BAG AND ITS USE TO PROVIDE ADMIXTURE FOR A HYDRAULIC COMPOSITION
The present invention relates to a bag and its use to provide an admixture for a
hydraulic composition to provide a specific function to the hydraulic composition.
Compostable bags comprising two layers of paper and an intermediate layer of a
film produced from corn starch are known. However, this type of bag is only
compostable under well-defined conditions and has to be treated by industrial
composting plants. This type of bag does not therefore reduce the quantity of waste to
be evacuated from jobsites.
Water-soluble bags for cement comprising one or more water-soluble layers and
optionally comprising a layer of paper, which may disintegrate, are known. However, the
main objective related to the use of this type of bags is to avoid generating waste on the
production site and avoid direct contact with the cement contained in the bag. Another
objective is to avoid a negative impact on the properties of the hydraulic compositions
obtained when the bag is used (for example incompletely dissolved film or negative
impact of the dissolution products). However, the addition of a particular function to a
hydraulic composition by the bag itself has not been considered.
With few exceptions, the admixture cannot be added during the production of a
hydraulic binder, such as cement. The admixtures cannot resist the high temperatures
involved. The admixtures for hydraulic compositions are generally added when a
hydraulic binder is mixed with water and other components of the composition. The
admixtures, either in solid or liquid form, have to be stored separately. Their addition
requires a separate step to measure the quantity of each admixture before it is added to
the mix.
The same is true for other components of the hydraulic compositions such as the
aggregates or the mineral additions, the production of which may comprise grinding
steps or heating steps.
The problem which the invention seeks to solve is to provide a new means of
supplying an admixture to a hydraulic binder or to other components of hydraulic
compositions, for example the aggregates and the additions.
Unexpectedly, the inventors have shown that it is possible to use a bag comprising
an admixture for a hydraulic composition in the wall of the bag.
The present invention seeks to provide one or more of the advantages listed
below:
- the use of a water-soluble bag makes it possible to avoid problems of dust
related to the handling of pulverulent materials, in particular hydraulic binders. The bags
may be handled, without being opened. Consequently, the user will not need to handle
the pulverulent material which could disperse very easily in the air.
- the water-soluble bags make it possible to simplify the handling of packing waste
on jobsites. The bags are used in totality for the production of hydraulic compositions, so
that there is no packing waste.
- the specific nature of the water-soluble bag can provide better protection of a
particulate material, and in particular of hydraulic binders, against gases (for example
oxygen or carbon dioxide). This improved protection makes it possible to consider
longer storage times. Protection against oxygen also makes it possible to avoid aging of
the compounds (chromium VI reducing agents) used to reduce chromium VI in the
hydraulic binders.. This makes it possible to reduce the necessary quantity of the
chromium VI reducing agents.
- handling of the pulverulent materials on jobsites is improved. Handling is first of
all simplified, because the water-soluble bag containing a particulate material is used as
such in the concrete mixer. It is therefore no longer necessary to open the bag before
use. Then, its ergonomics improve since it is no longer necessary to use a shovel to
load the particulate material into the concrete mixer.
- the running and organisation of existing pre-admixture units can be improved. In
existing pre-admixture units, if several different admixtures are used, it is necessary to
provide separate storage means, for example silos. However, silos take up a lot of
space and require technical means to handle the admixtures. In contrast, it is possible to
provide several different admixtures with the bags according to the present invention.
Different types of bags may be provided depending on the desired type of admixture.
The presence of several silos can thus be avoided.
The invention may be used in, for example the building industry, the chemical
industry (admixture suppliers), the cement industry or concrete mixing plants.
The invention relates to the use of a bag to provide an admixture for a hydraulic
composition, wherein a wall of the bag comprises a layer, said layer comprising a watersoluble
polymer, and wherein an admixture, preferably an admixture for a hydraulic
composition, is present in the wall of the bag.
A hydraulic composition generally comprises a hydraulic binder, water, aggregates
and admixtures. The aggregates include coarse aggregates and/or sand. They may be a
mineral or organic material. They may also be of wood or recycled materials or with a
base of waste material. A sand is generally an aggregate having a particle size less than
or equal to 4 mm. Coarse aggregates are generally aggregates having a particle size
greater than 4 to, for example, 20 mm.
A hydraulic binder comprises any compound which sets and hardens by hydration
reactions. The hydraulic binder comprises, for example cement, plaster or hydraulic
lime. Preferably, the hydraulic binder is a cement.
Preferably, a wall of the bag comprises a water-soluble polymer, said polymer
comprising the or an admixture.
Preferably, the water-soluble polymer comprises a polyvinyl alcohol.
Preferably, the bag comprises an internal layer which comprises a water-soluble
polymer, and an external layer which is insoluble in water.
Preferably, the bag contains cement, aggregates and/or mineral additions.
Preferably, the water-soluble polymer comprises a film-forming polymer, which has
a melting temperature and/or a melt flow rate, such that at least 80% by mass of the bag
dissolves after 10 minutes, more preferably after 6 minutes of mixing in a concrete
mixer.
Preferably, the water-soluble polymer comprises a film-forming polymer which is a
polyvinyl alcohol having a melting temperature from 155 to 185°C and/or a melt flow rate
higher than 3.0 g/10 min under 2.16 kg at 230°C as measured according to the method
described in the NFT 51-016 Standard. The principle of this method is the measurement
of a mass of melted polymer, which flows through a tube of given dimensions by the
action of a piston for a given length of time and at a given temperature. The tube has a
length of 8.0 mm, an inside diameter of 2.096 mm and is made of tungsten carbide. The
mass of the piston is 2.1 6 kg.
The melt flow rate of a polymer generally makes it possible to determine its
extruding capacity. Generally, the higher the molar mass of the studied polymer, the
lower the melt flow rate.
The present invention also relates to a bag, a wall of the said bag comprising a
layer, said layer comprising a water-soluble polymer, and an admixture, preferably an
admixture for a hydraulic composition, being comprised in the wall of the bag. The
water-soluble polymer alone may provide the admixture, or the admixture may be
dissolved or dispersed in the water-soluble polymer.
The term « one » is to be understood in the present description and accompanying
claims as « one or more ».
The films of water-soluble polymer may be moulded or, preferably extruded. The
extruding capacity of a polymer is generally determined by measuring the polymer's melt
flow rate.
The bag used according to the invention is generally a bag the material of which is
sufficiently resistant to make it possible to fill the bag with a particulate material, to
handle and transport the filled bag, and at the same time have a nature and a structure
such that it dissolves, disperses or disintegrates in water, preferably rapidly, during the
production of a hydraulic composition. Preferably, the bag dissolves, disperses or
disintegrates in water at a pH greater than or equal to 7 and by the effect of mechanical
mixing. The difference between the solubility and the dispersibility is that, in the second
case, small pieces of the bag remain intact (for example particles or fibres), but do not
have significant negative effects when the hydraulic composition is used. A
disintegratable bag is generally made of a material which loses its cohesion during the
mixing.
Preferably, the bag used according to the present invention comprises one or
more characteristics selected from the following list:
- sufficient mechanical properties to condition 5 to 25 kg of particulate materials;
- cold solubilisation, which is to say not requiring heating;
- solubilisation at a pH greater than or equal to 7 by the effect of a mixing action,
- sufficient water-repellency of the external layer or exterior of the bag to make
the bag substantially resistant or inert to water;
- sufficient impermeability to gases, for example to oxygen in the air and to
carbon dioxide. This impermeability is in particular important during the storage
time of the bags, in order to reduce or limit to a maximum the degradation of the
particulate materials contained in the bag.
Preferably, the bag has all the characteristics listed above.
Preferably, the dissolution of the bag takes place or is carried out in less than 70
revolutions of the blade in a concrete mixer.
Preferably, at least 80% by mass of the bag is dissolved after 10 minutes, more
preferably after 6 minutes of mixing.
Preferably, the dissolution of the bag takes place or is carried out in less than five
minutes, more preferably in less than four minutes of mixing.
According to one embodiment, the wall of the bag may comprise two layers. In this
case the external layer and the intermediate layer described hereinafter may be joined
together to form the external layer, and the internal layer may remain the same. Thus,
the external layer may provide water-resistance and/or low permeability to gases, for
example oxygen and/or carbon dioxide, and the internal layer may provide watersolubility
and mechanical strength.
Preferably, the wall of the bag comprises three layers:
- an external layer, insoluble in water, preferably hydrophobic, to resist water (its
thickness is as small as possible, for example less than or equal to 10 m h ,
preferably less than or equal to 5 mhi ) ;
- an intermediate layer which is not very soluble in water having low permeability
to gases (for example oxygen) (its thickness is as small as possible, for
example less than or equal to 20 mhi ) ;
- an internal water-soluble layer (generally thick enough to provide mechanical
strength, in particular to resist handling, transport and bag filling).
When the internal water-soluble layer comprises or provides an admixture, the
thickness of the layer (and hence the total quantity of water-soluble polymer) may be
modified to adjust the quantity of admixture.
Preferably, the total thickness of the wall of the bag is greater than or equal to 75
m h , more preferably greater than or equal to 100 m h .
Preferably, the total thickness of the wall of the bag is less than or equal to 500
mhi , more preferably less than or equal to 400 mhi , most preferably less than or equal to
200 mp .
According to another embodiment, the wall of the bag may comprise a specific
admixture or addition which makes it possible to decrease the thickness of the wall
under 75 mhi .
According to another embodiment, in addition to the two or three layers described
above, the bag may comprise an additional layer of paper, preferably paper capable of
disintegrating.
The bag's water-resistance may in particular be useful when placing on pallets,
during transport and storage of the bags filled with particulate material. The pallets used
may be damp. In addition, once completely loaded, the pallets may be covered with
packing film. Condensation could occur within the pallet covered with packing film.
In order to improve the efficiency of the bag in terms of impermeability to gases, it
is possible to add to the water-soluble polymer micas or other particles with a lamellar,
shape, zeolites or other micronic or sub-micronic particles. In this case, the action of the
said particles may depend on their size, their shape and their thickness/surface ratio.
It is possible to make the bags opaque by adding a mineral material or a pigment.
It is possible to print on the bag, for example to identify the product contained
inside the bag.
According to an embodiment of the present invention, it is possible to make
several small water-soluble bags and to place them inside a big bag, the big bag being
preferably recyclable. In particular, this embodiment presents the advantage of a more
precise dosage of the particulate materials when the entire bag is not necessary, and
the possibility of keeping the un-used particulate materials for a longer time. The un
used small water-soluble bags provide better protection of the particulate material
contained inside the bags, because the particulate material is not stored in the open air.
According to another embodiment of the present invention, the small water-soluble
bags may be placed inside a solid container, for example a case. In particular, this
embodiment presents the advantage of improved rigidity of the container, which
therefore provides better protection of the bags during handling and storage.
Preferably, the water-soluble polymer further comprises a plasticizing agent for the
polymer. A plasticizing agent is generally an agent modifying the mechanical properties
of a polymer (for example a film-forming polymer) which may for example make a plastic
film more flexible, in particular by lowering the glass transition temperature of the filmforming
polymer.
Preferably, the plasticizing agent comprises glycerine or a polyethylene glycol.
Preferably, the water-soluble polymer comprises up to 20% by mass of plasticizing
agent.
Preferably, the water-soluble polymer may comprise polymers of different origins.
The polymers may have a synthetic origin, for example polyvinyl alcohols or a natural
origin, for example corn starch. According to an embodiment of the invention, the wall of
the water-soluble bag further comprises an admixture making it possible to correct a
possible negative effect (for example a foaming effect) of the bag's dissolution products
on the hydraulic composition.
The films used for the production of the water-soluble bags are generally produced
by extrusion. However, it is also possible that only the internal layer is produced by
extrusion. In this case, the external layer, or the intermediate layer and the external
layer, may be produced by coating or by printing on the internal layer.
The water-soluble bag may be micro-perforated to adapt to certain packing
processes, including, for example, transport of cement by air flow.
The admixture used according to the invention is a product generally incorporated
during the mixing of a hydraulic composition to modify the properties of the hydraulic
composition in the fresh state and/or in the hardened state.
The water-soluble polymer itself may act as an admixture, or an admixture may be
added. The water-soluble polymer may be a mixture of polymers wherein one or more
polymers act as an admixture.
When an admixture is added, it may be dissolved or dispersed in the water-soluble
polymer, for example in the form of an emulsion.
The admixture is preferably a clay-inerting agent, a plasticizer, a superplasticizer,
a water-repellent (for example a stearate), an air-entraining agent, a dye, a setting
accelerator, a setting retarder, a thickener, an anti-shrinking agent, an anti-foaming
agent or a mixture thereof.
The admixture comprised in the wall of the water-soluble bag may be in the form
of encapsulated or micro-encapsulated particles or micro-particles.
Preferably, the film-forming polymer comprised in the bag is also an admixture. It
is possible to use a polymer to form the bag and to provide the or an admixture.
The admixture comprised in the wall of the bag may be water-soluble. It may be
dispersed in a layer forming the bag, or may be comprised in the wall of the bag. In the
second case, the admixture may, for example, be in the form of powder between two
layers of the wall of the bag.
Preferably, the admixture for hydraulic compositions is an air-entraining agent, for
example a polyvinyl alcohol having a hydrolysis rate less than 98%, more preferably less
than 95%.
Preferably, the admixture for hydraulic compositions comprises a clay-inerting
agent, for example a water-soluble polyvinyl alcohol having a viscosity less than or
equal to 45 mPa.s, preferably of 8 to 45 mPa.s, measured at 20°C in an aqueous
solution comprising 4% by mass of dry extract in a Hoppler viscosimeter according to
the DIN 53015 Standard.
The clays are generally aluminium silicates and/or magnesium silicates, in
particular phyllosilicates with a layer structure, typically spaced from approximately 7 to
approximately 14 Angstroms. Clays frequently found in sand may comprise in particular
montmorillonite, illite, kaolinite, muscovite and chlorite. The clays may be of the 2:1 type
but also of the 1: 1 type (kaolinite) or the 2:1 : 1 type (chlorite).
Non-swelling clays are generally clays whose inter-layer space does not increase
in the presence of water. Non-swelling clays comprise in particular clays of the 1: 1 type
(in particular kaolinite) or the 2:1 : 1 type (in particular chlorites).
A clay-inerting process generally comprises at least partially neutralising the
deleterious effects due to the presence of clay in a hydraulic composition, in particular a
hydraulic composition comprising a superplasticizer.
An example of an admixture comprised in the formulation of the water-soluble bag
may be an organic molecule comprising at least two atoms each capable of forming a
hydrogen bond. This molecule may in particular be a molecule adapted to reduce the
adsorption of a superplasticizer with a comb structure by the non-swelling clays. In the
remaining description, this organic molecule is called an inerting agent for non-swelling
clays.
A hydrogen bond is generally a non-covalent physical bond of the dipole-dipole
type, of low intensity (twenty times less than a typical covalent bond) and linking
molecules via a hydrogen atom. It requires a donor of a hydrogen bond and an acceptor
of a hydrogen bond. The donor is a compound comprising acidic hydrogen, that is to say
a heteroatom (for example nitrogen, oxygen or sulphur) carrying a hydrogen atom (for
example amines, alcohols or thiols). The acceptor is a heteroatom (only of nitrogen,
oxygen or sulphur) carrying lone pairs.
The atom capable of forming a hydrogen bond is generally an electronegative
atom, for example nitrogen, oxygen or sulphur, capable of forming at least one hydrogen
bond.
Preferably, the inerting agent for non-swelling clays comprises at least ten, more
preferably at least fifty, most preferably at least a hundred atoms each capable of
forming a hydrogen bond.
Preferably, the inerting agent for non-swelling clays is a polymer or a co-polymer
comprising at least one monomer having at least one atom capable of forming a
hydrogen bond.
Preferably, the inerting agent for non-swelling clays is selected from the group
consisting of an alkylene oxide (for example ethylene glycol and/or propylene glycol or
PEG), a crown ether, a polyvinyl alcohol, a gluconate, a heptagluconate, a
heptagluconic acid, a gluconic acid, a polysaccharide, in particular cellulose or chitin,
dextrin, derivatives of cellulose, chitosan, alginates, hemicellulose, pectin, polyols or
proteins or a mixture of these compounds.
Preferably, the inerting agent for non-swelling clays comprises hydroxyl
functions.
Preferably, the inerting agent for non-swelling clays is a polyvinyl alcohol (PVA).
By way of example, the PVA may be obtained by a process comprising a
polymerisation of at least one vinyl acetate monomer or an analogous compound and a
hydrolysis step.
Preferably, the PVA has a linear structure.
Preferably, the hydrolysis rate of the PVA is less than 98%, more preferably less
than 95%, most preferably less than 94%.
Preferably, the PVA has both a linear structure and a hydrolysis rate less than
98%, more preferably less than 95%, most preferably less than 94%.
It is possible to select macromolecules, in the family of PVA, making it possible to
produce water-soluble films, and to efficiently inert the clay impurities, in particular the
non-swelling clays, present in the sands, the coarse aggregates and in the mineral
additions of the hydraulic compositions. The choice of the range of PVA may be made
according to two criteria. On the one hand, the molecular weight of the PVA should be
sufficient to be able to form a film having sufficient mechanical properties. On another
hand, the molecular weight of the PVA should not be too high in order to retain an
inerting effect, without a negative impact on the viscosity of the hydraulic composition.
The molecular weight of a polymer, and in particular of the PVA, is correlated with the
viscosity of an aqueous solution at 20°C comprising 4% by mass of dry extract of this
polymer. In these conditions, the PVAs are preferably such that the corresponding
solution at 4% of dry extract and 20°C has a viscosity of 8 to 45 mPa.s, more preferably
8 to 35 mPa.s. The viscosity may be measured using the Hoppler viscosimeter
according to the DIN 53015 Standard.
The internal layer of the bag preferably has a high cold solubility. The PVA
generally comprise two types of monomeric units, that is to say monomeric units of the
vinyl alcohol type and monomeric units of the vinyl acetate type. The ratio (number of
vinyl alcohol monomeric units to the number of vinyl alcohol monomeric units and of
vinyl acetate monomeric units) represents the rate of hydrolysis. The rate of hydrolysis
should not be too substantial in the selection of PVA used in the internal layer. The rate
of hydrolysis is a parameter to take into account to adjust the solubility of the film. The
minimum rate of hydrolysis depends on the molecular weight of the PVA and of the
composition of the film.
The PVA may also carry other types of monomeric units, for example of the
hydrophobic, ionic type (anionic or cationic), or of the hydrophilic non ionic type. The
external layer(s) of the bag preferably have a lower solubility in water to that of the
internal layer.
According to a variant, the PVA used according to the present invention may also
carry monomeric units of the ethylene type.
The PVAs used according to the present invention are preferably clay-inerting
agents after solubilisation in the hydraulic composition.
Preferably, the PVAs used according to the present invention are polymers having
a molecular weight less than 1000000 g/mol, more preferably less than 500000 g/mol,
most preferably less than 100000 g/mol.
Swelling clays are generally clays having cations in their inter-layer spaces
capable of hydrating in the presence of water (vapour or liquid). Swelling clays,
generically called smectites, comprise in particular clays of the type 2:1 , for example
montmorillonite.
Another example of an admixture which may be used is a polymer having a
density of cationic charges greater than 0.5 meq/g and an intrinsic viscosity less than
1 dl/g. Swelling clays in the sands, coarse aggregates and/or the mineral additions are
thus inerted. In the following description, the cationic polymer as described above is
called an inerting agent for swelling clays.
Cationicity or density of cationic charges (in meq/g) represents the quantity of
charges (in mmol) carried by 1 g of polymer. This property can be measured by colloidal
titration by an anionic polymer in the presence of a coloured indicator which is sensitive
to the ionicity of the excess polymer.
Cationicity is determined in the following manner. 60 ml of a buffer solution of
sodium phosphate is introduced in a suitable vessel at 0.001 M - pH 6 and 1 ml of a
solution of o-toluidine blue at 4.1 x 10-4 M, then 0.5 ml of the solution of cationic
polymer to be measured.
This solution is titrated with a solution of potassium polyvinyl sulphate until the
colour changes. Cationicity is obtained by the following relation:
Cationicity (meq/g) = (V epvsk * Npvsk ) / (V pc
* Cpc)
wherein:
Vpc is the volume of solution of the cationic polymer;
Cpc is the concentration of cationic polymer in solution;
Vepvsk is the volume of solution of potassium polyvinyl sulphate; and
NpVSk is the normality of the solution of potassium polyvinyl sulphate.
Preferably, the inerting agent for swelling clays has a cationicity greater than
0.5 meq/g, more preferably greater than 1 meq/g, and most preferably greater than
2 meq/g.
Preferably, the inerting agent for swelling clays also has a molecular weight
expressed as an intrinsic viscosity less than 1 dl/g, more preferably less than 0.8 dl/g,
and most preferably less than 0.6 dl/g.
The inerting agent for swelling clays may be a polymer having a linear, comb or
branched structure. Preferably, the inerting agent for swelling clays is a polymer with a
linear structure or with a slightly branched structure.
The cationic groups of the inerting agent for swelling clays may in particular be
phosphonium, pyridinium, sulfonium and quaternary amine groups, the latter being
preferred. The inerting agent for swelling clays may be a polymer comprising a main
chain and pendent side groups. These cationic groups may be located on the main
chain of the inerting agent for swelling clays or on the pendent side groups.
The inerting agent for swelling clays corresponds, for example, to the cationic
polymers described in Patent Application WO2006032785.
The inerting agent for swelling clays may be obtained directly by a known process
of polymerisation, for example radical polymerisation, polycondensation or polyaddition.
It may also be prepared by post synthetic modification of a polymer, for example
by grafting groups carrying one or more cationic functions on a polymer chain carrying
appropriate reactive groups.
The polymerisation is carried out from at least one monomer carrying a cationic
group or from a precursor.
The inerting agents for swelling clays obtained from monomers carrying amine and
imine groups are particularly useful. Nitrogen may be quaternised after a known process
of polymerisation, for example by alkylation using, for example, methyl chloride or in an
acid medium by protonation.
The inerting agents for swelling clays comprising cationic groups of quaternary
amine are particularly suitable.
Particular mention may be made of the following monomers already carrying a
cationic quaternary amine function: ammonium diallyldialkyl salts, (meth)acrylates of
quaternised dialkylaminoalkyl, and (meth)acrylamides N-substituted by a quaternised
dialkylaminoalkyl.
Polymerisation may be carried out with non ionic monomers, preferably of a short
chain, carrying 2 to 6 carbon atoms. Anionic monomers may also be present as long as
the finally obtained polymer remains overall cationic.
Within the scope of modification of polymers by grafting, natural grafted polymers
may be mentioned, for example cationic starches.
Advantageously, the inerting agent for swelling clays comprises groups which are
only cationic in an acid medium. Tertiary amine groups, which are cationic by
protonation in an acid medium, are particularly preferred. The absence of an ionic
character in hydraulic compositions of the concrete or mortar type having an alkaline pH
makes it possible to improve their robustness compared to other ionic, in particular
anionic, compounds.
By way of example, cationic polymers of the family of polyvinyl amines may be
mentioned. These polymers may be obtained by polymerisation of N-vinylformamide,
followed by a hydrolysis. The quaternised polyvinylamines may be prepared as
described in Patent US 5,292,441 . The polymers of the polyethyleneimine type are also
suitable. The latter are quaternised by protonation.
The cationic polymers obtained by polycondensation of epichlorohydrin with a
mono- or dialkylamine, for example methylamine or dimethylamine, are particularly
preferred Their preparation is described for example in Patents US 3,738,945 and US
3,725,312.
The monomeric unit of the cationic polymer obtained by polycondensation of
dimethylamine and epichlorohydrin may be represented as follows:
The polymers of the polyacrylamide type modified by Mannich reaction are also
suitable, for example polyacrylamide N-substituted by a dimethylaminomethyl group.
The inerting agents for swelling clays obtained by polycondensation of
dicyandiamide and formaldehyde are also suitable. These polymers and their synthesis
are described in Patent FR 1 042 084.
According to a preferred embodiment, the inerting agent for swelling clays is
obtainable by condensation of dicyandiamide with formaldehyde in the presence of:
A) a polyalkylene glycol; and/or
B) a polyalkoxylated polycarboxylate, also called PPC; and/or
C) an ammonium derivative.
The precise chemical constitution of the inerting agent for swelling clays is not
known with precision. It is therefore described principally by means of its preparation
process.
Another example of admixture, which may be comprised in the wall of the watersoluble
bag according to the present invention is a superplasticizer.
A superplasticizer is generally an organic molecule making it possible to plasticize
hydraulic compositions or reduce the dosage of water required for the same consistency
of the hydraulic composition.
Preferably, the superplasticizer used according to the invention has a molecular
weight less than 200000 g/mol, more preferably less than 100000 g/mol and most
preferably less than 80000 g/mol.
The superplasticizer may have a linear, branched, comb or star structure.
A superplasticizer with a comb structure is particularly preferred. In this case, the
main chain is generally a hydrocarbon chain.
The superplasticizer may comprise carboxylic, sulphonic, or phosphoric groups.
The superplasticizer may further contain non-ionic side groups, in particular
polyether groups. The polyether groups generally comprise monomeric units of ethylene
oxide or propylene oxide or a combination of the two.
The superplasticizer may also further contain side groups of the di- or oligosaccharide
type (for example as described in Patent application EP 2072531 ) or of the
polyamine polyamide type (for example as in Patent application EP 2065349).
The superplasticizer may for example be an anionic polymer with a comb
structure, for example a polycarboxylate polyoxide (PPC), a polymer comprising at least
one amino-alkylene phosphonic group and at least one polyoxyalkylated chain, a
polymer comprising a hydrocarbon main chain, phosphonated side groups and
polyoxyalkylated side groups, or mixtures thereof.
A PPC comprises a copolymer of acrylic or methacrylic acids, and their
poly(ethylene oxide) (PEO) esters.
The PPC is, preferably, a copolymer comprising at least one monomeric unit of
formula (I)
and at least one monomeric unit of formula (II)
OR8
wherein R 1, R2, R3, independently represent a hydrogen atom, a linear or
branched alkyl radical having 1 to 20 carbon atoms, or a phenyl radical, or a -COOR8
radical with R8 independently representing a hydrogen atom, a linear or branched alkyl
radical having 1 to 4 carbon atoms or a monovalent, divalent or trivalent ion or a
quaternary ammonium radical;
R4 represents a linear or branched alkyl radical having 2 to 20 carbon atoms;
when there are at least two radicals R4, they may be identical or different;
R5 is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms or a
monovalent, divalent or trivalent ion, or a quaternary ammonium radical
or R5 represents a radical of formula
C)R6
— P-OR6
wherein the groups R6 are identical or different and represent a hydrogen atom,
an alkyl group having 1 to 20 carbon atoms or a monovalent, divalent or trivalent ion, or
a quaternary ammonium radical;
or R5 represents a radical of formula
R7
[ C H2 ] N '
[ C H ] — P 0 (R6)
with R7 representing a hydrogen atom or an alkyl group having 1 to 18 carbon
atoms, or a radical of formula
C
T - P (R6)
W independently representing an oxygen atom or a NH radical;
m is an integer from 0 to 2;
n is an integer equal to 0 or 1;
q is an integer equal to 0 or 1;
r is an integer from 0 to 500;
t is an integer from 0 to 18;
and the molar mass of said copolymer is from 10 000 to 400 000 daltons.
The integer m of monomeric units (I) and the integer m of monomeric units (II) are
independent and can be identical or different.
The integers t of the radical R5 of the monomeric unit (I) may be identical or
different.
The radicals R 1, R2, R3 and R4 (I) and W of the monomeric unit (II) are
independent and may be identical or different.
Preferably, a radical R 1 is a hydrogen atom.
Preferably, a radical R2 is a hydrogen atom.
Preferably, a radical R3 is a methyl radical.
Preferably, a radical R4 is an ethyl radical.
Preferably, the copolymer used according to the present invention or a salt thereof
has an integer r from 1 to 300, more preferably from 20 to 250, even more preferably
from 40 to 200, most particularly from 40 to 150.
The copolymer may comprise several different monomeric units according to
formula (I) in particular having different radicals R5.
The superplasticizer may be prepared by applying or adapting known methods. A
considerable number of superplasticizers as described are known per se. They may be
obtained directly by copolymerisation, a method described in Patents EP 0056627,
JP 58074552, US 5,393,343.
They may also be prepared by post-synthetic modification of a polymer, as
described for example in Patent US 5,614,017.
Another example of admixture which may be comprised in the wall of the watersoluble
bag according to the present invention may be an air-entraining agent.
An air-entraining agent is generally a molecule having surfactant properties. For
example, it is possible to use a film-forming polymer of the polyvinyl alcohol type (PVA)
having surfactant properties.
Preferably, the air-entraining agent comprises a water-soluble PVA having a
hydrolysis rate less than 98 more preferably less than 95%.
Preferably, the content of the bag used according to the invention is a particulate
material.
Preferably, the particulate material is a hydraulic binder, aggregates, a mineral
addition or mixtures thereof. The particulate material may be a hydraulic binder,
aggregates or a mineral addition. Preferably, the particulate material is a hydraulic
binder, for example a cement.
The present invention also relates to a process for the production of a hydraulic
composition comprising water, aggregates and a hydraulic binder, using a bag, wherein
a wall of the bag comprises a layer comprising a water-soluble polymer and wherein an
admixture, preferably an admixture for a hydraulic composition, is present in the wall of
the bag.
The present invention also relates to a process for the production of a hydraulic
composition comprising the following steps:
a. introduction of water and aggregates in a concrete mixer;
b. introduction of a hydraulic binder; and
c . optionally introduction of mineral additions and/or other admixtures;
in which a bag is introduced during step a and/or during step b and/or during step c, a
wall of the bag comprising a layer which comprises a water-soluble polymer and an
admixture, preferably an admixture for a hydraulic composition, being present in the wall
of the bag.
According to a feature of the invention at least one part of the aggregates in step a
and/or at least one part of the hydraulic binder in step b and/or at least one part of the
mineral additions in step c is contained in the bag.
According to a further feature of the invention the water-soluble bag is added
during step a. Preferably, at least one part of the aggregates in step a is contained in the
water-soluble bag. Preferably, the totality of the aggregates in step a is contained in the
water-soluble bag.
According to a further feature of the invention the water-soluble bag is added
during step b. Preferably, at least one part of the hydraulic binder in step b is contained
in the water-soluble bag. Preferably, the totality of the hydraulic binder in step b is
contained in the water-soluble bag.
According to a further feature of the invention the water-soluble bag is added
during step c . Preferably, at least one part of the mineral additions in step c is contained
in the water-soluble bag. Preferably, the totality of the mineral additions in step c is
contained in the water-soluble bag.
According to a further feature of the invention in the process, a water-soluble bag
is added during step a and during step b.
According to a further feature of the invention in the process, a water-soluble bag
is added during step a and during step c .
According to a further feature of the invention in the process, a water-soluble bag
is added during step b and during step c .
According to a further feature of the invention in the process, a water-soluble bag
is added during step a, during step b and during step c.
The hydraulic composition obtained by following the process makes it possible to
produce elements for the construction field.
Shaped articles for the construction field generally comprise any constituting
element of a construction, for example a floor, a screed, a foundation, a wall, a partition
wall, a ceiling, a beam, a work top, a pillar, a bridge pier, a concrete block, a pipeline, a
post, a cornice, an element of road works (for example a border of a pavement), a tile,
for example a roof tile, a surfacing (for example of a wall), a plaster board, an (acoustic
and/or thermal) insulating element.
Preferably, the content of the bag used according to the invention comprises a
particulate material, more preferably a hydraulic binder, aggregates or a mineral
addition, most preferably a hydraulic binder. According to a feature of the invention, the
contents of the bag may be a hydraulic binder and/or aggregates and/or a mineral
addition.
A hydraulic composition is generally a mix of a hydraulic binder, with water (called
mixing water), optionally aggregates, optionally additives, and optionally mineral
additions. A hydraulic composition may for example be a high performance concrete,
very high performance concrete, self-placing concrete, self-levelling concrete, selfcompacting
concrete, fibre concrete, ready-mix concrete, pervious concrete, insulating
concrete, accelerated concrete or coloured concrete. The term « concrete », is also to
be understood as concretes which have been submitted to a finishing operation, for
example bush-hammered concrete, exposed or washed concrete or polished concrete.
Pre-stressed concrete is also to be understood by this definition. The term « concrete »
comprises mortars, in this specific case concrete comprises a mix of a hydraulic binder,
sand, water, optionally additives and optionally mineral additions. The term « concrete »
comprises fresh concrete or hardened concrete. Preferably, the hydraulic composition
according to the present invention is a cement slurry, a mortar, a concrete, a plaster
paste or a slurry of hydraulic lime. Preferably, the hydraulic composition is a cement
slurry, a mortar or a concrete. The hydraulic composition may be used directly on
jobsites in the fresh state and poured into formwork adapted to the target application, or
at a pre-cast plant, or used as a coating on a solid support.
The mineral additions are generally finely divided materials used in the hydraulic
compositions (for example, concrete) of the hydraulic binders (for example, a cement) in
order to improve certain properties or to provide them with particular properties. They
may be, for example, fly ash (for example, as defined in the « Cement » NF EN 197-1
Standard, paragraph 5.2.4 or as defined in the EN 450 « Concrete » Standard),
pozzolanic materials (for example, as defined in the « Cement » NF EN 197-1 Standard
of February 2001 , paragraph 5.2.3), silica fume (for example, as defined in the
« Cement » NF EN 197-1 Standard, of February 2001 , paragraph 5.2.7 or as defined in
the prEN 13263 « Concrete » Standard:1998 or the NF P 18-502 Standard), slag (for
example, as defined in the « Cement » NF EN 197-1 Standard, paragraph 5.2.2 or as
defined in the NF P 18-506 « Concrete » Standard), calcined shale (for example, as
defined in the « Cement » NF EN 197-1 Standard, of February 2001 , paragraph 5.2.5),
limestone additions (for example, as defined in the « Cement » NF EN 197-1 Standard,
paragraph 5.2.6 or as defined in the NF P 18-508 « Concrete » Standard) and siliceous
additions (for example, as defined in the NF P 18-509 « Concrete » Standard) or
mixtures thereof.
The present invention also relates to a bag, wherein a wall of the bag comprises a
layer comprising a water-soluble polymer and wherein an admixture, preferably an
admixture for a hydraulic composition, is present in the wall of the bag.
Measurement of the intrinsic viscosity of a polymer
The intrinsic viscosity is generally the limit value of the reduced viscosity of the
polymer at infinite dilution. This value is correlated with the average molecular weight of
a polymer.
Measurements of the intrinsic viscosity of polymers are carried out in a solution of
NaCI 3 M, using a capillary viscosimeter of the Ubbelhode type, at 25°C.
The flowing time was measured in the capillary tube between two marks, for the
solvent and for the solutions of the polymer at different concentrations. The specific
viscosity was obtained for each concentration, by dividing the difference between the
flowing times of the solution of polymer and of the solvent, by the flowing time of the
solvent. The reduced viscosity was calculated by dividing the specific viscosity by the
concentration of the solution of polymer. By tracing the value of the reduced viscosity as
a function of the concentration of the solution of polymer, a straight line was obtained.
The intersection of this straight line with the y axis corresponded to the intrinsic viscosity
for a concentration equal to zero.
In the present specification, including the accompanying claims, unless otherwise
specified, percentages are by mass.
EXAMPLES
Raw materials
The following materials were used in the following examples:
- Cement : cement of type CEM I 52.5 N CE CP2 NF (from Le Havre -Lafarge
plant).
- Limestones :
Limestone 1: limestone which comprises approximately 90% by mass
passing through the 100 m h sieve (Supplier: OMYA; brand name:
Betocarb HP Entrain);
Limestone 2: : limestone which comprises approximately 90% by mass
passing through the 100 m h sieve (Supplier: OMYA; brand name:
Betocarb HP Erbray).
- Clays :
Clay 1: Montmorillonite from Sardinia (Supplier: Socodis; brand name:
MCC3);
Clay 2: lllite from Le Puy (Supplier: Socodis);
- Clay 3: Kaolinite (Supplier: AGS; brand name: BS3).
- Aggregates : the materials from the following list were used (the ranges of
aggregates are given in the list in the form of d/D wherein « d » and « D » are as defined
in the XPP 18-545 Standard):
Sand 1: siliceous sand with a diameter less than or equal to 0.315 mm
(Supplier: Fulchiron; brand name: PE2LS);
Sand 2: 0/1 rounded siliceous sand from the St Bonnet quarry; (Supplier:
Lafarge);
Sand 3: 0/5 rounded siliceous sand from the St Bonnet quarry; (Supplier:
Lafarge);
Standardized sand: siliceous sand conforming with the EN 196-1
Standard (Supplier: Societe Nouvelle du Littoral);
Coarse aggregate: 5/12 rounded siliceous aggregate from the St Bonnet
quarry; (Supplier: Lafarge); and
Coarse aggregate 2: 12/20 siliceous aggregate from the St Bonnet
quarry; (Supplier: Lafarge).
- Superplasticizer :
SP: polycarboxylate superplasticizer (Supplier: Chryso; brand name:
Optima 206).
- Thermoplastic polyvinyl alcohols (PVA) :
PVA-1 : PVA having a melting temperature of 159°C and a melt flow index
from 13.0 to 19.0 g/10 min under 2.16 kg at 190°C (Supplier: Kuraray;
brand name: LP TC 251 ) ;
PVA-2 : PVA having a melting temperature of 182°C and a melt flow
index from 3.5 to 4.5 g/10 min under 2.16 kg a 230°C (Supplier: Kuraray;
brand name: LP TC 661 ) ;
PVA-3: PVA having a viscosity of 4.0 mPa.s and a hydrolysis rate of 88%;
solution having 9.3% of PVA by dry mass and 1% of anti-foaming agent
by mass relative to the PVA (Supplier: Air Product; brand name: Surfynol
MD20);
PVA-4: PVA having a viscosity of 40.0 mPa.s and a hydrolysis rate of
88%; solution having 3.8% of PVA by dry mass and 1% of anti-foaming
agent by mass relative to the PVA (Supplier: Air Product; brand name:
Surfynol MD20);
PVA-5: PVA having a viscosity of 23.0 mPa.s and a hydrolysis rate of
88% (Supplier: Kuraray);
Example 1: Measurement of the dissolution of a film of polymer in a mortar
Measurement of the dissolution was carried out on an equivalent microconcrete,
the formula of which is given in Table 1 below.
Table 1 : Formula of mortar for Example 1
Components Mass (g)
Cement 479.7
Limestone 1 358.8
Standardized sand 1350
Sand 1 200
Total water 324.4
SP 2.88
The tested PVA films were bought directly in the form of films produced by
extrusion. The PVA films were cut into square pieces, 8.9 cm by 8.9 cm, for the
dissolution tests.
Table 2 : Mixing procedure
The batches were made in a Perrier mixer.
The spread measurement was carried out in a truncated bottomless mould, which
is a reproduction at the scale ½ of the Abrams cone (refer to the
NF P 18-451 Standard of 1981 ) :
- Top diameter: 50 +/- 0.5 mm;
Bottom diameter: 100 +/- 0.5 mm;
Height: 150 +/- 0.5 mm.
The other equipment required for this measurement was a glass plate and a steel rod
with a spherical tip having a diameter of 6 mm and a length of 300 mm.
The procedure for the spread measurement was the following:
place the cone on the glass plate;
fill the cone in three layers of identical volumes and tap the mortar
15 times with the rod between each layer;
level the top surface of the cone;
- lift the cone vertically;
measure the spread, that is to say, the diameter of the obtained disc of
mortar, according to four diameters at 45° using a calliper square.
The result of the spread measurement was the average of the four obtained values.
After the last spread measurement the mortar was placed in a bucket filled with
cold water. The mix was stirred using a big spoon, then the supernatant was passed
through a 2 mm sieve. The operation was renewed four times. The quantity of PVA film
remaining on the sieve was then determined. The results are given in Table 3 below.
Table 3 : Results of the dissolution of two PVAs in a mortar
According to Table 3 hereinabove, the tested PVAs (PVA-1 and PVA-2) dissolved
satisfactorily in the mortar (more than 80% dissolution).
Example 2: Inerting tests with PVAs
The inerting performances of two PVAs (PVA-3 and PVA-4) were evaluated from
the mortar spread values with or without the presence of clay. Clay inerting agents
generally make it possible to at least partially neutralise deleterious effects due to the
presence of clay in a hydraulic composition, in particular on the superplasticizers.
Table 4 below, lists the formulae of the tested mortars.
Table 4 : Formulae of tested mortars for Example 2
The procedure for the production of the mortar is given in Table 5 below.
Table 5 : Procedure for production of the mortar for Example 2
The spread measurements were carried out at 10 minutes and 30 minutes
following the same procedure as for Example 1. The density was measured at
10 minutes from the specific gravity determined according to the procedure described
below in Example 3.
Table 6 below gives the results.
Table 6 : Results of the inerting tests
According to Table 6 hereinabove, when comparing Test 1 with Test 2, the
addition of clay without PVA had a negative impact on the spread and rheological
retention. The spread at 10 minutes did decrease from 360 mm to 165 mm.
Furthermore, the spread between 10 and 30 minutes for Test 1 increased by 20 mm,
whilst the spread between 10 and 30 minutes for Test 2 decreased by 55 mm.
The spread at 10 minutes improved in Test 3 (presence of PVA-4) with 255 mm
compared to Test 2 (absence of PVA) with 165 mm. The spread loss between 10 and
30 minutes was only 25 mm for Test 3. In contrast, it should be noted that the value of
255 mm spread at 5 minutes was good. The spread at 10 minutes improved in Test 4
(presence of PVA-3) with 325 mm compared to Test 2 (absence of PVA) with 165 mm.
The spread loss in Test 4 between 10 and 30 minutes was 45 mm, but the spread at
30 minutes was 280 mm, which is a satisfactory value.
Example 3: Air-entrainment tests with P As
The air-entraining performance of a PVA (PVA-5) was evaluated.
The formula of the micro concrete on which the tests were carried out was the same as
the formula in Example 1 (see Table 1) .
Table 7 below, provides the densities for each of the constituents of the tested
mortar.
Table 7 : Determination of the density of each of the constituents of the tested mortar in
Example 3.
The production procedure of the mortar is given in Table 8 below.
Table 8 : Production procedure of the mortar for Example 3
The spread measurement procedure was the same procedure as the one
described in Example 1.
The principle of the entrained air measurement was the following. It was possible
to calculate the theoretical density of the mortar without air when knowing the density of
each of the mortar's constituents (see Table 7). The density of the mortar comprising a
PVA was measured following the procedure described hereinafter. It was possible to
deduce the quantity of entrained air by calculating the difference between the measured
density and the theoretical density.
The measurement procedure of the entrained air was the following:
slowly pour mortar in a732-ml plastic beaker of known mass;
gently tap the bottom of the beaker on the work top to settle the mortar as it is
poured;
add a slight excess of mortar;
level the mortar using a metal ruler;
wipe the edges of the beaker and weigh it;
deduce the density, then the percentage of air for comparisons between the
theoretical density and the measured density.
The obtained results are given in Table 9 below.
Table 9 : Results of the measurements of entrained air with PVA
According to Table 9 hereinabove, PVA-5 gave satisfactory values of entrained
air. For an addition of 100 ppm of PVA-5, the obtained mortar had 6.88% of entrained
air.
Example 4 : Tests with water-soluble bags
Water-soluble bags were produced by thermal welding using films of PVA-1 . Three
thicknesses of film were tested (Bag-1 : 100 m h , Bag-2: 75 m h and Bag-3: 50 m h ) .
45 litres of concrete were produced in a concrete mixer. The formulation of the
concrete was reported in Table 10 below. The production procedure of the concrete was
reported in Table 1 1 below.
A control concrete was produced without a bag of PVA. The other concretes
(Concrete-1 , Concrete-2 and Concrete-3) were produced from Bag-1 , from Bag-2 and
from Bag-3 respectively, comprising 13.51 kg of Cement.
Table 10: Formulation of concrete for Example 4
A- Mechanical loading and handling resistance of the bags
The three bags (Bag-1 , Bag-2 and Bag-3) were manually loaded with 13.51 kg of
cement and were handled in a typical manner (lift, carry and lay).
Bag-1 , which had a thickness of 100 m h , was the most satisfactory in terms of its
mechanical resistance to loading and handling. The bag was not torn.
Bag-2, which had a thickness of 75 m h , resisted to the test without being torn, but
appeared to be near the tearing point. It was nevertheless considered to be satisfactory.
Bag-3, which had a thickness of 50 m h and a single layer was not thick enough to
bear 13.51 kg of cement. The film was found to have stretched.
B- Concrete spreads and entrained air
The concretes obtained by following the procedure in Table 11 hereinabove were
tested for their spread and their quantity of entrained air. The spread was measured
according to the procedure described in the above examples. The quantity of entrained
air was measured with a concrete air meter (Supplier: Controlab). The results were
given in Table 12 below.
Table 12: Results in terms of spread and entrained air for Example 4
Concrete Spread at Spread at Entrained air
15 min (cm) 30 min (cm) (mass%)
Control 17.5 13.5 1.60
Concrete-1 20.0 16.0 5.85
Concrete-2 19.5 18.0 4.80
Concrete-3 19.0 16.5 4.25
According to Table 12 hereinabove, the three tested bags made it possible
improve the spread and the quantity of entrained air of the concretes.
Moreover, the three bags dissolved in a satisfactory manner during mixing in
concrete mixer.

CLAIMS
1. Use of a bag to provide an admixture for a hydraulic composition, wherein a wall of
the bag comprises a layer, said layer comprising a water-soluble polymer, and
wherein an admixture is present in the wall of the bag.
2. The use according to claim 1, wherein a wall of the bag comprises a water-soluble
polymer, said polymer comprising the or an admixture.
3. The use according to claim 1 or claim 2, wherein the water-soluble polymer
comprises a polyvinyl alcohol.
4. The use according to any one of the preceding claims, wherein the bag comprises
an internal layer which comprises a water-soluble polymer, and an external layer
which is insoluble in water.
5. The use according to any one of the preceding claims, wherein the bag contains
cement, aggregates and/or mineral additions.
6. The use according to any one of the preceding claims, wherein the water-soluble
polymer comprises a film-forming polymer, which has a melting temperature and/or
a melt flow rate such that at least 80% by mass of the bag dissolves after
10 minutes of mixing in a concrete mixer.
7. The use according to any one of the preceding claims, wherein the water-soluble
polymer comprises a film-forming polymer which is a polyvinyl alcohol having a
melting temperature from 155 to 185°C and/or a melt flow rate higher than
3.0 g/10 min under 2.16 kg at 230°C as measured according to the method
described in the NFT 51-016 Standard.
8. The use according to any one of the preceding claims, wherein the admixture
comprises a clay-inerting agent.
9. The use according to claim 8, wherein the clay-inerting agent comprises a watersoluble
polyvinyl alcohol having a viscosity of 8 to 45 mPa.s measured at 20°C in an
aqueous solution comprising 4% by mass of dry extract in a Hoppler viscosimeter
according to the DIN 53015 Standard.
10. The use according to any one of the preceding claims, wherein the admixture
comprises an air-entraining agent.
11. The use according to claim 10, wherein the air-entraining agent comprises a watersoluble
polyvinyl alcohol having a hydrolysis rate less than 98%.
12. A process for the production of a hydraulic composition comprising water,
aggregates and a hydraulic binder, wherein a bag as described in claim 1 is used.
13. A bag as defined in claim 1.