WO2010083801A1 - Method for producing a sulfate-resistant hydraulic binding agent having a high alite content and the use thereof - Google Patents

Abstract

The present invention relates to a method for producing a hydraulic binding agent from a firing product, comprising as the primary components finely ground limestone and at least diatomaceous earth as a siliceous component, as well as auxiliary sintering agents, wherein, depending on the purity of the limestone and diatomaceous earth, the firing product is designed such that by mixing the two primary components a ratio between CaO and SiO2 of 3:1 is adjusted, and the firing product is subsequently subjected to a firing process, wherein the CaCO3 of the limestone is pyrolyzed and an alite proportion of > 90% by weight forms in the firing product, wherein the auxiliary sintering agents not only bring about the formation of a glass phase, which favors a solid state reaction between the reactive calcium oxide formed after the pyrolysis of the CaCO3 and amorphous silicic acid from the diatomaceous earth, but as mineralizers also favors the formation of alite.

Description

METHOD FOR PRODUCING A SULPHATE-RESISTANT HYDRAULIC BIN WITH VERY HIGH ALIT CONTENT AND ITS USE

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DESCRIPTION

Technical area

The present invention relates to a novel process for

Production of a hydraulic binder from a kiln, consisting of present as main components present finely ground limestone and at least diatomaceous earth as silicate component, and sintering aids, in which the kiln is designed depending on the purity of the limestone and the Kieseigurs so that by mixing the two main components Ratio of calcium oxide (CaO) to silicon oxide (SiO ₂ ) of 3: 1 sets.

State of the art

For the production of cement - in particular Portland cement - are the raw materials limestone (CaCOs), clay (Al ₂ O ₃ - 2SiO ₂ - 2H ₂ O) with quartz sand (SiO ₂ ) and after the known state of the art process following a pre-crushing Iron oxide (Fe ₂ Os) mixed in a well-defined ratio to a so-called raw meal, where appropriate, correction substances such as bauxite, sand or iron ore are added. By mills the -Rohmehl is further crushed, dried and then fed via a preheater a Drehrohofen dusty, in which from the raw meal at temperatures between 1250 ° C to 1450 ⁰ C, the cement clinker is fired, so that after the thermal decomposition of the calcium carbonate (CaCÜ3 ) (so-called calcination reaction) a certain composition of CaO, SiO ₂ , alumina (Al ₂ θ3) and iron oxide (FeΣθ3) is present.

[0003] After milling with admixing of admixing substances (calcium sulfate, granulated slag, fly ash, limestone meal, burned oil shale, trass, etc.), the actual cement is produced. In this process form artificial mineral oils, which are largely responsible for the hydraulic properties of the binding agent. The most important component of the cement clinker is the mineral phase alite (tricalcium silicate (3CaOxSiO ₂ )), which gives the cement the desired properties such as rapid hardening and high strength.

During the subsequent clinker burning, after the above-described process, in addition to the main constituent alite, further clinker phases such as dicalcium silicate [C2S -elite], calcium aluminate (C3A) and calcium aluminate ferrite (C4AF) and free calcium oxide (CaO) are formed. Above a temperature of about 125O ⁰ C is formed under a decrease of CaO-content of a melt, said reinforced alite forms, which usually accounts for about 40 - is 80 wt .-% of the total binder.

The usual proportions of the individual phases in the cement clinker are shown in the following table:

The disadvantage of this applied according to the prior art method is that calcium aluminate reacts very quickly and would lead to rapid solidification of the binder without the addition of a sulfate carrier.

For this reason, calcium sulfate (gypsum and / or anhydrite) is added to Portland cements predominantly during grinding. However, the calcium aluminate makes the hardened concrete sensitive to a fαtαngriff. The formation of ettringite or ettringite-like phases by a sulfate attack is known to lead to expansion, cracking, and ultimately loss of strength in concrete and cement-based structures. In addition, it is known from cement chemistry that belite and calcium aluminate ferrite react only slowly. These components, which occur in different proportions in each Portland cement according to the above table, but bind CaO must be fired and ground. This means that the integration of these two phases consumes unnecessary energy, although the selective contribution of the phases to the hardening is very small.

Presentation of the invention

It is an object of the present invention to develop a binder which can slowly set even at elevated processing temperatures and can be easily adjusted to corresponding processing conditions. Another object of the present invention is to provide a binder which is resistant to sulfate. For this purpose, it is necessary to keep the proportions of belite (C ₂ S), calcium aluminate (C3A) and calcium aluminate ferrite (C4AF) in the binder as low as possible or preferably completely exclude and the percentage of alite (3CaOxSiO ₂ ) by an optimal mixing ratio in To make firing as high as possible.

According to the invention the above objects are achieved with the features of claim 1. Advantageous embodiments of the method according to the invention are specified in subclaims.

In contrast to the conventional Portlandzene clinker, according to the invention instead of limestone marl as a component with high

CaO content and clay / slate as carriers of SiO ₂ , Al ₂ O 3 and Fe ₂ Os - A - more precious, ie calcium carbonate-rich limestone as a carrier for CaO and diatomaceous earth as a carrier of SiO _{2 is} used.

It is already known from the prior art that alite is formed by firing a mixture of limestone and a silicon source, such as

Kieselguhr (diatomite) can be produced (see, inter alia, US 4,274,881 A, lines 20 to 23, column 5). Diatomaceous earth (also known as mountain flour, diatomaceous earth, diatomaceous earth, diatomite, infusorial earth, pebble, novaculite, novaculite, tripel, tripolite, tripolite, celite) is a whitish powdery substance consisting mainly of the silica shells of fossil diatoms. The peculiarity of kieselguhr is its mineralogical and physical nature. The shells of the diatomaceous earth consist mainly of amorphous (non-crystalline) silicon dioxide (SiO ₂ ) and have a very porous structure. Due to the amorphous state, the silica is much more reactive than the crystal-formed SiO ₂ in the quartz sand. Also, kieselguhr is much easier to grind up than quartz sand. The reaction of the silica (SiO ₂ ) from the kieselguhr and CaO, which forms during the deacidification of the calcium carbonate, also starts much earlier.

In order to keep the proportions of belite in the alit combustible to be produced as high as possible, it is necessary to prepare the mixture to be fired in such a way that a molar ratio of calcium oxide to silicon oxide of (at least) 3 : 1 is reached. The binder according to the invention is designed in such a way that an alite content of> = 90% by weight can be formed by the composition of the combustible material.

production method

For the production of cement clinker by the method according to the invention, the raw material batch according to generally well-known in the prior art method with the addition of water and more Zusαtzmitteln intimately mixed and pressed into Formkörpem. As additives serve special substances that cause the formation of the glass phase as a sintering aid on the one hand and thereby favoring the solid state reaction between the after the deacidification of calcium carbonate (CaCOs) resulting reactive calcium oxide (CaO) and the amorphous silica (SiO ₂ ) from the Contribute diatomaceous earth, and on the other hand, as mineralizers promote the formation of alite. As pressing process, the usual in the Kaisandsteinfertigung molding or roll press technology are used.

The moldings are dried and fired in a subsequent process. The firing units used are tunnel kilns, shaft kilns or rotary kilns. The process control is preferably to be chosen so that a complete conversion of CaO is achieved in the kiln (free-lime share CaO-free less 1, 5 wt .-%). In order to stabilize the alite formed in the kiln, the kiln is - as usual when firing Portland cement clinker - cooled quickly. The cooling air is used to dry the molded bodies.

embodiments

Based on the fact that in Alitgitter other oxides such as MgO, Al2O3, Fe ₂ θ3, ZnO, CaF ₂ , Mn ₂ θ3, BaO, P2O5 can be incorporated and stabilize the Alitbildung, such components on the main ingredients limestone powder and Diatomaceous earth introduced as impurities in the fuel mixture, or added as additives over up to 2 wt .-%, alone or in combination. Taking into account the impurities present in the diatomaceous earth, the composition of the burning material changes only insignificantly.

Depending on the application, the binder is ground to different Mahlfeinheiten. The grinding finenesses are in the range of 3000 cmVg to 6500 cmVg. For the grinding of products with a high grinding fineness, grinding aids which allow a reduction of the grinding energy costs are expediently added. The grinding fineness is determined by the usual method in cement technology (Blaine measurement). The grinding process used are grinding units which are suitable for the grinding of hard materials, but preferably those which permit a steep particle size distribution of the material to be ground.

In an advantageous embodiment, another, not previously mentioned in the literature sintering aid is added beyond that, namely recycled glass, in a correspondingly finely ground amount of up to 5 wt .-% added. Recycled glass is characterized by its health compatibility and ecological safety.

The special properties of the innovative binder, which can be specifically optimized for the specific requirements of the desired applications by the addition of conventional in building materials concrete admixtures such as retarders, accelerators, plasticizers, stabilizers, are achieved by the following features:

The binder is characterized by a high proportion of reactive Alit, whereby high early and final strengths can be achieved. Tricalcium aluminate is not contained in the binder at all or only as an extremely small constituent. There is no need to delay the rapid hydration of the C3A in the early stage of solidification by the addition of dihydrate or other sulfate carriers. The absence of C3A opens opportunities for the production of cements with long processing times even at higher temperatures, eg. B. borehole cements for oil production. The cement produced by the method according to the invention is resistant to sulphate; by the absence of C3A no sulfa impulse arises as a result of the sulfa drug attack from sulphate-containing solutions.

There are also no or not significant amounts of belite. Due to the absence of the slow-reacting component belite in the clinker produced by the innovative process, a higher strength potential results due to high alite contents. Under normal construction site conditions, the hardening potential of the belite, which is known to react only under prolonged storage under water, does not come into play. Under normal construction site conditions, the Belit fraction present in Portland cements may be considered inert.

In addition, there are no or not significant proportions of the aluminate-ferrite phase C4AF. Also, the strength contribution resulting from the C4AF when hardening conventional Portland cements should be neglected.

From the thus obtained alitreichen cement clinker cements with special properties by fine grinding and addition of additives such as gypsum and / or anhydrite, blastfurnace slag, limestone and diatomaceous earth or other pozzolanic materials are produced. The process according to the invention makes it possible to produce innovative and high-performance hydraulic binders having the following properties of the mortars and concretes to be produced therefrom:

The cements have favorable processing properties which can be adjusted to the respective field of application, have high early and final strength, are water-impermeable, resistant to carbonation and ultimately provide high protection of the steel reinforcement against corrosion. The fields of application for such binders are in the fields of chemical products such as tile adhesive, joint mortar, thin-bed mortar, adhesive and reinforcing mortar for thermal insulation systems, fillers, top plasters (precious plasters), concretes with high demands against attack by aggressive solutions containing sulfates and cloride , Deep hole cements for use in oil, gas, water or heat exploration and production drilling projects, as well as CO ₂ resistant well cements for sealing CO2 storage.

The inventive method for producing a hydraulic binder is not limited in its execution to the above-mentioned preferred embodiments. Rather, a variety of design variations are possible, which make use of the solution shown even with fundamentally different type of execution.

Claims

1. A method for producing a hydraulic binder from a kiln, consisting of as a main component present limestone and at least kieselguhr as silicate component, - and sintering aids, in which the firing material is designed according to the purity of the limestone and the kieseigur such that a ratio of CaO to SiO ₂ of 3: 1 is established by the mixing of the two main components, and the firing material is subsequently subjected to a firing process in which the CaCO-3 of the limestone is thermally decomposed and forms an aluminum content of> 90 wt .-% in the kiln, wherein the sintering aids on the one hand cause the formation of a glass phase, which promotes a solid-state reaction between the reactive calcium oxide and amorphous silica produced from the diatomaceous earth after the thermal decomposition of the CaCl 3, - and on the other hand, as mineralizers promote the formation of alite. 2. The method according to claim 1, characterized in that the firing process is performed so that the calsium oxide is completely converted to alite, that a free lime content of <1, 5 wt .-% is achieved in the kiln. 3. The method (1) according to claim 1 or 2, characterized in that one or more of the components MgO, Al2O3, Fe2Ü3, ZnO, CaF ₂ , Mn ₂ θ3, BaO, P2O5 are introduced over up to 2 wt .-% additives to stabilize the picture. 4. The method according to one or more of the preceding claims, characterized in that the binder is ground to finenesses in the range between 3000 cmVg and 6500 cm ² / g. 5. The method according to one or more of the preceding claims, characterized in that is added as a further sintering aid recycled glass in a correspondingly finely ground amount of up to 5 wt .-%.