Note: Descriptions are shown in the official language in which they were submitted.
4l~
The invention concerns a mortar based on clay and cement with a
proportion by weight of clay at least equal to that of cement, a mortar
resulting in finished products which are at the same time inexpensive and of
quality, in particular as regards their mechanical resistance and the sub-
stantial absence of cracking or shrinkage.
It also concerns methods of preparation and use of these mortars as
well as the products made by means of the latter.
It will be recalled that it is already known for a mortar to be
made by mixing or "gauging" clay, cement in a proportion by weight at most
equal to that of the clay, "gauging", water and certain mineral adjuvants
such as sodium phosphates, sodium carbonate or calcium carbonate; these
adjuvants exert in general a defloculating or wetting effect, allowing the
gauging water to disperse better in the mixture of clay and cement.
The inventors have discovered that such a deflocculating effect ~ -
even if it perhaps facilitates the mixing itself, leads to mediocre character-
:.,
istics of resistance and cohesion for the finished products after setting.
With the present invention, on the other hand, in addition to the
gauging water, there is added to the clay-cement mixture a hydrophilic agent,
capable of increasing the thixotropy of the mixture and cross-linking the pro-
duct by polymerization during the subsequent setting.
Thus, according to the present invention, there is provided a mortarcomprising a cement, clay in a proportion by weight at least equal to that of
the cement, gauging water, and additive selected from the group consisting of
urea-formaldehyde resins and derivatives thereo and melamine-formaldehyde
resins and derivatives thereo~, the dry weight of additive present being
between 1 and 20% of the total dry weight of the clay and cement.
In another aspect, the invention provides a method of preparing a
mortar which comprises mixing cement, clay in a proportion by weight at least
equal to that of the cement, gauging water, a~d additlves selected from the
group consisting of urea-ormaldehyde resins and derivatives thereof and
melamine-formaldehyde resins and derivatives thereof, the dry weight of said
additive being between 1 and 20% of the total dry weight of the clay and
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cement.
Furthermore, the invention provides in a set clay/cement product
in which the amount by weight of clay at least equalsthat of the cement and
in which a cross-linking agent is polymerised the improvement which comprises
reinforceMent dispersed through said product, said réinforcement comprising
cured resin selected rom the group consisting of cured urea-formaldehyde
and melamine formaldehyde resins and derivations thereof: .
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In preferred emb~dimerlt5 use is made of one and~or other
of the following features :
- the proportion by weight of clay in the clay-cement mixture is
between 2 and 4 times that of the cement,
- the clay used is basic ~pH greater than 8) or rendered basic by
the addition of silicates and/or of sodium aluminates,
- before mixing the clay with the cement, the quantity of adsorbed
water'present in this clay is reduced by adding to it an additive,
which is a flocculantand/or capable of giving the-clay water-repellent
properties,in a proportion by dry weight of the order of 0.5 to 5 parts
per thousand based on the dry weight ,of the clay,
- in a 'method according to the preceding paragraph, the additive ls a
flocculant constituted by polyeiectrolytes of the polyacrylamide type
or by cationic derivativss such as quaternary ammonium salts, or is a
water-repellent based on fatty amines, ''
- there is added to the clay cellulose or one of its derivates in the
form of a very fine powder or ln solution in a solvent neutral to . .
. . .
. . cement, at a dry weight percentage between 3 and 30% based on the dry
wzight of the clay~
- there i5 added to ons at least of the constituents oF the mortar
. aluminium powdar in a proportiqn by dry weight of the orcler of 0.1 to2 parts
. per thousand based on the dry weight o-P the said constituent,
: ' - there is added to the clay-cement.mixture a load of glass or the like
in the form of.fibres, powder or gel,
- there is.added t~ the. clay-cernent mixture a vinyl or acrylic or A.~,S
emulsion or the like, preferably diluted in water, at a clry solids
weight percentage betwsen 5 and Z5% bassd on ths dry weight of the
clay-cernsnt mixture,
- after use of ths r(lortar according to the inven-tion, the products
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made from this mortar are kept in an atmosphere saturated wlth
water vapour for several hours be-Pore being slowly dried. -
Ths invention involves, apart from these principal features,
certain other features which are preferably used at the same time and
which will be more explicitly mentioned hereafter.
In what follows some preferred embodiments of the invention
will bs desc~ribed in 3 non-limiting manner-
Clay being, by weight or volume, much less dear than cement,reduction of the cost of cements has long besn sought by mixing the
latter with clay.
But experisncs shows that products obtained from clay-cement-
water mixtures exhibit, after setting, mediocrs mechanical characteristics
and tend to crack because of the shrinkage induced on setting by the
removal of the gauging water.
To rendsr the clay-cement-water mixtures mors homogeneous,
it has already bsen propossd to add to these mixtures special ad~uvants
tending to "dsflocculate" or to "wet" the mixture, that is to say break
up the. agglomerates of the latter and to disperse the gauging
water throughout the body of the said mixture in a more uni-form way.
The inventors have discovered on the contrary that, by adding
. .
to the clay-cement-watsr mixture a hydrophilic and water retentive
agent to incrssse the thixotropy of ths mlxture and to ensure a cross-
llnkage of this mixture by polymerization on setting, one could obtain
-finlshed products exhibiting, a~ter setting, distinctly improvsd mechanical
characteristlcs, with the abssnce of cracks.
- ~ . Such an agent is chosen -Prom among amino-resins, substances
which posse~ adherent propertie~ of the same kind a5 those of gum
arablc and which are currently used for the gluing of plywoods or
compressed woods.
Among thsse amino-resins, those preferrod are the urea-
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formaldehyde or rnelamine-formaldehyde resins and their derivatives, in
pulverised form or, more generally, in the form of an aqueous solution
containing a minimum of 5% of water.
- The minimum dry weight percentage of this agent used
correspon~s to 1 or 2% of the''dry wsight of the clay-cement mixture.
The maximum weight percentage of the said agent is of the
order of 20%.
In particular if one supposes that the resin occurs in the
form of a solution containing 50% of water, that all the gaugin~ water ''
comes from this solution, and that the proportion by weight of the
cement in the clay-cement mixture'is ~/4, as the total contributinn of
' ' water to the mixture must correspond at the maximum to 25% by weight
of the cement, the maximum weight'of dry resin is of the order of 15%
of the dry weight o'f the clay-cement mixture.
- The clayconstituent of the mixture concerned can be pure
clay or clayey soil more or less loaded with sand.
It is preferable for it to be basic, its pH being greater
than ~l if this is not the case, it is advantageous to render it basic
.
by the addition of sodium silicates or sodium alurninates.
The cemsnt congtituent of the Inixture is pre~erably rich
ln calcium alurninates.
The proportion by weight of dry clay is at least equal to that
of the dry cement, the relation between thege two proportions prefsrably
bsing betwesn 2 and 4, whlch rneans that the clay is generally the
rna~ority of the mi-~ture.
' ' With a mortar composed in that way, that ia to aay with cernent,
clay preferably in a maJority proportion, water and an amino-r~sin,
one can rnake all the items currently made ln cernent, concrste and/or
clay sucn as bricka, tilea, pottery, panel5, glabs, plates corrugated
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or not, pipes, caissons etc., and in any suitable way, particularly
by sxtrusion, drawing, moulding, in~ection, casting, application
by trowel..., hot or even cold.
After fabrication, it is advisable to maintain the product
obtainsd in a humid atmosphere for soms hours, for example for 24
hours at 60 in an atmosphere saturated with ~ater, and then to leave
it to dry 910wly. ~ .
~ he ~setting which results from this is accompanied by a
polymerization with a slow progressive cross-linkags owing to the ~ -
resins, in spite of the alkalinlty of the medium; it is a~surprising
phenomenon, seeing that the said-resins are considered to be capable -
of undergoing polymerization only in the presence of acid catalysts.
The products obtained after such a slow setting exhibit a
cohesion and other mechanical properties which are very remarkable.
It is in this way that these propsrties are comparable to
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those of similar known products in asbestos-cement which comprise 30%
rnore of cement by volume and are consequently much heavier.
In a gsneral way, it is usual for the dried coherent products
according to the invention to exhibit mechanical resistance, to traction
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as much as to cornpression, of at least 30% greater than that of products
made from clay-cement mortars of identical composition but in the
absence of qmino-resins.
, The products in question have smooth exterior surfaces with a
beautiful appearance keeping the colours of the initial constituents
durably tespecially red lf pure clay predominatesJ white if the predominate
constituent is kaolln, which is a clay rich in white mica~.
In what follows there will oe described a certain number oF
othsr features allowing still further improvement oP the qualities of the
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above products.
According to one of these features, the clay is submitted, before
its mixture with the cement, to a treatment which is "flocculant" and/or
capable of'conferring water repellent qualitles on this clay, by
adding to the latter an appropriate additive in small amounts tnamely
0.5 to 5 parts by weight per thousand based on the dry weight of the clay)
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preferably by pulverisation oF a solution of this additive in water durin~
the premixing and pounding of the clay.
Such an additive is constituted for example : .
- by polyelectrolytes of the polyacrylamide type such as those distributed
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' under the name MAGNAFLOC R 155 by the CAVIEM Company,
- by quaternary ammonium salts such as those distributed under the name
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NORAMIUM M2SH by the PIERREFITTE-AUBY Company, especially if the clay
used is loaded with crystals of high specific surface and lamellars in
' particular,
- or by fatty amines such as those d:Lstributed under the name STABIRAM
677 S by the PIERREFITTE-AUBY Company.
According to another of the above fsaturss, cellulose or one
of itB derivates is added to ths clay, in a proportion by weight between
3 and 30%, in the form oP a vsry fine powder or of a solution in a
solvent which i3 nsutral relative to the cen~nt.
This allow~ reduction-of the denslty of the products obtained
whils lmproving their thermal and sound insulation, which offers valuable
advantage~ when ths products made'are intended for construction of
dwellings. '
' ' According to yet another of the abovs -Features, aluminium . '
~ ' in'the form of powder is added to ths clay or the cement. '~
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This metal creates a gaseous expans$on, which reduces
the density of the final product obtained. Moreover the aluminium
salts formed by the reaction of the aluminium with the lime present
in the cement ensure an excellent protection for the product against ~-
ageingand against chemical attack by the air and by carbonic acid.
The proportion by weight oF this addition of powder is
advantageously be~tween 0.1 and 2 parts per thousand based on the dry
weight of the clay-cement mixture to which the said powder is added.
According to yet another of the features mentioned abovs, '-
a vinyl, acryiic, A.~.S or the like solution in water is added to the ~'
clay-cement mixture, the weight percentage of this addition generally '""
being between S and 25% of the weight of the cemsnt.
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This allows the products obtained to be rendered particularly
waterproof and resistant to abrasion by giving their surfaces a glazed,
smooth and dense appearance.
~' To improvs the mechanical resistance of the products
- obtained, it is advantageous, according to yet anothsr o-F the above
features, to reinforce the rnortar used by'means of elements with a glass ' ''
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' 6ase, the elernents bein'g in the form of powder, gel tsilica) or
preferably irn the form of fibress the glass is, as a matter oF fact,
; ' dissolved superficially by the alkaline material wlth which it is closely
' mlxed, then is regenerated at the time of drying, -Porming a solid phase
which is closely bound to the crystals oP clay and cement.
There are thus provided mortars for the econornical making of '' -
products which, after setting, exhibit excellent mechanical resistance
and a tendency to cracking which is negligible, indeed non-existflnt.
1'hese products can be identified, not only by their excellent
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mechanical properties but also by chemical analysis which reveals in
particular the presence of macrornolecules of resin and traces of
flocculant which are incorporated therein.
As is evident, and as already results moreover from what
precedes, the invention is not limited at all to those of its modes
of application and realisation which have been more especially envisaged;
it enbraoes, on th oo~trary, all the var'ants th~r~of.
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