation of aggregate normally taken from nature

BEHAVIOUR OF ALUMINIUM STRUCTURES IN FIRE, A review

The interest in the application of aluminium as a structural material has been greatly increased in recent years. However, behaviour of aluminium structures when exposed to fire is still relatively unresearched. Due to low melting temperature of the alloy, aluminium structures have low fire resistance, but aluminium is reflective and has surface emissivity which is more than two times lower compared to carbon steel. The Eurocode facing this issue (EN 1999-1-2) is based mainly on the Eurocode for structural fire design of steel structures (EN 1993-1-2) and therefore is not fully suitable for the application on aluminium structures. Here, an overview of the structural behaviour of aluminium structures exposed to fire is given through the comparison with steel structures. As a conclusion, priorities for a future research are highlighted, which should provide a base for the next generation of modern codes for structural fire design of aluminium structures

ČELIČANSKA ZGURA KAO KORISTAN MATERIJAL ZA PROIZVODNJU BETONA

This paper aims to investigate the possibility of utilizing steel slags locally produced in Croatian plants as a concrete aggregate. Therefore, eight concrete mixtures were prepared with coarse slag fractions and different binders whose hardened state properties (compressive 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, dolomite. According to the obtained test results it can be concluded that concrete containing slag possesses acceptable mechanical properties and volume changes for its structural use but could represent a risk in terms of corrosion of reinforcement in case of slag with higher amount of sulphur in its chemical composition.U radu se istražuje mogućnost uporabe čeličanske zgure nastale u hrvatskim željezarama kao agregata u betonu. Pripremljeno je osam mješavina betona sa zgurom kao krupnom frakcijom i različitim vezivima te ispitana svojstva takvog betona u očvrslom stanju (tlačna čvrstoća, statički modul elastičnosti, volumne promjene i sklonost ka koroziji) i uspoređena sa svojstvima referentnog betona pripremljenog sa uobičajeno korištenim agregatom, dolomitom. Prema ostvarenim rezultatima ispitivanja može se zaključiti da beton sa zgurom u sastavu svojim mehaničkim svojstvima i volumnim promjenama zadovoljava uvjete za primjenu u konstrukciji ali može djelovati korozivno na armaturni čelik ukoliko zgura sadrži veći udio sumpora u kemijskom sastavu

Modifications of dolomite-based self-compacting concrete properties using mineral additives

U radu su opisana istraživanja svojstava samozbijajućih (SCC) betona spravljenih s dolomitnim filerom i materijalima koji posjeduju pucolanska svojstva, letećim pepelom i metakaolinom, kao zamjena za cement u različitim postotcima. Projektirano je sedam mješavina sa jednakim omjerom voda/prah i jednakim udjelom praškastog materijala. Ispitivanja svježih svojstava su se sastojala od ispitivanja rasprostiranja slijeganjem, ispitivanja L-kutijom i ispitivanja segregacije, a u očvrsnulom stanju je ispitana tlačna čvrstoća i modul elastičnosti za različite starosti betona od 2, 7, 14, 28 i 365 dana. Kako bi se pratila aktivnost dodanih mineralnih dodataka u betonske mješavine, ispitana je i toplina hidratacije. Dobiveni rezultati pokazuju da dodatak letećeg pepela u mješavinama poboljšava svojstva obradljivosti, dok uporaba metakaolina poboljšava mehanička svojstva. Usporena pucolanska aktivnost letećeg pepela usporava razvoj tlačne čvrstoće, ali rezultati dobiveni ispitivanjem nakon godinu dana starosti pokazuju da konačna čvrstoća betona s dodatkom letećeg pepela nije manja u odnosu na referentnu mješavinu.This paper addresses fresh and hardening properties of self compacting concretes (SCC) made with dolomite filler and pozzolanic materials, fly ash and matekaolin as cement replacement in different amounts. For this study, seven mixtures were prepared with a constant water-to-powder ratio and powder content. Fresh SCC properties were assessed by means of slump flow, L-box and sieve segregation test, while hardened properties were evaluated by means of compressive strength and modulus of elasticity at ages of 2, 7, 14, 28 and 365 days. In addition, the activity of mineral additives was assessed by heat of hydration measurement. Obtained results showed that mixtures containing fly ash exhibited better performance concerning workability properties needed for SCC, while cement replacement with metakaolin enhanced the mechanical properties. Slower pozzolanic activity of fly ash reflected in slower strength development, but ultimate strength obtained at the age of 365 days was not reduced by the presence of fly ash

Steel slag as a valuable material for concrete production

U radu se istražuje mogućnost uporabe čeličanske zgure nastale u hrvatskim željezarama kao agregata u betonu. Pripremljeno je osam mješavina betona sa zgurom kao krupnom frakcijom i različitim vezivima te ispitana svojstva takvog betona u očvrslom stanju (tlačna čvrstoća, statički modul elastičnosti, volumne promjene i sklonost ka koroziji) i uspoređena sa svojstvima referentnog betona pripremljenog sa uobičajeno korištenim agregatom, dolomitom. Prema ostvarenim rezultatima ispitivanja može se zaključiti da beton sa zgurom u sastavu svojim mehaničkim svojstvima i volumnim promjenama zadovoljava uvjete za primjenu u konstrukciji ali može djelovati korozivno na armaturni čelik ukoliko zgura sadrži veći udio sumpora u kemijskom sastavu.This paper aims to investigate the possibility of utilizing steel slags locally produced in Croatian plants as a concrete aggregate. Therefore, eight concrete mixtures were prepared with coarse slag fractions and different binders whose hardened state properties (compressive 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, dolomite. According to the obtained test results it can be concluded that concrete containing slag possesses acceptable mechanical properties and volume changes for its structural use but could represent a risk in terms of corrosion of reinforcement in case of slag with higher amount of sulphur in its chemical composition

Assessing condition of concrete pier after three decades of exposure to sea water

U radu su prikazane posljedice dugotrajnog izlaganja betonskih konstrukcija morskom okolišu, na primjeru betonskih blokova obalnog zida koji se nalaze u moru više od 30 godina. Na blokovima je provedeno ispitivanje mehaničkih (tlačna čvrstoća) i trajnosnih (plinopropusnost i kapilarno upijanje) svojstava, svojstava homogenosti (odskok sklerometrom i brzina prolaska ultrazvuka) te kemijska analiza (količina kloridnih i sulfatnih iona). Osim ispitivanja, provedeno je modeliranje ponašanja betona u morskoj vodi uz pomoć programskih paketa Stadium i Conclife.This paper presents the effects of long-term exposure of concrete structures to marine environment using as an example concrete blocks of a pier exposed to seawater for more than three decades. The blocks were tested to determine their mechanical characteristics (compressive strength), durability (gas permeability and capillary absorption), and chemical properties (quantity of chloride and sulphate ions). In addition, concrete behaviour in sea water was modelled using software packages Stadium and Conclife

ČELIČANSKA ZGURA KAO KORISTAN MATERIJAL ZA PROIZVODNJU BETONA

This paper aims to investigate the possibility of utilizing steel slags locally produced in Croatian plants as a concrete aggregate. Therefore, eight concrete mixtures were prepared with coarse slag fractions and different binders whose hardened state properties (compressive 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, dolomite. According to the obtained test results it can be concluded that concrete containing slag possesses acceptable mechanical properties and volume changes for its structural use but could represent a risk in terms of corrosion of reinforcement in case of slag with higher amount of sulphur in its chemical composition.U radu se istražuje mogućnost uporabe čeličanske zgure nastale u hrvatskim željezarama kao agregata u betonu. Pripremljeno je osam mješavina betona sa zgurom kao krupnom frakcijom i različitim vezivima te ispitana svojstva takvog betona u očvrslom stanju (tlačna čvrstoća, statički modul elastičnosti, volumne promjene i sklonost ka koroziji) i uspoređena sa svojstvima referentnog betona pripremljenog sa uobičajeno korištenim agregatom, dolomitom. Prema ostvarenim rezultatima ispitivanja može se zaključiti da beton sa zgurom u sastavu svojim mehaničkim svojstvima i volumnim promjenama zadovoljava uvjete za primjenu u konstrukciji ali može djelovati korozivno na armaturni čelik ukoliko zgura sadrži veći udio sumpora u kemijskom sastavu