FR2470103A1 - NEW PORTLAND CEMENT CLINKER HYDRAULIC BINDERS AND PROCESS FOR OBTAINING THE SAME - Google Patents

Abstract

THE SUBJECT OF THE PRESENT INVENTION IS A PROCESS FOR OBTAINING A HYDRAULIC BINDER. THIS PROCESS IS CHARACTERIZED IN THAT ARTIFICIAL PORTLAND CLINKER IS MIXED WITH HYDRATED ALUMINA IN SUFFICIENT QUANTITY SO THAT THE LIME WHICH IS RELEASED DURING HYDRATION OF THE PORTLAND CLINKER COMBINES FULLY FROM ITS ALUMINUM FORMATION. ONE OF THE FIELDS OF APPLICATION OF THE INVENTION RESIDES IN THE HYDRAULIC BINDERS INDUSTRY.

Description

24701 03

  NEW HYDRAULIC BINDERS FROM CLINKER DE-CIMENTS PORTLAND

AND METHOD OF OBTAINING.

  The present invention relates to new hydraulic binders based on Portland cement clinkers which, after hydration, do not contain hydrated lime Ca (OH) 2. In fact, it relates to a method of obtaining

  of these binders and some of their applications.

  It is well known that Portland cement during its hydration releases hydrated lime Ca (OH) 2, which renders these cements unsuitable for certain uses, inter alia involving a refractoriness at a temperature above about 5000C, or a stability vis-à-vis

  pure waters and / or certain acids.

  In fact, the release of hydrated lime results from the very nature of the cements whose main constituent is expressed by the formula: C3S (C = CaO, S = SiO2). So, it is well known that during the process

  of hydration of C3S, there is release of lime Ca (OH) 2.

  The principle of this hydration can be expressed schematically by the reaction: C3S + 3H + CSH + 2CH

(H = H 2 O)

  Moreover, it is known that in the building materials industry, it is possible to combine lime, which has appeared during hydration with additives such as pozzolans, to form hydrated calcium silicates. This reaction is late because it only begins after about 15 days of hardening. These cements are known by the term "pozzolanic cement" and are, more particularly, used for their

  stability with regard to pure water and / or certain acids.

  After hydration, if ordinary Portland cement is subjected to a temperature of the order of 400 to 500 ° C, the slaked lime Ca (OH) 2, released during hydration, is transformed into quicklime CaO, which , in the case of the shutdown of the installation, generates a resumption of humidity which causes a taste

  important and deteriorating structures.

  The pozzolanic cements can be used as refractory binders provided that the refractory concretes made from these cements are stored for several months in a humid atmosphere, so that the pozzolanic reaction is complete before bringing them to high temperature.

  The present invention is based on the surprising and unexpected finding of

  that it is possible, under defined conditions, to use

  Portland in unusual applications. The present invention relates to a process for obtaining binders obtained by mixing artificial Portland cement and hydrated alumina,

  used in sufficient quantity so that the lime that forms during the hy-

  Binder dratation combines completely from its formation with hydrated alumina.

  It follows that Ca (OH) 2 is never observed at any time.

  Preferably, the mixture is co-milled.

  The reaction between Ca (OH) 2 and Al (OH) n of the aluminous material is very rapid if the mixture is obtained by co-grinding the Portland cement and the aluminous material, such as the chemical alumina hydrates, the raw bauxites, the laterites. . If, however, the particle size of each of the constituents is such that 90% of the material is sieved by 40p, it is possible to

to do without such co-grinding.

  The binders according to the present invention are based on artificial Portland cement and alumina, this alumina hydrated alumina used

  in sufficient quantity that the incipient lime produced during the hydra-

  the binder is totally combined with hydrated alumina as

of his training.

  In fact, during the hydration of the binder according to the invention, the C3S gives rise to a release of lime which, as and when it is formed, reacts with the hydrated alumina to form hydrated calcium aluminates of the type C3AH6 or C4AHn or hydrated gehlenite silico-aluminates

C2ASH8 and hydrogrenates.

  It thus appears that no trace of Ca (OH) 2 is detected in the cement.

  In the present description, the use of the new hydraulic binders

  is more particularly examined in the context of refractory applications, although the invention should in no way be considered as being

limited to this application.

  Other advantages and characteristics of the invention will appear on reading the following description and examples given for illustrative purposes.

but non-limiting.

  Experimentally, it is easy to detect slaked lime by thermodifferential analysis (DTA), which is manifested by the appearance of an endothermic peak between 450 and 500 C,

  The analysis of the hydration products of the cement pastes can be

  completed by the examination of X-ray diffraction patterns (RX)

* EXAMPLE 1

  * Binder obtained by mixing from "SuperbLanc" -

  A binder is prepared by mixing: To 70% declinker of artificial Portland cement called "Superblank", * - 2.7% of gypsum, * 27.39% of alumina trihydrate AH3 resulting from the Bayer process, the particle size of these constituents being such that 90% of the material passes

with a sieve of 40p.

  Superblanc is a CPA sold by the company CIMENTS LAFARGE FRANCE,

  having the characteristic of not containing iron oxide.

  If one examines the evolution of the pasta of this composite cement compared to that of Superblanc alone, it appears from Table I, below: + -For Superblanc alone: * Ca (OH) 2 is in significant quantity at the maturity of ij and that 70-80% of the available lime releasable by the hydration of C3S is present

at the end of 7 days

  - For the composite cement object of Example 1:

  * Whatever the deadline, Ca (OH) 2 is never detected.

  In this example, the alumina AH3 was previously milled in a vibratory mill AUREC type for 30 min, resulting in a partial amorphization of the product The cement pastes were tempered with a water / cement ratio of 0.64 (E / C = 0.64

TABLE I

  - Set of X-ray diffraction peaks

  tF = Very High mf = moderately low F = Strong f = low mF = Moderately High tf = very low Timeout C3S AH3 Ca (OH) 2 C3AH6 C4AHn

1 day paste F - F - -

cement 7 days mF - tF - -

Superblank 28 d mF - tF - -

  Paste 1 day F tf - f f cement 7 j mF F - F f Example 1 28j f mF - F f

4 2470103

  On the other hand, there appear other phases that are not mentioned in the

  Table of Example 1, such as C2ASHs (hydrated gehyenite) and hydrochlorides

  garnets. The results of the ATD (1-day maturity, C storage and HR = 95%) recorded in the attached figure, lead to curve n 2 for the cement of Example 1, and curve No. i to Superblood with trihydrate

coarse uncrushed alumina.

  This diagram shows that the N 2 curve does not have a peak of 24 hours

characteristic of Ca (OH) 2.

* EXAMPLE 2

  The cement is such as that which is defined in Exemp.Le 1; he is

  once prepared by co-grinding under the same conditions.

  Examination of the X-ray diffraction cement shows a partial amorphization of the alumina trihydrate whereas Superblanc is only slightly affected by this

treatment.

  In pure paste at the end of 4 days, we do not observe Ca (OH) 2, but the presence of calcium aluminates hydrated (C3AH6 - C4AHn) as well as the

  hydrated gehlenite (C2ASH8). In fact, the hydration products are identical

  to the cement obtained by mixing after thorough grinding of the constituents

tuants.

  These two examples demonstrate the possibility of reacting, under certain conditions, the slaked lime released during the hydration of the

  C3S, main constituent of Portland, with hydrated alumina.

  This gives a cement which, after hydration, contains only

  hydrated calcium silicates, hydrated calcium aluminates, silicone silicates,

  hydrated calcium aluminates. The absence of Ca (OH) 2 and the removal of the disadvantages that result therefore allows the use of this type of cement

  especially in the refractory industry.

* EXAMPLES 3 to 32

  In the examples that are described above are examined three types of

  Portland clinker and various aluminous materials.

We start from three types of clinker:

  * Clinker A: clinker with high content of C3S and C3A.

  * Clinker B: clinker with low C3S content and high C3A content.

  * Clinker C: very low C3A clinker having the following potential mineral compositions deduced from chemical analysis:

24701È3!

  In addition, two types of bauxite are employed: - Bauxite A: iron-poor, - Bauxite B: iron-rich, having the following compositions: ## STR1 ## 90 60.90 O 0 0.05 0.05 30.85 3.45 0r05 0.05 100 Bauxite B 8.90 2.75 53.27 OO 0.10 0.05 23.63 11.27 0.05 0 , 02 100

* fire losses.

  From the X-ray diffraction spectra and taking into account the contents of alumina and water, it is possible to calculate the proportions of trihydrate (AH3) and monohydrate (AH) in each bauxite and the percentage of the different phases is given in Table II following:

TABLE II

TABLE II

- EXAMPLES 3 to 5

  In Examples 2/1: 3 to 5 the ratio clinker B / aluminous material A was C3 S C2S C3A C4AF SuLfate CaO TOTAL CaClCal Free CaSO4 Clinker A 68 17.40 7.75 0.80 0.35 4.05 100 ATCLinker B 57.5 21.60 7.20 9.80 1.60 0, 65 100 * CLinker C 66.3 15.35 0.50 14.50 0.40 1.55 100 AH3 Bayer Bauxite A Bauxite B

AH3 100% 87.2% 61.9%

AH - 4.7% 14.9%

Impurities - 8.1% 23.2%

  * Example 3 after mixing without co-grinding.

  * Example 4 after mixing and co-grinding for 2 hours.

  Example 5 after mixing and co-grinding for 6 hours.

  The co-grinding was not carried out as in the case of ExempLes 1 and 2

  in a vibratory mill, but in a conventional ball mill.

if that.

  Pure pastes of cements were stored at 20 C and 95% H.R.

  (relative humidity) or at 50 ° C. and 95% RH It is found at 20 ° C. and 95% RH by ATD and RX analysis that the cement of Example 3 (mixture without co-grinding) still contains slaked lime Ca (OH) 2 even after a very long storage time (3 months) while the cements that were developed by co-grinding do not contain Ca (OH) 2 from the 24 hour deadline. Storage at 50 ° C and 95% RH improves the reactivity of the mixture

  because Ca (OH) 2 has a maturity of 7 days at 20 C and 95% H.R. disappears.

TABLE III

  As for ExempLes.1 and 2, we also detect C2ASH8

  (hydrated gehlenite) and hydrogrenates.

247013.

  Conservation Example Echo C3S AH3 Ca (OH) 2 C3AH6 C4AHn

24 hrs F F F - -

3 7 j mF F tF - -

3 m f F tF - -

  C 24 hrs F F - mf f% hr 4 7 mf mf - mf f 3 mf mf - mf f 24 h Ff - mf f 7 mf mf - mf f 3 mf mf - mf f

24 hrs F F F - -

  3 7 mf mf - mf f 3 mff - mf f C 24h FF - mf f% HR 4 7 mf mf mf f 3 mff - mf f 24 h Ff - mf f 7 h mf mf - mf f 3 mff - mf f

24701 03

- EXAMPLES 6 to 8 -

  In these examples, we used clinker B and bauxite B in

the ratios 2/1.

  The pure cement pastes were stored at 20 C and

% RH and 50 C and 95% H.R.

  In Examples 6 to 8, it is found, as for the previous examples, that the reaction Ca (OH) 2 -AHn is immediate as soon as the cement is prepared by co-milling.

  This reaction is accelerated as the ambient temperature increases.

- EXAMPLE 9 to 27

  For the same purpose, other compositions have been examined by modifying

  the nature of the materials and the clinker / aluminous material ratio.

  EXAMPLES q to 27 The combination set represents 3 x 2 X 3 = 18 cases

(therefore Examples 9 to 27).

  Analysis of the pure pastes obtained in each of these Examples 9 to 27, after a hydration time of 24 hours, shows the absence of hydrated lime so much.

by X-ray diffraction only by ATD.

  It is obvious to those skilled in the art that the amount of aluminous materials should be adjusted to the hydrated lime content that can be released by hydration of the Portland cement, and taking into account the impurities.

  present in the aluminous material.

  In fact, the characteristic of pure composite cement pastes according to the invention is that after hydration, they never contain Ca (OH) 2, which makes it possible to use these binders as refractory binders, or in * Exempt 6 After mixing without co-grinding * Example 7 after mixing and co-grinding for 2 hours Example 8 after mixing and co-grinding for 6 hours No. Example Clinker Material Cmineuxr / Preparation atluminous Filler

A 57/43

"9 - 27 B B 67/33 Cobroyage

C 77/23

  2247010 3 i uses where the presence of slaked lime is contraindicated (resistance to pure water, certain acids ...)

- EXAMPLE 28 -

a) Stability in fire:

  A binder is prepared by blending 67% clinker A and 33% chemical AH 3

  from the Bayer process. The mixture is then co-milled for 2 hours.

  After hydration for 24h at 20 ° C. and 95% H.R., the pure pastes are steamed at 110 ° C. and then brought to 300-500-800-1100 ° C. for 6 hours.

  and finally naturally cooled in the oven.

EXAMPLE 28

  Intensity of pure pasta phases after heat treatment.

  Phase Mineral treatment temperature 200C 110C 3000C 5000oC 8000C 11000C 12500C C3S F F f f f f f

AH3 tF tF ...

Ca (OH) 2 ... .

CaO .. .....

C3AH6 F F F. -

C4AHn f .. ....

  C2AS -. . F F F C12A7 _ _ F F - t F F CA2 -. In conclusion, it can be seen that regardless of the firing temperature of the pure dough, the binder defined in this example never releases quicklime which may rehydrate, and in its use as

  that refractory binder can not be prohibited.

  * b) Moisture stability: From the cement defined in Example 28, .a, cubes having a

  edge of 10 cm of chamotte concrete were made and then treated

  a schematic thermal cycle shown in the table below.

  Compared to a control cement, activated cement-based cubes are

  remained intact while the control cement-based cells cracked.

2470103 1

T T

- EXAMPLE 29 to 31

  In Examples 29 to 32 the behavior of a composite cement is examined

  posite consisting of clinker C and bauxite B through conventional tests of refractory betons, that is to say by determination: - mechanical properties after heating, - post-dimensional variation (PVD),

  - subsidence temperatures under load.

  The temperature limit of use is between 1250-1300 C, because the post-

  dimension variation (PVD) is within the recommendation limits

PRE * (<1.5%).

  In general, the refractoriness of the cement will depend on the clinker / aluminous material ratio and the purity of the components (oxide content

of iron).

  The rheology of the cement can be modified by the additional addition of anhydrous or hydrated calcium sulphate or additives such as plasticizers,

  the fluidifiers, the water reducers.

  * Recommendations issued by the Union of Manufacturers of Refractory Products

Europeans.

  6h - 500 C no crack no crack h in wet room no crack no crack 6h - 800 C no crack crack in wet room no crack cracked cubes 6h - 110 C crack cracked cubes j wet room no crack cracked cubes Cement "activated" Witness EXAMPLES Nos. 29 to 31

  _ Characteristics of chamotte concrete (0-5 mm) dosed at 500 kg of cement per m3 of concrete - cobbled cement 2 h -

  Temperature for a Cement Composition 20 C 800 C 1100 C 1250 C sagging Cement composition under load Example E / C PVD time under load Clinker 6auxit Bauxinke / No. FCFCFCFC 1250 C 1% 2% 5% 10% Bauxite 1 d 15 35 15120 57 / 43 29 0.44 2 d 26 100 22 165 7.d 48215 30175 1d 18 80 19150 CB 67/33 30 0.44 2 d 33 125 26 185 103 500 - 0.3 1175 1235 1275 1300 7 d 5725040 335 33195 1 d 16 80 19 150 77/23 31 0.44 2 d 29 110 24 160 148 765 - 1.45 1195 1220 1250 1275 7j 5633537 320 31 195 - CD * F = Flexion in kg / cm2 ** C = Compression in kg / cm2 1 "4: - CD0 WA '2470103

- EXAMPLE 32

  A cement made by co-grinding clinker B and Bauxite B for 2 hours has a standardized sand handling (E / C = 0.5) of - after a rest of 3 minutes ............. 169 s - after a rest of 30 minutes .............. 268 s. After the addition of 0.104 (o, 1/1000) of sodium gluconate, the workability is changed to: rest time at 3 minutes .............. 14 s

  rest time 30 minutes .............. 34 s.

  The workability was measured using the LCL maniabiliter manufactured by the company known as Etablissements PERRIER in Montrouqe (France) according to the method described in the publication "Operating Procedure BF M-1i edited by Dunod (Paris)

in 1973.

  It is therefore found that the binders according to the present invention are capable of

  can be added with adjuvants conventional cement techniques.

  The nature of adjuvants will depend essentially on the nature and finesse

  materials constituting the new hydraulic binder.

  Of course, the present invention is not limited to the embodiments described and shown; it is capable of numerous variants accessible to those skilled in the art, depending on the intended applications

  and without departing from the spirit of the invention.

  Thus, the co-grinding time indicated in the various examples does not constitute

  not a lower limit, but an experimental indication.

  It is obvious that in the case of an industrial exploitation, the geometry

  the mill and its operating parameters will be optimized.

Claims (7)

REVENDI CATIONS   1.- A process for obtaining a hydraulic binder, characterized in that artificial PortlandPortland clinker is mixed with a hydrated alumina in an amount sufficient so that the lime which is released during the hydration of the Portland clinker combines totally from its formation with alumina. 2. A process according to claim 1, characterized in that the alumina   hydrated-and Portland clinker are cobroyé.   3. Method according to one of claims 1 and 2, characterized in that   the hydrated alumina is alumina trihydrate.   4. A process according to claim 3, characterized in that the tri-alumina   hydrated is the constituent of a natural bauxite or laterite.   5. A process according to any one of claims 1 to 4, characterized   in that additives such as fluidifiers can be added to said binder,   plasticizers, water reducers or calcium sulphate.   6.- As a new industrial product, a hydraulic binder based on artificial Portland cement clinker and alumina, characterized in that the alumina is hydrated alumina employed in sufficient quantity so that the lime which is formed when hydrating the cement combines totally   from its formation with hydrated alumina.   7. Application of the binders obtained using the process according to any one   conque of claims 1 to 5 for refractory use.