NL8006298A - A NEW HYDRAULIC BINDING BASED ON PORTLAND CEMENT CLAMPS AND A METHOD FOR PREPARING SUCH A BINDING AGENT. - Google Patents

Description

*> I 803365 / vdV / hh * '

Short designation: New hydraulic binder based on

Portland cement clinkers as well as a process for the preparation of such a binder.

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The invention relates to a new hydraulic binder based on Portland cement clinkers, which after hydration is free from lime hydrate or calcium hydroxide CaiOH 2, and more particularly to a process for the preparation of this binder, as well as to certain applications thereof.

As is known in Portland cement hydrated lime (CaiOH®) is formed during hydration, rendering the cement unsuitable for certain applications, including refractoriness at temperatures above about 500 ° C or insensitivity to pure water and / or certain acids.

The formation of calcium hydroxide depends on the cement type, the main component of which has the formula (Ca0) ^ SiO2. It is thus known that during hydration of (000) ^ 5102 calcium hydroxide is formed.

The hydration can be represented by the reaction scheme: (CaOj ^ SiOg + 3H2O → CaO.SiO2.H2O + 2Ca (0H) 2).

It is further known from the building materials industry that the calcium hydroxide formed by hydration can be mixed with additives, for example with pozzolanes, to form calcium hydrosilicate products. This reaction is delayed and does not start until 15 days after curing. These cements are known under the name "pozzolan cements" and are used in particular purely because of their resistance to water and certain acids.

After hydration, normal Portland cement, upon exposure to a temperature of 400 to 500 ° C, converts the hydrated lime CaiOH 4 formed into calcium oxide, which can then re-absorb water, allowing structures to expand and damage.

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Pozzolanic cement can be used as a refractory binder provided that the refractory concrete obtained from these cements is previously stored in a humid atmosphere for several months to terminate the pozzolanic reaction before exposure to high temperatures.

The present invention is based on the surprising and unexpected discovery that under certain circumstances it is possible to use these Portland cement types for other purposes.

The present invention therefore relates to a process for the preparation of a binder from a mixture of Portland cement and alumina hydrate, the latter in such an amount that the hydrate lime formed during the hydration of the binder completely with the gradually formed alumina hydrate responds. It follows that Ca (0H) 2 cannot be detected at any time.

Preferably, the mixture is prepared simultaneously grinding.

The reaction of Ca (OH) 2 with the aluminumoyxdehydrate of the aluminum-containing material takes place immediately when the Portland cement and the aluminum-containing material, for example chemically hydrated alumina, crude bauxite and laterite, are jointly ground. However, if the grain size of all components is such that 90% of the material passes through a 40μ screen, the joint grinding can be omitted.

The binders of the present invention are based on Portland cement and aluminum oxide, the amount of alumina in the form of hydrated alumina being such that the hydrate lime formed during hydration of the binder immediately reacts completely with hydrated alumina.

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During the hydration of the binder according to the invention, CCaOgSiC ^ lime is formed, which reacts immediately after formation with alumina hydrate ^ <^ pd ^ ^ yrminc ^ ^ pn ^ ^ calcium aluminum hydrates of the (CaO) *, / \ $ (CaO) ^ / 3 or 4 silyl lumines of hydrated (hlenite) and hydrogranates.

This means that no CaiOH® residues can be shown in the cement. * (CaO ^ .AlgOg.SiiHgO ^

In the present description, the use of the new hydraulic binders is more specifically investigated with regard to their refractory applications, but this does not limit the invention in any way.

The invention will now be further elucidated with reference to the following description and examples.

In the tests, slaked lime can easily be detected by differential thermal analysis (DTA) with an endothermic peak between 450 and 500 ° C.

/ CtXG

The analysis of the hydrat / products of the cement mortar without

sand can be supplemented with X-ray diffraction diagram studies. EXAMPLE I

. Binder obtained by mixing with "Superblanc".

A binder is prepared from a mixture of. 70% Portland cement clinker of the "Superblanc" trademark 20. 2.7% gypsum AljOg. ^ OJj. 27.3% alumina trihydrate y prepared by the Bayer process, these products having a grain size such that 90% of the material passes through a 40µ screen.

"Superblanc" is a Portland cement free of iron oxide and marketed by CIMENTS LAFARGE FRANCE.

If one compares the creation of the composite cement mortar without sand with Superblanc, Table A shows that: - in unmixed "Superblanc" 1: after 1 day large quantities of Ca (OH) 2 and 7 days 70-80% of the 30 (000 310 3102 hydration-formed lime may be present; -4- - CaiOH 2 cannot be detected in the composite cement of Example I at any time.

In this example, alumina nitrihydrate has been pre-ground in an AUREC vibratory mill for 30 minutes to yield a partial amorphous product.

The cement mortar without sand is mixed in the ratio Water / cement = 0.64 (W / C = 0.64).

TABLE_A x * AlgOg.CHgO) ^ xxxx (CaO ^ .Al ^ O ^ f ^ O ^ X Diffraction Peak Intensity ^ CaoJgSiOg κκκ 3 * 6

Material Time lapse ^ x 'xx CaiOH ^ xxx χχχχ "* 10 Pourable 1 day S 5

"SUPERBLANC" - 7 days VS - SS

mash .28 days vS zS

Pourable 1 day S zS Z Z

cement slurry 7 days vS $ S Z

15 of Vb I 28 days vS S S Z

according to the present invention 1 - 1 zS = very strong. s = strong vS = fairly strong zz = very weak z = weak vZ = fairly weak = imperceptible 20 However, other phases arise that are not shown in Table A or

Example I are mentioned, for example, (CaO ^ AlgO ^ SiOg. (HgOjg (hlenite hydrate) and hydrogrenades.

The results of the differential thermal analysis (after 1 day storage at 20 ° C and 95% relative humidity) are 25 in the drawing with curve 2 for the cement of Example I and curve 1 for "Superblanc" with crude not ground aluminum oxide hydrate.

This graph shows that curve 2 shows no peaks characteristic for Ca (0H) 2 after 24 hours of storage.

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EXAMPLE II

The cement is the same as that of Example 1 and is prepared in the same manner but is finely ground together.

The X-ray diffraction examination of the cement shows the partial amorphation of aluminum trihydrate, while "Superblanc" is only slightly affected by this treatment.

In the cement mortar without sand, no 0α (0Η) 3 is determined after 4 days of storage, but calcium aluminate hydrates (CaOjgA ^ Og. (HgQ ^ -iCaO ^ .AlgOgn ^ O and hlenite hydrate (CaO ^ .A ^ Og.S1O2.8H2O) are present. The hydration products are identical to those of cement, the mixture of which was obtained separately by long-term grinding of the components.

From these two examples it appears that under certain conditions the hydrate lime released by hydrating (CaO) gSiO2, the main component of Portland ether, can be reacted with hydrated alumina.

In this way, a cement is obtained which, after hydration, contains only calcium silicate hydrates, calcium aluminate hydrate and calcium silicon aluminate hydrates. The absence of CO 3 OH and the avoidance of the associated drawbacks thus makes it possible to use this type of cement in particular for refractory purposes.

EXAMPLES III to XXXII

In the examples described here, three types of Portland clinker and various aluminum-containing materials are examined.

The following three vowel types are used:. Vowel A: a vowel with a high content of (Ca0) gSiO2 and 25 (CaO) 3Al2O3. Clinker B: a clinker with a low content of (Ca0) 3SiO2 and (CaO) 3Al2O3. Vowel C: a very low vowel (CaO ^ A ^ Og content, with the following mineralogical compositions (calculated based on ft Ω 0 6 2 9 8 - 6 - from the chemical analysis): kCaOL | (CaO) 9 | ( CaO) J (CaO) .I alkali

SiQ siO kl O 'A12 ° 3 sulfonate Ca TOTAL

5l02 5l02 A12 ° 3Feo0, CaS04 5 Clinker A 68 17.40 7.45 0.80 0.35 4.05 100

Clinker B 577 * 5 21.60 7.20 9.80 ïTóO 0.65 100

Clinker C 66.3 15.35 0.50 14.50 0.40 1.55 100

Two types of bauxite are used for this purpose: - Bauxite A: with a low iron content 10 - Bauxite B: with a high iron content with the following compositions; .................................................. .............................. .................... ............ .. ..........

Si02 Ti02 A1203 CaO MgO S03 C02 L.0.I * K20 Na20 To-

Bauxite A 0.70 3.90 60.90 0 0 0.05 Q05 30.85 3.45 Q05 0.05 100

Bauxite B 8.90 2.75 53.27 0 0 0.10 Q05 23.63 LI, 27 Q05 Q02 100 15 * Loss on ignition

From the different X-ray diffraction spectra and taking into account the aluminum and water content, the amounts of trihydrate (A1203) .3H20 and monohydrate (A1203) .H20 in each bauxite species can be calculated, summarizing the percentages of the different 20 phases in Table B .

TABLE 8 /A1903.3H20__

/ (Bayer) Bauxite A Bauxite B

A12 ° 3 "3H2 ° KX $ 8 7.2% 61.9%

Al90vHo0__ ~ __4.7 ^ 14.9%

Cleanings - 8.1 $ 23.2% 8006298 * »- 7 -

EXAMPLES III to V

In Examples III to V, the ratio of clinker B to aluminum-containing material A is 2: 1.

«Example III after mixing without joint grinding« Example IV after mixing and grinding for 2 hours 5 «Example V after mixing and grinding for 6 hours

The joint grinding is not carried out in a vibrating mill as in Examples I and II, but in a normal ball mill.

The pure pourable cement slurry is stored at 20 ° C and 95% relative humidity.

At 20 ° C and 95% relative humidity, differential thermal analysis and the X-ray diffraction study indicate that the cement of Example III (mixing without joint crushing) still contains hydrate lime, even after long-term storage (3 months), while the cements prepared were no longer present due to joint grinding, after 24 hours of storage.

Storing at 50 ° C and 95% relative humidity improves the reactivity of the mixture because after 7 days at 20 ° C and 95% relative humidity there is no longer CaiOH2.

ft η η β? a 8 - 8-

TABLE C

storage Example time AH- Ca (0H) - | C-AH, C-AH

i v O /. ó O 1 \ course

~ 24 ~ ü S S S - I

7 d VS S ZS

5 3d Z SZS - -

IV 24 S $ - VZ Z

7 US USA - VZ Z

95 $ 3 Z USA - VZ Z

rel. V 24 S S I VZ Z

10 w ... 7 VS VZ - VZ Z

:; Γ9 ~ __ * __ z____w__z_ III 24 s S S -

50 ° C 7 VS VZ - VZ Z

& 3 Z Z - VZ Z

15 95 ^ IV 24 S S - VZ Z

rel. 7 VZ VZ - VZ Z

moist- 3 Z Z - VZ Z

ness

V 24 S S VZ Z

7 VZ VZ - VZ Z

3 Z Z - VZ Z

______

As in Examples I and II, (CaOjA ^ Og.SiOg. ^ O

(hydrated hlenite) and hydro grenades.

EXAMPLES VI to VIII

In these examples, clinker B and bauxite B in the ratio 2: 1 are used.

* Example VI after mixing without joint grinding 25 x Example VII after mixing jointly grinding for 2 hours x Example VIII after mixing and joint grinding for 6 hours

The cement mortar without sand is stored at 20 ° C and 95% relative humidity and at 50 ° C and 95% relative humidity.

In Examples VI to VIII, as in the preceding examples, it is noted that the CaiOH ^ -A ^ O ^. ^ O ^ reaction begins immediately when the cement is prepared by joint crushing.

8 0 0 6 2 9 S

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The reaction proceeds faster when the temperature is higher. EXAMPLES IX to XXVII

Further tests are conducted with other compositions, the composition of the material and the ratio of clinker to aluminum-containing material varying.

EXAMPLES IX fat XXVII

Example Clinker Aluminum-containing Clinker Preparation method material filler, IX-XXVII A A 57/43 joint B B 67/33 f ...

10 C 77/23 fine milling

The total number of combinations of this type is 3 x 2 x 3 s 18 (so examples IX to XXVII).

Analysis of the cement mortar without sand obtained according to Examples IX to XXVII shows from both the X-ray diffraction and the differential thermal analysis that no hydrate lime is present after 24 hours of hydration.

It will be obvious to those skilled in the art that the amount of aluminum-containing material is preferably adapted to the hydrate lime formed by hydrating Portland cement, taking into account impurities in both materials.

The feature of the cement mortar without sand according to the present invention is that after hydration Ca (OH) 2 is never present, so that this binder lends itself to applications where the presence of hydrate lime is disadvantageous.

EXAMPLE XXVIII 25 a) Refractoriness.

A mixture of 67% clinker and 33% chemical AlgOg 3H2O prepared by the Bayer process is prepared and ground together. After 24 hours of hydration at 20 ° C and a relative humidity of 95 $, the cement mortar without sand is dried at 110 ° C, - 10 - then heated for 6 hours at 300-500-800-1100-1250 ° C and then in the oven cooled,

Mineralo- Temperature gic '-—---- "-"

5 phase__20 ° C 110 ° C 300 ° C 500 ° C 800 ° C 1100 ° C 1250 ° C

(Ca0) 3.Si02 S S Z Z Z Z Z

U203.3H20 ZS ZS -

Ca (0H) 2 -----

CaO - - - -

10 (Ca0) vAlo0, S S S

.6H2CT 1 "(Ca0) -Al2 O3 Z - - - -. NH2 O

(Cao ^. A ^ O, - - Z S S

.Si09

(CaO) 12. (M2C 3) “-SS- ZS S

Cao. (Al203) 2 - ZS Z

! 5 Cao.Al203 - - - - - ZS (US

1 f .1 - —-. I i l,

Intensity of the cement mortar without sand after heating

Finally, it is noted that regardless of the fire temperature of the sand-free cement mortar, the binder of this example never releases re-hydratable lime and can thus be used as a refractory binder.

. b) Stability against moisture.

From the cement of Example XXVIII, a), 10 cm refractory cubes are prepared which are then subjected to the heat treatment described in the table below.

When compared with a blank cement sample, it is found that the cubes made of activated cement remain undamaged while the cubes of the blank sample show cracks.

8006298 - 11 - activated blank sample cement 6 h - 500 ° C no cracks no cracks 5 h in humid environment no cracks no cracks 5 6 h - 800 ° C no cracks cracks 5 days in damp environment no cracks cracks 6 h - 110 ° C no cracks cracks 5 days in humid environment no cracks cracks

EXAMPLES XXIX to XXXI

In Examples XXIX to XXXI, the behavior of the composite clinker C and bauxite B cement is tested for refractoriness according to coated methods, ie by determining: - the mechanical properties after heating - the linear changes after burning 15 - the refractoriness under temperature load,

The temperature limit is at 1250-1300 ° C, since the linear changes after burning are within the ERP recommendations * (é i 1.5 «.

The general rule applies that the refractoriness of the cement 20 depends on the ratio of clinker to aluminum-containing material and on the purity of the components (the iron oxide content).

The rheology of the cement can be changed by adding anhydrous or hydrated calcium sulfates or additives such as plasticizers, fluxes, water-binding agents, etc.

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EXAMPLE XXXII

The workability of a cement obtained by grinding clinker B and bauxite B together for 2 hours when used as mortar with quartz sand (W / C = 0.5): - after standing for 3 minutes. ..169 s 5 - after standing for 30 minutes ............ 268 s

After adding 0.1% (0.1 / 1000) sodium gluconate this becomes: - after standing for 3 minutes ............ 14 s - after standing for 30 minutes ........ 34 s.

The flowability is measured using a flow technique with the apparatus known under the name "Maniabilimetre L.C.L.", sold by Etablissements Perrier in Montrouge, France, as described in "Mode Operatoire B F M-1" by French publisher Dunod 1973.

This shows that the binders of the present invention may contain auxiliary materials used in the cement / general industry. The type of tools depends on the nature and fineness of the material that makes up the new hydraulic binder.

The duration of, for example, the joint grinding as indicated in the various examples does not constitute a lower limit, but only represents an experimental indication.

It goes without saying that in industrial applications the mill construction as well as the operating parameters can be adjusted to achieve optimum efficiency.

The time lapse in this description refers to the hardening time.

8006298

Claims (7)

1. Process for the preparation of a hydraulic binder, characterized in that Portland clinker is mixed with an amount of hydrated aluminum oxide such that the hydrate lime formed during hydration of the Portland clinker completely reacts with the aluminum oxide. A method according to claim 1, characterized in that the hydrated alumina and the Portland clinker are ground together. 3. Process according to claim 1 and / or 2, characterized in that the hydrated alumina consists of alumina trihydrate. A method according to claim 3, characterized in that aluminum oxide trihydrate is a component of natural bauxite or laterite. Method according to one or more of claims 1 to 4, characterized in that additives such as fluxes, plasticizers, water-binding agents or calcium sulfate are used. 6. Portland cement and alumina based hydraulic binder, characterized in that the alumina is a hydrated alumina used in amounts such that the hydrate lime which forms during the hydration of the cement is completely formed during formation. the hydrated alumina reacts. 8 0 0 6 2 9 8 -15- - 15 - Use of a binder according to claim 6 or obtained using the method according to one or more of claims 1 to 5 for refractory purposes. 8006298