EP0923506A2 - Method for producing sulfate cement or sulfate cement aggregates - Google Patents

Method for producing sulfate cement or sulfate cement aggregates

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Publication number
EP0923506A2
EP0923506A2 EP98909205A EP98909205A EP0923506A2 EP 0923506 A2 EP0923506 A2 EP 0923506A2 EP 98909205 A EP98909205 A EP 98909205A EP 98909205 A EP98909205 A EP 98909205A EP 0923506 A2 EP0923506 A2 EP 0923506A2
Authority
EP
European Patent Office
Prior art keywords
gypsum
slag
sulfate
cement
slags
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP98909205A
Other languages
German (de)
French (fr)
Other versions
EP0923506A3 (en
Inventor
Alfred Edlinger
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Holcim Ltd
Original Assignee
Holderbank Financiere Glarus AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Holderbank Financiere Glarus AG filed Critical Holderbank Financiere Glarus AG
Publication of EP0923506A2 publication Critical patent/EP0923506A2/en
Publication of EP0923506A3 publication Critical patent/EP0923506A3/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B7/00—Hydraulic cements
    • C04B7/14—Cements containing slag
    • C04B7/147—Metallurgical slag
    • C04B7/153—Mixtures thereof with other inorganic cementitious materials or other activators
    • C04B7/21—Mixtures thereof with other inorganic cementitious materials or other activators with calcium sulfate containing activators
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B5/00—Treatment of  metallurgical  slag ; Artificial stone from molten  metallurgical  slag 
    • C04B5/06—Ingredients, other than water, added to the molten slag or to the granulating medium or before remelting; Treatment with gases or gas generating compounds, e.g. to obtain porous slag
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/42—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells
    • C09K8/46—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells containing inorganic binders, e.g. Portland cement
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding

Definitions

  • the invention relates to a method for producing sulfate cement or sulfate cement additives.
  • blast furnace slag was ground with 15% by weight calcium sulfate in the form of raw gypsum and about 2% by weight Portland cement was added.
  • the presence of hydrated lime in the first hardening stage has turned out to be necessary, because otherwise a dense gel layer will form primarily before sulfatic hardening takes place.
  • blast furnace slags are unsuitable for the production of sulphate metallurgical cement. This is all the more true as conventional blast furnace slags generally have a relatively low alumina content, so that the desired formation of sulfoaluminates is unsuccessful or insufficient, so that the risk of gypsum blowing remains. Finally, a high lime content is required, which is also generally not the case with blast furnace slag. For all of the reasons mentioned, sulphate metallurgical cements have gained no importance in construction practice.
  • the invention now aims to provide a method of the type mentioned at the beginning with which it is possible to achieve cement or cement aggregates with excellent resistance to sulfate and sea water and which can be used, for example, as borehole cements, the risk of gypsum blowing being avoided with certainty.
  • the process according to the invention essentially consists in mixing hydraulically active synthetic slags with a slag basicity CaO / SiO 2 between 1.35 and 1.6, such as waste incineration slags and / or blast furnace slags mixed with steel slags after reduction of metal oxides in the melt, and an Al2 ⁇ -3 content of 10 to 20% by weight and an iron oxide content of less than 2.5% by weight with 5 to 20% by weight, based on the total mixture of an alkaline earth metal sulfate, such as raw gypsum, exhaust gypsum , Flue gas desulfurization system gypsum, gypsum or anhydrite mixed in ground or crushed form.
  • the AI2O3 content can be set to the specified values of 10 to 20% by weight, whereby by reducing the liquid slag not only the heavy metal content but also the Iron oxide content must be brought below 2.5% by weight in order not to subsequently observe any undesirable side effects. Because such a highly purified synthetic slag is now used, a number of materials which are difficult to dispose of, such as, for example, flue gas desulfurization system gypsum, raw gypsum, exhaust gypsum, but also gypsum and anhydrite can be used as alkaline earth metal sulfate carriers.
  • the slags must be ground to a much lower fineness than was the case with known sulfate smelter cements, and it is particularly not necessary to grind the slags together with gypsum, as was the case in the past, in order to achieve a correspondingly good, homogeneous mixture guarantee.
  • the usual blending of raw gypsum with the slag in the production of sulphate metallurgical cements presents a number of difficulties during grinding. In such mixtures, gypsum has a tendency to smear, so that the desired fineness cannot be easily achieved.
  • the high degree of fineness required for a homogeneous distribution of the gypsum can therefore only be achieved with great difficulty.
  • the synthetic slag according to the invention it is sufficient to grind this slag to a much lower fineness and to subsequently add gypsum in a correspondingly lower fineness, although the desired homogeneity of the mixture can nevertheless be achieved.
  • the procedure is advantageously such that a grinding fineness of the synthetic slags between 2800 and 3500 cm ⁇ / g is selected, such grinding fineness being significantly less than the grinding fineness required for known sulphate metallurgical cements.
  • the procedure is advantageously such that the Al 2 O 3 content is set between 12 and 18% by weight.
  • CaS04 is advantageously used in amounts of between 8 and 15% by weight, with a corresponding rapid hardening being ensured by selecting the slag basicity to be greater than 1.45, preferably about 1.5.
  • the AI2O3 content can be adjusted in a particularly simple manner by adding clays or alumina, this adjustment being able to take place in the liquid slag phase.
  • Steel slags usually contain about 16% by weight SiO 2, 50% by weight CaO and 1% by weight Al 2 O 3. Such steel slags can thus be used as lime carriers to adjust the basicity of other slags, such as waste incineration slags, which are mostly to be addressed as acid slags.
  • Blast furnace slags are usually also referred to as acidic slags and are rarely available with a slag basicity greater than 1.1 or 1.2.
  • Blast furnace slag cements usually contain SiO 2 in amounts of approximately 37% by weight and CaO in amounts of approximately 32% by weight.
  • AI2O3 is usually contained in an amount of about 13% by weight, so that mixtures of steel slags and blast furnace slags in liquid form after the basicity of the AI2O3 content has been appropriately adjusted and after the excessive chromium and iron content of steel slags has been reduced , for example using a metal bath, are suitable for a synthetic slag which subsequently converts to sulfate cement can be worked.
  • Waste incineration slags are generally also referred to as acidic slags, such slags generally being characterized by an Al 2 O 3 content of the order of 10 to 25% by weight and a basicity of less than 0.5.
  • Such slags thus contain significantly higher proportions of SiO 2 than CaO and are also not suitable for themselves as a starting material without appropriate adjustment of the basicity and corresponding reduction of the metal oxides.
  • the appropriate slag mixture for the required hydraulically active synthetic slag must be set in the liquid phase to ensure the desired basicity values between 1.35 and 1.6, only this basicity can ensure that the sulfoaluminate reaction without a primary hydration below
  • the use of hydrated lime or Portland cement is made possible, since otherwise the formation of a gel layer would hinder this reaction.
  • a sulfate smelter cement was produced and compared with a cement produced according to the invention.
  • This comparison showed that the compressive strength development in the cement according to the invention is characterized by a higher final strength with a slightly lower strength after 3 days.
  • the compressive strength values for sulfate metallurgical cement after 3 days were 41 N / mm 2 compared to 38 N / mm 2 for the cement according to the invention. After 28 days, a compressive strength of 76 N / mm 2 could be achieved with sulphate metallurgical cement, whereas the cement according to the invention gave values of 82 N / mm 2 .
  • the flexural strength of the cement according to the invention was about twice as high as that of known sulphate metallurgical cements.
  • Sulphate metallurgical cement achieved a bending strength of 7 N / mm 2 , where against values of 14 N / mm 2 were achieved with the cement according to the invention.
  • the cement according to the invention is characterized by a significantly lower tendency to shrink. While cracking was observed in metallurgical cements and conventional blast furnace slag mixed cements, cracking was largely excluded in the cement according to the invention due to the significantly lower tendency to shrink and was also not observed.
  • the grinding fineness was determined in the course of the Blaine tests in accordance with ASTM standard C 204-55.
  • the sulphate smelter cement used in the comparative experiments was ground up much more elaborately and was used with a fineness of 5000 cm / g, whereas the cement according to the invention used in the comparative experiments was ground only to 3000 cm 2 / g fineness.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)
  • Processing Of Solid Wastes (AREA)
  • Soil Conditioners And Soil-Stabilizing Materials (AREA)
  • Treating Waste Gases (AREA)

Abstract

The invention relates to a method for producing sulfate cement or sulfate cement aggregates by mixing hydraulically active synthetic slags with a CaO/SiO2 slag basicity of between 1.35 and 1.6, such as refuse incineration slag and/or blast furnace slag mixed with steel slag after reduction of the metal oxides in the molten mass, containing 10 to 20 weight per cent Al2O3, less than 2.5 weight per cent iron oxides, and 5 to 20 weight per cent of an alkaline earth sulfate, in relation to the total mixture, for example crude gypsum, waste gas gypsum, gypsum from flue gas desulfurization plants, gypsum or anhydrite in ground or crushed form.

Description

Verfahren zur Herstellung von Sulfatzement oder Sulfatzement- zuschlaαstoffenProcess for the preparation of sulfate cement or sulfate cement additives
Die Erfindung bezieht sich auf ein Verfahren zur Herstellung von Sulfatzement oder Sulfatzementzuschlagstoffen.The invention relates to a method for producing sulfate cement or sulfate cement additives.
Bereits zu Beginn dieses Jahrhunderts wurde entdeckt, daß granulierte Hochofenschlacke nicht allein durch Kalk oder Portlandzement zur hydraulischen Aushärtung angeregt werden kann, sondern daß derartige Schlacken auch durch Kombination mit Gips in Mengen von etwa 10 bis 15 Gew. % zur Erhärtung befähigt sind. Trotz dieser Erkenntnis blieb jedoch die technische Verwendung dieser Erkenntnis beschränkt. Gips als Vertreter für derartige Sulfate birgt nämlich die Gefahr mit sich, daß ein Gipstreiben bewirkt wird. Der beim Gipstreiben auftretende örtliche Raumbedarf des kristallwasserreichen Reaktionsproduktes führt zu einer Sprengwirkung. Dies gilt vor allen Dingen dann, wenn, wie bei bekannten Sulfathüttenzementen, die anfängliche Erhärtung nur durch Beimengungen von Portlandzementklinker als Kalkträger aus- gelöst werden konnte. Bei den bekannten Sulfathüttenzementen wurde Hochofenschlacke mit 15 Gew.% Kalziumsulfat in Form von Rohgips vermählen und etwa 2 Gew.% Portlandzement zugesetzt. Die Anwesenheit von Kalkhydrat im ersten ErhärtungsStadium hat sich als notwendig herausgestellt, weil sich sonst primär eine dichte Gelschicht bildet, bevor es überhaupt zu einer sulfatischen Aushärtung kommt.Already at the beginning of this century it was discovered that granulated blast furnace slag cannot be stimulated hydraulically by lime or Portland cement alone, but that such slag can also be hardened by combining it with gypsum in quantities of approximately 10 to 15% by weight. Despite this knowledge, the technical use of this knowledge remained limited. Gypsum as a representative of such sulfates runs the risk of causing gypsum. The local space requirement of the reaction product, which is rich in water of crystallization, occurs when gypsum is cast, which leads to an explosive effect. This applies above all if, as with known sulfate smelter cements, the initial hardening could only be triggered by adding Portland cement clinker as a lime carrier. In the known sulfate smelter cements, blast furnace slag was ground with 15% by weight calcium sulfate in the form of raw gypsum and about 2% by weight Portland cement was added. The presence of hydrated lime in the first hardening stage has turned out to be necessary, because otherwise a dense gel layer will form primarily before sulfatic hardening takes place.
In diesem Zusammenhang ist es von Bedeutung, daß der Erhärtungsmechanismus von Sulfathüttenzementen nicht mit der alkalischen Erregung des Hydratationsprozesses bei Portlandzementen zu vergleichen ist. Bei Hüttenzement reicht die Anwesenheit von Kalkhydrat zur Auslösung der Hydratation, wohingegen im Falle der bekannten Sulfathüttenzemente eine echte Reaktion ablaufen muß, in deren Verlauf Gips in Kalziumsulfoaluminat übergeführt wird. Erst dieses Sulfoaluminat bewirkt die erforderliche Erhärtung, wobei der Umstand, daß ein Gipstreiben mit Sicherheit vermieden werden muß, dazu geführt hat, daß bei den bekannten Hütten- zementen eine hohe Mahlfeinheit von wenigstens 4000 bis 6000 cm^/g eingehalten werden muß. Im übrigen hat sich herausgestellt, daß die meisten Hochofenschlacken für die Herstellung von Sulfathüttenzement ungeeignet sind. Dies gilt umso mehr als übliche Hochofenschlacken in der Regel einen relativ geringen Tonerdegehalt aufweisen, sodaß die gewünschte Ausbildung von Sulfoaluminaten nicht oder nur unzureichend gelingt, sodaß wiederum die Gefahr des Gipstreibens verbleibt. Schließlich ist ein hoher Kalkgehalt erforderlich, welcher gleichfalls bei Hoch- ofenschlacke in der Regel nicht vorliegt. Sulfathüttenzementen haben aus all den genannten Gründen keine Bedeutung in der Baupraxis erlangt.In this context it is important that the hardening mechanism of sulphate metallurgical cements cannot be compared to the alkaline excitation of the hydration process in Portland cements. In the case of metallurgical cement, the presence of hydrated lime is sufficient to trigger hydration, whereas in the case of the known sulphate metallurgical cements, a real reaction must take place, in the course of which gypsum is converted into calcium sulphoaluminate. It is only this sulfoaluminate that causes the necessary hardening, the fact that gypsum must be avoided with certainty has led to the fact that in the known smelters cements a high fineness of at least 4000 to 6000 cm ^ / g must be observed. In addition, it has been found that most blast furnace slags are unsuitable for the production of sulphate metallurgical cement. This is all the more true as conventional blast furnace slags generally have a relatively low alumina content, so that the desired formation of sulfoaluminates is unsuccessful or insufficient, so that the risk of gypsum blowing remains. Finally, a high lime content is required, which is also generally not the case with blast furnace slag. For all of the reasons mentioned, sulphate metallurgical cements have gained no importance in construction practice.
Die Erfindung zielt nun darauf ab, ein Verfahren der eingangs genannten Art zu schaffen, mit welchem es gelingt Zement oder Zementzuschlagstoffe mit ausgezeichneter Sulfat- und Meerwasserbeständigkeit zu erreichen und welche sich beispielsweise als Bohrlochzemente einsetzen lassen, wobei die Gefahr eines Gipstreibens mit Sicherheit vermieden wird. Zur Lösung dieser Auf- gäbe besteht das erfindungsgemäße Verfahren im wesentlichen darin, daß man hydraulisch aktive synthetische Schlacken mit einer Schlackenbasizität CaO/Siθ2 zwischen 1,35 und 1,6, wie z.B. Müllverbrennungsschlacken und/oder Hochofenschlacken vermischt mit Stahlschlacken nach Reduktion von Metalloxiden in der Schmelze, und einem Al2<-3-Gehalt von 10 bis 20 Gew.% und einem Gehalt an Eisenoxiden von unter 2,5 Gew.% mit 5 bis 20 Gew.% bezogen auf die Gesamtmischung eines Erdalkalisulfates, wie z.B. Rohgips, Abgasgips, Rauchgasentschwefelungsanlagengips , Gips oder Anhydrit in gemahlener bzw. zerkleinerter Form vermischt. Dadurch, daß nun nicht natürlich vorkommende Schlacken, welche in aller Regel den geforderten Bedingungen in keiner Weise entsprechen, sondern eine hydraulisch aktive synthetische Schlacke eingesetzt wird, gelingt es nun die Voraussetzungen für eine vollständige Unterbindung des Gipstreibens zu schaffen und einen Zement oder Zementzuschlagstoff herzustellen, welcher sich durch verbesserte Meerwasserbeständigkeit und verbesserte Sulfatbeständigkeit auszeichnet. Dadurch, daß nun eine synthetische Schlacke verwendet wird, gelingt es bereits bei der Synthese der Schlacke die von Hochofenschlacken in aller Regel nicht erreichbare Schlackenbasizität zwischen 1,35 und 1,6 einzustellen, wobei dies beispielsweise dadurch gelingt, daß Müllverbrennungs- schlacken mit Stahlschlacken vermischt werden und die in derartigen Schlacken enthaltenen Metalloxide reduziert werden. In der Schmelze kann, sofern dies durch die gewählte Ausgangsschlacke noch nicht gewährleistet ist, der AI2O3-Gehalt auf die vorgegebenen Werte von 10 bis 20 Gew.% eingestellt werden, wobei durch das Reduzieren der flüssigen Schlacken nicht nur der Gehalt an Schwermetallen sondern auch der Gehalt an Eisenoxiden unter 2,5 Gew.% gebracht werden muß, um in der Folge keine unerwünschten Nebenwirkungen zu beobachten. Dadurch, daß nun eine derartige hochgereinigte synthetische Schlacke eingesetzt wird, können als Erdalkalisulfatträger eine Reihe von schwer zu entsorgenden Materialien, wie beispielsweise Rauchgasentschwefe- lungsanlagengips, Rohgips, Abgasgips, aber auch Gips und Anhydrit eingesetzt werden. Die Schlacken müssen hiebei auf wesentlich geringere Mahlfeinheit vermählen werden, als dies bei bekannten Sulfathüttenzementen der Fall war und es ist insbesondere nicht erforderlich die Schlacken gemeinsam mit Gips zu vermählen, wie dies in der Vergangenheit der Fall war, um eine entsprechend gute, homogene Durchmischung zu gewährleisten. Das bei der Sulfathüttenzementherstellung übliche Vermengen von Roh- gips mit der Hüttenschlacke bereitet beim Vermählen eine Reihe von Schwierigkeiten. Gips hat in derartigen Mischungen die Tendenz zum Schmieren zu neigen, sodaß die gewünschte Mahlfeinheit nicht ohne weiteres erzielt werden kann. Die geforderte hohe Feinheit für eine homogene Verteilung des Gipses, wie dies bei Sulfathüttenzementen erforderlich war, läßt sich daher nur mit großen Schwierigkeiten erzielen. Demgegenüber genügt es bei Wahl der erfindungsgemäßen synthetischen Schlacke diese Schlacke auf eine wesentlich geringere Mahlfeinheit zu vermählen und Gips in ebenfalls entsprechend geringerer Mahlfeinheit nachträglich zuzumischen, wobei dennoch die gewünschte Homogenität der Mischung erzielt werden kann. Erfindungsgemäß wird mit Vorteil so vorgegangen, daß eine Mahlfeinheit der synthetischen Schlacken zwischen 2800 und 3500 cm^/g gewählt wird, wobei eine derartige Mahlfeinheit deutlich geringer ist, als die für bekannte Sulfathüttenzemente geforderte Mahlfeinheit.The invention now aims to provide a method of the type mentioned at the beginning with which it is possible to achieve cement or cement aggregates with excellent resistance to sulfate and sea water and which can be used, for example, as borehole cements, the risk of gypsum blowing being avoided with certainty. To solve these problems, the process according to the invention essentially consists in mixing hydraulically active synthetic slags with a slag basicity CaO / SiO 2 between 1.35 and 1.6, such as waste incineration slags and / or blast furnace slags mixed with steel slags after reduction of metal oxides in the melt, and an Al2 <-3 content of 10 to 20% by weight and an iron oxide content of less than 2.5% by weight with 5 to 20% by weight, based on the total mixture of an alkaline earth metal sulfate, such as raw gypsum, exhaust gypsum , Flue gas desulfurization system gypsum, gypsum or anhydrite mixed in ground or crushed form. The fact that not naturally occurring slags, which generally do not meet the required conditions in any way, but that a hydraulically active synthetic slag is used, now creates the conditions for a complete suppression of gypsum blowing and produces a cement or cement aggregate, which is characterized by improved seawater resistance and improved sulfate resistance. Because now a synthetic If slag is used, the slag basicity, which is generally not attainable by blast furnace slag, can be set between 1.35 and 1.6 already in the synthesis of the slag, this being achieved, for example, by mixing waste incineration slag with steel slag and that in such slag contained metal oxides can be reduced. In the melt, if this is not yet guaranteed by the selected starting slag, the AI2O3 content can be set to the specified values of 10 to 20% by weight, whereby by reducing the liquid slag not only the heavy metal content but also the Iron oxide content must be brought below 2.5% by weight in order not to subsequently observe any undesirable side effects. Because such a highly purified synthetic slag is now used, a number of materials which are difficult to dispose of, such as, for example, flue gas desulfurization system gypsum, raw gypsum, exhaust gypsum, but also gypsum and anhydrite can be used as alkaline earth metal sulfate carriers. The slags must be ground to a much lower fineness than was the case with known sulfate smelter cements, and it is particularly not necessary to grind the slags together with gypsum, as was the case in the past, in order to achieve a correspondingly good, homogeneous mixture guarantee. The usual blending of raw gypsum with the slag in the production of sulphate metallurgical cements presents a number of difficulties during grinding. In such mixtures, gypsum has a tendency to smear, so that the desired fineness cannot be easily achieved. The high degree of fineness required for a homogeneous distribution of the gypsum, as was required with sulfate metallurgical cements, can therefore only be achieved with great difficulty. In contrast, if the synthetic slag according to the invention is selected, it is sufficient to grind this slag to a much lower fineness and to subsequently add gypsum in a correspondingly lower fineness, although the desired homogeneity of the mixture can nevertheless be achieved. According to the invention, the procedure is advantageously such that a grinding fineness of the synthetic slags between 2800 and 3500 cm ^ / g is selected, such grinding fineness being significantly less than the grinding fineness required for known sulphate metallurgical cements.
Um die gewünschte Sulfoaluminatreaktion in der Folge sicherzustellen wird mit Vorteil so vorgegangen, daß der AI2O3 -Gehalt zwischen 12 und 18 Gew.% eingestellt wird.In order to ensure the desired sulfoaluminate reaction subsequently, the procedure is advantageously such that the Al 2 O 3 content is set between 12 and 18% by weight.
Mit Vorteil wird CaS04 in Mengen zwischen 8 und 15 Gew.% eingesetzt, wobei eine entsprechende rasche Abhärtung dadurch gewährleistet werden kann, daß die Schlackenbasizität größer 1,45, vorzugsweise etwa 1,5, gewählt wird.CaS04 is advantageously used in amounts of between 8 and 15% by weight, with a corresponding rapid hardening being ensured by selecting the slag basicity to be greater than 1.45, preferably about 1.5.
Der AI2O3 -Gehalt kann in besonders einfacher Weise durch Zusatz von Tonen oder Tonerde eingestellt werden, wobei diese Einstellung in der flüssigen Schlackenphase erfolgen kann.The AI2O3 content can be adjusted in a particularly simple manner by adding clays or alumina, this adjustment being able to take place in the liquid slag phase.
Üblicherweise sind in Stahlschlacken etwa 16 Gew.% Siθ2 50 Gew.% CaO und 1 Gew.% AI2O3 enthalten. Derartige Stahlschlacken können somit als Kalkträger zur Einstellung der Basi- zität von anderen Schlacken, wie beispielsweise Müllverbrennungsschlacken, eingesetzt werden, welche zumeist als saure Schlacken anzusprechen sind. Hochofenschlacken sind gleichfalls in der Regel als saure Schlacken anzusprechen und nur in den seltensten Fällen mit einer Schlackenbasizität von größer als 1,1 oder 1,2 erhältlich. Üblicherweise enthalten Hochofenschlackenzemente Siθ2 in Mengen von etwa 37 Gew.% und CaO in Mengen von etwa 32 Gew.%. In derartigen Hochofenschlacken ist allerdings AI2O3 in der Regel in einer Menge von etwa 13 Gew.% enthalten, sodaß Gemische aus Stahlschlacken und Hochofenschlacken in flüssiger Form nach entsprechender Einstellung der Basizität des AI2O3 -Gehaltes und nach Reduktion des zu hohen Chrom- und Eisengehaltes von Stahlschlacken, beispielsweise unter Verwendung eines Metallbades, für eine synthetische Schlacke geeignet sind, welche nachfolgend zu Sulfatzement ver- arbeitet werden kann. Analoges gilt für die Verwendung von Müll- verbrennungs- bzw. Kehrrichtverbrennungsanlagen, Schlacken oder Stäuben, welche gleichfalls aufgrund der enthaltenen Metalloxide durch entsprechende Reduktion über einem Metallbad zuvor gerei- nigt werden müssen, um in entsprechender Zusammensetzung als synthetische Schlacke für die Herstellung von Sulfatzement Verwendung finden zu können. Auch Müllverbrennungsschlacken sind in der Regel als saure Schlacken zu bezeichnen, wobei sich derartige Schlacken in der Regel durch einen AI2O3 -Gehalt in der Größenordnung von 10 bis 25 Gew.% und eine Basizität von weniger als 0,5 auszeichnen. Derartige Schlacken enthalten somit wesentlich höhere Anteile an Siθ2 als an CaO und sind für sich gesehen ohne entsprechende Einstellung der Basizität und entsprechende Reduktion der Metalloxide gleichfalls nicht für sich gesehen als Ausgangsmaterial geeignet. Auch hier muß die geeignete Schlackenmischung für die geforderte hydraulisch aktive synthetische Schlacke in der flüssigen Phase eingestellt werden, um die gewünschten Basizitätswerte zwischen 1,35 und 1,6 zu gewährleisten, wobei nur diese Basizität sicherstellen kann, daß die Sulfoaluminatreaktion ohne eine primäre Hydratation unter Einsatz von Kalkhydrat bzw. Portlandzement ermöglicht wird, da andernfalls die Ausbildung einer Gel-Schicht diese Reaktion behindern würde.Steel slags usually contain about 16% by weight SiO 2, 50% by weight CaO and 1% by weight Al 2 O 3. Such steel slags can thus be used as lime carriers to adjust the basicity of other slags, such as waste incineration slags, which are mostly to be addressed as acid slags. Blast furnace slags are usually also referred to as acidic slags and are rarely available with a slag basicity greater than 1.1 or 1.2. Blast furnace slag cements usually contain SiO 2 in amounts of approximately 37% by weight and CaO in amounts of approximately 32% by weight. In such blast furnace slags, however, AI2O3 is usually contained in an amount of about 13% by weight, so that mixtures of steel slags and blast furnace slags in liquid form after the basicity of the AI2O3 content has been appropriately adjusted and after the excessive chromium and iron content of steel slags has been reduced , for example using a metal bath, are suitable for a synthetic slag which subsequently converts to sulfate cement can be worked. The same applies analogously to the use of waste incineration or waste incineration plants, slags or dusts, which, likewise due to the metal oxides contained, have to be cleaned beforehand by appropriate reduction over a metal bath in order to be used in a suitable composition as synthetic slag for the production of sulfate cement to be able to find. Waste incineration slags are generally also referred to as acidic slags, such slags generally being characterized by an Al 2 O 3 content of the order of 10 to 25% by weight and a basicity of less than 0.5. Such slags thus contain significantly higher proportions of SiO 2 than CaO and are also not suitable for themselves as a starting material without appropriate adjustment of the basicity and corresponding reduction of the metal oxides. Again, the appropriate slag mixture for the required hydraulically active synthetic slag must be set in the liquid phase to ensure the desired basicity values between 1.35 and 1.6, only this basicity can ensure that the sulfoaluminate reaction without a primary hydration below The use of hydrated lime or Portland cement is made possible, since otherwise the formation of a gel layer would hinder this reaction.
Zu Vergleichszwecken wurde ein Sulfathüttenzement hergestellt und mit einem erfindungsgemäß hergestellten Zement verglichen. Bei diesem Vergleich stellte sich heraus, daß die Druckfestigkeitsentwicklung bei dem erfindungsgemäßen Zement sich durch eine höhere Endfestigkeit bei geringfügig geringerer Festigkeit nach 3 Tagen auszeichnet. Die Druckfestigkeitswerte betrugen für Sulfathüttenzement nach 3 Tagen 41 N/mm2 gegenüber 38 N/mm2 bei dem erfindungsgemäßen Zement. Nach 28 Tagen konnte mit Sulfathüttenzement eine Druckfestigkeit von 76 N/mm2 erreicht werden, wohingegen der erfindungsgemäße Zement Werte von 82 N/mm2 ergab. Die Biegefestigkeit war beim erfindungsgemäßen Zement etwa doppelt so hoch wie bei bekannten Sulfathüttenzementen. Sulfathüttenzement erreichte eine Biegefestigkeit von 7 N/mm2, wohin- gegen mit dem erf indungsgemäßen Zement Werte von 14 N/mm2 erzielt wurden .For comparison purposes, a sulfate smelter cement was produced and compared with a cement produced according to the invention. This comparison showed that the compressive strength development in the cement according to the invention is characterized by a higher final strength with a slightly lower strength after 3 days. The compressive strength values for sulfate metallurgical cement after 3 days were 41 N / mm 2 compared to 38 N / mm 2 for the cement according to the invention. After 28 days, a compressive strength of 76 N / mm 2 could be achieved with sulphate metallurgical cement, whereas the cement according to the invention gave values of 82 N / mm 2 . The flexural strength of the cement according to the invention was about twice as high as that of known sulphate metallurgical cements. Sulphate metallurgical cement achieved a bending strength of 7 N / mm 2 , where against values of 14 N / mm 2 were achieved with the cement according to the invention.
Bei diesen vergleichenden Versuchen wurde beobachtet , daß sich der erfindungsgemäße Zement durch eine wesentlich geringere Schwindneigung auszeichnet . Während bei Hüttenzementen und üblichen Hochof enschlackenmischzementen Rißbildungen beobachtet wurden, waren beim erfindungsgemäßen Zement aufgrund der wesentlich geringeren Schwindneigung Rißbildungen weitestgehend ausge- schlössen und wurden auch nicht beobachtet .In these comparative experiments it was observed that the cement according to the invention is characterized by a significantly lower tendency to shrink. While cracking was observed in metallurgical cements and conventional blast furnace slag mixed cements, cracking was largely excluded in the cement according to the invention due to the significantly lower tendency to shrink and was also not observed.
Die Mahlfeinheit wurde im Zuge der Untersuchungen nach Blaine gemäß ASTM-Standard C 204-55 bestimmt . Der in den Vergleichsversuchen verwendete Sulfathüttenzement wurde wesentlich aufwendi- ger und f einer vermählen und mit einer Mahlfeinheit von 5000 cm /g eingesetzt , wohingegen der in den Vergleichsversuchen herangezogene erfindungsgemäße Zement lediglich auf 3000 cm2 /g Mahlfeinheit gemahlen wurde . The grinding fineness was determined in the course of the Blaine tests in accordance with ASTM standard C 204-55. The sulphate smelter cement used in the comparative experiments was ground up much more elaborately and was used with a fineness of 5000 cm / g, whereas the cement according to the invention used in the comparative experiments was ground only to 3000 cm 2 / g fineness.

Claims

Patentansprüche : Claims:
1. Verfahren zur Herstellung von Sulfatzement oder Sulfatzement- Zuschlagstoffen, dadurch gekennzeichnet, daß man hydraulisch aktive synthetische Schlacken mit einer Schlackenbasizität CaO/Siθ2 zwischen 1,35 und 1,6, wie z.B. Müllverbrennungs- schlacken und/oder Hochofenschlacken vermischt mit Stahlschlacken nach Reduktion von Metalloxiden in der Schmelze, und einem AI2O3 -Gehalt von 10 bis 20 Gew.% und einem Gehalt an Eisenoxiden von unter 2,5 Gew.% mit 5 bis 20 Gew.% bezogen auf die Gesamtmischung eines Erdalkalisulfates, wie z.B. Rohgips, Abgasgips, Rauchgasentschwefelungsanlagengips, Gips oder Anhydrit in gemahlener bzw. zerkleinerter Form vermischt.1. A process for the preparation of sulfate cement or sulfate cement additives, characterized in that hydraulically active synthetic slags with a slag basicity CaO / SiO 2 between 1.35 and 1.6, such as Waste incineration slag and / or blast furnace slag mixed with steel slag after reduction of metal oxides in the melt, and an AI2O3 content of 10 to 20% by weight and a content of iron oxides of less than 2.5% by weight with 5 to 20% by weight based on the total mixture of an alkaline earth metal sulfate, such as Raw gypsum, exhaust gypsum, flue gas desulfurization system gypsum, gypsum or anhydrite mixed in ground or crushed form.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß eine Mahlfeinheit der synthetischen Schlacken zwischen 2800 und 3500 cm2/g gewählt wird.2. The method according to claim 1, characterized in that a fineness of the synthetic slags between 2800 and 3500 cm 2 / g is selected.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der AI2O3-Gehalt zwischen 12 und 18 Gew.% eingestellt wird.3. The method according to claim 1 or 2, characterized in that the AI2O3 content is set between 12 and 18 wt.%.
4. Verfahren nach Anspruch 1, 2 oder 3, dadurch gekennzeichnet, daß CaS04 in Mengen zwischen 8 und 15 Gew.% eingesetzt wird.4. The method according to claim 1, 2 or 3, characterized in that CaS04 is used in amounts between 8 and 15 wt.%.
5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß die Schlackenbasizität größer 1,45, vorzugsweise etwa 1,5, gewählt wird.5. The method according to any one of claims 1 to 4, characterized in that the slag basicity greater than 1.45, preferably about 1.5, is selected.
6. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß der AI2O3 -Gehalt durch Zusatz von Tonen oder Tonerde eingestellt wird. 6. The method according to any one of claims 1 to 5, characterized in that the AI2O3 content is adjusted by adding clays or alumina.
EP98909205A 1997-04-09 1998-03-12 Method for producing sulfate cement or sulfate cement aggregates Withdrawn EP0923506A3 (en)

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AT0061197A AT404723B (en) 1997-04-09 1997-04-09 METHOD FOR PRODUCING SULFATE CEMENT OR SULFATE CEMENT ADDITIVES
AT61197 1997-04-09
PCT/AT1998/000066 WO1998045218A2 (en) 1997-04-09 1998-03-12 Method for producing sulfate cement or sulfate cement aggregates

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