Patent Description:
Concrete is a very widely used construction material with high strength and good durability. In addition to sand and/or aggregates and water, it also contains Portland cement as a hydraulic binder, which produces strength-forming phases by solidifying and curing in contact with water. Concrete based on Portland cement clinker is thus one of the most important binders worldwide.

By adding various mineral components, such as, e.g., granulated blast-furnace slag, fly ash, natural pozzolans, calcined clays or ground limestone to Portland cement, Portland composite cements having different properties can be produced. At the same time, the carbon dioxide footprint of the cement can be reduced by substituting Portland clinker by the cited mineral components. The production of Portland clinker results in high carbon dioxide emissions, emitted during the calcination and decarbonation of the raw materials, and from the burning of the fuels to heat the kiln to the desired temperature of about <NUM> '<NUM>. The use of mineral components in Portland cement has been an established practice for more than <NUM> years and is regulated in numerous cement and concrete standards.

The mineral additions, typically between <NUM> and <NUM>% by weight of the total weight of binder weight, are in most applications ground granulated blast furnace slag, fly ash, pozzolans, ground limestone or mixtures thereof. It is known that in such composite binders, increasing the content of the mineral components negatively affects the strength development of hardened concrete, and delays the setting times.

Also, when concrete compositions are prepared using binders that contain high amounts of mineral components, other problems may occur. A typical problem is a poor rheology, and more precisely a significant increase in viscosity.

The present invention aims at solving this problem, by providing a low carbon concrete composition, which is characterized by a reduced viscosity, shortened setting times, and satisfactory strength development. The present invention is also directed to method of preparation of this low carbon concrete composition. Thanks to a reduced content in Portland clinker in the binder, emissions of carbon dioxide during manufacturing are also reduced.

<CIT> as well as <CIT> both disclose compositions comprising inter alia a pozzolanic compound in combination with a cationic polymer and a (super)plasticizer.

The invention has for object a concrete composition comprising:.

Advantageously, limestone and/or fly ash represents at least <NUM>% by weight of the total weight of the binder.

Preferably, limestone is in the form of particles having a Dv90 less than or equal to <NUM>, and preferably a Dv97 less than or equal to <NUM>. In particular, limestone is in the form of particles and is composed of:.

Preferably, fly ash is in the form of particles having a Dv50 comprised between <NUM> to <NUM>.

The hydraulic binder may further comprise up to <NUM>% by weight, compared to the total weight of the binder, of additional mineral component, such as slag, calcined clay, silica fume and combinations thereof.

Preferably, the water to binder ratio is comprised between <NUM> and <NUM>, preferentially between <NUM> and <NUM>.

Preferably, the cationic polymer comprises cationic groups selected from the group comprising phosphonium group, pyridinium group, sulphonium group, quaternary amine group and combination thereof.

The cationic polymer may be obtained by polycondensation of epichlorohydrin with a mono-or dialkylamine, in particular methylamine or dimethylamine.

Preferably, the cationic polymer content ranges from <NUM> % to <NUM>% by weight, preferentially from <NUM> % to <NUM>% by weight, more preferentially from <NUM>% to <NUM>% by weight of the total weight of the binder.

Preferably, the water-reducing additive comprising at least one phosphonic amino-alkylene group further comprises a poly oxyalkyl chain.

The water-reducing additive comprising at least one phosphonic amino-alkylene group may correspond to compound having the formula (<NUM>):
<CHM>
in which:.

Preferably, the content of water reducing agent comprising at least one phosphonic amino-alkylene group ranges from <NUM>% to <NUM>% by weight, preferentially from <NUM>% to <NUM>% by weight, more preferentially from <NUM>% to <NUM>% by weight of the total weight of the binder. Preferably, the weight ratio (water reducing agent comprising at least one phosphonic amino-alkylene group) / (cationic polymer) preferably ranges from <NUM> to <NUM>, more preferably from <NUM> to <NUM>.

The invention has also for object a pre-mix comprising:.

The invention has also for object a process for preparing concrete composition, comprising mixing of:.

The invention has also for object a hardened concrete object based on the concrete composition as defined above and below.

The invention has also for object the use of a cationic polymer as defined above and below to reduce the setting time of a concrete composition comprising:.

As used herein, the term "concrete" refers to a composition comprising hydraulic binder and aggregates which in presence of water forms a paste which sets and hardens by means of hydration reactions and processes and which, after hardening, retains its strength and stability even under water. When the aggregates are sand only, the composition is usually called "mortar". Specifically, concrete is as defined in standard EN <NUM>-<NUM> of April <NUM>. The terms "concrete" and "concrete composition" will have the same meaning in the present disclosure.

As used herein, the term "premix" refers to a composition comprising hydraulic binder and admixture, the composition is suitable to be mixed with water and aggregates for preparing a concrete.

As used herein, the term « hydraulic binder » refers to a material which sets and hardens by hydration, for example cement. Preferably, the cement is a defined in standard NF EN <NUM>-<NUM> of April <NUM>. The terms "binder" and "hydraulic binder" will have the same meaning in the present disclosure.

As used herein, the term "admixture" refers to a material other than water, aggregates, hydraulic binder, and fiber reinforcement that is used as an ingredient of concrete composition to modify its freshly mixed, setting, or hardened properties and that is added to the batch before or during its mixing. The terms "admixture" and "chemical admixture" will have the same meaning in the present disclosure.

As used herein, the term "water reducing agent" refers to an admixture which reduces the amount of mixing water by <NUM>% to <NUM>% in weight, preferably by <NUM>% to <NUM>% in weight, for a given workability. Water reducing agents that reduce the amount of mixing water by <NUM>% to <NUM>% in weight are also called superplasticizers.

As used herein, the term "clays" refers to aluminium silicates and/or magnesium silicates, in particular phyllosilicates with a layered structure, the layers typically having a separation of approximately <NUM> to approximately <NUM> Angstroms. In the sands, montmorillonite, illite, kaolinite, muscovite and chlorites are encountered in particular. The clays can be of <NUM>:<NUM> type but also of <NUM>:<NUM> type (kaolinite) or of <NUM>:<NUM>:<NUM> type (chlorites). The term "swelling clays" refers to clays which have cations in their interlayer spaces capable of hydrating in the presence of water (vapour or liquid). Swelling clays, generically referred to as smectites, comprise in particular clays of <NUM>:<NUM> type, such as montmorillonite.

As used herein, the term "inerting of clay" refers to at least partial neutralization of the harmful effects due to the presence of the clay in a concrete composition.

The D10 corresponds to the 10th centile of the volume distribution of particle sizes, i.e. <NUM>% of the volume consists of particles for which the size is less than D10 and <NUM>% with a size greater than D10. The D50 corresponds to the median or 50th centile of the volume distribution of particle sizes, i.e. <NUM>% of the volume consists of particles for which the size is less than D50 and <NUM>% with a size greater than D50. The D90 corresponds to the 90th centile of the volume distribution of particle sizes, i.e. <NUM>% of the volume consists of particles for which the size is less than D90 and <NUM>% with a size greater than D90. The D97 corresponds to the 97th centile of the volume distribution of particle sizes, i.e. <NUM>% of the volume consists of particles for which the size is less than D97 and <NUM>% with a size greater than D97.

The D10, D50, D90, D97 of particles is generally determined by laser diffraction. The particle size distribution of the different powders are obtained with a laser Malvern MS2000 granulometer. The measurement is carried out in a suitable medium (for example, in an aqueous medium); the size of the particles should be comprised between <NUM> and <NUM>. The light source consists of a red He-Ne laser (<NUM>) and a blue diode (<NUM>). The optical model is the Fraunhofer one, the computation matrix is of the polydisperse type. A measurement of background noise is first of all carried out with a pump rate of <NUM>,<NUM> rpm, a stirring rate of <NUM> rpm and a measurement of noise over <NUM>, in the absence of ultrasonic waves. It is then checked that the light intensity of the laser is at least equal to <NUM>%, and that a decreasing exponential curve is obtained for the background noise. If this is not the case, the lenses of the cell have to be cleaned.

A first measurement is then carried out on the sample with the following parameters: pump rate of <NUM>,<NUM> rpm, stirring rate of <NUM> rpm, absence of ultrasonic waves, obscuration limit between <NUM> and <NUM>%. The sample is introduced in order to have an obscuration slightly greater than <NUM>%. After stabilization of the obscuration, the measurement is carried out with a duration between the immersion and the measurement set to <NUM>. The measurement duration is of <NUM> (<NUM>,<NUM> analyzed diffraction images). In the obtained granulogram, the fact that a portion of the population of the powder may be agglomerated should be taken into account.

Next a second measurement (without emptying the tank) is then carried out with ultrasonic waves. The pump rate is brought to <NUM>,<NUM> rpm, the stirring to <NUM>,<NUM> rpm, the ultrasonic waves are <NUM> % emitted (<NUM> Watts). This rate is maintained for <NUM> minutes, and then one returns to the initial parameters: pump rate <NUM>,<NUM> rpm, stirrer rate of <NUM> rpm, absence of ultrasonic waves. After <NUM> (for removing the possible air bubbles), a measurement is made for <NUM> (<NUM>,<NUM> analyzed images). This second measurement corresponds to a powder de-agglomerated by ultrasonic dispersion.

Each measurement is repeated least twice in order to check the stability of the result. The apparatus is calibrated before each working session by means of a standard sample (silica C10 Sifraco) the grain size curve of which is known. All the measurements shown in the description and the announced ranges correspond to the values obtained with ultrasonic waves.

The molecular weight of the cationic polymers can be determined by chromatographic analysis or from the intrinsic viscosity according to the formula of Mark-Houwink: <MAT>.

The measurements of the intrinsic viscosity of the cationic polymers are done with a capillary viscometer such as the Ubbelhode type in a solution of <NUM> NaCl at <NUM>.

The flowing time of the solvent and the solutions of the polymer at different concentrations are measured in a capillary tube between two marks. The intrinsic viscosity is obtained from the « reduced » viscosities at different concentrations.

For more details concerning this measurement, the following work is recommended: <NPL>.

The density of the cationic charge (cationicity) given in meq/g represents the quantity of charges (in mmol) carried by <NUM> of polymer. This value can be measured by colloidal titration or by pH titration.

The charge density of a cationic polymer can be measured by an anionic polymer with a known level of ionicity, for example potassium polyvinylsulphate, in the presence of an indicator for which the color depends on the nature of the excess polymer.

Specifically, the cationicity can be determined in the following manner:
<NUM> of a buffer solution of sodium phosphate at <NUM>, pH <NUM> and <NUM> of o-toluidine blue solution at <NUM>. <NUM>-<NUM> M, then <NUM> of cationic polymer solution to be measured are introduced into an appropriate container.

This solution is titrated with a solution of potassium polyvinylsulphate until the indicator changes.

The cationicity is obtained with the following relationship: <MAT> where:.

The principle of the spread measurement consists in filling a truncated spread measurement cone with the hydraulic composition to be tested, then releasing the said composition from the said truncated spread measurement cone in order to determine the surface of the obtained disk when the hydraulic composition has finished spreading. The truncated spread measurement cone corresponds to a reproduction at the scale Y2 of the cone as defined by the NF P <NUM>-<NUM> Standard, <NUM>. The truncated spread measurement cone has the following dimensions:.

The entire operation is carried out at <NUM>° C. The spread measurement is carried out in the following manner:.

The result of the spread measurement is the average of the four values, +/-<NUM>.

The viscosity measurement consists in measuring the flow time through a truncated viscosity measurement cone of a hydraulic composition to be tested. The truncated viscosity measurement cone has the following dimensions:.

The truncated viscosity measurement cone further comprises first and second marks which may be parallel marks provided on the sides of the truncated cone and defining planes perpendicular to the axis of the truncated cone. The first mark is closer to the base of the larger diameter than the second mark. The distance between the two marks is <NUM>, the first mark being at <NUM> from the base with the larger diameter.

The entire operation is carried out at <NUM>. The viscosity measurement of a concrete composition is carried out in the following manner:.

The strength is measured by preparing cement mortars. The detailed protocol is described in the European cement Standard EN <NUM>-<NUM> (September <NUM>), the only difference is that polystyrene moulds are used instead of steel moulds.

The cement mortars are prepared as follows:
The mortar is made using a Perrier type of mixer. The entire operation is carried out at <NUM>. The preparation method comprises the following steps:.

The setting times is measured by maturometry, by measuring the temperature within the concrete composition as a function of time. As the chemical reactions that induce the setting of cement upon addition of water are exothermic, measuring the temperature of the concrete composition as a function of time provides a comparative assessment of setting times.

Slump flow is measured according to the protocol described in the standard NF EN <NUM>-<NUM> (June <NUM>).

The viscosity measurement consists in measuring the time for the concrete to get out the Abrams cone placed inverse position (kind of truncated viscosity Abrams cone).

The strength is measured in agreement with the standard NFEN <NUM>-<NUM> (June <NUM>). The test is carried out at <NUM>.

The concrete composition of the present invention comprises binder, admixtures, water, aggregates. It is suitable for use in any known concrete applications. In particular, the concrete composition is more suitable for structural concrete applications.

The pre-mix of the present invention comprises binder and admixtures.

These components are as disclosed below.

In the present invention, the binder comprises Portland clinker, a mineral addition selected from the group consisting of limestone, fly ash or combination thereof, and optionally other mineral components.

Limestone and/or fly ash is the main constituent in weight of the binder, i.e. representing at least <NUM>% by weight, even more preferentially at least <NUM>% by weight of the total weight of the binder.

Preferably, the limestone and/or fly ash content ranges from <NUM>% to <NUM>% by weight, preferentially from <NUM> to <NUM>% by weight, more preferentially from <NUM>% to <NUM>% by weight of the total weight of the binder.

Preferably, the mineral addition is composed of <NUM>% to <NUM>% limestone, more preferably <NUM>% to <NUM>%, in weight by total weight of the mineral components.

The limestone used in the binder is as defined in the standard EN197-<NUM> of April <NUM>. It comprises ground calcium carbonate, the calcium carbonate content calculated from the calcium oxide content is at least <NUM>% by weight of the weight of the limestone. Preferentially, the clay content, determined by the methylene blue test in accordance with EN <NUM>-<NUM> of June <NUM>, shall not exceed <NUM>% by weight of the total weight of the limestone. The total organic carbon (TOC) content, when tested in accordance with EN <NUM> of September <NUM>, shall not exceed <NUM>% by weight of the total weight of the limestone.

Advantageously, limestone used in the binder is in the form of particles having a Dv90 less than or equal to <NUM>, and preferably a Dv97 less than or equal to <NUM>. Advantageously, limestone used in the binder is in the form of particles having a Dv90 ranging from <NUM> to <NUM>, preferably in the form of particles having a Dv97 ranging from <NUM> to <NUM>. Advantageously, limestone used in the binder is in the form of particles having a Dv50 ranging from <NUM> to <NUM>, advantageously ranging from <NUM> to <NUM>.

Advantageously, the limestone used in the binder is composed of several fractions, such as two fractions, characterized by different finenesses. Using several fractions of limestone has the advantage of improving the particle packing density of the binder, and the concrete. This will improve both the rheology and the strength development of the resulting concrete. A good particle packing of the binder can be achieved by using two fractions of ground limestone:.

In case two fractions of limestones are used, the weight ratio between the coarser fraction and the finer fractions is comprised between <NUM> and <NUM>, preferentially between <NUM> and <NUM>.

The fly ash used in the binder is as defined in the standard EN197-<NUM> of April <NUM>. Fly ash is generally obtained by electrostatic or mechanical precipitation of dust-like particles from the flue gases from furnaces fired with pulverized coal. Fly ash may be siliceous or calcareous in nature.

Siliceous fly ash consists essentially of reactive silicon dioxide and aluminium oxide. The remainder contains iron oxide and other compounds. The proportion of reactive calcium oxide is preferably less than <NUM>% by mass. The reactive silicon dioxide content is preferably more than <NUM>% by mass.

Calcareous fly ash consists essentially of reactive calcium oxide, reactive silicon dioxide and aluminium oxide. The remainder contains iron oxide and other compounds. The proportion of reactive calcium oxide is preferably more than <NUM>% by mass, more preferably more than <NUM>% by mass.

Advantageously, fly ash used in the binder is in the form of particles having a Dv50 comprised between <NUM> to <NUM>.

Portland clinker is as defined in the standard EN197-<NUM> of April <NUM>, and is made by sintering a precisely specified mixture of raw materials (raw meal, paste or slurry) containing elements, usually expressed as oxides, CaO, SiO2, Al2O3, Fe2O3 and small quantities of other materials. The raw meal, paste or slurry is finely divided, intimately mixed and therefore homogeneous. Portland clinker is a hydraulic material which shall consist of at least two-thirds by mass of calcium silicates (3CaO · SiO2 and 2CaO · SiO2), the remainder consisting of aluminium and iron containing clinker phases and other compounds. The weight ratio (CaO)/(SiO2) shall be not less than <NUM> and the content of magnesium oxide (MgO) shall not exceed <NUM> % by weight, compare to the total weight of the Portland clinker.

Preferably, the Portland clinker content ranges from <NUM> to <NUM>% by weight, preferentially from <NUM> to <NUM>% by weight, more preferentially from <NUM> to <NUM>% by weight of the total weight of the binder.

The binder may optionally contain additional mineral components, which are different from the limestone or fly ash described above. All those listed in the cement standards EN <NUM>-<NUM> of April <NUM>, except limestone and fly ash, are suitable. Granulated blast furnace slags, pozzolanic materials such as calcined clays, burnt shale, silica fume and combinations thereof are particularly advantageous. More specifically, slag, calcined clay and combinations thereof are particularly advantageous. More specifically, silica fume is particularly advantageous when the mineral addition is fly ash.

Preferably, the additional mineral component does not constitute more than <NUM>% by weight of the total weight of the binder. Preferably, the additional mineral component content ranges from <NUM>% to <NUM>% by weight, more preferably from <NUM>% to <NUM>% by weight, even more preferably from <NUM>% to <NUM>% by weight of the total weight of the binder.

Advantageously, the binder consists in Portland clinker, limestone and/or fly ash, and optionally other mineral components disclosed above.

Advantageously, the concrete composition or the premix does not comprise other hydraulic binder than the binder disclosed above.

The concrete composition or the premix may further comprise calcium sulphate.

Calcium sulphate used according to the present invention includes gypsum (calcium sulphate dihydrate, CaSO<NUM>. <NUM><NUM>O), hemi-hydrate (CaSO<NUM>. <NUM>/<NUM><NUM>O), anhydrite (anhydrous calcium sulphate, CaSO<NUM>) or a mixture thereof. The gypsum and anhydrite exist in the natural state. Calcium sulphate produced as a by-product of certain industrial processes may also be used. Preferably, the calcium sulphate content ranges from <NUM>% to <NUM>% by weight for <NUM>% in weight of binder.

As used herein, the term "water" used with regard to the concrete composition preferably relates to the water added for mixing and the water of the admixtures, such as the water of water reducing agent.

The water content is expressed in a water to binder weight ratio. The water to binder ratio is preferentially comprised between <NUM> and <NUM>, more preferentially between <NUM> and <NUM>.

Any known aggregates suitable for the preparation of concrete may be used for the present invention. The aggregates have advantageously a maximum size of <NUM>.

The aggregates can comprise or consist in sand.

Any known sand suitable for the preparation of concrete is suitable for the present invention. The sand has advantageously a maximum size of <NUM>, preferentially <NUM>. The sand has advantageously a minimum size of <NUM> or of <NUM>. Preferably, the sand is a siliceous sand such as quartz sand, a calcined or non-calcined bauxite sand, a silica-calcareous sand or mixtures thereof.

The concrete composition will advantageously comprise:.

the percentages corresponding to proportions relative to the total dry volume.

When the aggregates comprise sand and gravel, the mass ratio of the quantity of sand to the quantity of gravel is preferably from <NUM>:<NUM> to <NUM> :<NUM>, more preferably from <NUM>:<NUM> to <NUM>:<NUM>, even more preferably from <NUM>:<NUM> to <NUM>:<NUM>.

The concrete composition and the premix of the present invention contain chemical admixtures.

It was surprisingly found that the combination of a clay inerting agent and of a water reducing agent comprising at least one phosphonic amino-alkylene group has a positive impact on concrete viscosity, flow, setting times and compressive strength. Furthermore, it was surprisingly found that the combination of both of these admixtures has a synergistic effect.

The clay inerting agent is a cationic polymer, having a cationic charge density of strictly higher than <NUM> meq/g, preferably strictly higher than <NUM> meq/g. Examples are disclosed in <CIT>, <CIT> and <CIT>. The cationic polymer is advantageously as further detailed below.

Preferably, the cationic polymer content ranges from <NUM>% to <NUM>% by weight, preferentially from <NUM>% to <NUM>% by weight, more preferentially from <NUM>% to <NUM>% by weight of the total weight of the binder.

Examples of the water reducing agent comprising at least one phosphonic amino-alkylene group are disclosed in <CIT> and <CIT>. They are preferably diphosphonate compounds. They are compounds comprising a poly oxyalkylene chain and a phosphonic amino-alkylene group. The water reducing agent comprising at least one phosphonic amino-alkylene group is advantageously as further detailed below.

Preferably, the content of water reducing agent comprising at least one phosphonic amino-alkylene group ranges from <NUM>% to <NUM>% by weight, preferentially from <NUM>% to <NUM>% by weight, more preferentially from <NUM>% to <NUM>% by weight of the total weight of the binder.

The weight ratio (water reducing agent comprising at least one phosphonic amino-alkylene group) / (cationic polymer) preferably ranges from <NUM> to <NUM>, more preferably from <NUM> to <NUM>.

The addition of cationic polymer to a concrete composition comprising a water reducing agent comprising at least one phosphonic amino-alkylene group allows to:.

In particular, the setting time of the mortar composition is less than <NUM> hours, the measurement being done according to the method described above.

Preferably, the slump flow value of the mortar composition is from <NUM> to <NUM>, preferably from <NUM> to <NUM>, the measurement being done according to the method described above.

In addition, the viscosity of the mortar composition is improved by the use of water reducing agent comprising at least one phosphonic amino-alkylene group.

Preferably, the flow time through a truncated viscosity measurement cone of the mortar composition at <NUM> is less <NUM>, preferably less than <NUM>, more preferably less that <NUM>, the measurement being done according to the method described above.

Preferably, the setting time is suitable for the intended uses and the viscosity is lowered.

Furthermore, the mortar obtained after hardening has good mechanical properties, in particular in terms of compressive strength after <NUM> hours and after <NUM> hours, the measurement being done according to the method described above.

Preferably, the average compressive strength is greater than or equal to <NUM> MPa, preferably greater than or equal to <NUM> MPa, at <NUM> <NUM> hours after mixing.

For note, the chemical admixtures are available:.

In the present disclosure, the content in chemical admixture always refers to the dry matter content of the active ingredient.

In the present invention, the chemical admixture may be supported on inorganic particles. The inorganic particles are preferably made of an inorganic material suitable to support the chemical admixture, meaning that the material forming the inorganic particle is inert with regard to the chemical admixture.

In other terms, the inorganic material forming the inorganic particles is not likely to be attacked by the chemical admixture or to modify the chemical structure of the admixture.

Preferably, the particles used as support of the chemical admixture are particles based on silica or on alumina.

Silica-based particles comprise at least <NUM>% of silica, preferably at least <NUM>% of silica, and even more preferably at least <NUM>% of silica, in % expressed by weight relative to the weight of inorganic particles.

The silica-based particles may contain precipitated silica, siliceous stone, or mixtures thereof. Precipitated silica is silica obtained by a precipitation reaction of a silicate, in particular an alkali metal silicate such as sodium silicate with an acid such as sulfuric acid. Siliceous stone may in particular be diatomite. Diatomite is a naturally occurring, soft, siliceous sedimentary rock that is usually crumbled into a fine white to off-white powder. It has a particle size ranging from less than <NUM> to more than <NUM>, typically from <NUM> to <NUM>. Diatomite typically comprises from <NUM> to <NUM>% of silica, <NUM> to <NUM>% of alumina and <NUM> to <NUM>% of iron oxide, in % expressed by weight relative to the weight inorganic particles.

The first admixture is an inerting agent for clays, especially for swelling clays.

The clay inerting agent is a cationic polymer having a cationic charge density strictly greater than <NUM> meq/g, preferably greater than <NUM> meq/g and more preferably greater than <NUM> meq/g. The cationic polymer in the composition has preferably a cationic charge density less than <NUM>.

The cationicity is measured at a pH strictly inferior to <NUM>.

The cationic polymer in the composition has a molecular weight expressed by an intrinsic viscosity less than <NUM> dl/g, preferably less than <NUM> dl/g and more preferably less than <NUM> dl/g. The cationic polymer in the composition has preferably a molecular weight expressed by an intrinsic viscosity above <NUM>,<NUM>.

Preferably, the cationic polymer is water-soluble.

The polymer can have a linear, comb or branched structure, preferably a linear structure or a comb structure.

The cationic polymer preferably comprises groups selected from phosphonium group, pyridinium group, sulphonium group, quaternary amine group and combination thereof. In particular quaternary amine groups are preferred. For note, the polymer can comprise tertiary amine groups or imine groups which are quaternized by protonation in an acidic medium, i.e. at a pH < <NUM>. The cationic groups can be located on the main chain or on the side groups of the polymer.

The cationic polymer is preferably a comb-polymer comprising polyoxyalkylenated groups as side groups.

The cationic polymer can be obtained directly by a known polymerization process, such as radical polymerization, polycondensation or polyaddition, post-synthetic modification of a polymer, as disclosed in <CIT>, <CIT> and <CIT>. In the context of the modification of polymers by grafting, mention may be made of grafted natural polymers, for example cationic starches.

Specifically, the polymer can be obtained by polymerisation of monomers including cationic monomers, their precursors, and their combination.

Cationic monomers are preferably selected from diallyldialkylammonium salts, quaternized dialkylaminoalkyl (meth)acrylates, (meth)acrylamides N-substituted by a quaternized dialkylaminoalkyl, and their combinations.

Suitable precursors of cationic monomers are specifically monomers carrying amine or imine groups. The nitrogen can be quaternized after polymerization in a known way as disclosed in <CIT>, <CIT> and <CIT>.

The polymerization can further be carried out with non-ionic monomers, preferably comprising a short chain, more preferably comprising from <NUM> to <NUM> carbon atoms. Preferably, non-ionic monomer is selected from methoxypolyethylene glycol (meth)acrylate, acrylamide, N-vinylpyrrolidone, hydroxyethyl (meth)acrylate, N-vinyl-N-methylacetamide, alkyl (meth)acrylates and combination thereof. Anionic monomers can also be present, provided that the polymer finally obtained remains cationic overall.

Specific examples of cationic polymers are:.

The polymers obtained by condensation of dicyandiamide with formaldehyde, optionally in the presence of other compounds, in particular of a polyalkylene glycol (A), of a polyalkoxylated polycarboxylate (B) and/or of a quaternization agent (C) are advantageously prepared as disclosed in <CIT>, page <NUM>, line <NUM> to page <NUM>, line <NUM> et page <NUM>, lines <NUM> to <NUM>, and page <NUM> lines <NUM>-<NUM>, and page <NUM>, line <NUM> to page <NUM>, line <NUM>, herein included by reference.

The polyalkylene glycol (compound A) is preferably a compound of formula (III):.

By way of example, it can be polyethylene glycol, polypropylene glycol, an ethylene oxide/propylene oxide copolymer or a mixture of these different compounds. Preferably, it is polyethylene glycol.

The molecular weight, Mw, of compound A is preferably from <NUM><NUM> to <NUM><NUM>/mol.

The polyalkoxylated polycarboxylate (compound B) is a comb polymer which comprises a main hydrocarbon chain to which both lateral carboxylic groups and alkoxylated groups are connected, in particular groups of propylene oxide (PO), ethylene oxide groups (EO) and/or combinations thereof. The lateral groups may be ionic or non-ionic. It is preferably a compound having the following formula (II):
<CHM>
where.

The level of ester of the compound B, given by the ratio p/(m+p), may be from <NUM> to <NUM>% and in particular from <NUM> to <NUM>%.

The ammonium derivative (compound C) has as main role that of increasing the ionic nature of the polymer by introducing cationic functional groups. The ionic nature of the polymer contributes greatly to its solubility in water and to its affinity for clays, especially for swelling clays.

Preferably, the ammonium ion of the ammonium derivative is of following formula (IV):.

in which: the R<NUM> groups are identical or different and correspond to H or to a C<NUM>-C<NUM> alkyl group.

Mention may be made, as examples of appropriate ammonium derivatives, of ammonium halides, for example ammonium chloride, ammonium bromide and ammonium iodide, ammonium sulphate, ammonium acetate, ammonium formate, ammonium nitrate or ammonium phosphate, ammonium formate being preferred.

Polymers obtained by polycondensation of epichlorohydrin with a mono- or dialkylamine are particularly preferred.

Water reducing agent comprising at least one phosphonic amino-alkylene group.

Examples of the water reducing agent comprising at least one phosphonic amino-alkylene group can be found in the patent <CIT> or in <CIT>. They are compounds comprising a phosphonic amino-alkylene group and preferably a poly oxyalkylene chain. They are preferably diphosphonate compounds.

The water reducing agent advantageously corresponds to compounds having following Formula (<NUM>):
<CHM>
in which:.

For avoidance of doubts, N stands for nitrogen.

The compounds or the salts of the compounds according to Formula (<NUM>) may be used. The salts of the compounds according to formula (<NUM>) may be stœchiometric or not, mixed or not, and are constituted with alkali metals, alkali earth metals, amines or quaternary ammoniums.

An example of a process for preparation of the compounds of Formula (<NUM>) is described in <CIT>, page <NUM>, line <NUM> to page <NUM>, line <NUM>, herein incorporated by reference.

Preferably compounds of Formula (<NUM>) satisfy one or many of the following recited definitions:.

Advantageously, Q is selected from ethylene, cyclo-hexene or n-hexene;.

The following compound of formula (<NUM>) is particularly preferred:
<CHM>.

When they are in the state of salt, the compounds according to Formula (<NUM>) are preferably sodium, calcium or diethanolamine salts.

In another embodiment, the water reducing agent advantageously corresponds to compounds having following Formula (<NUM>):
<CHM>
in which:.

The M group may be identical or different. Preferably, the M group does not comprise a phosphate group. Each M group may have a molar mass greater than <NUM>/mol. The total molar mass of all the M groups of a same molecule is preferably comprised from <NUM><NUM> to <NUM><NUM>/mol.

Preferably, the number p is less than twice the number y. Preferably p ranges from <NUM> to <NUM>.

Preferably the Q group comprises <NUM> to <NUM> carbon atoms, and preferably <NUM> to <NUM> carbon atoms. Advantageously, Q is selected from ethylene, cyclo-hexene or n-hexene.

In addition to the above described chemical admixtures, the concrete composition or the premix may further comprise a water reducing agent which does not comprise phosphonic amino-alkylene group. The concrete composition or the premix may comprise from <NUM> to <NUM>% by weight, compared to the total weight of the binder, of water reducing agent which does not comprise phosphonic amino-alkylene group.

The water reducing agents include, for example lignosulfonates, hydroxycarboxylic acids, carbohydrates and other specialized organic compounds, e.g. glycerol, polyvinyl alcohol, sodium alumino-methyl-siliconate, sulfanilic acid and casein as well as superplasticizers. Superplasticizers can be selected from sulfonated condensates of naphthalene formaldehyde (generally a sodium salt), sulfonate condensates of melamine formaldehyde, modified lignosulfonates, polycarboxylates, e.g. polyacrylates (generally sodium salt), polycarboxylate ethers, copolymers containing a polyethylene glycol grafted on a polycarboxylate, sodium polycarboxylates-polysulfonates, and combinations thereof. In order to reduce the total amount of alkaline salts, the superplasticizer may be used as a calcium salt rather than as a sodium salt.

Mixing can be done by any known methods.

Preferably, the binder is prepared during a first step, and the aggregates and water are added during a subsequent step.

Calcium sulphate, if any, is added during the first step.

Chemical admixtures can be added during the first step if they are in a dried state or supported on inorganic particles. Liquid chemical admixtures are added during the subsequent step.

In an embodiment, a pre-mix comprising the binder, the admixtures and optionally the calcium sulphate is first prepared. In that embodiment, admixtures are in a dried state, preferably flash dried, or supported on inorganic particles.

In a variant, that pre-mix can be mixed with aggregates and water.

In a variant, that pre-mix can be mixed with aggregates and the resulting mix can be mixed with water later. That resulting mix is a dry ready-mix concrete, usable by simply mixing with water.

In all embodiments, the mixing is done using a conventional mixer at a concrete mixing plant or directly in a drum-truck mixer, for a mixing time usual in the field.

The concrete composition of the invention may be cast to produce, after hydration and hardening a cast article for the construction field. Such cast articles, that comprise the concrete composition of the invention, also constitute an object of the invention. Cast articles for the construction field include, for example, a slab, a floor, a screed, a foundation, a wall, a partition wall, a beam, a work top, a pillar, a bridge pier, a masonry block of concrete, optionally foamed concrete, a pipe, a conduit, a post, a stair, a panel, a cornice, a mold, a road system component (for example a border of a pavement), a roof tile, a surfacing (for example of a road), a jointing plaster (for example for a wall) and an insulating component (acoustic and/or thermal).

The invention makes it possible to respond to the need to reduce CO<NUM> emissions while having concrete composition whose rheology at fresh state is improved. Low carbon concrete compositions, because of their specific binder composition, tend to be sticky and do not flow easily. The admixtures used in this invention have been found to remedy this problem.

Also, water-reducing additive comprising at least one phosphonic amino-alkylene group have been used as water reducers since a long period of time. The resulting concrete compositions have excellent rheological properties, but usually tend to have long setting strength and low early strength. The admixture composition of the present invention was surprisingly found to advantageously provide short setting times.

The invention is also directed to the use of a cationic polymer as defined above to reduce the setting time of a concrete composition comprising:.

The following examples illustrate the invention without limiting it.

In all of the tests below, the following components are used in the amounts provided in the table below.

The mortars are prepared taking into account the amount of water absorbed by the sand, and the amount of water added by the liquid admixtures. In all tests, normalized sand has a sand humidity of <NUM>% and absorbs water in an amount of <NUM> wt. -% of its weight. In all tests, the content of chemical admixture, if any, is expressed in % in weight of solid content in liquid admixture compared to total weight of the binder.

The composition of the mortars is described in the following table.

REF1, REF2 and REF3 are reference mortar compositions comprising one chemical admixture, which is a water reducing agent. REF1, REF2 and REF3 do not comprise cationic polymer.

REF4 is reference mortar composition comprising one chemical admixture, which is a cationic polymer. REF4 composition does not comprise water reducing agent.

COMPAR1 and COMPAR2 are comparative mortar compositions comprising two chemical admixtures: a cationic polymer and a water reducing agent. In these comparative compositions, the water reducing agent does not comprise phosphonic amino-alkylene group.

INV is mortar composition according to the invention comprising two chemical admixtures: a cationic polymer and a water reducing agent. In this composition according to the invention, the water reducing agent comprises phosphonic amino-alkylene group.

The rheology, compressive strength and setting time of the mortar compositions are measured. All tests are carried out at <NUM>.

The results are provided in the table below and in <FIG> and <FIG>.

: not measurable. The concrete composition forms a bloc so quickly that slump flow and viscosity cannot be measured.

: in view of the rheology which cannot be measured, compressive strength has not been determined.

Results in table <NUM> demonstrates that for all mortar compositions comprising a water-reducing agent, the addition of a cationic polymer improves the slump flow of the concrete composition while the water-reducing agent content can be reduced. The use of water reducing agent comprising phosphonic amino-alkylene group improves viscosity of the concrete composition.

The measured temperature as a function of time is a good indicator of the setting time of the mortar as it refers to the dissolution of anhydrous that immediately convert into hydrates.

<FIG> shows that the addition of a cationic polymer to a mortar composition comprising a PCE water-reducing agent is suitable to reduce the dosage of PCE water-reducing agent to reach the initial slump flow target (from <NUM> wt. % to <NUM> wt. %) but this has no significant impact on the setting times: the recorded maximum temperature is recorded at around <NUM> hours in both cases.

<FIG> shows that the addition of a cationic polymer to a mortar composition comprising a PAE water-reducing agent is suitable to reduce the dosage of PAE water-reducing agent to reach the initial slump flow target (from <NUM> wt. % to <NUM> wt. %) but this has no significant impact on the setting times: the recorded maximum temperature is recorded at around <NUM> hours in both cases.

<FIG> shows that the addition of a cationic polymer to a mortar composition comprising a water-reducing agent comprising at least one phosphonic amino-alkylene group is suitable to reduce the dosage of water-reducing agent comprising at least one phosphonic amino-alkylene group to reach the initial slump flow target (from <NUM> wt. % to <NUM> wt.

In the same time, it strongly reduces the setting time: the recorded maximum temperature occurs at about <NUM> hours for REF3 and is reduced to about <NUM> hours when a small amount of a cationic polymer is added. Finally, the addition of a cationic polymer has no significant impact on the viscosity of the mortar that remains extremely low.

Thus, the mortar of the invention has a suitable setting time and a low viscosity.

The following components are used in the amounts provided in the table below.

The rheology, compressive strength and setting time of the concrete compositions are measured. All tests are carried out at <NUM>.

The results are provided in the table below:.

Claim 1:
Concrete composition comprising:
- a hydraulic binder, wherein the hydraulic binder comprises Portland clinker and mineral addition selected from the group consisting of limestone, fly ash or combination thereof, the limestone and/or fly ash representing at least <NUM>% by weight of the total weight of the binder;
- a cationic polymer having a cationic charge density greater than <NUM> meq/g, preferably greater than <NUM> meq/g, and an intrinsic viscosity less than <NUM> dl/g;
- a water-reducing additive comprising at least one phosphonic amino-alkylene group;
- aggregates, and
- water.