EP2560929A1

EP2560929A1 - Rapid hydraulic binder for concrete parts and structures

Info

Publication number: EP2560929A1
Application number: EP11731429A
Authority: EP
Inventors: Serge Sabio; Xiaolin Pardal; Christine Chaumilliat
Original assignee: Lafarge SA
Current assignee: Lafarge SA
Priority date: 2010-04-20
Filing date: 2011-04-19
Publication date: 2013-02-27
Also published as: FR2958931B1; FR2958931A1; CA2796176A1; WO2011131904A1; US20130035423A1

Abstract

The present invention relates to a rapid hydraulic binder comprising cement; a setting and hardening accelerator comprising hydrated calcium silicate seeds, a first superplasticizer and a second superplasticizer different from the first superplasticizer and having a maximum fluidizing action at 20°C after the maximum fluidizing action at 20°C of the first superplasticizer.

Description

RAPID HYDRAULIC BINDER FOR CONCRETE PARTS AND WORKS

The invention relates to fast hydraulic binder compositions used for the manufacture of concrete parts and structures.

By the term "rapid hydraulic binders" for mortar or concrete is meant according to the present invention hydraulic binders rapid setting and hardening. Concretes comprising such binders in their compositions, once used, acquire important mechanical characteristics in the short term. They preferably have a compressive strength Rc of at least 1 MPa at 4 hours for the fluid concretes and at least about 1 MPa at 5 hours for the self-compacting concretes (or self-compacting). In addition, they have a compressive strength Rc of at least 12 MPa at 24 hours. In addition, the workability time for fluid or self-compacting concretes (or self-compacting), is preferably from one hour thirty minutes minimum to two hours maximum.

The workability of the fluid concretes is measured by the height of subsidence at the Abrams cone -or slump- value (according to the French standard NF P 18-451, of December 1981) and it is estimated that a concrete is fluid when this sag is at least 150 mm, preferably at least 180 mm.

The workability of self-compacting (or self-compacting) concretes is usually measured from slumpflow, or spreading, according to the procedure described in the document entitled "Specification and Guidelines for Concrete Compacting Concrete, EFNARC, February 2002, p. 23 "; the value of the spread is greater than 650 mm for self-compacting concretes (and in general less than 800 mm).

Workability is the length of time that fresh concrete can be used satisfactorily. This is in practice the time during which the slump or spread is greater than a given threshold.

The invention relates to concretes, and more particularly to fluid or self-compacting concretes (or self-compacting), intended for the production of parts and works, for example prefabricated parts in the factory, or realizations on building sites, especially walls. concrete, slabs, etc.

Patent application EP 1 893 548 filed in the name of Lafarge and Chryso discloses a rapid hydraulic binder comprising cement, a superplasticizer, calcium nitrite and a formic derivative. The formic derivative may be in the aldehyde form and corresponds, for example, to formaldehyde.

Although such a rapid hydraulic binder can be used for producing a fluid concrete or self-compacting (or self-compacting), it has the disadvantage to use a formic derivative, which, at least in the case of formaldehyde, is a toxic compound.

There is therefore a need for a method of manufacturing concrete parts and structures having a long workability, leading to a rapid acquisition of short-term mechanical strength even at temperatures below 10 ° C, and thus allowing increase the rate of reuse of the formwork, the concrete using a fast hydraulic binder not including toxic form derivative.

For this purpose, the present invention provides a hydraulic binder comprising:

from 99.5 to 90%, preferably from 99 to 95% by weight of cement relative to the weight of the hydraulic binder;

from 0.5 to 10%, preferably from 1 to 5% by weight relative to the weight of the hydraulic binder of all the following components:

a setting and hardening accelerating agent comprising hydrated calcium silicate seeds;

a first superplasticizer; and

a second superplasticizer different from the first superplasticizer and having a maximum fluidizing action at 20 ° C subsequent to the maximum fluidizing action at 20 ° C of the first superplasticizer.

The invention offers advantages, since it allows the manufacture of a fluid concrete or self-compacting (self-compacting) using a hydraulic binder not comprising toxic form derivative.

In particular, advantageously, the present invention enables the manufacture of easy-to-use concrete compositions. These compositions have a suitable rheology, preferably involving a workability time (after mixing) of a minimum hour and a maximum of two hours and a very fast curing phase.

Advantageously, the present invention allows the manufacture of a fluid concrete, in particular a fluid concrete having a slump of at least 15 cm, preferably at least 18 cm, at 90 minutes.

Advantageously, the present invention allows the manufacture of a self-compacting concrete, especially a self-compacting concrete having a spread greater than 650 mm at 90 minutes.

The invention has the advantage that it can be used in the building industry, the chemical industry (adjuvants), the construction industry, the cement industry or the construction markets (building, civil engineering or construction industry). prefabrication). In particular, the rapid hydraulic binder according to the invention can be used for the production and / or repair of road pavement. In addition, the rapid hydraulic binder according to the invention can be used for the accelerated dismantling of concrete parts, in particular for the realization of walls using rapid stripping and for the production of prefabricated beams.

The invention also relates to a hydraulic binder accelerator mixture comprising cement, the mixture comprising a setting and hardening accelerating agent comprising hydrated calcium silicate seeds; a first superplasticizer; and a second superplasticizer different from the first superplasticizer and having a maximum fluidizing action at 20 ° C subsequent to the maximum fluidizing action at 20 ° C of the first superplasticizer.

The invention also relates to a concrete or mortar comprising a rapid hydraulic binder according to the invention mixed with water.

By the term "hydraulic binder" is meant according to the present invention a powdery material which, when mixed with water, forms a paste which sets and hardens as a result of hydration reactions, and which after curing retains its resistance and stability even under water. The hydraulic binder can be a cement according to EN 197-1.

Other advantages and characteristics of the invention will become clear from reading the description and examples given by way of purely illustrative and nonlimiting that will follow.

By the term "hydraulic composition" is meant according to the present invention a mixture of a hydraulic binder, with mixing water, optionally aggregates, optionally adjuvants, and optionally mineral additions. A hydraulic composition can for example be a high performance concrete, a very high performance concrete, a self-leveling concrete, a self-leveling concrete, a self-compacting concrete, a fiber concrete, a ready-mixed concrete or a concrete colored. By the term "concrete" is also meant concrete having undergone a finishing operation, for example bush-hammered concrete, deactivated or washed concrete, or polished concrete. This definition also includes prestressed concrete. The term "concrete" includes mortars; in this case the concrete comprises a mixture of a hydraulic binder, sand, water, optionally adjuvants and possibly mineral additions. The term "concrete" according to the invention denotes indistinctly fresh concrete or hardened concrete. Preferably, the hydraulic composition according to the invention is a cement slurry, a mortar or a concrete. The hydraulic composition according to the invention can be used directly on site in the fresh state and poured into a formwork adapted to the intended application, or else in prefabrication, or as a coating on a solid support.

By the term "setting" is meant according to the present invention the transition to the solid state of a hydraulic binder by chemical reaction of hydration. The setting is usually followed by the hardening phase.

By the term "hardening" is meant according to the present invention the increase of the mechanical strengths of a hydraulic binder, after the end of the setting phase.

By the term "aggregates" is meant according to the present invention gravel, chippings and / or sand.

By the term "mineral additions" is meant according to the present invention a finely divided mineral material used in concrete in order to improve certain properties or to bring it particular properties. These are, for example, fly ash (as defined in the EN 450 standard), silica fumes (as defined in the standard prEN 13263: 1998 or NF P 18-502), slag (such as defined in standard NF P 18-506), calcareous additions (as defined in standard NF P 18-508) and siliceous additions (as defined in standard NF P 18-509).

By the term "Portland cement" is meant according to the present invention a CEM I type cement, CEM II, CEM III, CEM IV or CEM V according to the standard "Cement" NF EN 197-1.

According to the present invention, the term "setting and hardening accelerating agent" is understood to mean an adjuvant which reduces the duration which precedes the beginning of the setting of a hydraulic binder and accelerates the acquisition of mechanical strengths of the hydraulic binder, in particular the resistance to compression.

By the term "plasticizer / water reducer" is meant according to the present invention an adjuvant which, without modifying the consistency, makes it possible to reduce the water content of a given concrete, or which, without modifying the water content , increases the slump / spread of concrete, or produces both effects at the same time. The EN 934-2 standard specifies that the water reduction must be greater than 5%. The water reducers may, for example, be based on lignosulfonic acids, hydroxycarboxylic acids or treated carbohydrates.

By the expression "superplasticizer" or "superfluidifier" or "super-water reducer" is meant according to the present invention a water reducer which makes it possible to reduce by more than 12% the quantity of water necessary for the production of water. a concrete. A superplasticizer has a fluidizing action since, for the same quantity of water, the working time of the concrete is increased in the presence of the superplasticizer.

The expression "superplasticizer with immediate effectiveness" is understood to mean, according to the present invention, a superplasticizer whose maximum fluidizing action at 20 ° C. is generally obtained in the first fifteen minutes following the initial contact of the superplasticizer with the hydraulic binder for dosages. conventional.

By the term "superplasticizer with delayed efficiency" is meant according to the present invention a superplasticizer whose fluidizing action increases over time at least on part of the window of workability desired of the hydraulic composition. The maximum fluidizing action at 20 ° C of the superplasticizer is then obtained at least more than fifteen minutes after the initial contact of the superplasticizer with the hydraulic binder. The fluidizing action of the immediate-acting superplasticizer and the delayed-efficiency superplasticizer is measured by a spreading and / or settling measurement, for example according to EN 12350-2 "Tests for fresh concrete - Part 2: Test of 'slump'. The fluidizing action of the superplasticizer is maximal when the measured spreading / settling of the hydraulic composition comprising only this superplasticizer is maximal.

The increase in the fluidizing action of the superplasticizer can be obtained by increasing the capacity of the superplasticizer to be adsorbed by the mineral components (especially the cement grains) of the hydraulic composition. For this purpose, one possibility is to increase the density of anionic charges of the superplasticizer. An increase in the charge density of the superplasticizer can be obtained by two different phenomena that can occur simultaneously:

the increase in the number of charges borne by the polymer; and

the reduction of the molecular weight of the polymer.

The reduction of the molecular weight of the superplasticizer can be achieved by choosing a superplasticizer comprising a main chain and pendant chains (at least three) connected to the main chain and which can separate from the main chain when the superplasticizer is in the hydraulic composition.

The separation of pendant chains and / or the increase of the number of charges carried by the superplasticizer can be obtained by choosing a superplasticizer comprising hydrolysable chemical functions which, under the effect of hydroxide ions (OH ^" ) in the hydraulic composition, can transform to provide COO carboxylate functions ^" . Hydrolysable chemical functions are, for example, anhydrides, esters and amides. A hydrolyzable polymer is a polymer comprising hydrolysable chemical functions under the conditions of basicity and in the workability window of the hydraulic composition.

Accelerating agent for setting and hardening

According to an exemplary embodiment, the setting and hardening accelerating agent comprises, in addition to hydrated calcium silicate seeds, another component also having a setting acceleration and hardening action.

According to an exemplary embodiment, the setting accelerator and hardening agent further comprises a calcium salt.

According to an exemplary embodiment, the calcium salt is calcium nitrite.

According to another embodiment, the calcium salt is calcium nitrate or a mixture of calcium nitrite and calcium nitrate. Preferably, the calcium salt is water soluble. Preferably, the calcium salt is not a calcium carbonate.

The weight ratio between the hydrated calcium silicate seeds and the calcium salt may vary from 2% to 98%, preferably from 10% to 50%.

The setting and hardening accelerating agent, comprising hydrated calcium silicate seeds and optionally the calcium salt, is present in the composition of the accelerator mixture in amounts which may vary from 25 to 90% by dry weight relative to dry accelerator mixture, preferably from 50 to 90%. In general, the amount of setting and hardening accelerating agent, including hydrated calcium silicate seeds and optionally calcium salt, in the final hydraulic binder can range from 0.1% to 9%, preferably from 0.2% to 5%, more preferably 0.2% to 2% by weight of dry extract relative to the dry hydraulic binder.

According to an exemplary embodiment, the rapid hydraulic binder does not include formaldehyde. It may optionally include a non-toxic formic derivative such as calcium formate. According to an exemplary embodiment, the rapid hydraulic binder does not include a formic derivative.

Superplasticizer with immediate effectiveness or first superplasticizer

The first superplasticizer can be any immediate-use superplasticizer conventionally used in industry, for example those defined in the European standard EN 934-2. Examples of the first superplasticizer are polyox polyphosphonate or polysulfonate polyox type superplasticizers or polyalkylene oxide polycarboxylate type (also known as PCP). An example of a first superplasticizer is that described in EP-A-537872, US20030127026 and US20040149174.

An example of a first superplasticizer corresponds to a copolymer comprising a unit of formula (I)

and a unit of formula (II)

R9

O

R10

where R1, R2, R3, R6, R7 and R8, which may be identical or different, are a hydrogen atom, a linear or branched alkyl radical having from 1 to 20 carbon atoms, or an aromatic radical, or a -COOR1 radical 1 with R 1 1 representing a hydrogen atom, a linear or branched alkyl radical having from 1 to 4 carbon atoms, a monovalent, divalent or trivalent cation or an ammonium group;

R10 is a hydrogen atom, a linear or branched alkyl radical having 1 to 20 carbon atoms, or an aromatic radical; R4 and R9, which may be identical or different, are a linear or branched alkyl radical having from 2 to 20 carbon atoms;

R 5 is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms or an anionic or cationic group, for example a phosphonate group, a sulfonate group, a carboxylate group, etc. ;

W is an oxygen or nitrogen atom or an NH radical;

m and t, which are identical or different, are integers ranging from 0 to 2;

n and u, identical or different, are integers equal to 0 or 1; q is an integer equal to 0 or 1;

r and v, which are identical or different, are integers ranging from 0 to

500;

and the molar mass of said copolymer ranges from 10,000 to 400,000 daltons. Preferably, the radical R 1 or R 6 is a hydrogen atom. Preferably, the radical R2 or R7 is a hydrogen atom. Preferably, the radical R3 or R8 is a methyl radical or hydrogen. Preferably, the radical R4 or R9 is an ethyl radical.

Preferably, the copolymer used according to the invention or a salt thereof has an integer from 1 to 300, preferably from 20 to 250, more preferably from 40 to 200, even more preferably from 40 to 150.

The first superplasticizer may correspond to a salt of the copolymer defined above.

The copolymer may comprise several different units according to formula (I) having, in particular, different radicals R5.

An example of a first superplasticizer is that obtained by polymerization: of an ionic monomer of phosphonic, sulfonic or carboxylic type, preferably carboxylic and advantageously of (meth) acrylic type; and

a monomer of the polyoxyalkyleneglycol (meth) acrylate type (having from 1 to 4 carbon atoms), for example of the polyethylene glycol (PEG) (meth) acrylate type, the molecular weight of which is, for example, from 100 to 10000, preferably from 500 to 7500 and advantageously from 750 to 5000.

The first monomer / second monomer molar ratio can vary widely, for example 90/10 to 45/55, preferably 80/20 to 55/45.

It is possible to use one or more monomer (s), for example those chosen from: (a) acrylamide type, for example N, N-dimethylacrylamide, 2,2'-dimethylamino (meth) acrylate or its salts, 2,2'-dimethylaminoalkyl (meth) acrylate or its salts with the alkyl group and in particular ethyl and propyl, and generally any monomer comprising an amine or amide type function;

(b) hydrophobic type, for example alkyl (meth) acrylate having from 1 to 18 carbon atoms, in particular methyl or ethyl.

The amount of this third monomer may vary from 5 to 25 mol% of the total monomers.

The first superplasticizer is preferably in liquid, solid or waxy form.

The dosage of the first superplasticizer relative to the hydraulic binder generally varies from 0.1 to 5% by weight (percentage calculated from the solids content of the first superplasticizer), preferably from 0.1 to 2% by weight relative to to the mass of the hydraulic binder. When the first superplasticizer is liquid, the amount of the first plasticizer is preferably 1 to 10, preferably 2 to 7 liter per cubic meter of fresh concrete.

The first superplasticizer can be a mixture of immediate-use superplasticizers, a mixture of at least one immediate-acting superplasticizer and a plasticizer, for example a lignosulfonate, or a mixture of at least one immediate-acting superplasticizer. and a gluconate molecule.

Delayed Superplasticizer or Second Superplasticizer

The second superplasticizer is a superplasticizer whose fluidizing action increases at least temporarily over time in the conditions of basicity and in the window of workability of the hydraulic composition. Preferably, the second superplasticizer has no initial fluidifying action, that is to say that the initial slump / spreading of the hydraulic composition (within 5 minutes after the mixing of the components of the hydraulic composition) does not vary irrespective of the concentration of the delayed-release superplasticizer.

According to an exemplary embodiment of the present invention, the density of adsorption sites of the second superplasticizer increases in the workability window of the hydraulic composition.

According to an exemplary embodiment of the present invention, the anionicity of the second superplasticizer increases in the hydraulic composition in the workability window. The second superplasticizer may comprise a hydrolyzable polymer under the conditions of basicity and in the workability window of the hydraulic composition. The hydraulic composition obtained during the manufacture of a concrete according to the invention having a basic pH, hydrolysis reactions occur which cause a modification of the structure of the hydrolyzable polymer and a modification of the properties of the hydrolysable polymer, in particular an increase in the fluidizing action of the hydrolyzable polymer. According to an exemplary embodiment, the hydrolysable polymer is of the polycarboxylate type of polyalkylene oxide.

Examples of delayed efficiency superplasticizers are described in EP 1 136 508, WO 2007/047407 and US 2009/0312460.

An example of a second superplasticizer is a copolymer comprising at least one unit according to formula (I) and at least one unit according to formula (II).

The second superplasticizer may be a mixture of delayed-release superplasticizers.

The second superplasticizer may comprise a monomer selected from acrylamide and its derivatives, acrylonitrile and its derivatives, alkyl acrylates, hydroxyalkyl acrylates, polyethylene glycol acrylates, carboxylic anhydrides which can be copolymerized and imides can be copolymerized.

According to an exemplary embodiment, the second superplasticizer corresponds to a copolymer comprising at least one unit according to formula (I) as defined above:

and at least one unit of formula (III)

where R6, R7, R10 and W are as previously defined.

According to an exemplary embodiment of the present invention, the ratio between the number of units of formula (III) and the total number of units of the superplasticizer with delayed action is sufficient to cause an increase in the fluidizing action of the superplasticizer in the at least a part of the desired workability window of the hydraulic composition so that the maximum fluidizing action at 20 ° C of the superplasticizer is generally obtained at least more than fifteen minutes after the initial contact of the superplasticizer with the hydraulic binder .

According to an exemplary embodiment of the present invention, R 3 is hydrogen, n is 1, m is 0 and q is 1. In this case, the delayed-effectiveness superplasticizer may comprise a single unit of formula (III).

According to an exemplary embodiment of the present invention, R3 is an alkyl radical having 1 carbon atom, n is 1, m is 0 and q is equal to 1. In this case, when the number r of the units of formula (I) is greater than 100, the delayed-acting superplasticizer comprises more than 80% of units of formula (III) relative to the total number of units of the deferred superplasticizer. Preferably, when the number r of the units of formula (I) varies from 50 to 100, the delayed-acting superplasticizer comprises more than 70% of units of formula (III) relative to the total number of units of the superplasticizer acting delayed. Preferably, when the number r of the units of formula (I) is less than 50, the delayed-acting superplasticizer comprises more than 50% of units of formula (III) relative to the total number of units of the delayed-acting superplasticizer. .

According to an embodiment of the present invention, R3 is hydrogen, n is 0, m is 1, q is 1, and W is an oxygen atom. In this case, when the number r of the units of formula (I) is greater than 100, the delayed-acting superplasticizer comprises more than 80% of units of formula (III) relative to the total number of units of the superplasticizer acting delayed. Preferably, when the number r of the units of formula (I) varies from 50 to 100, the delayed-acting superplasticizer comprises more than 70% of units of formula (III) relative to the total number of units of the superplasticizer acting delayed. Preferably, when the number r of the units of formula (I) is less than 50, the delayed-acting superplasticizer comprises more than 50% of units of formula (III) relative to the total number of units of the delayed-acting superplasticizer.

The second superplasticizer is present in the composition of the accelerator mixture in amounts which can vary from 1 to 5% by weight, percentages calculated from the dry extracts of the constituents of the accelerator mixture. With respect to the mass of the final hydraulic binder, the amount of the second superplasticizer can vary from 0.01 to 1%, preferably from 0.05 to 0.5% by weight (percentage calculated from the dry extract of the second superplasticizer) relative to the mass of the hydraulic binder. The amount of the second superplasticizer in dry extract relative to the setting and setting accelerating agent may vary from 1 to 10% relative to the amount of setting and setting accelerating agent.

Hydraulic binder and composition

The fast hydraulic binder intended for a hydraulic composition generally comprises, with respect to the mass of the dry hydraulic binder:

99.5 to 90% by weight of Portland cement; and

0.5 to 10% by weight of the accelerator mixture.

Advantageously, the rapid hydraulic binder comprises:

99 to 95% by weight of Portland cement; and

- 1 to 5% by weight of the accelerator mixture.

Portland cement is typical and conforms to the cement families described in European Standard EN 197-1. CEMI 52.5 N or R, CEM2 cements of type 32.5, 32.5 R, 42.5 or 42.5 R can be used. The cement may be of the type HRI (High Initial Strength).

Advantageously, the Portland cement is a cement, preferably ground to a fineness of at least 3000 cm ² / g, preferably at least 3500 cm ² / g.

The soluble alkali content is preferably less than 1%, advantageously less than 0.4% by weight, expressed as Na ₂ equivalent. Advantageously, the amount of C4AF is less than 8% by weight, advantageously less than 4%. , and the amount of C3S clinker is greater than 60% by weight.

The final amount of the accelerator mixture depends on the use temperature of the hydraulic composition, the exact method of use of the hydraulic composition, the level of resistance to be obtained, etc. Moreover, this quantity is adjusted according to the final quantities of the various components in the final mixture of the hydraulic composition. The hydraulic composition may, in addition to the accelerator mixture, comprise other types of additives typically used in concrete.

Examples of additives that can be used are air entraining, defoamers, corrosion inhibitors, shrinkage reducing agents, fibers, pigments, rheology modifiers, precursors of hydration, pumpability assistants, alkali reducing agents, reinforcing agents, water-repellent compounds and mixtures thereof.

In the case where the hydraulic composition is a concrete, the concrete compounds can be used in the following order:

according to a first embodiment, all of the components of the accelerator mixture are added from the start, during the mixing of the concrete, in the concrete plant; the cement and the complete accelerator mixture are tempered, namely the setting and hardening accelerating agent, the first superplasticizer and the second superplasticizer. Mixing in the concrete batching plant can be done in a stationary mixer or in a truck mixer when it is used as a mixer. The invention also relates to the process in which all the components are introduced during the mixing of the fast binder with the aggregates and the water.

according to a second embodiment, the setting and setting accelerating agent, comprising the hydrated calcium silicate seeds and optionally a calcium salt, is added at a later time relative to the other components of the accelerator mixture, for example in the spinning truck, before the start of the concrete batching plant, or during the central / construction site trip, or on the site just before casting. The invention also relates to the process in which the setting and hardening accelerating agent is introduced after kneading the other components of the fast hydraulic binder with the aggregates and the water.

According to the second embodiment, the times chosen for this delayed introduction can be from 10 to 90 minutes, preferably 20 to 60 minutes after the mixing of the other components of the accelerator mixture, the first superplasticizer and / or the second superplasticizer. The invention also relates to the process in which the setting and hardening accelerating agent is introduced from 10 to 90 minutes, preferably from 20 to 60 minutes after the mixing of the other components of the fast hydraulic binder with the aggregates and the water. The first embodiment is preferred because the various constituents (cement, components of the accelerator mixture) can then all be added and metered precisely in a single stage at the concrete plant.

In general, the mass ratio of effective water / dry binder (E / C ratio) generally varies from 0.3 to 0.65.

The final composition comprises conventional aggregates (sands, gravel and / or pebbles). Preferably, the constituents of the final composition have a size less than or equal to 20 mm, preferably less than or equal to 10 mm in the case of self-compacting concretes (or self-compacting). The composition can thus be pumped easily.

The dry weight ratio of aggregates / hydraulic binder generally varies from 4 to

5.

The concrete compositions according to the invention are easy to use and their cost is low. They have a suitable rheology, preferably involving a working time (after mixing) of a minimum hour and an hour and a half to two hours maximum and a very fast curing phase. The workability time of these concretes according to the invention generally varies from 1 hour 30 to 2 hours. Workability duration means the fluidity maintenance time, which corresponds to the duration that precedes the start of setting; in general the slump values (fluid concrete) are at least 15 cm, preferably at least 18 cm.

The concrete according to the invention may be a fluid concrete, especially a fluid concrete having a slump at 90 minutes of at least 15 cm, preferably at least 18 cm. It can have a compressive strength of at least 1 MPa, preferably at least 2 MPa, 4 hours after the end of mixing and at least 12 MPa at 24 hours, measured on cylindrical specimens of dimension 16 cm x 32 cm.

The concrete according to the invention may also be a self-compacting concrete, especially a self-compacting concrete having a spread greater than 650 mm at 90 minutes. It can have a compressive strength of the order of at least 1 MPa, preferably at least 2 MPa, at 5 h from the end of mixing, and at least 12 MPa at 24 h, measured on specimens cylindrical of dimension 16 cm x 32 cm.

When the mixing is carried out in a spin truck, the time is counted from the moment when the last component of the concrete composition is introduced into the truck-router.

These two properties, sufficient duration of workability and strong short-term strengths, make it possible to produce a precursor concrete composition in a central unit. concrete and then transported to a construction site by truck-router, the composition hardening quickly once poured. These qualities of the binder also make it possible to pump it mechanically thanks to its fluidity and to flow it or pump it into a formwork by obtaining a fast hardening phase. It is therefore possible to dismantle and then reinstall the formwork quickly, in order to proceed to a new pouring of the concrete.

The fast binder for fluid or self-compacting concretes (autocompactants) according to the invention is easy to pump or to cast, in particular without vibration in the case of self-compacting concretes, which makes it, for example, particularly suitable for the manufacture of concrete walls.

The invention relates particularly to the manufacture of concrete walls, by pouring and / or pumping. The invention is useful for the manufacture of concrete walls at outside temperatures varying in particular from 5 ° C to 30 ° C, in particular below 10 ° C. A concrete wall can be defined in masonry as "any vertical wall and solid concrete banché".

Furthermore, the invention also provides a method of manufacture, including concrete walls, by double stripping daily at temperatures less than or equal to 10 ° C, in particular using the accelerator mixture according to the invention. The invention provides such a method that allows to cast two concrete walls in a day, even at low temperatures. The compositions according to the invention having rapid setting properties even at low temperature make it possible to perform this double stripping. It is therefore possible to break with the traditional approach, and perform double-stripping, even at low temperatures.

Examples illustrate the invention without limiting its scope.

EXAMPLES

The present invention is illustrated by the following non-limiting examples. In the examples, the products and materials used were available from the following suppliers:

Product or material Supplier

(1) Lafarge Portland cement - Saint Pierre La Cour or Lafarge - Le Havre

(2) Sand 0/4 mm Mauzac, France

(3) OMYA limestone filler

BETOCARB HP Orgon (4) Glenium Adjuvant 27 BASF

(5) Glenium SKY537 Adjuvant BASF

(6) BASF X-Seed Adjuvant

(7) Rheotec Z60 BASF admixture

(8) Chrysoxel Time Chryso Adjuvant

(9) BASF SPAH8 Adjuvant

The product X-Seed was a solution comprising 20% of dry extract comprising in particular hydrated calcium silicates (CSH).

Glenium 27 and Glenium SKY537 products were immediate-acting superplasticizers.

Rhéotec Z60 was a delayed acting superplasticizer.

Formulation of a mortar equivalent to a concrete

The following concrete formulation (1) was considered:

Table 1: Formulation (1) of concrete

According to the theory of equivalent concrete mortars described in the article titled "The Concrete Equivalent Mortar (MBE) Method - A New Tool for Formulating Adjuvant Concretes" in the names of A. Schwarzentruber and C. Catherine and published in the journal Materials and Structures Volume 33 / Number 8, October 2000, it is possible to use a mortar having characteristics of rheology and resistance representative of what would be obtained with the concrete according to the formulation (1).

The mortar according to the following formulation (2) was equivalent to the concrete according to the formulation (1). Table 2: Mortar formulation (2)

Cement was the cement produced by Lafarge from the site of Le Havre or Saint Pierre La Cour. This cement was of the CEM I 52.5 type according to the EN 197-1 standard.

Mortar preparation protocol

• Put the sands in a mixing bowl;

• At T = 0: start mixing at low speed (140 rpm) and simultaneously add the wetting water in 30 seconds, then continue mixing at low speed (140 rpm) for up to 60 seconds;

• At T = 60 seconds: stop mixing and let stand for 4 minutes;

• At T = 5 minutes (T = 0 for the rheology maintenance test): add the Portland clinker and knead at low speed (140 rpm) for

1 minute ;

• At T = 6 minutes: add the mixing water (+ optional adjuvants) in 30 seconds (while mixing at low speed (140 rpm);

• At T = 6 minutes and 30 seconds: knead at high speed (280 rpm) for 1 minute;

• At T = 7 minutes and 30 seconds: stop mixing.

Span measurement protocol

The principle of the spreading measurement consisted in filling a reference cone frustum with the composition to be tested and then in releasing said frustoconical composition in order to determine the surface of the disc obtained when the composition finished spreading. The reference cone frustum was a ½ scale reproduction of the cone as defined by NF P 18-451, 1981. The reference cone frustum had the following dimensions:

-diameter of the circle of the upper base of the trunk of: 50 +/- 0.5 mm;

-diameter of the circle of the lower base: 100 +/- 0.5 mm; and height: 150 +/- 0.5 mm.

The protocol for measuring the spreading was as follows:

• Fill the reference cone trunk in one step with the mortar to be tested;

• Spread the mortar homogeneously in the truncated cone;

• Shave the upper surface of the truncated cone;

• lift the truncated cone vertically;

Measure at the highest point the sag at +/- 1 mm and / or measure the spread at four diameters at 45 ° with calipers. The result of the spread measurement is the average of the four values at

+/- 1 mm.

Method of measuring the compressive strength

The compressive strength was measured on a parallelepipedal sample having a length of 16 cm, a width of 4 cm and a height of 4 cm according to the EN 196-1 standard regardless of the expiry of the measurement.

For mortars made according to the formulation (2), the target spread was greater than 200 mm for at least 90 minutes and the target compressive strength was greater than or equal to about 1 MPa after 4 hours after the end of the mixing. For concretes made according to the formulation (1), the targeted spreading was greater than 500 mm for at least 90 minutes and the target compressive strength was greater than or equal to about 1 MPa after 4 hours after the end of the mixing. EXAMPLE 1

One liter of mortar according to formulation (2) at 20 ° C was prepared. The cement produced by Lafarge at the Le Havre site was used. The X-Seed solution has been used as a setting and hardening accelerator. The first superplasticizer, noted SP, was Glenium 27. The second superplasticizer, noted PH, was Rhéotec Z60. Compression and compression (RC) measurements were made at 20 ° C by varying the concentration of the X-Seed setting and curing accelerator. The concentrations were expressed as a percentage by mass of dry extract relative to the mass of cement. The results of these tests are collated in the following Table 3: Table 3

The present invention has made it possible to obtain a workability time of the mortar greater than 1 hour 30 without causing a delay for the acquisition of resistance at young ages. A workability of 1 h 30 was obtained while maintaining the speed of acquisition of resistance to young ages. One explanation is that the first superplasticizer plays a more important role in the delayed acquisition of resistance at younger ages than the second superplasticizer. As a result, since the present invention has made it possible to reduce the concentration of the first superplasticizer, the speed of acquisition of resistance at young ages has been maintained or even improved compared to a mortar comprising only the first superplasticizer in greater concentration. In addition, a working time of the mortar greater than 1 h 30 could be obtained through the fluidizing action of the second superplasticizer which has increased over time.

EXAMPLE 2

One liter of mortar according to formulation (2) was prepared at 20 ° C. The cement produced by Lafarge at the Le Havre site was used. A mixture of the X-Seed product and a solution of calcium nitrite was used as a setting and hardening accelerator. The calcium nitrite solution was an aqueous solution comprising 30% solids calcium nitrite Ca (NO ₂ ) 2

The superplasticizer SP was Glenium 27. The superplasticizer PH was Rhéotec Z60. Spread and compressive strength measurements were made at 20 ° C by varying the concentration of the X-Seed setting and curing accelerator and the calcium nitrite solution. The concentrations were expressed as a percentage by weight of dry extract relative to the mass of cement binder. The results of these tests are collated in the following Table 4: Table 4

A workability of the mortar greater than 1 h 30 was obtained without delaying the acquisition of resistance to young ages. A duration of workability of 1 h30 was thus obtained while maintaining the speed of acquisition of resistance to young ages.

EXAMPLE 3

One liter of mortar according to formulation (2) was prepared at 20 ° C. The cement produced by Lafarge at the site of Saint Pierre La Cour was used. X-Seed has been used as a setting and hardening accelerator. The concentration of X-Seed was 0.8% expressed as a percentage by weight of dry extract relative to the amount of cement. The SP superplasticizer was Glenium SKY537. The concentration of Glenium SKY537 was 0.25% expressed as a percentage by weight of dry extract relative to the quantity of cement. The superplasticizer PH was Rhéotec Z60. The concentration of Rhéotec Z60 was 0.20% expressed as a percentage by weight of dry extract relative to the quantity of cement. Spread and compressive strength measurements were made at 20 ° C. The results of these tests are summarized in Table 5 below:

Table 5

X-Seed SP PH Placement (mm) RC (MPa) (% in (% in (% in

mass mass mass 5 15 30 60 90

4 h 6 hrs 24 h extract extract extract min min min min min

dry) dry)

0.8 0.25 0.20 270 260 290 310 270 0.86 5.3 35.2 A workability of the mortar greater than 1 h 30 was obtained without delaying the acquisition of resistance to young ages. A duration of workability of 1 h30 was thus obtained while maintaining the speed of acquisition of resistance to young ages.

EXAMPLE 4

One liter of mortar according to formulation (2) was prepared at 20 ° C. The cement produced by Lafarge at the site of Saint Pierre La Cour was used. A mixture of the X-Seed product and the calcium nitrite solution described above was used as a setting and hardening accelerator. The concentration of X-Seed was 0.8% expressed as a percentage by weight of dry extract relative to the amount of cement. The concentration of calcium nitrite solution was 1.5% expressed as a percentage by weight of dry extract relative to the amount of cement.

The superplasticizer SP was Glenium 27. The concentration of Glenium 27 was 0.25% expressed as a percentage by weight of dry extract relative to the amount of cement. The superplasticizer PH was Rhéotec Z60. The concentration of Rhéotec Z60 was 0.20% expressed as a percentage by weight of dry extract relative to the quantity of cement. Spread and compressive strength measurements were made at 20 ° C. The results of these tests are collated in the following table 6:

Table 6

EXAMPLE 5 A concrete according to the formulation (1) at 20 ° C was prepared. The cement produced by Lafarge at the Le Havre site was used. X-Seed has been used as a setting and hardening accelerator. The concentration of X-Seed was 0.8% expressed as a percentage by weight of dry extract relative to the amount of cement. The superplasticizer SP was Glenium 27. The concentration of Glenium 27 was 0.15% expressed as a percentage by weight of dry extract relative to the quantity of cement. The superplasticizer PH was Rhéotec Z60. The concentration of Rhéotec Z60 was 0.20% expressed as a percentage by weight of dry extract relative to the quantity of cement.

Spread and compressive strength measurements were made at 20 ° C. The results of these tests are collated in the following Table 7:

Table 7

EXAMPLE 6

A concrete according to the formulation (1) at 20 ° C was prepared. The cement produced by

Lafarge at the site of Saint Pierre La Cour was used. X-Seed has been used as a setting and hardening accelerator. The concentration of X-Seed was 1%, expressed as a percentage by mass of dry extract relative to the quantity of cement. The SP superplasticizer was Glenium SKY537. The concentration of Glenium SKY537 was 0.15% expressed as a percentage by weight of dry extract relative to the quantity of cement. The superplasticizer PH was Rhéotec Z60. The concentration of Rhéotec Z60 was 0.20% expressed as a percentage by weight of dry extract relative to the quantity of cement.

Spread and compressive strength measurements were made at 20 ° C. The results of these tests are summarized in Table 8 below: Table 8

The examples described above have shown that, all other conditions being equal, the hydraulic binder according to the invention has made it possible to manufacture a concrete having a long workability time and resulting in rapid acquisition of short-term mechanical strengths independently of the source of cement supply.

Claims

1. Fast hydraulic binder comprising:

a first superplasticizer; and

Hydraulic binder according to claim 1, characterized in that the setting and hardening accelerating agent further comprises a calcium salt.

Hydraulic binder according to claim 2, wherein the calcium salt is calcium nitrite.

4. Hydraulic binder according to any one of claims 1 to 3, characterized in that it does not include formaldehyde.

5. hydraulic binder according to claim 4, characterized in that it comprises no formic derivative.

Hydraulic binder according to any one of claims 1 to 5, wherein the second superplasticizer comprises a hydrolyzable polymer.

Hydraulic binder according to Claim 6, in which the second superplasticizer comprises a monomer chosen from acrylamide and its derivatives, acrylonitrile and its derivatives, alkyl acrylates, hydroxyalkyl acrylates and polyethylene glycol acrylates. , copolymerizable carboxylic anhydrides and copolymerizable imides.

8. Hydraulic binder according to any one of claims 1 to 7, wherein the second superplasticizer is polyalkylene oxide polycarboxylate type.

9. hydraulic binder according to any one of claims 1 to 8, comprising, relative to the mass of the hydraulic binder:

from 0.1% to 9% of the setting and hardening accelerating agent;

from 0.1 to 5% by mass of solids content of the first superplasticizer; and from 0.01 to 1% by mass of dry extract of the second superplasticizer.

Hydraulic binder according to any one of claims 1 to 8, wherein the amount of setting and hardening accelerating agent in the hydraulic binder is from 0.2% to 5% by mass of dry extract relative to to the mass of the hydraulic binder.

1 1. Hydraulic binder according to any one of claims 1 to 10, wherein the amount of dry extract of the second superplasticizer relative to the setting and hardening accelerating agent, is 1 to 10% of the amount of the accelerator agent setting and hardening.

12. Accelerator mixture for hydraulic binder, the hydraulic binder comprising cement, the mixture comprising a setting accelerator and hardening agent comprising hydrated calcium silicate seeds; a first superplasticizer; and a second superplasticizer different from the first superplasticizer and having a maximum fluidizing action at 20 ° C subsequent to the maximum fluidizing action at 20 ° C of the first superplasticizer.

13. Concrete comprising a hydraulic binder according to one of claims 1 1 1 tempered with water.