Agents for inerting clays in hydraulic compositions
The invention relates to agents for inerting clays present in hydraulic compositions.
Hydraulic compositions are compositions Comprising a hydraulic binder. A
hydraulic binder is a binder which is formed and hardened by chemical reaction with
water. As hydraulic binders, mention may be made of plaster, calcium sulfates, calcium
aluminates, lime and cement compositions, which allow preparation of hydraulic
compositions, notably mortars and concretes, notably prefabricated concretes and ready-
to-use concretes. These concretes may notably be intended for the building industry, civil
engineering structures and for prefabrication.
It is known how to add fluidifying agent or superplasticizers, notably
superpiasticizers, such as polyoxyalkylene polycarboxylates (PCP), to hydraulic binders
such as cements, plasters, calcium sulfates or lime, in order to reduce the water content
of hydraulic binder slurry. Consequently, hydraulic binder slurry after hardening, has a
denser structure. This is expressed by a higher mechanical strength.
Incorporation of these admixtures into ,the hydraulic compositions have allowed
considerable technical development; nevertheless there remain difficulties related to their use,
i.e. their sensitivity to concrete composition variations and notably their sensitivity to variations
in the quality of the sands and granulates.
Thus, the presence of adsorbing impurities such as clays (montmorillonite, illite,
kaolinite,...) in hydraulic compositions generate fluctuations of properties, in particular
considerable fluidity variations, due to a drop in the efficiency of these superplasticizers. This
sensitivity is expressed by an increase in the required dose of admixture, which may cause
losses of properties (compressive strength, cracking, durability...). This overdosage further has
to be determined by preliminary tests and is therefore a source of additional cost.
By the term of <> are designated aluminum and/or magnesium silicates either
hydrated or not, notably phyllosilicates with a structure of sheets typically spaced apart by
about 7 to about 14 angstroms. This term however is also directed to clays of other types,
notably fibrous and amorphous clays. Various types of clays exist which are different by their
structure and the number of sheets which they include. Among the clays frequently
encountered in sands and granulates, mention may notably be made of montmorillonite, illite,
kaolinite, muscovite and chlorite.
The clays may be of the 2:1 type (montmorillonite) but also of the 1:1 type (kaolinite) or
of the 2:1:1 type (chlorite). The most currently encountered clays in sands, granulates and lime
fillers entering the composition of hydraulic compositions are kaolinite of formula Si2O5AI2(OH)4,
montmorillonite of formula Si8O20AI4(OH)4 and illite of formula KAI2(AlSi3O10)(OH)2.
These clays form a family of lamellar solids which have the remarkable property of
adsorbing or inserting cationic or neutral molecules between their sheets.
Thus, montmorillonite has a charge deficiency which varies between 0.6 and 0.9
because of isomorphic substitutions both in the tetrahedral and/or octahedral layers.
Electrical compensation is ensured by the insertion of more or less hydrated cations in the
interfoliar space. One of the consequences is that it may receive water molecules in the
interfoliar space and form what is called a swelling clay.
Illite which has the same crystalline structure differs by the type and number of
substitutions. The space between the sheets is larger in montmorillonite than in illite where
more voluminous K+ ions are found very close to the substitution points and are firmly inserted
between the sheets and therefore prevent swelling of this clay.
Kaolinite ore is formed by about 100 sheets which are difficult to dissociate. The
cohesion forces present in kaolinites are mainly of the electrostatic type, completed by
interaction forces of the Van der Waals type and hydrogen bonds between the hydroxyl
groups of a layer and the oxygen atoms of the adjacent layer. The bond is strong enough
to prevent any swelling phenomenon between the layers.
Only montmorillonite is therefore capable of easily giving insertion compounds with
organic polymer molecules; this should be much more difficult with kaolinite and illite.
Depending on the nature of the clay and according to the pH of the medium, either
adsorption or intercalation will therefore be observed on these clays, or both joint phenomena.
The admixtures, notably the superplasticizers, added to the organic compositions are
adsorbed at the surface of the clays and/or are inserted between the sheets making up the
clays. The superplasticizers trapped in the clays are then no longer capable of playing their role
for improving the dispersion of aqueous suspensions of hydraulic binders.
Therefore it is necessary to inert the clays.
Thus, in order to avoid undesirable adsorption of superplasticizers of the
polycarboxylate type (PCP) on clays and therefore a loss of efficiency, WO 98/58887 proposes
before adding the superplasticizer in the sand-cement mixture, the introduction of a sacrificial
molecule: polyethylene glycols, or further inorganic or organic cations, notably quaternary
ammoniums, which may be inserted into the sheets of the clays. The described method
consists of putting the dry sand in contact with the sacrificial molecule by spraying the product
in an aqueous solution. However, it is necessary to add a content of polyethylene glycol or of
cation relatively to the cement in order to again find almost the totality of the efficiency of the
polymeric admixture.
Documents WO2006/032785 and WO2006/032786 respectively recommend the use
of a cationic polymer which may be linear or branched or of a mixture comprising a cationic
polymer and an anionic polymer. The described method consists of putting dry sand in contact
with the cationic polymer or the cationic polymer/anionic polymer mixture by spraying the
product in an aqueous solution. The suggested cationic polymers are obtained by
condensation of epichlorhydrin with dimethylamine or further dicyandiamide with formaldehyde.
However, increasingly restrictive legislations aim at limiting the use of formaldehyde.
Document EP1201617 recommends, in order to increase the durability of
compositions of hydraulic binders loaded with non-heat treated clays, the use of alkaline
silicates or soluble salts of divalent or trivalent metals such as calcium nitrate. However,
the described agents do not yet give entire satisfaction.
Moreover, Zhang et al. (SOIL. SCI. Soc. Am. J. 54, 59-66, 1990) teaches that
acetate anions are repelled by the anionic charges present on the montmorillonite clay.
One of the objects of the present invention is to provide a method for inerting clays
of a hydraulic composition.
For this purpose, according to a first aspect, the object of the invention is a method
for inerting clays in a hydraulic composition comprising a step consisting of putting a
hydraulic composition or a constituent of a hydraulic composition in contact with a
compound of the following formula (I):
R-COO-, (Mn+)1/n (I)
wherein:
R represents a group selected from H, alkyl and phenyl,
- n represents an integer comprised between 1 and 5, preferably between 1 and 4,
Mn+ represents a cation selected from:
- H+,
- a divalent, trivalent or tetravalent metal cation, and
- a group [HNR1R2R3]n+, wherein R1 R2, and R3 represent independently of each
other, H or a linear, branched or cyclic, optionally aromatic, saturated or
unsaturated hydrocarbon chain, optionally substituted with one or several
substituents selected from a hydroxyl and a group NR4R5, wherein R4 and R5
represent independently H or an alkyl optionally substituted with a group
NR6R7, wherein R6 and R7 represent independently H or an alkyl,
it being understood that the groups R1, R2, and R3 may be bound together and
form a ring with the nitrogen atom bearing them.
In the sense of the present application, an alkyl is a linear or branched, optionally
cyclic saturated hydrocarbon aliphatic group, comprising from 1 to 8 carbon atoms,
preferably from 1 to 4 carbon atoms, as examples, mention may be made of methyl, ethyl,
propyl, isopropyl, butyl, isobutyl and tertiobutyl groups.
The hydrocarbon chain preferentially comprises from 1 to 8 carbon atoms, notably
from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms.
The agent inerting clays of formula (I) applied in the inerting method is a salt
consisting of an anion R-COO- and of a cation Mn+, n representing the charge of the
cation.
The compounds of formula (I) are actually useful for inerting clays of hydraulic
compositions, i.e. for inhibiting swelling of the clays, and/or inhibiting adsorption on the
clays or between the sheets of the clays of admixtures used in hydraulic compositions,
notably superplasticizers. Thus, the compounds of formula (I) give the possibility of
reducing, or even suppressing the loss of fluidity of the hydraulic compositions due to the
clays. Generally, the compounds according to the invention give the possibility of
suppressing the loss of fluidity of mortars and concretes based on cement binders over a
period of 60 mins, notably 90 mins, preferably 120 mins.
The compounds of formula (I) applied in the inerting method also have the
following advantages:
- they allow reduction in the amount of water or of fluidifying agent required for
obtaining a desired fluidity for the hydraulic composition,
- they are efficient with different clays, in particular, the compounds of formula (I) are
performing inerting agents for clays of type 2:1 (montmorillonite) but also of type
1:1 (kaolinite) or 2:1:1 (chlorite).
they do not perturb the mechanical strengths of the hydraulic composition neither
in a short term nor in a long term, even in the case of overdosage,
- they do not have any delaying effect on setting,
- they are stable over time and withstand heat and frost
The compounds of formula (I) applied in the inerting method include an anion of
formula R-COO-. Typically, R represents H or an alkyl including from 1 to 4 carbon atoms.
In a preferred embodiment, R represents H or a methyl. The anion is then the formate
anion or the acetate anion. The compounds comprising these anions are actually either
commercial compounds, or easy to prepare from formic acid or acetic acid. They are
inexpensive and are particularly efficient as inerting agents.
The compounds of formula (I) applied in the inerting method also include a cation.
The cation may be a proton. In this case, the compound is a carboxylic acid of formula
RCOOH. The formic or acetic acids are preferred compounds.
The cation may also be a divalent, trivalent or tetravalent metal cation. The
compounds comprising monovalent cations are actually less performing. Preferably, the
metal cations are bivalent or trivalent. Indeed, generally the salts including bivalent or
trivalent metal cations are less expensive than salts including tetravalent metal cations.
Divalent metal cations are typically earth alkaline metal cations, notably selected from
magnesium, calcium and barium ions. Aluminium is an example of a trivalent metal cation.
The cation may also be a group [HNR1R2R3]n+ wherein n, R1, R2, and R3 are as
defined above.
In an embodiment, R1, R2, and R3 represent H and the cation of the compound of
formula (I) is the ammonium cation +NH4. In another embodiment, R1 and R2 represent H
and R3 is different from H. The cation is then a primary ammonium. R3 may for example
be a phenyl, the cation then being the anilinium ion. R3 may also represent a linear or
branched alkyl, the cation then being for example monoethylammonium or
monoisopropylammonium. In another embodiment, R3 represents H and R1 and R2 are
different from H. The cation is then a secondary ammonium. R1 and R2 may notably be
alkyl groups. The cations may for example be diethyl ammonium or
diisopropylammonium. In another embodiment, R1, R2, and R3 are different from H. The
cation is then a tertiary ammonium. Thethylammonium or ethyldiisopropylammonium are
examples of suitable tertiary ammonium.
In an embodiment, at least two of the groups R1, R2, and R3 are hydrocarbon
chains bound together and at least two of the groups R1, R2, and R3 form a ring with the
nitrogen atom bearing them, which may be saturated, unsaturated or aromatic.
Pyrrolidinium, piperidinium, pyridinium cations are examples of these cations. Two of the
groups R1, R2, and R3 may be grouped and bound to the nitrogen atom through an imine
bond, like the pyridinium cation.
In an embodiment, in the formula (I) of the compound used as an inerting agent, at
least one of the R1, R2, and R3 represent a hydrocarbon chain substituted with a hydroxyl
and/or with a group -NR4R5 as defined above. When the cation [HNR1R2R3]n+ includes one
or several -NR4R5, groups, the nitrogen of the group -NR4R5 may be protonated
(-+NHR4R5) or non-protonated.
In an embodiment, the group R3 is a group -(CH2)q-NR4R5 and the compound used
as an inerting agent has the following formula (II):
R-COO", +[HR1R2N-(CH2)q-NR4R5] (II),
wherein R, R1, R2, R4 and R5 are as defined above and q represents an integer from 1 to
6, preferably from 1 to 4. When the group -NR4R5 of the compound formula (II) is
protonated, the compound has the following formula (IT):
R-COO-, 2+[HR1R2N-(CH2)q-NHR4R5]1/2 (H'),
Wherein R, R1, R2, R4, R5 and q are as defined above. Preferably, in the compounds of
formula (II) or (IT), R1, R2, R4and R5 represent independently H or alkyl groups, preferably
H or methyl. The mono- or di-protonated forms of diethylaminopropylamine of
tetramethylpropylene diamine are examples of suitable cations.
In another embodiment, at least one of the groups R4 and R5 represent an alkyl
substituted with a group NR6R7, wherein R6 and R7 represent independently H or an alkyl,
notably H or a methyl. In an embodiment, the group R3 is a group -(CH2)q-NR4-(CH2)r-
NR6R7 (R5 represents -(CH2)r-NR6R7) and the compound used as an inerting agent has
the following formula (III):
R-COO-,+[HR1R2N-(CH2)q-NR4KCH2)rNR6R7] (III),
wherein R, R1, R2, R4, R5, R6, R7 and q are as defined above and r represents an integer
from 1 to 6, preferably from 1 to 4 (independently of the value of q). The cation of the
compound may also be in a diprotonated form (R-COO-, 2+[HR1R2N-(CH2)q-HNR4-(CH2)r
NR6R7]1/2 or R-COO-, 2+[HR1R2N-(CH2)q-HR4-(CH2)r-HNR6R7]1/2) or a triprotonated form
(R-COO-, 3+[HR1R2N-(CH2)q-HNF4-(CH2)rHNR6R731/3). For example the mono-, di- or
tri-protonated forms of dimethylaminopropyl-aminopropylamine may be used as a cation.
In another embodiment, at least one of the R1, R2, and R3 represents a
hydrocarbon chain substituted with a hydroxyl. Preferably, at least one of the R1, R2, and
R3 represent an alkyl substituted with a hydroxyl. The protonated forms of amino alcohols
are actually particularly suitable cations. Thus, the protonated forms of
monoethanolamine, diethanolamine, thethanolamine, s-butylethanoiamine (marketed by
ARKEMA® under the name of ALPAMINE® N41) and 2-dimethylamino-2-methyl-1-
propanol (marketed by ANGUS Chemical® under the name of DMAMP®-80) are
particularly suitable cations.
Generally, when a compound of formula (I) in which Mn+ represents HNR1,R2R3 is
applied in the method, the pKa of the cation [HNR1R2R3]n+ is greater than 8, typically
greater than 10, notably greater than 12. By pKa of the cation is meant the pKa of the
acid/base pair [HNR1R2R3 ]n+/[NR1R2R3](n-1)+. These pKa are actually suitable for
maintaining the amine in the protonated form [HNR1R2R3]n+.
Advantageously, the inerting method applies compounds of formula (I) which are
soluble in water. Typically, the compounds have a solubility in water of more than 5 g/L, or
even more than 10 g/L. Compounds of formula (I) including less than 12 carbon atoms,
notably less than 10 carbon atoms, in total (by taking into account the cation and the
anion) are more preferred.
The compounds of formula (I) useful as agents for inerting clays may notably be
prepared by:
- reaction of carboxylic acids RCOOH with metal hydroxides (calcium hydroxide,
magnesium hydroxide, barium hydroxide...) for preparing metal carboxylates (calcium
magnesium, barium carboxylate...),
- neutralization of carboxylic acids RCOOH with an amine HNR1R2R3, for example
ammonia, an aliphatic or aromatic amine, a diamine or a polyamine, or an
amino-alcohoi.
In an embodiment, the method for inerting clays in a hydraulic composition
comprises the step consisting of putting one of the constituents of a hydraulic composition
in contact with a compound of formula (I). A hydraulic binder, a granulate, a mineral
addition, water, an admixture used during the preparation of the hydraulic composition
(such as a superplasticizer, anti-air-drag additive or a fluidifying agent) are examples of
constituents of a hydraulic composition.
Generally, the clay to be inerted stems from the granulate, notably from sand
and/or filler. Sometimes, the hydraulic binder also includes clay. This is notably the case
of CEM II /A-L, A-LL, B-L or B-LL cements with lime and cements with pozzolans such as
CEM IV or V AorB.
A hydraulic binder is a binder which is formed and which hardens by chemical
reaction with water. As hydraulic binders, mention may be made of plaster, calcium
sulfate, lime and cement compositions.
By « granulates », is meant a set of mineral grains with an average diameter
comprised between 0 and 125 mm. Depending on their diameter, the granulates are
classified into one of the following six families: fillers, wind-blown sands, sands,
sand-gravel mixes, grits and ballast (XP P 18-545 standard). The most used granulates
are the following:
- fillers, which have a diameter of less than 2 mm and for which at least 85% of the
granulates have a diameter of less than 1.25 mm and at least 70% of the granulates
have a diameter of less than 0.063 mm,
- sands with a diameter comprised between 0 and 4. mm (in the 13-242 standard, the
diameter may range up to 6 mm),
- sand-gravel mixes with a diameter of more than 6.3 mm,
- grits with a diameter comprised between 2 mm and 63 mm.
The sands are therefore comprised in the definition of a granulate according to the
invention.
The fillers may notably be of limestone or dolomitic origin.
By « mineral addition », is meant a finely divided mineral material used in concrete
in order to improve certain properties or to give it particular properties. The NF EN 206 - 1
standard distinguishes two types of mineral additions: quasi-inert additions (of type I) and
additions with a pozzolan nature or hydraulic latency (of type II).
The additions of type 1 are:
- limestone fillers according to the EN 12620:2000 standard
pigments, compliant with EN 12878
- limestone additions, compliant with the NF P 18-508 standard
- siliceous additions compliant with the NF P 18-509 standard
The additions of type II group:
- flying ashes, compliant with the NF EN 450 standard
silica fumes, complaint with EN 13263-1
Superplasticizers are admixtures called « water reducing agents » which are used
for reducing the amount of water required for mixing hydraulic compositions. The following
superplasticizers may notably be used in the compositions according to the invention:
- sulfone salts of polycondensates of naphthalene and of formaldehyde, commonly
called polynaphthalene sulfonates or further superplasticizers based on naphthalene;
- sulfone salts of polycondensates of melamine and of formaldehyde, commonly called
melamine-based superplasticizers;
lignosulfonates;
- polyacrylates;
products based on polycarboxylic acids, notably polycarboxylate comb copolymers
which are branched polymers for which the main chain bears carboxylic groups and
for which the side chains consist of sequences of the polyether type, in particular
polyethylene oxide, such as for example poly [(meth)acrylic acid - grafted -
polyethylene oxide]. The superplasticizers of the ranges CHRYSO®Fluid Optima,
CHRYSO®Fluid Premia and CHRYSO®Plast Omega marketed by Chryso, may notably
be used.
According to a second aspect, the object of the invention is a hydraulic
composition comprising a hydraulic binder, at least one granulate, water and a
superplasticizer and further comprising a compound of formula (I) as defined above. The
hydraulic composition may comprise more than one granulate, for example sand and a
filler. In an embodiment, the hydraulic composition comprises a filler, notably a limestone
filler. In an embodiment, the hydraulic composition further comprises at least one mineral
addition and/or admixtures, for example an anti-air-drag additive or an anti-foaming agent.
Generally, the hydraulic composition comprises from 0.005 to 2% by weight,
notably from 0.01% to 2% by weight, preferably from 0.05 to 1.5% by weight of a
compound of formula (I).
The aforementioned hydraulic compositions may notably be concrete or mortar.
According to a third aspect, the object of the invention is a method for preparing
the aforementioned hydraulic composition, comprising the step consisting of mixing a
hydraulic composition or a constituent of a hydraulic composition with a compound of
formula (!).
The inerting agent of formula (I) may actually be mixed with a hydraulic
composition or else with one of its constituents before being put into contact with the other
constituents in order to form the hydraulic composition.
In the aforementioned inerting method and in the aforementioned method for
preparing a hydraulic composition, it is of course possible to put a precursor of a
compound of formula (!) in contact with the composition or one of its constituents. A
precursor is a chemical compound which, put into contact with the other constituents of
the composition, leads to the formation of a compound of formula (I). These precursors
may notably be:
- a carboxylic acid of formula RCOOH and a metal hydroxide including a divalent,
trivalent or tetravalent metal cation, which, when they are put into contact, form a
compound of formula R-COO", (Mn+)1/n wherein Mn+ represents a divalent, trivalent or
tetravalent metal cation,
- the carboxylic acid RCOOH and an amine HNR1,R2R3 (wherein R1, R2, and R3 are as
defined above), which, when they are put into contact, form a compound of formula
R-COO-, (Mn+)1/n wherein Mn+ represents a group [HNR1R2R3].
However, generally, a compound of formula (I) gives the possibility of better
maintaining fluidity of the hydraulic compositions than its precursors. It is generally
preferable to use a compound of formula (I) as an inerting agent than two distinct salts,
one comprising the anion R-COO" and the other one the cation Mn+.
Mixing of a hydraulic composition or one of its constituents with a compound of
formula (I) or with its precursors may be carried out in a quarry, a concrete producing unit,
or during the preparation of dry mortar.
According to an embodiment, the compound of formula (I) (or a precursor) is mixed
with water prior to the introduction of this water into the hydraulic composition. Thus, the
invention relates to a method for preparing an aforementioned hydraulic composition,
comprising the steps:
- mixing a compound of formula (I) with water, and then
- mixing the obtained mixture with a hydraulic binder, at least one granulate, and
optionally a superplasticizer.
Generally, the water applied during mixing is mixing water, i.e. the water
incorporated to the mixture of hydraulic binder and of granulates in order to cause its
setting and giving the concrete its plasticity, therefore its workability. The quality of the
mixing water should meet the EN 206-1 standard.
According to another embodiment, the compound of formula (I) (or a precursor) is
mixed with a superplasticizer before introducing this water into the hydraulic composition.
Thus, the invention also relates to a method for preparing the aforementioned hydraulic
composition, comprising the steps:
mixing a compound of formula (I) with a superplasticizer, and then
- mixing the obtained mixture with at least one granulate, one hydraulic binder and
water.
According to another embodiment, the compound of formula (I) (or a precursor of a
compound of formula (I)) is mixed with a hydraulic binder, before introducing this hydraulic
binder into the hydraulic composition. Thus, the invention also relates to a method for
preparing an aforementioned hydraulic composition, comprising the steps:
- mixing a compound of formula (I) with a hydraulic binder, and then
mixing the obtained mixture with at least one granulate, water and optionally a
superplasticizer.
The hydraulic binder is preferably cement. The step for mixing the compound of
formula (I) with cement may notably be carried out during grinding of the cement.
According to another embodiment, the compound of formula (I) (or a precursor of a
compound of formula (I)) is mixed with a granulate, notably in a quarry, before introducing
this granulate into the hydraulic composition. Thus, the invention also relates to a method
for preparing the aforementioned hydraulic composition, comprising the steps:
- mixing a compound of formula (I) with at least one granulate, and then
- mixing the obtained mixture with a hydraulic binder, water, and optionally a
superplasticizer.
The first step gives the possibility of inerting the clays present in the granulate
before its introduction into the hydraulic composition, and of thereby obtaining a
pre-treated granulate, i.e. for which the clay is inerted. Advantageously, the clay contained
in the pretreated granulate is inerted by the compound of formula (I) before adding the
granulate to the other constituents of the hydraulic composition. The pretreated granulate
may notably be pretreated sand or pretreated filler, notably a pretreated limestone filler.
According to a fourth aspect, the object of the invention is a pretreated granulate
which may be obtained by mixing a granulate with a compound of formula (I) as defined
above. The pretreated granulate may notably be pretreated sand or pretreated filler,
notably a pretreated limestone filler or a pretreated dolomitic filler.
This pretreated granulate is useful for preparing a hydraulic composition as defined
above. The mixing may be carried out either by mixing a granulate with a compound of
formula (I) in the form of a powder, or by spraying a solution, generally a hydroalcoholic or
aqueous solution, preferentially an aqueous solution, of a compound of formula (I) onto
the granulate, preferably a dry granulate (with an optional drying step after spraying).
According to a fifth aspect, the object of the invention is an additive for inerting clay
comprising a superplasticizer and a compound of formula (I) as defined above.
The preferred additive for inerting clay comprises a compound of formula (I) as
defined above and a polyoxyalkylene polycarboxylate (PCP) superplasticizer.
According to a sixth aspect, the object of the invention is the use of compound of
formula (1) as defined above or of one of its precursors for inerting clays of hydraulic
compositions.
According to a seventh aspect, the object of the invention is the use of a
pretreated granulate as defined above, notably of a pretreated sand or a pretreated filler
for inerting clays of hydraulic compositions.
According to an eighth aspect, the object of the invention is the use of an additive
for inerting clay as defined above for inerting clays of hydraulic compositions.
EXAMPLES
In order to evaluate the performance of the compounds as agents inerting clays, the
workability of mortar or concrete compositions made with granulates or naturally clayey
fillers or added with 1% of montmorillonite and additived with an inerting agent, was
evaluated by measuring the slump flow diameter. The methylene blue values of the
granulates and fillers mentioned in the Examples are representative of the amounts of
clays which they contain. The ciay-inerting agents were evaluated as :
- Sand pretreatment agent: the agent is introduced with the water for pre-wetting,
- A clay neutralizing additive: the agent is introduced with mixing water.
The clay-inerting agents were evaluated on standard formulations of self-compacting
concrete and of equivalent concrete mortar.
All the experiments for which the results are indicated in a same table were conducted
with the same proportion of superplasticizer, unless indicated otherwise.
By «pre-wetting water», is meant a portion of the total water which is used for humidifying the
granulates before the mix, allowing simulation of the hygrometric condition of the granulates,
often humid, in a concrete factory or on the site.
EXAMPLE 1 : Effect of the addition of an inerting agent in hydraulic compositions
Composition of the evaluation formulations
Mortar formulation : All the inerting agents were evaluated in the mortar formulation
below, in which sands without clays are totally or partly replaced with naturally clayey
sands or clean sands added with clay. The different constituents of the mortar formula are
expressed in g.
CEM I 52.5 N LE HAVRE (cement) 624.9
Betocarb P2 ERBRAY (limestone filler) 412.1
FULCHIRON (windblown sand) 587.7
AFNOR standardized sand 1,350
Total water 375.1
The cement CEMI 52.5N Le Havre was provided by Lafarge, the filler Erbray from
Omya, the wind-blown sand Fulchiron by Fulchiron (with a methylene blue value of
0.5 g/kg) and sand standardized by the Societe Nouvelle du Littoral (with a methylene
blue value of less than 0.2 g/kg).
Superplasticizers CHRYSO®Fluid Optima 203, 224 or 300 (CHRYSO) were used
with variable superplasticizer levels based on the weight of total binder (filler + cement =
1,037 g) with which a target slump flow of 320 mm + or-20 mm may be attained.
The clay percentage (w/w) is expressed based on the total sand, i.e. AFNOR sand
and FULCHIRON (windblown sand). Montmorillonite KSF used in the test is marketed by
ALDRICH®.
Concrete formulation: The inerting agents were evaluated in the concrete formulation below,
in which 0/4 Berniere sand was added with montmorillonite or partly substituted with different
clayey sands.
The different constituents of the concrete formulation are expressed in kg/m
Cement CEM I 52.5N CP2 SAINT PIERRE LA COUR (Lafarge) 280
Limestone filler Betocarb P2 ERBRAY (OMYA) 160
0/4 sand from BERNIERES 900
4/10 gravel from VILLERMAIN 165
8/16 gravel from LOIRE 663
Total water 200
Superplasticizers CHRYSO®Fluid Optima 203, 224 or 300 (CHRYSO) were used.
The KSF montmorillonite used in the tests is marketed by ALDRICH.
Preparations of formulations for mortar and concrete tests
For mortar tests : The cement used is CEM I 52,5N CE CP2 NF® from the Le Havre factory
(Lafarge), and the superplasticizer used is CHRYSO®FIuid Optima 224.
The reference mortar formulation is prepared according to the following kneading
procedure:
- sands (0/2 AFNOR® + 0/1 Fuichiron®) (the mixture forming a clean sand) are dry
mixed in a mixer of the type Perrier® at a low rate for 30 seconds before introducing
the pre-wetting water and kneading is continued for a further 30 seconds,
- after having left the mixture (sand +water) at rest for 4 minutes, the cement and the
filler are added and are then mixed for 1 minute at a low rate,
- next, the water for the mix is added within 30 seconds with the superplasticizer and
they are mixed at a low rate for 90 seconds,
- the mixer is stopped in order to scrape the walls of the kneading bowl by means of a
flexible scraper for 30 seconds. Finally, mixing is carried out at a high rate (298 rpm)
for 1 minute.
Case of natural clayey sands
The aforementioned kneading procedure was followed while replacing the clean
sand with a clayey sand. The slump flow measurement at 5 minutes was conducted within
the 30 seconds which followed the end of the kneading.
Case of sands added with clay
The aforementioned kneading procedure was followed while replacing the clean
sand with clayey sand, i.e. an initially ciean sand which was contaminated with clay
(montmorillonite). The mortar is prepared as indicated above, except that the amount of
filler is reduced by the added clay content, in order to maintain a constant level of fines in
the composition. The experiments were conducted with 1% of added clay, which
corresponds to a usual percentage of clays in most sands.
The clayey sand is prepared by mixing a sand with a grain size from 0 to 2 mm
stemming from a mixture of two clean sands: 0/1 Fulchiron® sand and 0/2 AFNOR®
standardized sand having methylene blue values of 0.5 g/kg and less than 0.2 g/kg,
respectively (test according to the NF-EN 933-9 standard), with 1% by weight of
montmorillonite and the pre-wetting water at a low rate (142 rpm).
The slump flow measurement at 5 minutes was conducted within the 30 seconds
following the end of the kneading.
For concrete tests : the evaluation of the agents for inerting the clays was carried out in a
formulation of self-compacting concrete of the ready-to-use concrete type in which the clean
sand was replaced with clayey sand or added with 1% by weight of KSF montmorillonite. The
efficiency of the clay-inerting agents was examined comparatively with the formulation with
clean sand not added with montmorillonite. The cement used is CEM I 52,5N CE CP2 NF from
the factory of Saint Pierre La Cour (Lafarge). The superplasticizer CHRYSO® Fluid Optima 224
was diluted in water up to a concentration of 20%, its pH is established at a value between 5
and 6 by means of soda. An anti-air-drag additive is also added in order to eliminate any
influence of trapped bubbles on the rheology of the slurry. The clay inerting agent was
introduced into the mixture with the water for the mix. The reference concrete formulation is
prepared according to the following kneading procedure:
granulates (sands and gravel) are dry mixed in a mixer of the Rayneri® type at a low
rate for 30 seconds before introducing the pre-wetting water (1/3rd of the total amount
of the total water) and continuing kneading for up to 1 minute,
after having left the mixture of pre-humidified granulates at rest for 4 minutes, the
cement and the filler are added and they are mixed for 1 minute at a low rate,
- next, the water for the mix is added within 30 seconds with the superplasticizer and
mixing is performed at a low rate for 1 minute and 30 seconds.
Rheological measurements.
The workability of the mortars was evaluated by measuring slump flow (measurement of the
diameter of the mortar pool formed on a flat plate after casting). A test inspired from the PR NF
EN 12350-8 standard is performed according to the following operating mode. The cone used
is a reproduction to a scale of one half of the Abrams cone (see NF P 18-451 standard, 1981):
Diameter of the upper base circle : 50 ± 0,5 mm
Diameter of the lower base circle: 100 ± 0,5 mm
Height: 150 ±0.5 mm
The dimensions of the slump flow plate should be greater than or equal to 600 x 600 mm2.
The mortar or the concrete is poured into the cone continuously and the excess of
mortar at the surface of the cone is leveled. In order to carry out spreading, the cone is
lifted perpendicularly to the plate while rotating by a quarter turn. By means of a flexible
spatula, the mortar adhered on the inner walls of the cone is recovered while remaining
close to the surface of the formed cake in order not to force slump flow of the cake. After
having waited for the mortar or concrete to set into place and having attained its maximum
spread, the average diameter (to within +1mm) of the cake is determined by carrying out 3
measurements (along axes forming an angle of 120 degrees between them). The
workability of the concrete was evaluated according to the PR NF EN 12350-8 standard
project. The tests were conducted at 20°C. The slump flow was measured at 5, 30, 60 and
90 minutes along 2 diameters at 90° from each other. In the experiments hereafter, T0
corresponds to the instant when the cement is added to the humid granulates.
The closer the result of the Theological measurement is to the reference (concrete
or mortar comprising a clay-free sand), the more performing is the inerting agent. The role
of inerting agents is actually to obtain fluidity for hydraulic compositions comprising clays
identical with that obtained for a clay-free composition.
EXAMPLE 1a : Results with mortar tests with clean sand or sand added with clay
The performances of different inerting agents according to the invention were tested.
The superplasticizer CHRYSO®Fluid Optima 203 was used in the compositions of Example 1a
(with a mass concentration identical for the tests for which the results are grouped in a same
table).
Low molar mass carboxylic acids were examined : formic acid, and acetic acid (R
represents H or Me and Mn+ represents H in formula (I) according to the invention). Table 1
provides the results of the Theological measurements. The percentages are expressed in %
based on the total sand weight (w/w).
In the following experiments, the inerting agents have the formula (1) in which R
represents a methyl (the anion is an acetate) and Mn+ represents H or a group
[HNRiR2R3ln+.
The acetates of amino-alcohols were prepared by an equimoiar mixture of acetic acid
and of an amino-alcohol. Monoethanolamine is marketed by BASF®, diethylaminopropylamine
(DEAPA), ethyldiisopropylamine (EDIPA), diisopropylamine (DIPA) and s-butyl
monoethanolamine (ALPAMINE N41®) are marketed by ARKEMA®. The examined
dimethylaminoethylpropanoi is marketed by ANGUS Chemical®. These inerting agents were
put into an aqueous solution (a 72% active material content (concentrations in g for 100 g of
solution) for ammonium acetate, 81% for monethanolamine acetate, 86% for
ethyldiisopropylamine acetate and 73% for diisopropylamine acetate). Tables 2 and 3 provide
the results of Theological measurements. The percentages are expressed in % based on the
total sand weight (w/w).
Experiments were also conducted by using divalent metal cations (an earth alkaline
metal ion). Calcium acetate and magnesium acetate are products (powders) marketed by
KEMIRA® (NL) and distributed in France by IMCD®. These inerting agents were put into an
aqueous solution, at mass concentrations of 20% for calcium acetate, 25% for magnesium
acetate. Table 4 provides the results of the rheological measurements. The percentages are
expressed in % based on the total sand weight (w/w).
The results of Tables 1-4 show that the compounds of formula (I) are performing
agents for inerting clays.
The performances of the inerting agent (MeCOO~)2Mg2+ were also compared with
those obtained when MgCI2 on the one hand (comprises Mg2t ions) and acetic acid
MeCOOH on the other hand are used separately (mortar type tests). Table 5 provides the
results of the rheological measurements. The percentages are expressed in % based on
the total sand weight (w/w).
The carboxylate anion - metal cation combination is more performing in terms of
maintaining fluidity of the prepared hydraulic compositions in the presence of sand added
with clay than the constituents of these mixtures (carboxylic acid and metal salt) taken
separately. This optimum performance seems to result from a synergistic effect between
the carboxylate anion and the metal cation.
EXAMPLE 1 b : Results with mortar tests with sand naturally comprising clays
The RHEU sand (LAFARGE) is particularly rich in clays (methylene blue value of
4.2 g/kg). It is difficult to use it as a single sand and to obtain a hydraulic composition having
satisfactory fluidity. Consequently it is often used in a mixture with other sands. In the following
experiments, the designation «RHEU sand» in fact means a mixture of 30% of RHEU sand
and 70% of FULCHIRON sand. The percentages are expressed in % based on the total sand
weight (w/w). The superplasticizer CHRYSO®Fluid Optima 203 was used in the compositions
of Example 1b (with a mass concentration which is identical in the different tests).
These results show that the four studied agents for inerting clays allow partial
compensation for the detrimental effect of the clays contained in the RHEU sand.
Magnesium and ammonium acetates prove to be the most performing for inhibiting the
clays of RHEU sand.
EXAMPLE 1c : Results when using another cement
In the reference mortar formulations below, the cement from Le HAVRE was
substituted with the cement from SAINT-PIERRE LA COUR (LAFARGE). The percentages are
expressed in % based on the total sand weight (w/w). The superplasticizer CHRYSO®Fluid
Optima 206 was used in the compositions of Example 1c (with a mass concentration which is
identical in the different tests).
With the inerting agents, calcium, ammonium and magnesium acetate, it is also
possible to reduce the undesirable effect related to the presence of clays in mortar
formulations based on cement from SAINT-PIERRE LA COUR.
The compounds are therefore considered to be robust towards composition variations of
the cements.
EXAMPLE 1d : Results with concrete tests
Calcium acetate and magnesium acetate are products (powders) marketed by
KEMIRA® (Nl_) and distributed in France by IMCD®. Monoethanolamine acetate was
prepared by an equimolar mixture of acetic acid and of monoethanolamine.
These inerting agents were put into an aqueous solution, at mass concentrations
of 20% for calcium acetate, 25% for magnesium acetate and 81% for monoethanolamine
acetate. They were used at levels of 0.2 and 0.4 % by dry weight based on the weight of
the sand.
The clean sand used is BERNIERE sand. In the following experiments, the designation
«RHEU sand» in fact means a mixture of 30% of RHEU sand and 70% of BERNIERE
sand.
The influence of the quality of the sand for inerting agents: calcium acetate (R
represents a methyl) (Mn+ represents Ca2+), magnesium acetate (Mn+ represents Mg2+) or
monoethanolamine acetate (Mn+ represents +H3NCH2CH2OH), was tested. Table 8
provides the result of the Theological measurements. The superplasticizer CHRYSO®Fluid
Optima 224 was metered so as to have a slump flow of 700 mm + or - 20 mm (with a
mass concentration which is identical in the different tests).
Upon reading these results, it is concluded that:
- an inerting agent level comprised between 0.2 and 0.25% by dry weight based on the
sand weight gives the possibility of neutralizing the detrimental effect of the clays
contained in the studied sands,
- magnesium acetate appears to be slightly more efficient than calcium acetate.
EXAMPLE 1e: Addition of a clay-inerting agent in a mortar containing a clayey
limestone filler
The mortar composition is identical with the one of Example 1. The operating
methods for preparing the hydraulic compositions are similar to those of Example 1 while
replacing the constituents with those of the two lists above and the superplasticizer with
CHRYSO®Fluid Premia 100 marketed by CHRYSO {with a mass concentration which is
identical in the different tests).
The limestone filler is either the filler Void® provided by Carmeuse (clay-free, it is
used as a reference), or a naturally clayey limestone filler (filler Les Aucrais® marketed by
Carmeuse) for which the blue value is 2.66 g/kg.
The inerting agent used, i.e. magnesium acetate in a 25% by mass aqueous
solution, was introduced with the pre-wetting water into the mixture of the sands and of
the filler. The inerting agent was used at levels of 0.2 and 0.45 by dry weight based on the
weight of the limestone filler. The Theological measurements were conducted by following
the same procedure as the one described in Example 1.
Table 9 provides the results of the Theological measurements. In the following
example, the inerting agent percentage is expressed in % by weight based on the
limestone filler weight (w/w).
The introduction of magnesium acetate at a level of 0.2% or 0.4% by weight
relatively to the limestone filler has a substantial effect on the inerting of the clays
contained in the limestone filler.
EXAMPLE 1f: Adding an agent for inerting the clays in a concrete containing a
clayey limestone filler and a clayey granulate
The composition of the concrete is the following:
Concrete composition mix (30 kg)
CEMU/AS42.5N 4.19
FILLER TDKS(F) 2.75
0/2RHIN 10.38
4/8 MOSELLE (G1) 4.45
8/16 MOSELLE (G2) 5.73
TOTAL WATER 2.38
The inerting agent used is monoethanolamine acetate. The superplasticizer used
in the formulation is CHRYSO®Fluid Optima 203 marketed by CHRYSO (with a mass
concentration which is identical in the different tests). Table 10 provides the results of the
Theological elements. The percentages are expressed based on the total binder weight
(filler and granulates G1 and G2).
The use of 0.2% of monoethanolamine acetate allows attenuation of the
detrimental effect of the clays contained in the filler (methylene blue value of 2.66 k/kg)
and in the fines of the granulates (methylene blue value from 3.3 to 5 g/kg) of the
composition of the concrete (the spread passes from 520 mm to 655 mm).
EXAMPLE 2: Determination of the compressive strengths of hydraulic
compositions comprising the inerting agents according to the invention.
The concretes were prepared by following the procedures described in Example 1
by using the superplasticizer CHRYSO®Fluid Optima 224 (with a mass concentration
which is identical in the different tests).
The early resistance was evaluated by measuring the compressive strength Rc of
cubic specimens 15x15x15 cm3 of concrete after 24 hours according to the EN 12390-3
standard. Table 11 provides the obtained results.

These experiments show that the presence of inerting agents according to the
invention does practically not affect the strength of the obtained concretes. The
mechanical properties of the concrete are preserved.
CLAIMS
1.- A method for inerting clays in a hydraulic composition comprising a step
consisting of putting a hydraulic composition or a constituent of a hydraulic composition in
contact with a compound of the following formula (I):
R-COO-, (Mn+)1/n (I)
wherein :
- R represents a group selected from H, an alkyl and a phenyl,
n represents an integer comprised between 1 and 5,
- Mn+ represents a cation selected from :
- H+,
- a divalent, trivalent or tetravalent metal cation, and
- a group [HNR-,R2R3]n+, wherein R1, R2, and R3 represent independently of each
other, H or a linear, branched or cyclic, saturated or unsaturated hydrocarbon
chain, optionally aromatic, optionally substituted with one or several
substituents selected from a hydroxyl and a group NR4R5, wherein R4 and R5
represent independently H or an alkyl optionally substituted with a group
NR6R7, wherein R6 and R7 represent independently H or an alkyl,
it being understood that the groups R1, R2, and R3 may be bound together and form a
ring with the nitrogen atom bearing them.
2.- The clay-inerting method according to claim 1, wherein R represents H or a
methyl.
3.- The clay-inerting method according to claim 1 or 2, wherein Mn+ represents
[HNR1R2R3]n+ wherein at least one of the R1, R2, and R3 represents a hydrocarbon chain
substituted with a hydroxyl and/or with a group NR4R5.
4.- The clay-inerting method according to any of claims 1 to 3, wherein Mn+
represents [HNR1R2R3]n+ and the pKa of the cation [HNR1R2R3]n+ is greater than 8.
5.- The clay-inerting method according to claim 1 or 2, wherein Mn+ represents an
earth alkaline metal cation, preferably selected from a magnesium, calcium and barium
cation.
6.- A hydraulic composition comprising a hydraulic binder, at least one granulate,
water and a superplasticizer and further comprising a compound of formula (I) as defined
in any of claims 1 to 5.
7'.- The hydraulic composition according to claim 6, comprising from 0.005 to 2%
by weight of compound of formula (I).
8.- The hydraulic composition according to claim 6 or 7, wherein the hydraulic
composition is a concrete or a mortar.
9.- A method for preparing a hydraulic composition according to any of claims 6 to
8, comprising the step consisting of mixing a hydraulic composition or a constituent of a
hydraulic composition with a compound of formula (I) as defined in any of claims 1 to 5.
10.- The method for preparing a hydraulic composition according to claim 9,
comprising the steps:
- mixing a compound of formula (I) with water, and then
mixing the obtained mixture with a hydraulic binder, at least one granulate and
optionally a superplasticizer.
11.- The method for preparing a hydraulic composition according to claim 9,
comprising the steps:
- mixing a compound of formula (I) with a hydraulic binder, and then
mixing the obtained mixture with at least one granulate, with water and optionally a
superplasticizer.
12.- The method for preparing a hydraulic composition according to claim 11,
wherein the hydraulic binder is cement and the mixing of the compound of formula (I) with
the cement is carried out during grinding of the cement.
13.- The method for preparing a hydraulic composition according to claim 9,
comprising the steps:
- mixing a compound of formula (I) with a superplasticizer, and then
mixing the obtained mixture with a hydraulic binder, at least one granulate and water.
14.- The method for preparing a hydraulic composition according to claim 9,
comprising the steps:
- mixing a compound of formula (I) with at least one granulate, and then
- mixing the obtained mixture with a hydraulic binder, water and optionally a
superplasticizer.
15.- A pretreated granulate which may be obtained by mixing a granulate with a
compound of formula (I) as defined in any of claims 1 to 5.
16.- An additive for inerting clay comprising a superplasticizer and a compound of
formula (I) as defined in any of claims 1 to 5.
17.- The use of a compound of formula (I) as defined in any of claims 1 to 5 for
inerting clays of hydraulic compositions.

ABSTRACT

The invention relates to:
- a method for inerting clays in a hydraulic composition comprising one step consisting
of putting a hydraulic composition or a constituent of a hydraulic composition in
contact with a compound of the following formula (1):
R-COO-, (Mn+)1/n (I),
a hydraulic composition comprising said compound of formula (I),
- a method for preparing said hydraulic composition,
- a pretreated granulate which may be obtained by mixing a granulate with said
compound of formula (I),
an additive for inerting clay comprising a superplasticizer and said compound of
formula (I), and
the use of said compound of formula (I) for inerting the clays of hydraulic
compositions.