HU188570B - New hydraulic addition of portland-cement clinker base and method for producing same - Google Patents

Abstract

A hydraulic binder is obtained by mixing Portland cement clinker with hydrated alumina in such proportions that the Ca(OH)2 formed during the hydration of the Portland cement clinker combines completely with the alumina as it is formed.

Description

The new hydraulic binder contains alumina trihydrate of natural origin or artificially produced alumina or equivalent alumina-containing mineral material to bind total calcium hydroxide (60-80%) in the hydration of the cement. next to portland cement. The new hydraulic binder is prepared by mixing or grinding Portland cement clinker and alumina trihydrate or a mineral containing it, optionally using conventional cement additives such as gypsum, flux, etc. adding.

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BACKGROUND OF THE INVENTION The present invention relates to a novel hydraulic binder based on Portland Clinker Clinker and a process for its preparation.

The new hydraulic binders of the present invention do not contain calcium hydroxide after hydration. The invention also relates to the use of binders.

Portland cement is known to release hydrated lime (Ca (OH) ₂ ) during hydration, which renders the cement unsuitable for certain applications, including applications that require refractory properties at temperatures above 500 ° C or require resistance to pure water and / or against specific acids.

The formation of slaked lime is due to the nature of Portland cement itself. The main component of cement is represented by the formula CjS, where C = CaO; S = SiO ₂ . During the hydration process, slaked lime is formed from the C ₃ S component. This hydration process can be schematically described by the following reaction equation:

C ₃ S + 3H-> CSH + 2CH where H = H ₂ 0.

It is also known in the building materials industry that it is possible to bind calcium hydroxide formed during the hydration process with additives such as pozzolanics to form hydrated calcium silicates. However, this reaction does not begin until after 15 days of curing. These types of cements are called pozzol Chain and are used especially because of their resistance to water and certain acids.

If ordinary Portland cement is heated to 400 to 500 ° C after hydration, the hydrated slaked lime, CatOHh, released during hydration, is converted to calcium oxide, which can subsequently absorb water and cause significant swelling and damage to the structures.

While pozzolanic cement can be used as a refractory binder, it is a prerequisite that refractory concrete produced with such cement is stored for several months in a humid atmosphere, thereby ensuring the complete reaction of pozzolanic materials before the high temperature is exposed to the concrete.

There has been already attempts to ordinary portland cement properties improve by using various additives in such a way as to be so enriched Portland cement suitable for special purposes, for example, at temperatures around 500 ^° C, or for use in buildings exposed to natural or acidic waters.

It has thus been proposed to bind the calcium hydroxide formed during the hydration of the cement in silicate form by the addition of reactive silica derivatives such as silico-aluminates or "silica fumes" obtained during ferro-silicon production; the use of acidic phosphates as additives has been proposed for the same purpose, cf. for example, K.D. Nyekrasov and N.P. Idanova, Perspectives d'utilisation du ciment Portland a durcissement rapid; en tant que liánt pour beton réfractaires, Bull. Soc., Fr.

Bow Ceram., 1973, No. 98, 25-29; V. Lach: The Effect of

Ceramic Stabilizers on Bonding of Free Lime in Refractory Portland Cement Concrete, A IX. szilikátj; Proceedings of the Industrial Conference, Budapest 1968, 675t 689; V. Lach: Influence et Emploi de Stabilisateurs

I 2 if j?

Cerainiques dans les Refractairs a Base de Ciment Port- / land, Teplotechna Conférence Bétons Refractaires ^,; j Olomouc, 1967; in addition, no. French patent description (Didicr-Werke A.— G.). However, the disadvantages of these hitherto proposed methods are that concrete made with silicate additives may be more difficult to form and with phosphate containing additives foreign substances may be introduced into the concrete which may otherwise cause undesirable effects.

The present invention is based on the surprising discovery that the hydration of lime hydrated during the hydration of Portland cement can be completely absorbed and the disadvantages and consequences of lime hydration release can be completely eliminated by reacting with high-grade anhydrous binders to produce refractory or other oxide is mixed in an amount sufficient to bind the lime hydrate formed.

As reactive alumina, aluminum oxide trihydrate (A1 (OH) ₃ ), which reacts well with calcium hydroxide formed during hydration of the cement, can be used, either naturally occurring mineral (hydroglylite, gibbsite) or artificially prepared alumina such as by the known Bayer process. . However, aluminum oxide trihydrate can be used for the purposes of the invention in varying amounts of alumina mono-. natural minerals containing hydrates and other mineral substances, in particular bauxite and laterite (laterite is a bauxite colored brick red from iron oxides, cf. Römpp, Chemical Lexicon, Vol. 2, 498, Budapest 1960) ; in the latter case, the amount to be used shall be determined taking into account the alumina trihydrate content of the mineral.

The present invention thus relates to a novel hydraulic binder containing Portland cement and alumina which, as aluminum oxide, contains predominantly alumina trihydrate to bind all calcium hydroxide formed during the hydration of the cement in a chemical reaction, optionally known per se and with hydraulic additives commonly used in additives.

The novel Portland cement based hydraulic binder according to the present invention is prepared by mixing a Portland cement clinker with a sufficient amount of alumina trihydrate to bind all of the calcium hydroxide liberated during the hydration of the cement or, if desired, a mineral containing alumina trihydrate. other additives known in the art and commonly used in hydraulic binders, such as binder accelerators (eg gypsum), cement mortar fluxes, plasticizers or water retention agents.

The amount of calcium hydroxide formed during the hydration of the Portland cement depends on the chemical composition of the Portland cement clinker used and is specific to the clinker. Portland cement clinker consists mainly of tricalcium silicate (3CaO.SiO ₂ or C ₃ S) and dicalcium silicate (2CaO.SiO ₂ or C ₂ S), but their proportions can vary widely; tricalcium silicate may be present in the clinker in amounts of 15-70%, dicalcium silicate 9-63%, so that the total amount of calcium silicates may generally be 65-88%, the remainder consisting mainly of calcium aluminates, calcium ferrites and the like . Given

From the chemical composition of the Portland cement clinker to be used in the case of -2188 570 h? 1, 3CaO.SiO ₂ + 2H ₂ O = CaO.SiO ₂ + 2Ca (OH) ₂ and

The reaction equations for 2CaO.SiO ₂ + H ₂ O = CaO.SiO ₂ + Ca (OH) _{2 make} it easy to calculate the minimum required amount of alumina trihydrate, which is 100 parts by weight based on the extreme clinker compositions considered in practice. typically 25-40 parts by weight per clinker of pure A1 (OH) ₃ or bauxite or laterite containing such an amount of alumina trihydrate and thus 60-40% by weight of the finished hydraulic binder (based on the total amount of Portland cement and alumina trihydrate). It contains 80% Portland cement and 20-40% alumina trihydrate or equivalent alumina-containing minerals. In the remainder of this specification, Figs. after example IV. Table 5 summarizes the five different clinkers representing virtually verbal extremes of C ₃ S and C ₂ S and C ₃ S + C ₂ S, respectively, and Table 3-27. For the A, B and C clinkers in Examples 1 to 4, the calculated amounts of the required Al (O) ₃ and Bauxite A and B in the Examples, calculated from the clinker composition as described above.

The above-mentioned conventional cement additives, which may be used in small amounts (0.1-3%), do not affect the lime hydrate binding effect of the hydrated alumina.

In case theoretically required amount of greater than or aluminum oxidtrihidrátnak calculated as described above in admixture with Portland cement in the presence of A1 (OH) ₃ reacts mészhidráttal formed during the hydration perfectly time it is generated, which means that if during the hydration chemical composition of the concrete mix differential thermal analysis, the presence of calcium hydroxide in the product is never observed, regardless of the time elapsed.

The mixing of the components is preferably carried out by grinding. The reaction between calcium hydroxide and hydrated alumina is instantaneous when the mixture is prepared by co-milling Portland cement with an alumina-containing material such as hydrated alumina, crude bauxite or laterite. Conversely, if the individual components have a particle size such that 90% of the material passes through a 40 µm screen, milling may be omitted.

During the hydration of the binder according to the invention, lime is released from the C ₃ S component which, upon formation, reacts with the hydrated alumina. This results in hydrated calcium aluminates of the type C ₃ AH ₆ or C ₄ AH _n or silicate aluminates and hydrogensates of the C ₂ ASH _s hydrated gehlenite type.

Consequently, no traces of calcium hydroxide can be detected in the cement.

In the present specification, the novel hydraulic binder of the present invention will be tested primarily for applications where fire resistance is an important requirement. However, the invention is not limited to such applications.

The invention will now be described in more detail with reference to the following examples and the accompanying drawings, with reference to the advantages and features. The attached figure is a graphical representation of the results of a differential thermal analysis.

The presence of lime hydrate can be easily detected by differential thermal analysis: an endothermic peak appears at 450-500 ° C.

The analysis of hydration products in cement mortar can be supplemented by examination of X-ray diffraction diagrams.

Example 1 Binder prepared from "Superblanc" ^R ) by mixing.

To make a binder, mix the following components:

- 70% "Superblanc"' ^R > (artificial Portland cement clinker, manufactured by Ciments Lafarge France; practically free of iron oxide).

- 2.7% plaster

- 27.3% alumina trihydrate (AH ₃ ) prepared by the Bayer process. This component consists of particles that pass through 90% of the 40 µm screen.

Comparing the behavior of the cement paste made from the resulting mixture with the behavior of the cement paste made from Superblanc ' ^R ' clinker alone, the following can be observed, as shown in Table I:

- Superblanc® alone can be used to detect significant amounts of calcium hydroxide after 1 day. After 7 days, 70-80% of the available amount of lime that can be liberated by C ₃ S hydration is present.

No calcium hydroxide was detected in the mixture of Example 1, however much time elapsed.

In this example, alumina of formula AH _{3 was} pre-milled for 30 minutes in an AUREC ' ^r ^ swing crusher. This gave a partially amorphous material.

The cement slurry was prepared using a water / cement ratio of 0.64 (V / C = 0.64).

-3188 570 /, Table

Intensity of X-ray diffraction peaks

Material Elapsed time C ₃ S. AH ₃ Ca (0 H) ₂ C ₃ AH ₆ C ₄ AH _n Supcrblaiic ( ^R ) One day E - E - _ cement paste 7 days kE - not - - 28 days kE - not - - Example 1 One day E not Gy Gy cement paste 7 days kE E E Gy 28 days kGy E - E Gy

nE = very strong E = strong kE = medium strong nGy = very weak í

Gy = weak kGy = moderately weak

- = not detectable j

Other phases also occur which are not shown in Table I, such as C ₂ AsH ₈ (hydrated gehlenite) and hydrogens.

After the samples were stored at 20 ° C and 95% relative humidity for 1 day, differential yield analysis was performed. The curves obtained are shown in the attached figure. Curve 2 refers to the cement of Example 1 and curve 1 relates to a mixture of Superblanc® ^R 4 and coarse unground alumina trihydrate.

Curve 2 shows that, after 24 hours of storage, no calcium hydroxide peak occurs.

Example 2

The cement of Example 1 was prepared using the same method but using co-milling.

X-ray diffraction analysis of the resulting cement showed that the alumina trihydrate had become partially amorphous, but that Superblanc® ^{R was} hardly affected by this treatment.

No calcium hydroxide was observed in the cement paste after 4 days of storage, but hydrated calcium aluminates (C ₃ AH ₆ - C ₄ AH _n ) and hydrated gehlenite (C ₂ ASH ₈ ) were present. The hydration products correspond to those obtained with very finely ground cement.

These two examples illustrate the possibility of reacting under certain conditions with the hydrated alumina, the calcium hydroxide liberated during the hydration of C ₃ S, the major component of Portland cement.

In this way, cement is obtained which, after hydration, contains only hydrated calcium silicates, hydrated calcium aluminates and hydrated calcium silicoaluminates. Since calcium hydroxide is not present below the disadvantages arising from the presence of calcium hydroxide, and allowing the use type of cement according to the invention, particularly in the field of fire-resistant building materials ^35.

3-32. example

In the examples below, three types of Portland cement clinker and various alumina containing materials are tested. We start with three types of clinker:

- clinker A: large clinker containing C ₃ S and C ₃ A;

- clinker B: small clinker containing C ₃ S and C ₃ A;

- clinker C: very small clinker containing C ₃ A;

with a mineral composition according to the chemical analysis of:

i;

r.

c for ₃ s C ₂ S c ₃ a C ₄ AF CaS0 ₄ Free CaO Other altogether “The clinker 68 17.40 7.45 0.80 0.35 4.05 1.95 100 “Clinker B 57.5 21.60 7.20 9.80 1.60 0.65 1.65 100 Clinker C 663 15.35 0.50 14.50 0.40 1.55 1.40 100

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We use two types of bauxite, among others:

- "THE" bauxite: low iron content - "b" bauxite: high iron content They are composed as follows: , A ”bauxite Β-bauxite SiO 0.70 8.90 TiO ₂ 3.90 2.75 A1 ₂ Oj 60.90 53.27 CaO 0 0 MgO 0 0 SO ₃ 0.05 0.10 CO ₂ 0.05 0.05 glow 30.85 23.63 loss Fe ₂ O ₃ 3.45 11.27 K ₂ O 0.05 0.05 Na ₂ O 0.05 0.02 altogether 100 100

From the various X-ray diffraction spectra, the proportions of trihydrate (AH ₃ ) and monohydrate (AH) in each bauxite can be calculated taking into account the alumina and water contents. The percentages of the various phases are shown in Table II. is shown in the table.

Example 3-5

3-5. in Examples 2 to 1, the ratio of clinker B to alumina A is 2: 1.

Example 3: Mixing without simultaneous grinding

Example 4: Mixing and simultaneous grinding for 2 hours

Example 5: Mixing and simultaneous grinding for 6 hours

Contrary to Examples 1 and 2, the simultaneous grinding of the components is carried out in a ball mill rather than in a swinging crusher.

Pure cement slurry is stored at 20 ° C and 95% relative humidity.

Differential thermal analysis and X-ray diffraction studies showed that the cement of Example 3, in which the components were mixed without grinding, still contains calcium hydroxide for a long period (3 months) at 20 ° C and 95% relative humidity. However, the cements to which grinding was applied did not contain calcium hydroxide after 24 hours storage.

Storage at 50 ° C and 95% relative humidity improves the reactivity of the mixture by removing calcium hydroxide remaining after 7 days when stored at 20 ° C and 95% relative humidity.

II. spreadsheet

AH ₃ Bayer "A" bauxite Bauxite B ah ₃ 100% 87.2% 61.9% AH 4.7% 14.9% Polluting materials 8.1% 23.2%

Table III

Storage Example number Elapsed time C33 s AH ₃ Ca (OH) ₂ C ₃ AH ₆ C ₄ AH _n 20 ° C 24 hours E E E and 3 7 days kE E not - - 95% 3 months Gy E not - - relative air 24 hours E E kGy Gy 4 7 days kE kE - kGy Gy 3 months Gy kE - kGy Gy moisture 24 hours E E kGy Gy 5 7 days kE kGy - kGy Gy 3 months Gy kGy - kGy Gy

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Storage Example number Elapsed time Ca ₃ S ah ₃ Ca (0 H) ₂ c ₃ ah ₆ C ₄ AH _n 50 ° C 24 hours E E E __ _ and 3 7 days kE kGy . - kGy Gy 95% 3 months Gy Gy - kGy Gy relative 24 hours E E _ kGy Gy air- 4 7 days kGy kGy - kGy Gy 3 months Gy Gy - kGy Gy moisture 24 hours E E _ kGy Gy 5 7 days kGy kGy - kGy Gy 3 months Gy Gy - kGy Gy

As in Examples 1 and 2, C ₂ ASH ₈ (hydrated gehlenite) and hydrogens are detected.

6-8. example

In these examples, bauxite "B" and "B" are used in a ratio of 2: 1.

Example 6: Mixing without simultaneous grinding

Example 7: Mixing and simultaneous grinding for 2 hours Example 8: Mixing and simultaneous grinding for 6 hours

The pure pulp is stored at 20 ° C and 95% relative humidity and at 50 ^U / 95% relative humidity.

6-8. In Examples 1 to 4, it was observed that, as in the previous examples, the Ca (O) ₂ - AH _n reaction immediately occurs when the cement is prepared by grinding. This reaction occurs faster as the temperature increases.

9-27. example

Further studies are conducted on different mixtures using different materials and different clinker / alumina ratios.

Example number klinker Alumina Clinker / additive Preparation THE THE 57/43 9-27. B B 67/33 grinding to C 77/23

The total number of mixtures of this type is 3 · 2 · 3 = 18 (which is why these tests form Examples 9-27).

9-27. Pure cement paste was prepared from each of the blends of Example 1, and after 24 hours of hydration, X-ray diffraction and differential thermal analysis was performed on each sample. Both types of tests showed that none of the samples contained calcium hydroxide.

One skilled in the art will recognize that the alumina trihydrate-containing additive should be used in an amount sufficient to completely bind the calcium hydroxide expected to be formed during the hydration of the Portland cement, taking into account the presence of alumina trihydrate in the additive. too.

The method of calculating the minimum amount of pure alumina trihydrate required or for this purpose containing alumina trihydrate with other minerals is described in the introduction to this specification. The required quantities of A1 (OH) ₃ and Bauxite A and B in the above examples were calculated by five different Portland cement clinkers representing the practically normal extremes of the C ₃ S and C ₂ S contents, respectively. for clinker A, "Β" and "C" in Table IV below. Table.

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ι.

ARC. spreadsheet

Clinker no. The clinker The theoretical amount of Ca (OH) ₂ released per 100 parts of clinker Required AI (0H) ₃ for conversion 3CaO.Al ₂ O ₃ .6H ₂ Ova (parts) Required amount of bauxite containing 87.2% A1 (OH) ₃ (part) 61.9% A1 (OH) ₃ Bauxite Required (part) C ₃ S hold% C ₂ S without% First 64 9 45.41 31.90 36.58 '· 51.53 Second 15 63 36.84 25.89 29.69 41.82 Third 70 18 53.18 37.36 42.85 60.35 4th 35 48 43.37 30.48 34.95 49.24 5th 53 15 40.85 28.70 32.91 46.36 THE 68.0 17.40 51.54 36.22 41.54 58.51 B 57.5 21.60 46.61 32.75 37.56 52.91 C 66.3 15.35 49.64 34.88 40.00 56.35

An essential feature of the pure cement paste according to the invention is that it never contains calcium hydroxide after the hydration process has taken place. As a result, it can be used as a refractory binder and is preferred in all cases where the presence of calcium hydroxide is undesirable (for example, resistance to water or certain acids is required).

Example 28 (a) Fire resistance

A binder is prepared by mixing 67% clinker A and 33% AH ₃ (made by the Bayer process). The mixture was then ground for 2 hours. The hydration is carried out for 24 hours at 20 ° C and 95% relative humidity, and the pure cement slurry is dried at 110 ° C and heated at 300, 500, 800, 1100 and 1250 ° C for 6 hours and finally in the oven. let it cool down.

Phase intensities in pure cement paste after heat treatment

Mineralogy phase 20 ° C Treatment temperature 1250 ° C 110 ° C 300 ° C 500 ° C 800 ° C 1100 ° C C ₃ S. E E Gy Gy Gy Gy Gy ah ₃ not not - - - - - Ca (0H) 2 - - - - - - - CaO - - - - - - - C ₃ AH ₆ E E E - - - - C ₄ AH _n Gy - - - - - - C ₂ AS - - - - Gy E E Cl2 A7 - - E E - not E ca ₂ - - - - - not Gy CA - - - - - nGy kE

Based on the results of the above test, it could be determined that water could be taken up again. Thus, the binder is utilized for a refractory binder depending on the firing temperature of the pure cement paste, without letting go of the binder, which

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(b) Resistance to moisture

The cement of Example 28 is made into chamfered cube cubes 10 cm in length, which are then subjected to the heat treatment described below.

The activated cement cubes according to the invention were not damaged during the heat effects, while the cube made from the comparative cement sample without AH ₃ was cracked.

activated cement comparative sample 6 hours at 500 ° C no crack no crack 5 hours in a humid place no crack no crack 6 hours at 800 ° C no crack cracks 5 days in a humid place no crack cracks 6 hours at 110 ° C no crack cracks 5 days in a humid place no crack cracks

29-31. EXAMPLE 2 The refractory properties of cement made of "C" clinker and "B" bauxite are investigated, that is, the following characteristics5 are determined:

mechanical properties after heating

- dimensional changes after heating

- reaction to fire (temperature).

The application temperature range is between 1250 and 1300 ° C since the dimensional change after heating is within the range (<± 1.5%) prescribed by the Syndicat des Fabricants de Produits Réfractaires Européens.

m In general, the fire resistance of cement depends on the quantity ratio of clinker to alumina and the purity of the components (iron oxide content).

The Theological properties of modified cement anhydrous or water-containing calcium sulfate · _20, or additives, e.g. lágyiíószerek, fluxing agents or dehydrating agents as desired.

Table V.

Properties of 500 kg / rt of ³ cemented concrete (the components were ground for 2 hours)

klinker Cement composition of Bauxite Gold Example number w / c Elapsed time 20 ° C 800 ° C H Ny H Ny One day 15 35 C B 57/43 29th 0.44 2 days 25 100 7 days 48 215 One day 18 80 C B 67/33 30th 0.44 2 days 33 125 7 days 57 250 40 335 One day 16 80 C B 77/23 31st 0.44 2 days 29 110 7 days 56 335 37 320

H = bending, kg / cm ² Ny = pressure, kg / cm ²

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Table V (continued)

Example number V / C elapsed time 1100 H C Ny 1250 H C Ny Change in size 1250 ° C 1% Fire resistance ° C) 2% 5% load 10% One day 15 120 29th 0.44 2 days 22 165 7 days 30 175 One day 19 150 30th 0.44 2 days 26 185 103 500 -0.3 1175 1235 1275 1300 7 days 33 195 One day 19 150 31st 0.44 2 days 24 160 158 765 -1.45 1195 1220 1250 1275 7 days 31 195

Example 32 By grinding "B clinker B" and "Banxite B" for 2 hours, cement is prepared which is used as a mortar with quartz sand - V / C = 0.5. The resulting mortar can be used as follows:

169 minutes after standing 268 seconds after standing

When 0.1% (0.1 / 1000) sodium gluconate is added, the utility varies as follows:

minutes after minutes 14 seconds minutes after 34 seconds

Usability is measured by a flow method using a Maniabilimetre LCL (manufactured by Etablissements Perrier, Montrouge, France). The applied measurement method was published as "Mode Opératoire BFM-1", published by Dunod, Paris, 1973.

In view of the above, auxiliaries such as those currently used in the cement industry can be added to the binders of the present invention. The nature of these excipients essentially depends on the nature and fineness (particle size) of the binder components of the invention.

The time given for the simultaneous grinding of the components in the above examples is experimental only and is not considered to be a lower limit.

It will be understood that in the industrial application of the invention, the design of the mill and the parameters of the mill are chosen by those skilled in the art to achieve optimum results.

The term "elapsed time" used in this description is heat treatment! or hardening time.

Patent claims

Claims (4)

1. Hydraulic binder of Portland cement and alumina, optionally containing additives commonly used in the cement industry such as gypsum, joint accelerator, fluxing agent and / or water binder, characterized in that 60% to 80% by weight of total Portland cement and alumina trihydrate. Portland cement and 20-40% alumina trihydrate or equivalent alumina-containing minerals. A process for the production of a hydraulic binder according to claim 1, characterized in that 100 parts by weight of Portland cement clinker, in the preserved state or by grinding, contain 25 to 40 parts by weight of alumina trihydrate or equivalent amount of alumina based on the alumina content. containing at least 0.1% to 3%, based on the total weight of this mixture, of a conventional cementitious additive such as gypsum, flux, curing agent and / or water binder. The process according to claim 2, wherein the alumina trihydrate is a naturally occurring or artificially produced aluminum hydroxide. 4. A process according to claim 2, wherein the alumina-containing mineral is bauxite or laterite.