BE1020896A3 - ACCELERATOR FOR TAKING AND CURING HYDRAULIC BINDERS AND CEMENTITIOUS COMPOSITION COMPRISING SAID ACCELERATOR - Google Patents

Description

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ACCELERATOR FOR TAKING AND CURING HYDRAULIC BINDERS AND CEMENTITIOUS COMPOSITION COMPRISING SAID ACCELERATOR

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The subject of the present invention is a hydraulic binder setting and curing accelerator, the cementitious compositions containing said hydraulic binder setting and curing accelerator, and their uses, in particular in sprayed concretes or sealing mortars and mortars. rigging.

Shotcrete is a product transported at great speed by compressed air through a pipe and projected onto a surface or support to which it must adhere. The shotcrete compositions make it possible to apply a layer of hydraulic binder on supports which have a slope, arches or overhangs. By way of example, mention may be made in particular of the entirety of the walls of underground tunnels or tunnels. These compositions must be sufficiently fluid to be pumpable, but also sufficiently firm to adhere to the wall on which they are projected without flowing along it.

In addition to these constraints, those skilled in the art must also take into account other factors, such as the temperature of the medium, which may vary depending on the location and the time of implementation of the shotcrete. The temperature of the medium strongly influences the concrete resistances in the short and long term. If the medium is too cold the concrete will not show satisfactory mechanical resistance in the short term. If the medium is too hot the long-term mechanical strength will be lower than what can normally be expected.

Sealing and setting mortars make it possible to fix anchor bars in highly stressed concrete structures, thanks to very high resistance to tearing. They can be used whatever the building site configuration (ceiling, wall and floor). They are generally in the form of ready-to-use "premix" (mixture of binders, sands and admixtures) and are used after mixing with water either manually or mechanically (by pumping). Unlike sealing mortars , the setting mortars are fluid, they ensure an easy filling of the cavities, as for the setting of heavy machines or with strong vibrations (turbines, machine tools, centrifuges ...) by creating a homogeneous support, uniform and resistant.

In these applications (sealing or wedging), resistance to young age is essential to meet the short time required by this type of work. It can be obtained by using as a binder a Class R Portland cement (fast curing); but often very high mechanical strengths in the short term are required, and they can be obtained only by the use of special aluminous or sulfoaluminous cements. These special binders also offer the advantage, when judiciously formulated, to lead to obtaining reduced or even compensated withdrawal, property sought in this type of application.

In addition, the temperature of the surrounding medium also influences the short-term and long-term mechanical strengths of the sealant and cushioning mortar compositions.

The skilled person must have a composition that can remain fluid and manipulable over a longer or shorter period, but evolving to a firmer consistency or setting quickly from the moment it is implemented. This last constraint can be satisfied by adding a setting accelerator and hardening to the composition. As setting and hardening accelerators known to those skilled in the art, mention will in particular be made of nitrate salts, chlorine salts, alkanolamines, formaldehyde, thiocyanates, colloidal silica suspensions, alkaline aluminates.

However, these accelerators of setting or hardening can alter the mechanical characteristics of resistance in the long term, and especially do not make it possible to obtain in the very short term (3 hours) sufficiently high mechanical strengths, especially at low temperature, such as temperatures below 10 ° C, or even of the order of 5 ° C.

The use of aluminous and sulfo-aluminous cements or clinkers as setting and hardening accelerators is also known to those skilled in the art.

However, the implementation of setting or hardening accelerators such as aluminous and sulfoaluminous cements or clinkers is delicate. Indeed, any modification or dosage error in the combination of this type of accelerator with a hydraulic binder (Portland cement) may, depending on the temperature of the medium, inhibit or accelerate the hydration reactions of this binder, making it difficult to mastered the mechanical performance of the hydraulic binder / accelerator assembly.

Overall, these setting and hardening accelerators are known for their actions at ordinary temperatures (about 20 ° C), but they are not necessarily suitable for use in more "extreme" temperature conditions.

There is a need for those skilled in the art wishing to use hydraulic binder compositions at high or low temperatures (from + 5 ° C to + 35 ° C), and wishing to obtain satisfactory short and long term strengths. (greater than 0.4 MPa, at 3 hours, and greater than 30 MPa, at 28 days), to have a setting and hardening accelerator that does not jeopardize the integrity of the structure in the long term.

An object of the present invention is therefore to provide a setting accelerator and hardening of hydraulic binders overcoming the aforementioned drawbacks.

Another object of the present invention is to provide a setting and hardening accelerator for cementitious compositions suitable for the implementation of sealing mortars, setting mortars, or cast concrete, and more particularly adapted for the implementation. at low or high temperatures, requiring high short-term compressive strength (Rc) while maintaining good long-term mechanical compressive strength (Rc).

The present invention makes it possible to meet these various objectives by means of an accelerator for setting and hardening hydraulic binders comprising the following mass proportions: from 25 to 35% of at least one sulphoaluminous clinker, from 45 to 55% of at least one source of sulphates having a solubility of greater than 4 g.L'1 in water at 20 ° C, and - from 10 to 20% of at least one source of sulphates having a solubility of less than 4 g.L 1 in water at 20 ° C, said clinker containing calcium aluminate mineralogical compounds.

In the present invention the solubilities are considered in pure water at a temperature of 20 ° C.

The mineralogical phases are indicated by their usual name followed by their cement notation. The primary compounds are represented in the cement notation by: C for CaO, S for SiO 2, A for Al 2 O 3, for SO 3 H for H 2 O; this notation is used throughout this text.

In the context of the present invention, the accelerator for setting and curing hydraulic binders is intended to be added to a hydraulic binder to form a cementitious composition.

"Hydraulic binder" means a hydraulic binder as defined in EN 197-1, and in particular the definition in paragraph 4: "finely ground mineral material which, when mixed with water, forms a paste which hardens and hardens as a result of reactions and processes of hydration and which, after hardening, retains its resistance and stability even under water. "

By "finely ground" means a Blaine fineness of about 2500 to 5000 cm2 / g.

"Calcium aluminate mineralogical compounds" means any mineralogical phase resulting from the combination of alumina (of chemical formula AI2O3, or "A" in cement notation), and of calcium oxide (of chemical formula CaO, or "C" in cement notation) with other mineral species such as sulphates (of chemical formula S03, or in cement notation), iron oxide (of chemical formula Fe203, or "F" in cement notation) or fluorine.

The sulfoaluminous clinker may be mixed with aluminous clinker, sulfobelitic clinker, and / or fluoroaluminous clinker.

By "sulfoalumineux" is meant any material resulting from the firing at a temperature between 900 ° C and 1350 ° C of mixtures containing at least one source of lime, at least one source of alumina and at least one source of sulfates. The sulfoaluminous clinker which can be part of the accelerator for setting and hardening of hydraulic binders according to the present invention contains a content of Yeelimite (chemical formula 4Ca0.3Al203.S03 or C4A3 $ in cement notation) greater than 30% by weight, preferably between 50 and 70% by weight. The content of Belite (of chemical formula 2Ca0.SiO 2 or C2S in cement notation) of said sulfoaluminous clinker is advantageously such that the weight ratio Yeelimite by Belite is greater than or equal to 1.5.

By "sulfobelitic" is meant any material resulting from the firing at a temperature between 900 ° C and 1350 ° C of mixtures containing at least one source of lime, at least one source of alumina and at least one source of sulfates. The sulfobelitic clinker which can be part of the accelerator for setting and curing hydraulic binders according to the present invention contains a content of Yeelimite (of chemical formula 4Ca0.3Al203.S03 or C4A3 $ in cement notation) greater than 30% by weight, preferably between 50 and 60% by weight. The Belite content of said sulfobelitic clinker is advantageously greater than 20% by weight, such that the Yeelimite by Belite mass ratio is less than 1.5.

By "fluoroalumineux" is meant the product resulting from the high temperature firing (generally 1250-1350 ° C) of a Portland cru containing fluorine CaF2 in an amount such that the resulting clinker contains at least 15% of calcium fluoroaluminate. CnA7CaF2.

The Blaine fineness of these sulfoaluminous, sulfobelitic or fluoroaluminous clinkers is about 2500 to 5000 cm 2 / g.

Advantageously, said calcium aluminate mineralogical compounds contained in said clinker are selected from Yeelimite (C4A3 $), Mayenite (C12A7), calcium monoaluminate (CA), tetracalcium aluminoferrite (C4AF), tricalcium aluminate (C3A), or a combination of several of these compounds, preferably a combination of eliimite and one or more other calcium aluminate mineralogical compounds.

Advantageously, the total mass of said mineralogical compounds of calcium aluminate type contained in the clinker represents more than 30% by weight of the total mass of the clinker, in particular more than 50% by weight, that is to say that the clinker according to the present invention contains aluminate-type mineralogical phases and that the sum of these phases represents, advantageously, at least half of the mass of the clinker.

Preferably, a mineralogical compound of calcium aluminate type is predominantly present in all said calcium aluminate-type mineral compounds contained in the clinker, and represents more than 30% by weight of the total weight of the clinker, in particular more than 50% by weight. Very preferably, this majority aluminate type mineral phase is Yeelimite (C4A3 $).

By "sulphate source" is meant a substance at the origin of the dissolution of sulphate ions. The most obvious sulphate sources are sulphate salts, plaster, sludge or other sulphate-rich industrial by-products (eg phosphogypsum, titanogypsum). The sulphate sources can be used as a mixture. These products are rarely available in industrial quantities with high purity, their cost would be prohibitive. It is therefore appropriate to consider mixtures of products that may possibly contain impurities. In this case, those skilled in the art will adapt the amounts of the sulphate sources by reasoning on the desired number of moles of sulphate (expressed in SO 3 - 3 in cement notation).

In the present invention, the solubility of a sulphate source is likened to the solubility of the sulphate ions it contains. In other words, to determine the solubility of a source of non-pure sulphates, the solubility of the main species of sulphate ions composing this source is considered.

It has surprisingly been found that the presence of these two sulphate sources is essential to obtain the desired resistance performances for the cementitious compositions.

More particularly, it has been found that both types of sulfate sources appear to have an important role at different stages of hydrate formation.

The presence of at least one source of sulphates having a solubility of greater than 4 g / L ensures the formation of ettringite which contributes to the development of short-term material resistances. Ettringite is formed from the aluminate phases from both the hydraulic binder and the clinker.

The presence of at least one source of sulphates having a solubility greater than 4g.L'1 makes it possible to ensure that the waste water contains sufficient available sulphate ions to form all the possible ettringite as a function of the phases. in the presence.

The objective is to ensure that there is no formation of hydrated calcium monosulfoaluminate (AFm or C3AC $ H12 in cement notation). In fact, a deficiency of sulphates causes the formation of hydrated calcium monosulfoaluminate by decomposition of ettringite. This hydrated calcium monosulfoaluminate, very unstable, does not control the strength of the cement matrix. In addition, exposure to a source of sulfates in solution in water after the curing step would cause a so-called "delayed" ettringite formation reaction from the hydrated calcium monosulfoaluminate. Delayed ettringite formation is accompanied by swelling and can cause expansion, scaling, and even structural explosions.

The presence of at least one source of sulphates having a solubility of less than 4g.l'1 makes it possible to ensure a prolonged release of sulphates within the cement matrix throughout the maturation. In particular, it makes it possible to ensure that the hydration reactions that take place over the long term do not modify the species formed rapidly at the beginning of the setting (for example, a conversion of ettringite to hydrated calcium monosulfoaluminate).

Typically, calcium sulphates, especially gypsum or anhydrite, are added to the Portland clinker during its manufacture to form a hydraulic binder. For example, these additions of gypsum, at a level of 3 to 8% (as a percentage by weight, addition of pure gypsum) are carried out in order to regulate the setting and in particular to avoid the phenomena of setting "flash" of Portland cement.

During the tests, it was found that the sulphate source milled with the Portland clinker alone does not solve the problem of obtaining sufficient mechanical resistance in the short and long term over a wide range of temperatures (see more far the comparative examples).

Advantageously, said at least one source of sulphates having a solubility of less than 4 g.L'1 is chosen from gypsum (CaSO4.2H2O), anhydrite (CaSO4), or a mixture thereof. As an indication the solubility of the gypsum is 2.4 g.L'1, and that of the anhydrite 2.1 g.L'1, in pure water, at 20 ° C.

It is possible that the clinker contains calcium sulphates having a solubility of less than 4g.L'1 (residual sulphates), these residual sulphates at concentrations always less than 10%, and very often less than 5% by mass, come from cooking the vintage cement. This residual calcium sulphate content is not sufficient for the implementation of the present invention. Regardless of the residual sulphate content, it is necessary to add another sulphate source having a solubility of less than 4 g / l.

Advantageously, said at least one source of sulphates having a solubility greater than 4 g.L'1 is chosen from aluminum sulphate dodéca to octadéca hydrate (Al2 (SO4) 3, 12 to 18 H20), iron tetra sulfate at hydrated hepta (Fe (SO 4), 4 to 7 H 2 O), plaster (CaSO 4 · H 2 O), or a mixture thereof. As an indication, the solubility of the iron sulfate 7.H 2 O is 300 μl -1, the solubility of the aluminum sulfate 14-16.H 2 O is 364 g.l -1, and that of the hemihydrate ( plaster) is 8.5 g.L'1, in pure water, at 20 ° C.

The characteristic distinguishing the two sulphate sources is actually the kinetics of dissolution. But this characteristic is difficult to determine a priori because it depends on multiple parameters. In fact, it must be determined experimentally for each sulphate considered according to numerous conditions such as: the temperature, the salinity of the medium (nature and concentration of the ions present), the pH, etc. Other characteristics such as The fineness of grinding of the sulphate source, and its degree of crystallization, also have a significant influence on the kinetics of dissolution. In practice, it is easier to consider the solubility of species in water at a given temperature. These characteristics are well known to those skilled in the art (CRC Handbook of Chemistry and Physics (92nd edition), William M. Haynes, Editions: CRC Press / Taylor and Francis).

It has been observed that solubility makes it possible to estimate the kinetics of dissolution of a species without resorting to long experiments. Estimation errors are possible, but this criterion has the advantage of being simple to implement and to allow a first selection that can be completed by accurate dissolution kinetics tests if necessary.

The present invention can be implemented with a combination of several clinkers. However, for reasons of simplicity of implementation, it is preferred to carry out the present invention with a single clinker (sulfoaluminous clinker) containing calcium aluminate mineralogical compounds. Very preferably, said accelerator for setting and curing hydraulic binders thus contains only one clinker.

Very preferably, said accelerator for setting and curing hydraulic binders comprises a single source of sulphates having a solubility greater than 4 g.L -1.

Very preferably, said accelerator for setting and curing hydraulic binders comprises a single source of sulphates having a solubility of less than 4 g · L -1.

According to a preferred embodiment of the invention, said accelerator for setting and curing hydraulic binders comprises a single clinker (sulphoaluminous clinker), a single source of sulphates having a solubility greater than 4 g.L'1, and a single sulphate source having a solubility of less than 4 g.

It is obvious to those skilled in the art that the simplest embodiment of the present invention is the combination of three sources each corresponding to the clinker and the two sulphates respectively in order to obtain the ternary mixture of the setting accelerator and hardening of hydraulic binders according to the invention. Nevertheless more complex embodiments with one, two, or three compound sources, i.e. made of a mixture, are also possible to implement the present invention.

The present invention differs from the compositions that may exist in the prior art by "over-sulphating" of the cementitious composition. Regardless of the amount of sulphates having a solubility of less than 4 grams per liter contained in the hydraulic binder to which the accelerator for setting and curing hydraulic binders is added, the present invention includes an additional addition of sulphates having solubility. less than 4 g.L1.

Thus, the cementitious composition that is the subject of the invention can in no way correspond to the simple mixture of a hydraulic binder (for example Portland cement) with a clinker (a sulphoaluminous clinker) and a source of sulphates having a solubility of greater than 4 g. 1 (eg aluminum sulphate), even though the hydraulic binder or clinker would contain significant quantities of sulphate source having a solubility of less than 4 g.

More specifically, the accelerator for setting and curing hydraulic binders is characterized by a proportion greater than 5% of said source of sulphates having a solubility of less than 4 g.L'1, said quantity of 5% not taking into account the mass of the source of sulphates having a solubility of less than 4 g.L'1 may possibly be contained in said clinker, and may come from the cooking cement vintage.

The calcium sulphate contents of hydraulic binders and clinkers are product-specific information and are provided by the producers. In the absence of such data or doubt as to the exact content, these values can be determined, for example, by X-ray diffraction analysis with phase quantification by the Rietveld method.

In particular, said accelerator for setting and curing hydraulic binders is characterized by a proportion greater than 5% of said source of sulphates having a solubility of less than 4 g.l -1, irrespective of the mass of the sulphate source. having a solubility of less than 4 g.L'1 being able to be contained in said hydraulic binder.

Advantageously, in a particular hydraulic binder setting and curing accelerator of the present invention, the molar ratio between said source of sulfates having a solubility of less than 4 g.L -1, and said calcium aluminate mineralogical compounds. is between 0.3 and 55, preferably between 0.4 and 12.

Advantageously also, in a particular accelerator for setting and curing hydraulic binders, the molar ratio between said source of sulphates having a solubility of greater than 4 g.l -1, and said calcium aluminate-type mineralogical compounds, is included between 0.15 and 27, preferably between 0.3 and 10.

The tests carried out have shown that the abovementioned molar ratios between: - on the one hand, sulphate sources having a solubility of less than 4 g.L'1, including those present in the clinker, and the content of mineralogical compounds of type calcium aluminates present in the clinker, and - secondly, sulphate sources having a solubility greater than 4 g.L'1, and the content of mineralogical compounds of calcium aluminate type present in the clinker, make it possible to to obtain high mechanical resistance in the short and long term over a wide range of temperatures ranging from + 5 ° C to + 35 ° C.

It is important to note that these molar ratios concern the accelerator for setting and hardening of hydraulic binders and not the cementitious composition containing said accelerator. In other words, the amount of sulphate sources having a solubility of less than or greater than 4 g / l, which are optionally present in the hydraulic binder, has no influence on the aforementioned molar ratios.

Advantageously, the molar ratio between said source of sulphates having a solubility of less than 4 g.L'1 and said mineralogical compounds of calcium aluminate type is between 1.5 and 12.

Preferably, the molar ratio between said source of sulphates having a solubility greater than 4 g.L'1 and said mineralogical compounds of calcium aluminate type is between 1.8 and 8.

Very preferably, the accelerator for setting and hardening hydraulic binders according to the present invention is characterized in that -ledit clinker, is a sulphoaluminous clinker containing more than 30% by mass of Yeelimite, preferably 50% to 70% by mass of Yeelimite and the said source of sulphates having a solubility of greater than 4 g is aluminum sulphate, and the said source of sulphates having a solubility of less than 4 g is gypsum or anhydrite .

The present invention also relates to a cementitious composition containing a hydraulic binder, an accelerator setting and curing as described above, and optionally water.

The cementitious composition, according to the present invention, is also capable of containing, in addition to the accelerator for setting and hardening of hydraulic binders, and the hydraulic binder: fillers, additions, additives, additions or a combination of those this. The present invention uses the term "hydraulic binder", but it is obvious to those skilled in the art that a combination of different known binders, for example two different Portland-type cements, can perform the same function without substantially modifying the characteristics. of the present invention.

By "wire" is meant a finely ground mineral material of which 85% of the elements have a diameter less than 80 .mu.m. Fillers are used to optimize compactness by filling voids.

By "addition" is meant a finely ground mineral material having or not a pozzolanic effect. The term "pozzolanic effect" here means a contribution to the development of mechanical strengths. The additions are generally finely ground and have a diameter of less than 400 μm, in particular less than 150 μm. The additions can be milled separately from the hydraulic binders or cobbled with them.

Among the fillers and additions having a pozzolanic effect, mention may be made of: blast furnace slags, fly ash and silica fumes. Among the fillers and additions having no pozzolanic effect, mention may be made of: calcareous fillers and siliceous fillers.

"Adjuvant" means a substance within the meaning of EN 206.1, and in particular the definition of paragraph 3.1.22: a product added to the concrete during the mixing process, in small quantities in relation to the mass of cement, to modify the properties of fresh or hardened concrete.

By "addition" is meant substances or materials which may be added to the cementitious composition, but which are not additives, fillers or adjuvants as described herein. By way of an example of addition, mention may be made of: fibers used to reinforce the structure (metallic, organic, mineral), oxides conferring photo catalytic properties (TiO 2), heavy particles making it possible to isolate radiation (particles of ores, particularly iron), the electrically conductive particles for shielding constructions against electromagnetic radiation by providing Faraday cages (such as graphite), thermal conductive particles (metals), phase-change particles ( PCM: "phase change materials") for storing heat energy in a structure, or light particles improving thermal and acoustic insulation (organic particles such as polystyrene or minerals such as vermiculite, perlite, silico-aluminates or melted and blown glasses).

Preferably, said hydraulic binder is a Portland type binder selected from CEM I, II, III, IV or V, preferably CEM I, more particularly CEM I PM ES. "PM ES" denotes a binder having a low content of tricalcium aluminate (C3A), especially at most 5%, in accordance with NF P 15-317 and NF P 15-319.

Preferably, the total amount of SO.sub.3, from said source of sulphates having a solubility of less than 4 g.L'1, contained in said cementitious composition, is strictly greater than 5% of the total mass of said cementitious composition.

In this preferred embodiment, the cementitious composition according to the present invention contains more source of sulphates having a solubility of less than 4 g.l -1, which is possible to obtain by the use of a sulphated hydraulic binder. to the maximum of the possibilities of the norm. The standard EN 197-1 (paragraph 9.2.3) imposes a maximum quantity of S03 varying from 4 to 5% (in mass) according to the type of cement.

In a particular embodiment of the present invention, the mass ratio between said setting and hardening accelerator and said hydraulic binder is from 0.1 to 0.2; preferably from 0.14 to 0.18, more preferably from 0.15 to 0.17.

If this mass ratio is less than 0.1, it is likely that resistances developed in the short term, and under low temperature conditions, are not sufficient.

If this mass ratio is greater than 0.2, it is likely that the resistances developed in the long term, and under conditions of high temperatures, are not sufficient.

Preferably, the mass ratio between said setting accelerator and curing hydraulic binders and said hydraulic binder is about 0.16.

Advantageously, the cementitious composition defined above is used in a temperature range of between 5 ° and 35 ° C.

In a particular embodiment, said cementitious composition according to the invention contains, in addition to said accelerator for setting and curing hydraulic binders and said hydraulic binder, one or more adjuvants, in particular superplasticizers, set retarders; still more particularly one or more adjuvants chosen from plasticizers, other setting accelerators than that of the present invention (for example nitrates, thiocyanates and / or chlorides), other accelerators of hardening than that of the the present invention (especially alkaline carbonates), air entraining agents (especially sodium lauryl sulphates), anti-shrinkage agents, anti-bubbling or antifoaming agents, waterproofing agents (for example calcium stearate), -sedimentation (in particular bentonites, atapulgites), inorganic or organic colored pigments, latices (in particular styrene-butadiene copolymers or vinyl acetate-vinyl versatate or vinyl acetate-acrylic monomer), and rheology modifiers (in particular modified polysaccharides or not, preferably diutane gums, xanthan gums, gelanic gums, welan gums, and especially retent water, preferentially starch ethers, cellulose ethers).

Advantageously, said cementitious composition contains, in addition to said setting and hardening accelerator and said hydraulic binder, a superplasticizing admixture, in particular a polycarboxylate.

Advantageously, said cementitious composition contains, in addition to said setting and hardening accelerator and said hydraulic binder, a setting retarding adjuvant, in particular a polycarboxylic acid, preferably tartaric acid or citric acid. Paradoxically, retarding additives may be of interest in the context of the present invention, particularly in the context of the implementation of wet sprayed concretes. Indeed, this type of implementation requires a precise control of the setting time in order to avoid any setting of the binder mixture in the pumping and projection devices.

The present invention also relates to the use of the above cementitious compositions containing said accelerator for setting and curing hydraulic binders in a concrete, in particular a shotcrete, a mortar, in particular a sealing mortar or setting mortar, a coating , a grout or a cement paste.

By "grout" or "cement paste" is meant the addition of water to the cementitious composition according to the present invention. The distinction between these two names is related to the mass ratio between water and cement, if the ratio is less than 0.35 the mixture is called cement paste, if the ratio is greater than 0.35 the mixture is called grout .

"Coating" means a grout or a cement paste, to which are added very fine aggregates, that is to say with a diameter of between 150 pm and 1 mm (for example fillers).

By "mortar" is meant a grout or a cement paste, to which fine aggregates are added, that is to say aggregates whose diameter is between 150 μm and 4 mm (for example sand), and possibly very fine aggregates.

By "concrete" is meant a mortar to which are added coarse aggregates, that is to say aggregates whose diameter is greater than 4 mm.

Usually concretes, mortars, coatings, grouts and cement pastes are added.

Shotcrete and its applications are the subject of the standard NF P 95-102.

Sealing mortars are defined by standard NF EN 1504-6.

The setting mortars are defined by standard NF P 18-821.

Advantageously, the present invention relates to the use of a cementitious composition as defined above, mixed with fine aggregates, coarse aggregates with a maximum diameter of less than 12 mm, optionally very fine aggregates, water, and possibly adjuvants, to obtain a shotcrete.

By "sand" is meant a mixture of aggregates consisting of very fine aggregates, or fine aggregates, or a combination of fine and fine aggregates.

A distinction is made between setting accelerators and hardening accelerators. The setting accelerators act on a delay ('stiffening' time of the material), whereas the hardening accelerators act on the mechanical strengths. As a result, the setting accelerators do not necessarily make it possible to obtain high resistance in the short term. In the context of the present invention, it is necessary to have both characteristics (setting and hardening) to achieve this effect.

Preferably, the use of the cementitious composition as defined above is characterized in that said shotcrete has a setting time of less than 5 minutes, especially less than 1 minute, preferably a setting time almost instantaneous.

The setting time of the shotcrete produced by the cementitious composition according to the present invention is almost instantaneous after addition of water, which is why the use of shotcrete according to the present invention is preferably done by the dry route. It is also possible to implement the invention in the context of wet shotcrete, but this involves the addition of a setting retarder (eg citric acid or tartaric acid).

The dry way and the wet way differ essentially by the moment when the water is added. Dry spray is also distinguished by the absence of mixing itself. The previously homogenized dry mixture is fed into a pipe (by compressed air) to a lance at the end of which water is added. The water flow is adjustable to adjust the water content of the projected material. Pre-humidification of the order of 5% (by mass) can be added upstream to avoid the disadvantages due to dust emissions during the projection.

Advantageously, the present invention relates to the use of a cementitious composition as defined above, mixed with fine aggregates, water, optionally very fine aggregates, and optionally adjuvants, to obtain a sealing mortar or rigging.

The distinction between sealing mortar and setting mortar is tenuous and lies in the consistency of the material obtained. The setting mortar is characterized by a consistency much more fluid than that of the mortar; this higher fluidity can be obtained by increasing the water / fuel ratio. The consistency of the mortars is determined according to standard NF EN 1015-3. If the spreading at the jig table is greater than 200 mm, then the mortar is qualified fluid (Standard NF EN 1015-6 Table 1). A setting mortar has a spread greater than 200 mm. In contrast, a sealing mortar has a spread of less than or equal to 200 mm.

By way of example, a setting mortar having a setting time of between about 1 and 4 hours can be prepared from a cementitious composition containing from 0.1 to 1% by weight of a setting-retarding adjuvant. according to the invention.

By way of example also, a sealing mortar having a setting time of between approximately 1 and 2 hours may be prepared from a cementitious composition containing from 0.1 to 1% by weight of a retarding adjuvant of taken according to the invention.

Among the many applications of sealing mortars, we can mention: - the sealing of columns, beams, acroteria - the sealing of doors, windows and finishing elements - the sealing of street furniture, signaling elements - the sealing of manholes on high traffic roads with recirculation almost immediate.

The use of a retarding agent is necessary in this type of application (wedging and sealing) in order to be able to set up the cementitious composition before it is set.

Advantageously, the use of the cementitious composition according to the invention is carried out in a temperature range of between about 5 ° C. and 35 ° C.

The present invention also relates to a concrete or a mortar containing the cementitious composition defined above, and used at temperatures ranging from + 5 ° C to + 35 ° C, characterized in that it has a mechanical compressive strength to 3 hours greater than 0.4 MPa, in particular 1 MPa, preferably 2 MPa, and a compressive strength at 28 days greater than 30 MPa ,.

The advantageous value of 0.4 MPa is used in the context of the present invention to signify that the product has already exceeded the end of setting and that it has reached a sufficient level of hardening or sufficient structuring thus avoiding flows on the floor. The product is no longer "workable" on its support.

I - Materials and methods

standards

The definition of Portland clinker is taught by the European standard EN 197-1.

The controls of the mechanical properties of the cements were carried out according to the European standard EN 196 paragraphs there 7.

1-Materials used 1.1 Aggregates

Two mixtures of 0 / 8mm aggregates from SOCLI were used; they are both screened and present four fractions or granulometric slices mentioned in Table 1 (in mass%):

Table 1 1.2 Cement / Clinker Portland Cement

CEM I 52.5 N PM ES HRC cements (low C3A content, NF P 15.317 and NF P 15.319 standards) from the Beaucaire (Calcia), Gaurain (Calcia) and St Vigor (Lafarge) plants were used. Their composition is presented in Table 2 (in mass%).

Table 2

Sulfo-aluminous Clinker

A sulfoaluminous clinker marketed under the name Alipre (Italcementi, Guardiaregia, Italy) was used in all the examples below, except in Example 9. This clinker contains about 60% by weight of Yeelimite (calcium sulfoaluminate: C4A3 $).

An experimental sulphoaluminous clinker containing about 30% of Yeelimite was also used only in Example 9. This clinker was prepared in the laboratory by high temperature baking of a raw material composed in particular of limestone, clay, bauxite and gypsum which are mixtures of different oxides, in particular CaO, SiO 2 Al 2 O 3, Fe 3 O 2 and SO 3. The art of composing a vintage according to the desired clinker mineralogy is well known to those skilled in the art (Special Inorganic Cernent, Ivan Older, 2000, CRC Press). The main mineralogical phases of these two sulphoaluminous clinkers are presented in Table 3 (in mass%).

Table 3 1.3 Adjuvant

Accelerator setting and curing according to the present invention.

The curing and hardening accelerator formulation comprises aluminum sulphate (Al 2 (SO 4) 3 to 16 H 2 O) (Metausel), micronized natural anhydrite (calcium sulphate, Anhydrite Mosellan Company), and Alipar sulfo-aluminous clinker.

Take Accelerator according to the prior art

A powder setting accelerator for dry sprayed concrete marketed by SIKA was used (Sigunit 49AF).

superplasticizer

The superplasticizer used is Melflux 2651 F (BASF). It is a superplasticizer of the family of polycarboxylates in the form of powder.

2- Method 2.1 Proportions of constituents Aggregates

Several assays in sand and aggregates were tested: 698, 713, 722, 726 kg of sands and aggregates per ton of dry formulation.

Portland cement: Several cement dosages were used: 240, 250, 260 kg of cement per tonne of dry formulation.

Accelerator: The accelerator / cement ratios indicated in the formulations are mass ratios.

Superplasticizer: Some formulations contain a superplasticizer. Unless specifically indicated, these formulations are dosed at 0.9% by mass of superplasticizer relative to the cement.

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Water: Two water dosages were used: E / C = 0.45 and 0.385 (Water / Portland Cement Weight Ratio) These dosages correspond respectively to Water / Total powder ratios = 0.12 and 0.10. Total powder refers to all of the solid constituents of the cementitious composition, that is to say the Portland-type cement, sulfo-aluminous clinker, sulphate sources and aggregates (sand and gravel).

2.2 Implementation

The tests were implemented according to the following protocol:

Prepare 1.8 kg of a mixture including all components of the curing accelerator, Portland cement and aggregates and / or sands.

Introduce this mixture in a mixing bowl of 3 liters, mix for 1 minute at low speed (140 rpm with epicyclic train (or planetary) operating the mixing blade 1 turn / second) to ensure good homogeneity of the mixture.

Cover the mixing bowl with a waterproof plastic cover, then keep this set for 24 hours in the desired climatic environment (temperature, humidity).

Spray exactly 1.8 kg of the mixture with water at the desired temperature, mix for 20 seconds at 280 rpm with planetary gear set of 2 revolutions / second (High Speed).

The mechanical strength tests must then be carried out without delay because the setting takes place very quickly.

2.3 Chemical and mineralogical analyzes

The analyzes of the different chemical compositions, in particular the different determinations of the S03 value of the sulphate sources, were carried out by X-ray fluorescence spectrometry (Magix spectrometer, Panalytical).

The mineralogical analyzes relating to the different phases of the clinkers constituting this hydraulic binder or cement were carried out by X-ray diffraction (XRD), with a quantification of the mineralogical phases by the Rietveld method (XPERT PRO, Panalytical, EVA and TOPAS software).

2.4 Mechanical characterizations

The tests for mechanical resistance to bending and compression according to EN 196-1, and density in the cured state were carried out on mortar specimens (dimensions: 4 cm x 4 cm x 16 cm), different temperatures: - specimens are made at 5 ° C and stored in air at 5 ° C, at 90% RH (relative humidity).

- Specimens are made at 20 ° C and stored in air at 20 ° C, under 75% H.R.

- Specimens are made at 35 ° C and stored in air at 35 ° C, under 90% H.R.

Il - Results

The composition of the hardening accelerator according to the present invention is expressed as a weight percentage of the three constituents: sulfo-alumina clinker, a source of sulphates having a solubility of greater than 4 g.L'1 (aluminum sulphate), and a source of sulphates having a solubility of less than 4 g.L'1 (micronised natural anhydrite).

The quantities of Portland cements and aggregates are expressed in kg per tonne of fresh concrete.

The indicated temperature is the temperature at which the samples were prepared and the measurements made.

The compressive strengths (Rc) are expressed in MPa at 3 hours, 7 days and 28 days after the beginning of mixing. The start of mixing corresponds to the moment of contact between the water and the powder previously mixed dry.

EXAMPLES

The formulations presented in Examples 1 to 9 (Tables 2 to 10) gave "functional" samples (4 x 4 x 16 specimens), that is to say having compressive strengths greater than 0.4 MPa. at 3 hours and above 30 MPa at 28 days for application temperatures ranging from + 5 ° C to + 35 ° C.

Nevertheless, the samples containing a weight percentage of sulphoaluminous clinker between 25 and 35% of the setting and hardening accelerator according to the invention exhibit mechanical compressive strengths (Rc) at 3 hours at 5 ° C. minus 1.46 MPa.

The sulfoaluminous clinker contains about 60% Yeelimite C4A3 and about 3% C% (% by weight).

Example 1: Different proportions of sulfo-aluminous clinker / aluminum sulphate

Table 4

The accelerator compositions used in formulations 1 (comparative), 2, 3 and 11 (comparative) (Table 4) have a constant content of micronized anhydrite (20%), but vary in sulphoaluminous clinker content (between 25 and 65%). %) and therefore in aluminum sulphate (between 15 and 55%).

These four formulas make it possible to see that at low temperature (5 ° C.) an increase in the proportion of sulfoaluminous clinker in the composition of the accelerator is unfavorable to the mechanical strength at 3 hours. On the other hand, the mechanical strength at 3 hours and at 5 ° C. is improved with an increase in the content of aluminum sulphate in the composition of the accelerator.

Example 2: Different Sources of Granulates and Portland Cement

The accelerator used in formulations 3, 4 and 5 (Table 5) has a constant composition; it comprises 35% of sulfoaluminous clinker, 45% of aluminum sulphate, and 20% of micronized anhydrite (percentages by weight).

These formulations were tested to evaluate on the one hand the influence of the origin of the origin of the aggregates (formulations 3 and 4), and on the other hand the influence of the origin of the origin of the cement (formulations 4 and 5) on mechanical performance. It can be observed that the effect of the accelerator used in these three formulations is not modified by the change in the origin of the cement or aggregates.

Example 3: Variation of the aluminum sulphate content

Table 6

Formulations 7 (comparative) and 10 (Table 6) have a mass ratio of sulfo-aluminous clinker to sulfo-aluminous clinker and constant anhydrite (0.73). These two formulations differ in the content of aluminum sulphate in the composition of the accelerator.

It can be seen that an increase in the amount of aluminum sulphate improves the mechanical strength at 3 hours but is unfavorable for longer-term performances (7 days and 28 days).

Example 4: Different proportions Aluminous sulpho clinker / aluminum sulphate

The accelerator compositions used in Formulations 8 (Comparative) and 10 (Table 7) have a close C $ / C4A3 ratio (about 2.3), but are distinguished by their very different A $ 3 / C4A3 ratios.

It can be seen that a high ratio A $ 3 / C4A3 $ favors short-term mechanical strengths and disadvantages long-term mechanical strengths (especially at high temperature). These observations correspond to those taken from Example 1.

Example 5: Presence of a superplasticizer (Melflux 2651 F)

Table 8

All these formulations yielded functional samples (4x4 x 16 specimens), i.e., with compressive strengths greater than 0.4 MPa, at 3 hours; and greater than 30 MPa, at 28 days, for processing temperatures ranging from + 5 ° C to + 35 ° C.

Formulations 12 (comparative), 13 and 14 (Table 8) are respectively of the same composition as formulations 1 (comparative), 2 and 3 (Table 2), with in addition a superplasticizer dosed at 0.9% by weight relative to to cement.

It is generally observed that the presence of the superplasticizer improves the mechanical performance of concretes, in particular those measured at 7 days and 28 days.

Example 6: Concrete projected realization on site in a gallery

Table 9

Table 9 shows the characteristics of cast concrete, according to the present invention, made on samples of 3 tons of concrete used with granules of Cormeilles (formulation 17) and Wasselonne (formulation 18). In both Gaurain cement formulations (CEM I 52.5 N PM ES "HRC") was used. The tests took place in a gallery at 14 ° C. and 95% relative humidity.

The superplasticizer (Melflux 2651F) is dosed at 0.5% relative to the cement (mass ratio). The E / C ratio is 0.38. The sum of the mass of the accelerator according to the present invention and the mass of the superplasticizer, represents 4.3% of the total mass of the concrete obtained (dry).

Resistance measurements were performed on cubic specimens (10 x 10 x 10 cm). The 24 hour measurement for formulation 18 is an average of two results.

Example 7 (comparative)

The formulations presented in Table 10 are so-called "non-functional" formulations, that is to say that they do not make it possible to obtain the desired resistances (compressive strengths greater than 0.4 MPa, at 3 hours and greater than 30 MPa, at 28 days, for operating temperatures ranging from + 5 ° C. to + 35 ° C.) in the context of the present invention.

Three formulations were carried out in order to demonstrate that the source of sulphates having a solubility of less than 4 g / l present in Portland cement (Table 2) is not sufficient to allow an acceleration of the hardening and setting (formulations without addition of anhydrite).

A last formulation (22) makes it possible to compare the accelerator according to the present invention with an accelerator of the prior art, Sigunit 49 AF (Sika).

Table 10

Formulation 19 (Comparative) The accelerator used in formulation 19 comprises 30% sulfo-aluminous clinker, 70% aluminum sulfate, and no micronized anhydrite (percentages by weight).

Formulation 19 uses Portland cement from Beaucaire.

It is observed that the resistance values at 28 days are half of those expected. This formulation is considered "non-functional" because the mechanical strengths obtained at 5 ° C or 35 ° C are less than 30 MPa.

Formulation 20 (Comparative) The accelerator used in formulation 20 comprises 30% sulfo-aluminous clinker, 70% aluminum sulfate, and no micronized anhydrite (percentages by weight).

Formulation 20 uses Portland cement from Gaurain and an accelerator to Portland ratio of 0.14.

It is observed that the resistances at 28 days are acceptable at low temperature, but much too low at 35 ° C. They are less than the 30 MPa required.

Formulation 21 (Comparative) The accelerator used in formulation 21 comprises 30% sulfo-aluminous clinker, 70% aluminum sulfate, and no micronized anhydrite (percentages by weight).

The formulation 21 is comparable to the formulation 19, with the exception of the cement used, the nature of which varies. Formulation 21 uses Portland cement from Gaurain.

It is observed that the resistances at 28 days are too weak at 20 ° C and below the required 30 MPa. The change in the nature of the CEM I does not make it possible to obtain the required performances of 30 MPa in compressive strength at 28 days.

Formulation 22 (comparative)

Formulation 22 comprises a curing accelerator marketed under the name Sigunit 49 AF by the company SIKA, in place of the accelerator according to the present invention.

Formulation 22 utilizes an accelerator to Portland ratio of 0.14.

It is observed that the resistances at 28 days are weak at low temperature. The resistances are also much too low at 28 days at high temperature. At 35 ° C, they stabilize very quickly at very low values: of the order of 5 MPa from 7 days.

Claims (15)

1. An accelerator for setting and hardening hydraulic binders comprising the following mass proportions: from 25 to 35% of at least one sulphoaluminous clinker, from 45 to 55% of at least one sulphate source having a solubility greater than 4 g.L'1 in water at 20 ° C, and - from 10 to 20% of at least one source of sulphates having a solubility of less than 4 gl "1 in water at 20 ° C, said clinker containing calcium aluminate mineralogical compounds. 2. setting and hardening accelerator according to claim 1, characterized in that said mineralogical compounds of calcium aluminate type contained in said clinker, are selected from Yeelimite (C4A3 $), Mayenite (C12A7), the mono aluminate of calcium (CA), tetracalcium aluminoferrite (C4AF), tricalcium aluminate (C3A), or a combination of several of these compounds; preferably a combination of Yeelimite and one or more other calcium aluminate mineralogical compounds. 3. setting and hardening accelerator according to claims 1 and 2, characterized in that said at least one source of sulphates having a solubility of less than 4 gL -1 is selected from gypsum (CaSO 4 .2H 2 O), anhydrite ( CaSO4), or a mixture thereof. 4. Setting accelerator and hardening according to any one of claims 1 to 3, characterized in that said at least one source of sulfates having a solubility greater than 4 g.L'1 is selected from aluminum sulfate dodeca hydrated octadeca (Al 2 (SO 4) 3, 12 to 18 H 2 O), hydrated tetra-heptal iron sulphate (Fe (SO 4), 4 to 7 H 2 O), plaster (CaSO 4 .H 2 O) or a mixture thereof. this. A setting and hardening accelerator according to any of claims 1 to 4, characterized in that the molar ratio between said source of sulphates having a solubility of less than 4 gL -1, and said calcium aluminate mineralogical compounds is between 0.3 and 55, preferably between 0.4 and 12. 6. Accelerator setting and curing according to any one of claims 1 to 4, characterized in that the molar ratio between said source of sulfates having a solubility greater than 4 g.L'1, and said mineralogical compounds aluminates type calcium, is between 0.15 and 27, preferably between 0.3 and 10. 7. Setting and hardening accelerator according to any one of claims 1 to 6, characterized in that the clinker is a sulphoaluminous clinker containing more than 30% by weight of the elite (C4A3 $), preferably 50 to 70% by mass. of Yeelimite, and the said source of sulphates having a solubility of greater than 4 gl -1 is aluminum sulphate, and the said source of sulphates having a solubility of less than 4 g.It is gypsum or anhydrite. . 8. A cementitious composition containing a hydraulic binder, a setting accelerator and hardening according to any one of the preceding claims, and optionally water. 9. Cementitious composition according to claim 8, characterized in that said hydraulic binder is a binder of Portland type selected from CEM I, II, III, IV or V, preferably a CEM I, more particularly a CEM I PMES. 10. Cementitious composition according to claims 8 and 9, characterized in that the mass ratio between said setting accelerator and hardening and said hydraulic binder is from 0.1 to 0.2; preferably from 0.14 to 0.18, more preferably from 0.15 to 0.17. 11. Cementitious composition according to any one of claims 8 to 10, characterized in that said cementitious composition contains, in addition to said setting and hardening accelerator and said hydraulic binder, one or more adjuvants, selected from superplasticizers, and / or or set retarders. 12. Use of a cementitious composition as defined in any one of claims 8 to 11, in admixture with fine aggregates, coarse aggregates with a maximum diameter of less than 12 mm, optionally very fine aggregates, with water, and possibly additives, to obtain a shotcrete. 13. Use of a cementitious composition according to any one of claims 8 to 11, mixed with fine aggregates, water, optionally very fine aggregates, and optionally adjuvants, to obtain a sealing mortar or rigging. 14. Use of a cementitious composition according to any one of claims 8 to 11, characterized in that it is carried out in a temperature range of between 5 ° C and 35 ° C. 15. Concrete or mortar containing a cementitious composition according to any one of claims 8 to 11 and implemented at temperatures between 5 and 35 ° C, characterized in that it has a compressive strength at 3 o'clock greater than 0.4 MPa, in particular 1 MPa, preferably 2 MPa, and a compressive strength at 28 days greater than 30 MPa.