Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
3~
The present invention is related to novel hydraulic binders based
on Portland cement clinkers which, after hydra~ion, are free of hydr-
lime or calcium hydroxide Ca(OH)2 . In fact, it relates to a proc-
ess for the obter,tion of these binders as well as to certain of their
applications.
It is well known that Portland cement during the course of its hy-
dratation liberates hydrated lime Ca(OH)2 which renders the cements un-
suitable for certain uses, requiring , among other things, a refractory
character at a temperature higher than about 500C, or a stability with
respect to pure water and/or certain acids.
In fact, the formation of hydrated lime results from the nature
itself of the cements whose principal constituent is expressed by the
formula C3S (C = CaO; S = Sio2). Thus, it is well known that during the
hydratation process of C3S hydrated lime is produced.
The nature of this hydration may be expressed schematically
by the reaction : C3S + 3H -~ CSH + 2cH
(H - H2O)
Moreover, it is known that in the construction materials industry
it is possible to combine the lime which appears during the hydration
with additive substances such as pozzolanes in order to form hydr-
ated ca'lcium silicates. This reaction is delayed since it does not
start until 15 days after hardening. These cements are known by the
term '"pozzolanic cements~and are especially used for their stability
with respect to pure waters and certain acids.
. ~
1~.3~ 3
After hydration, if ordinary Portland cement is subjected
to a temperature in the range of 400 to 500C, the hydrated lime
Ca(OH)2 liberated during the course of the hydration, is trans-
formed into calcium oxide which, may subsequently rehydrate
and provoke swelling and deterioration of structures.
The pozzolanic cements may be used as refractory binders
on condition that the refractory concretes obtained from these
cements several months previously are stored in a humid atmos-
phere in order that the pouzzolanic reaction may be complete beforebringing them to a high temperature.
The present invention is based on the surprising and unexpected
observation that it is possible, in defined conditions, to use
these Portland cements in unusual applications.
The present invention relates to a process for the obtention
of binders obtained from a mixture of Portland cement and hydrated al-
umina, the latter used in a quantity sufficient for the lime hydrate
which is formed during the hydration oF the binder to combine
completely with the hydrated alumina as its formation proceeds.
This means that the presence of Ca(OH)2is never observed regardless
of the lapse of time.
Preferably the mixture is co-ground. The reaction between
Ca(OH)2 and the hydrated alumina of the aluminous material
is instantaneous if the mixture is obtained by co-grinding of the
Portland cement and an aluminous material, such as chemical
1~ 38~3
hydrated alumina, raw bauxites and laterites. If, however, the
granulometry of each of the constituents is such that 90% of the
material passes through a 40~ s;eve , such co-grinding may be
omm;tted.
The binders according to the present invention are based on
Portland cement and alumina, which alum~na cons;sts of hydrated
alum;na used in sufficient quantities for the nascent lime hyd-
rate produced during the hydration of the binder to combine
completely w;th the hydrated alumina as fast as it;is formed,
In fact, during the hydration of the binder according to the
invention, the C3S gives rise to the liberation of the lime which,
as it is formed, reacts with the hydrated alumina to form
hydrated calcium aluminates of c3AH6 or CLIAHn type or silico-
aluminates of hydrated(gehlenite type) C2ASH8 and hydrogarnets.
This means, therefore, that no trace of Ca (OH) 2 i s detectable
in the cement.
In the present description, the use of novel hydraulic binders
is more especially examined in the framework of refractory applications
althouth the invention may in no way be considered as being limited
to this application.
The advantages and characteristics of the invention will become
apparent whilst reading the following description and examples given
by way of illustration but without limiting the scope of said invention.
On the experimental level, slaked lime is easy to detect through
d;fferentialthermal analys;s(DTA) showing an endothermic
peak between 450 and 500 C.
1~3~3
Analysis of the products of the hydration of the neat
cement paste may be completed by examination of the X- ray diff-
f~action diagrams..
EXAMPLE 1
_ _ _ _ _ _ _ _ _
b;nder obtained by mixture from Superblanc
a binder is prepared from a mixture of
70 % Portland cement clinker calle~ Superblanc
2.7% gypsum
. 27.3% trihydrate alumina AH3 produced by the sayer process
the granulometry of these products being such that 90% of the
material passes through a ~0~ sieve.
Superblanc ~ a Portland cement, substantially free of iron
oxide sold by the com~any CIilENTS LAFARGE FR~NCE.
If the evolution of the compos;te neat cement paste is
examined in comparison with that of the Superblanc ~ alone, it appears
from TABLE I below that :
- for the Superblanc ~ alone :
Ca(Ot1) 2 is present in large quantities after 1 day and 70-80% of
the available lime able to be formed by the C3S hydratation is
present after 7 days;
- for the composite cement, object of EXAMPLE 1 :
whatever the time lapse, Ca(OH)2 is never detected.
In this example, AH3 alumina had previously been ground in a
25 vibro-mill of the AUREC ~ type for 30 minutes, leading to a
1~3~ 3
partial1y amorphous product.
The neat cement paste was mixed at a water/cement ratio
of 0.64 (W/C = 0.64)
TAsLE I
x diffraction peaks intensities
__ _ __ __ __ _ __ .
MATERIAL LAPSE OF TIM C35 P~13 Ca(OH)2 C3AH6 C4AHn
~ _
cAsTAsL~ 1 d s _ S _ _
supERsLANc 7 d fS _ vs _ _
SLURRY 28 d fS _ vS _ _
CASTABLE 1 d S vS _ W W
CEMENT SLURRY 7 d fS S _ S W
Ex~MPLE 1 28 d fW S _ S W
PRESENT INVENTION _ _ _______ ________ _ ______Y ,
vS = very strong S = strong fS = fairly strong
vW = very weak w = weak fW = fairly weak - = not detect-
able
On the other hand, other phases occur which are not cited in TAsLE I
of EXAMPLE 1, such as C2ASHg (hydrated gehlenite)and hydrogarnets.
The results of DTA (after 1 day storage at 20C and R.H(relative
humidity = 95%) recorded on the annexed drawing lead to curve n 2 for
the cement of EXAMPLE 1 and curve n 1 for the Superblanc ~ with coarse
non-ground hydrated alumina.
This diagram shows that the curve n 2 for 24 hours storage does
not present a peak characteristic of Ca(OH)2.
EXAMPIE_2
The cement is such as that defined in EXAMPLE1 and is obtained
according to the same method although submitted to co-grlnding
Examination of the cement by X diffraction shows a partial amorph-
isation of the trihydrate alumina while the Superblanc ~ is only
slightly affected by this treatment.
In the neat cement paste after 4 days storage no Ca(OH)2
is observed but hydrated calcium aluminates (C3AH6 - C4AHn)
as well as hydrated gehlenite (c2AsH8, are present.In fact, the hydration pro-
ducts are identical to those of the cement obtained from the mixtureafter prolonged grinding of each of the constituents.
These two examples reveal the possibility of causing to react, under
certain conditions, thehydratelime liberated during the hydration of
C3S, principal constituent of Portland cement, with the hydrated alumina.
Thus a cement is obtained which, after hydration only contains
hydrated calcium silicates, hydrated calcium aluminates and hydrated
calcium silico-aluminates. The absence of Ca(oH)2 and the overcoming of
the consequent drawbacks which result therefrom thus enable the use
of this type of cement and especially in the refractory field.
EXAMPLES 3 to 32
________________
In the examples which are described here-under three types of
Portland clinker and different aluminous material are examined.
Operation proceeds with three types of clinkers :
. Clinker A : clinksr having a high C3S and C3A content;
..Clinker B : clinker having a low C3S and C3A content;
. Clinker C : clinker having a very low C3A content
havina the followlna Dotenf.ial mineraloaical comwsitions (calculated
from their chemical analysis):
------~ ------------
alkalin free
C3SC2sC3A C4 AF sulpho- CaO TOTAL
_
clinker A 68 17.40 7.45 0.80 0.35 4.05 100
_
clinker B 57.521.60 7.20 9.80 1.60 0.65 100
clinker C 66 315 35 O.SO 14 SO 0 40 1.55 100
Two types of bauxite, among others, are used :
- Bauxite A : low iron content
- Bauxite B : high i ron content
having the following compositions;
_ . I ,____ ~ _ . _ _
S;O ~ TiO2 AL203 CaOMgO SO3 CO2 L-O.I Fe203 K20 Na20 TotaL
_ . _ _
BauxiteA 0,70 3,90 60,9G O O 0,05 0,05 30,85 3,45 0,05 O,OS 100
l _ _ . _
~auxiteB 8,90 2,75 53,27 O O 0,10 0,05 23,6~ 11,2~ 0,05 0,02 100
* loss on ignition
From the different X diffraction spectra and -taking into account the
aluminium and water content, it is possible to calculate the proportions
of trihydrate ~AH3) and monohydrate (AH) i n each bauxite; the percentage
of the different phases is given in the following table
TABLE II
AH~ Bayer Bauxite A Bauxite B
AH3 100% 87.2% 61.9%
_
AH _ 4.7% 14.9%
_ .
impurities _ 8.1% 23.2%
. ` 1~3~ 3
EXAMPLES 3 to 5
____ __________
In Examples 3 to 59 the clinker B/aluminous material A ratio
is 2:1.
__.
* Example 3 after ~ixture ~ithout co-grinding
* Example 4 after mixture and co-grinding for 2 h
. _ _ _ . __
* Example 5 after mixture and co-grinding for 6 h
__ ,. l
The co-grinding was not carried out as ;n EXAMPLES 1 and 2 in a
vibro-mill but . in a conventional ball-mill.
The pure castable cement slurries were stored at 20C and g5% R.H.
It is observed at 20C and 95% by DTA and XR that the cement of
EXAMPLE 3 (mixture without co-grinding) still contains thehvdratelime
even after a long storage period (3 months) while the cements wh;ch were
made by co-grinding no longer contain Ca(OH)2 after 24 hours
storage.
Storage at 50C and 95% R.H. improves the reactivity of the
mixture since the Ca(OH)2 present after 7 days at 20C and 95% R.H.
disappears. -- ~~~-~
~3~3~3
TABLE III
_ _ _ _ _ _ _ _ _ _
, ... Time _______ __~______ ~ __~_____ __~_____
Storage Example lapse C3S AH3 Ca(OH~2 C3AH6 C4AHn
_ 24 h 5 S S _
3 7 d W S vS _
20C 24 S S _ fW W
4 7 fS fS _ fW W
& 3 W fS _ fW W
24 S S _ fW W
95%R.H 5 7 fS fW _ fW W
3 W fW _ fW W
____N____ . I . ._. 24 S ' S S _~ _
3 7 fS fW _ fW W
3 W W _ fW ~ W
o 24 S S _ fW -W
50 C 4 7 fW fW _ fW W
~ _ 3 W W _ fW W
95%R.H. 5 247 fW fW _ fW . W
. . 3 W W _ fW W
15 As in Examples 1 and 2, C ASH ( hydrated gehlenite) and hydrogannets
are detected.
EXAMPLES 6 to 8
In these examples, clinker B and bauxite B were used in a 2:1 ratio.
_____
* Example 6 after mixture without co-grinding .
* Example 7 after mixture and co-grinding for 2 h
* EXAMPLE 8 ~
The neat cement paste was stored respectively at 20C and 95%R.H
and at 50C and 95% R.H.
~3~3
In Examples 6 to 8, it was observed that as for the preceedillg exam-
p7es the Ca~OH)2-A~n reaction is immediate whenever the cement
is prepared by co-grinding.
This reaction is accelerated when the temperature is in-
creased.
EXAMPLE 9 to 27
_______________
Furthertests were carried out on other compositions, the nature
of the material and the clinker/aluminous material ratio of which
were modified.
EXAMPLES 9 to 27
-- a Lumi no~ls ~;~
n exampleclinker A 57/43 preparation
9 ~ 1B _ 67/33 ~ ~ r i n~ ~ ~9
The total of the combinations represents 3 x 2 x 3 = 18 cases of this
type (thus Examples 9 to 27).
The analysis of the neat cement paste obtained from
each of these examples 9 to 27 after a hydratation time of 24 hours,
shows the absence of hydrated lime both by X diffraction and DTA.
It is obvious for a man skilled in the art that it is advisable
to adjust the quantity of aluminous material to the hydrated lime
liable to be formed by hydratation of the Portland cement, taking
into account the impurities present in both materials.
In fact, the characteristic of the neat cement paste
according to the invention is that after hydration
never contain Ca(OH)2, therefore enabling the use of these binders
in apPlications where the presence of lime hydrate is ill-advised.
EXAMPLE Z8
_ _ _ _ _ _ _ _ _
a) fire stability
A mixture is prepared from 67% clinker and 33% chemical AH3
produced from the Bayer process. The mixture is then co-ground during
2 hours. After hydration for 24 hours at 20C and 95% R.H.
the neat cement paste is dried at 110C then heated to
300-500-800-1100-1250C for 6 hours and finally cooled in the oven.
__~ _
mineralogical treatment temperature
phase 20C110C 300C500C 800 1100C 1250c
_ _ _
C3S S S W W W W W
AH3 vS vS _ _ _ _
C ~OH) 2 _ _ _ _
C4AHn W _ _ _ _ _
c2AS _ _ _ _ w S S
~, _ _ S S _ vS S
Intensity of the neat cement paste_ after heat tre_tment *
1~3~Q3
To conclude, it is observed that whatever the firing temperature of
the neat cement paste, the binder defined in this example never
liberates lime liable to be rehydrated and thus it maY be used as
a refractory binder.
b) humidity stability
From the cement defined in Example 28, a,(10 cm cubes of
fire clay concrete Were prepared, then treated according to a
thermic cycle as shown in the table below.
Compared to a reference cement sample, the cubes made from an activated
cement base remained intact while the cubes of the reference sample
cement present cracks.
~ tivated cement
~_
6 h - 500C no cracking no cracking
5 h in humid conditions no cracking no cracking
6 h - 800C no cracking crackings
15 5 days in humid conditions no cracking crack;ngs
6h - 110C no crack;ng crackings
5 days in humid conditions no cracking crackings
- ,....................... _
EXAMPLE 29_to 31
In Examples 2~to 31 the behaviour of a composite cement constituted
20 from Clinker C and bauxite B is examined ~y conventional tests
for refractory purposes, i.e. by determination of :
- the mechanical properties after heat;ng
- the linear change after firing
- refractiveness under load (temperatl~res).
The service temperature limit ls in the range 1250C-1300C, since
1~3~
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14
~3~ 3
the linear chanqe after firing lies within the E~P
recommendations* (< + 1.5%).
As a general rule, the refractarity of tbe cement will depend on
the clinker/aluminous material ratio and the purity of the constituents
(iron oxide content).
The rheology ofthe cement may be modified by complementary addition
of anhydrous or hydrated calcium sulphates or additives such as plasticizers~
fluidizers, water reducers.
EXAMP~E 32
___________.
A cement realized by co-grinding clinker B and bauxite B for
2 hours has a workability when used as a mortar with silica sand (W/C = 0.5)
- after settling of 3 mn ................... 169 s
- after settling of 30 mn .................. 268 s
After addition of 0.1% (0.1/1000) sodium gluconate, this changes to :
- after settling of 3 mn ................... 14 s
- after settling of 30 mn .................. 34 s
The workability was measured by a flow technique with the apparatus
known as "Maniabilimetre L.C.L." sold by Etablissements Perrier in Mont-
rouge, France according tothe method described in the "Mode Opératoire
B F M-l" edited by the French Publishers Dunod 1973.
It is thus observed that the binders according to the present invention
are liable to have added auxiliary agents used currently in cement techniques.
The nature of these auxiliary agents will depend essentially on the nature
and the fineness of the materials constituting the novel hydraulic binder.
Of course, the present invention is in no way limited to the embodi-
ments shown and represented, it has many variations within the reach
;3~1~3
of a man skilled in the art, according to the applications envisaged
and without departing from the spirit of the invention.
Thus, the duration of the co-grinding indicated in various examples
does not constitute a lower limit; but simply an experimental indication.
S It is obvious in the case of indus,tr,ial use that the constr-
uction of the m;ll as well as its operating parameters could be
adapted to render optimum efficiency.
By time lapse is meant in the present description curing or hardening
- time.
16
