ES2546052A2 - Hydraulic binder setting and curing accelerator and cement composition containing said accelerator - Google Patents

Abstract

Hydraulic binder setting and curing accelerator comprising the following content by weight: DEG 25 to 35 % of at least one sulfoaluminate clinker, - 45 to 55 % of at least one sulphate source with a solubility higher than 4 g. L-1 in water at 20 DEG C, and DEG 10 to 20 % of at least one sulphate source with a solubility of less than 4 g.L-1 in water at 20 DEG C, said clinker containing calcium aluminate-type mineralogical compounds. The cement composition containing said setting and curing accelerator can be used at temperatures of 5 DEG C to 35 DEG C, and to obtain a sprayed concrete or a grouting or bedding mortar with enhanced mechanical compression strength.

Description

Accelerator for setting and hardening of hydraulic binders and cement composition containing said accelerator

A subject of the present invention is a setting accelerator and hardening of hydraulic binder, cement compositions containing said setting accelerator and hardening hydraulic binder, as well as their uses, in particular, in projected concrete or sealing mortars and of draft. The shotcrete is a product transported at high speed by compressed air through a tube and projected on a surface or a support to which it must adhere. The shotcrete compositions make it possible to apply a layer of hydraulic binder on supports that have an inclination, vaults or overhangs. By way of example, we can mention, in particular, all the walls of underground galleries

or of tunnels. These compositions must be sufficiently fluid to be pumpable, and also firm enough to adhere to the wall on which they are projected without flowing along it. In addition to these difficulties, the person skilled in the art must also take into account other factors, such as the temperature of the medium, which may vary depending on the place and the moment of application of the shotcrete. The temperature of the medium greatly influences the strengths of concrete in the short and long term. If the medium is too cold, the concrete will not present satisfactory mechanical resistance in the short term. If the medium is too hot, the long-term mechanical resistance will be less than what can normally be expected. Sealing and draft mortars allow anchor bars to be fixed in highly requested concrete works, thanks to very high tear resistance. You can use whatever the configuration of the work (ceiling, wall and floor). They are generally presented in the form of a "premix" ready for use (mixture of binders, sands and adjuvants) and are used after kneading with water either manually or mechanically (by pumping). Unlike sealing mortars, draft mortars are fluid, ensuring easy filling of the cavities, such as for the setting of heavy machines or strong vibrations (turbines, machine tools, centrifuges ...) creating a homogeneous, uniform support and tough. In these applications (sealed or openwork), resistance at an early age is essential to respond to the short deadlines imposed by this type of work. They can be obtained using as a binder a Portland R cement (fast hardening);

but very high mechanical strengths are often required in the short term, and can only be obtained through the use of special aluminous or sulfoaluminous type cements. These special binders offer, on the other hand, the advantage, when judiciously formulated, of leading to obtaining reduced or even compensated withdrawal, property sought in this type of application.

In addition, the temperature of the surrounding medium also has an influence on the short-term and long-term mechanical strengths of the sealing and setting mortar compositions. The person skilled in the art must have a composition that can remain fluid and manipulable for a more or less long period, but which evolves towards a firmer consistency or set quickly from the moment it is applied. This last difficulty can be satisfied by the addition of a setting and hardening accelerator to the composition. By way of setting and hardening accelerators known to those skilled in the art, we will mention, in particular, nitrate salts, chlorine salts, alkanolamines, formaldehydes, thiocyanates, colloidal silica suspensions or alkaline aluminates. However, these setting or hardening accelerators can alter the mechanical characteristics of long-term resistance, and above all they do not allow obtaining such high mechanical strengths in the short term (3 hours), especially at low temperatures, such as temperatures below 10ºC, or even on the order of 5ºC. The use of aluminous and sulfo-aluminous cement or clinkeres as setting and hardening accelerators is also known to those skilled in the art. However, the use of setting or hardening accelerators such as aluminous and sulfo-aluminous cement or clinkeres is delicate. In fact, any modification or dosage error in the combination of this type of accelerator with a hydraulic binder (Portland cement) can, depending on the temperature of the medium, inhibit or accelerate the hydration reactions of this binder, making it difficult to control the Mechanical results of the hydraulic binder / accelerator assembly. Globally, these setting and hardening accelerators are known for their actions at current temperatures (around 20ºC), but they do not inevitably adapt to use in more “extreme” temperature conditions. There is a need, for the person skilled in the art, who wishes to use hydraulic binder compositions at high or low temperatures (from + 5 ° C to + 35 ° C), and who wishes to obtain satisfactory short and long term resistance (greater than 0.4 MPa, at 3 hours; and greater than 30 MPa, at 28 days), of having a setting and hardening accelerator that does not jeopardize the integrity of the structure in the long term.

An objective of the present invention is therefore to propose a setting and hardening accelerator of hydraulic binders that mitigate the aforementioned drawbacks. Another objective of the present invention is to propose a setting and hardening accelerator for cement compositions adapted for the use of sealing mortars, draft mortars, or projected concrete, and more specifically adapted for application at low or high temperatures. , requiring a high short-term mechanical resistance to compression (Rc) while maintaining good long-term mechanical compression resistance (Rc). The present invention allows to answer these different objectives thanks to a setting accelerator and hardening of hydraulic binders that include the following mass proportions: 25 to 35% of at least one sulfo-aluminous clinker, of 45 to 55% of at least a source of sulfates having a solubility greater than 4 gL-1 in water at 20 ° C, and -of 10 to 20% of at least one source of sulfates having a solubility of less than 4 gL-1 in water at 20 ° C, said content containing clinker mineralogical compounds of calcium aluminates type. In the present invention the solubilities are considered in pure water at a temperature of 20 ° C. Mineralogical phases are indicated by their usual name followed by their chemical cement notation. The primary compounds are represented in the chemical notation of cement by: C for CaO, S for SiO2, A for Al2O3 for SO3, H for H2O; This notation is used throughout this text. Within the framework of the present invention, the setting and hardening accelerator of hydraulic binders is intended to be added to a hydraulic binder to form a cement composition. By "hydraulic binder" is meant a hydraulic binder within the meaning of EN 197-1, and, in particular, the definition in paragraph 4: "finely ground mineral material which, kneaded with water forms a paste that sets and hardens following reactions and hydration processes and which, after hardening, retains its resistance and its own stability under water. ”By“ finely ground ”, a Blaine fineness of approximately 2500 to 5000 cm2 / g is understood. By "mineralogical compounds of calcium aluminate type", any mineralogical phase that results from the combination of alumina (chemical formula Al2O3, or "A" in chemical cement notation), and calcium oxide (chemical formula) CaO, or "C" in

chemical cement notation) with other mineral species such as, for example, sulfates (chemical formula SO3, or "$" in chemical cement notation), iron oxide (chemical formula Fe2O3, or "F" in notation cement chemistry) or fluorine. The sulfo-aluminous clinker can be mixed with an aluminous clinker, a sulphobelitic clinker, and / or a fluoroaluminous clinker. By "sulfo-aluminous", any material resulting from the cooking 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 is designated. The sulfo-aluminous clinker that can be part of the setting and hardening accelerator of hydraulic binders according to the present invention contains a Yeelimite content (chemical formula 4CaO3AI203.SO3 or C4A3 $ in chemical cement notation) greater than 30% by weight , preferably between 50 and 70% by weight. The Belita content (of chemical formula 2CaO.SiO2 or C2S in chemical cement notation) of said sulfo-aluminous clinker is advantageously such that the mass ratio between Yeelimite and Belita is greater than or equal to 1, 5. By “ sulfobelitic ”means any material resulting from cooking at a temperature between 900ºC and 1350ºC of mixtures containing at least one source of lime, at least one source of alumina and at least one source of sulfates. The sulfobelite clinker that can be part of the setting and hardening accelerator of hydraulic binders according to the present invention contains a Yeelimite content (of chemical formula 4CaO.3AI2O3.S03 or C4A3 $ in chemical notation of cement) greater than 30% by weight , preferably between 50 and 60% by weight. The content in Belita of said sulfobelitic clinker is advantageously greater than 20% by weight, such that the mass ratio between Yeelimite and Belita is less than 1, 5. By "fluoroaluminous", the product resulting from cooking is designated high temperature (generally at 1250-1350 ° C) of a Portland crude containing CaF2 fluorine in an amount such that the resulting clinker contains at least 15% of C11A7CaF2 calcium fluoroaluminate. The Blaine fineness of these sulfo-aluminous, sulphobelitic or fluoroaluminous clinkeres is approximately 2500 to 5000 cm2 / g. Advantageously, said calcium aluminate mineralogical compounds contained in said clinker are selected from Yeelimite (C4A3 $), Mayenite (C12A7), calcium mono aluminate (CA), tetracalcium aluminoferrite (C4AF), tricalcium aluminate (C3A),

or a combination of several of these compounds, preferably a combination of Yeelimite and one or more calcium aluminate mineralogical compounds. Advantageously, the total mass of said calcium aluminate mineralogical compounds contained in the clinker, represents more than 30% by mass of the total clinker mass,

in particular, more than 50% by mass, that is to say that the clinker according to the present invention contains aluminate mineralogical phases and that the sum of these phases advantageously represents at least half of the clinker's mass. Preferably, a calcium aluminate mineralogical compound is mostly present in the set of said calcium aluminate mineralogical compounds contained in the clinker, and represents more than 30% by mass of the total clinker mass, in particular, more than 50% by mass. Most preferably, this majority aluminate mineralogical phase is Yeelimite (C4A3 $). By "source of sulfates", a substance is designated at the origin of the sulfate ion solution. The most obvious sources of sulfates are sulfate salts, gypsum, mud or other sulfate-rich industrial by-products (for example phosphor plaster and titanoyeso). Sulfate sources can be used in admixture. These products are rarely available in industrial quantities with high purity, their cost would be prohibitive. It is therefore appropriate to consider mixtures of products that may eventually contain impurities. In this case, the person skilled in the art will adapt the desired amounts of sulfate sources by reasoning about the number of moles of sulfate (expressed in SO3 "$" in chemical cement notation). In the present invention the solubility of a sulfate source is assimilated to the solubility of the sulfate ions it contains. That is, to determine the solubility of a source of non-pure sulfates, the solubility of the main species of sulfate ions that make up this source is considered. It was surprisingly found that the presence of these two sulfate sources is essential to obtain the desired resistance results for cement compositions. More specifically, it was found that each of the two types of sulfate sources seems to play an important role in different stages of hydrate formation. The presence of at least one source of sulfates having a solubility greater than 4g.L-1 ensures the formation of etringite that participates in the development of the resistance of the material in the short term. Etringite is formed from the aluminate phases from both the hydraulic binder and the clinker. The presence of at least one source of sulfates having a solubility greater than 4g.L-1, ensures that the kneading water contains enough sulfate ions available to form all possible etringite depending on the phases in presence. The objective is to ensure that there is no formation of hydrated calcium monosulfoaluminate (AFm or C3AC $ H12 in chemical cement notation). Indeed, a lack of sulfates involves the formation of calcium hydrosulfoamumin decomposed by calcium

of the Etringite. This highly unstable hydrated calcium monosulfoaluminate does not allow the resistance of the cement matrix to be controlled. In addition, exposure to a source of sulfates in solution in the water after the hardening stage would cause an etringite formation reaction called "deferred" from the hydrated calcium monosulfoaluminate. The formation of deferred etringite is accompanied by inflation and can cause expansion, scaling, even structure explosions. The presence of at least one source of sulfates having a solubility of less than 4g.L-1 makes it possible to ensure a prolonged release of sulfates within the cement matrix throughout maturation. It allows, in particular, to ensure that the hydration reactions that take place in the long term do not change the species formed rapidly at the beginning of the setting (for example, a conversion of etringite into hydrated calcium monosulfoaluminate).

Classically, calcium sulfates, in particular gypsum or anhydrite, are added to the Portland-type clinker during its manufacture to constitute a hydraulic binder. For example, these plaster additions up to a maximum of 3 to 8% (in mass percentage, addition of pure plaster) are made in order to regulate the setting and, in particular, avoid the “flash” setting phenomena of the Portland cement During the tests, it was found that the source of ground sulfates with the Portland clinker does not allow itself to respond to the problem of obtaining sufficient mechanical resistance in the short and long term in a wide range of temperatures (see comparative examples below) . Advantageously, said at least one source of sulfates having a solubility of less than 4 g.L-1 is chosen from gypsum (CaSO4.2H2O), anhydrite (CaSO4), or a mixture thereof. By way of indication, the solubility of the plaster is 2.4 g.L-1, and that of the anhydrite is 2.1 g.L-1, in pure water, at 20 ° C. It is possible that the clinker contains calcium sulfates that have a solubility of less than 4g.L1 (residual sulfates), these residual sulfates in concentrations always below 10%, and very often below 5% by mass, come from cooking the cement cement This residual calcium sulfate content is not sufficient for the use of the present invention. Whatever the residual sulfate content, it is necessary to add another sulfate source that has a solubility of less than 4g / L. Advantageously, said at least one source of sulfates having a solubility greater than 4 gL-1 is chosen from the aluminum sulfate dodeca to octadeca-hydrate (Al2 (SO4) 3.12 to 18 H2O), of tetra a iron sulfate hepta-hydrated (Fe (SO4), 4 to 7 H2O), gypsum (CaSO4.1 / 2H2O), or a mixture of these. By way of indication, the solubility of iron sulfate 7.H2O is 300 g.L-1, the solubility of aluminum sulfate 14-16.H2O is 364 g.L-1,

and that of hemihydrate (gypsum) is 8.5 g.L-1, in pure water, at 20 ° C. The characteristic that distinguishes the two sulphate sources is actually the dissolution kinetics. But this characteristic is difficult to determine a priori since it depends on multiple parameters. In fact, it must be determined experimentally for each sulfate in question based on numerous conditions such as: temperature, salinity of the medium (nature and concentration of the ions present), pH, etc. Other characteristics such as the fineness of grinding of the sulphate source, and its degree of crystallization, also significantly influence the dissolution kinetics. In practice, it is easier to consider the solubility of the 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 allows estimating the dissolution kinetics of a species without resorting to long experiments. Estimation errors are possible but this criterion has the advantage of being simple to use and allowing a first selection that can be completed by precise dissolution kinetics tests if necessary. The present invention can be used with a combination of several clinkeres. However, for reasons of simplicity of use, it is preferred to carry out the present invention with a single clinker (sulfo-aluminous clinker) containing calcium aluminate mineralogical compounds. Very preferably said setting and hardening accelerator of hydraulic binders only contains, therefore a single clinker. Very preferably said setting and hardening accelerator of hydraulic binders comprises a single source of sulfates having a solubility greater than 4

g.L-1.

Very preferably said setting and hardening accelerator of hydraulic binders includes a single source of sulfates having a solubility of less than 4 g.L-1. According to a preferred embodiment of the invention, said setting and hardening accelerator of hydraulic binders comprises a single clinker (sulfoaluminous clinker), a single source of sulfates having a solubility greater than 4 gL-1 and a single source of sulfates which has a solubility of less than 4 gL-1. It is clear to the person skilled in the art that the simplest embodiment of the present invention is the combination of three sources that correspond respectively to the clinker and the two sulfates in order to obtain the ternary mixture of the setting accelerator and hardening of hydraulic binders according to the invention. However, more complex embodiments with one, two, or three composite sources, that is, constituted by a mixture, are also possible to employ the

present invention The present invention is distinguished from compositions that may exist in the prior art by an "over-sulfated" cement composition. Whatever the amount of sulfates having a solubility of less than 4 gL-1 contains in the hydraulic binder to which the setting and hardening accelerator of hydraulic binders is added, the present invention includes a supplementary addition of sulfates having a lower solubility. at 4 gL-1. Thus the cement composition object of the invention can never correspond to the simple mixing of a hydraulic binder (for example of Portland cement) with a clinker (a sulfo-aluminous clinker) and a sulphate source having a solubility greater than 4 gL-1 (for example, aluminum sulfate), even if the hydraulic binder or clinker contained significant amounts of sulfate source having a solubility of less than 4

g.L-1.

More specifically, the setting and hardening accelerator of hydraulic binders is characterized by a proportion greater than 5% of said sulphate source having a solubility of less than 4 gL-1, said quantity of 5% does not take into account the mass of The source of sulfates having a solubility of less than 4 gL-1 may eventually be contained in said clinker, and may proceed from the cooking of cementitious crude. The calcium sulphate contents of hydraulic binders and clinkeres are information specific to each product and are provided by the producers. In case of absence of such data or doubt about the exact content, these values can be determined for example by X-ray diffraction analysis with quantification of the phases by the Rietveld method. Especially, said setting and hardening accelerator of hydraulic binders is characterized by a proportion greater than 5% of said sulphate source having a solubility of less than 4 gL-1, and whatever the mass of the sulphate source that It has a solubility of less than 4 gL-1 and can be contained in said hydraulic binder. Advantageously, in a particular setting and hardening accelerator of hydraulic binders of the present invention, the molar ratio between said sulfate source having a solubility of less than 4 gL-1, and said calcium aluminate mineralogical compounds, it is comprised between 0.3 and 55, preferably between 0.4 and 12. Advantageously also, in a particular setting and hardening accelerator of hydraulic binders, the molar ratio between said sulphate source having a solubility greater than 4 gL-1, and said calcium aluminate mineralogical compounds, is between 0.15 and 27, preferably between 0.3 and 10.

The tests carried out showed that the previously mentioned molar ratios between: - on the one hand, the sources of sulfates having a solubility of less than 4 gL-1, even those present in the clinker, and the content of aluminate-type mineralogical compounds of calcium present in the clinker, and - on the other hand, the sources of sulfates having a solubility greater than 4 gL-1, and the content in mineralogical compounds of calcium aluminates type present in the clinker, allow to obtain high mechanical resistance to Short and long term in a wide temperature range that can range from + 5ºC to + 35ºC approximately. It is important to keep in mind that these molar ratios refer to the setting and hardening accelerator of hydraulic binders and not to the cement composition containing said accelerator. Presented differently, the amount of sulfate sources that have a solubility of less than or greater than 4 g.L-1, which are eventually present in the hydraulic binder have no influence on the molar ratios previously mentioned. Advantageously, the molar ratio between said sulfate source having a solubility of less than 4 gL-1 and said calcium aluminate mineralogical compounds is comprised between 1, 5 and 12. Preferably, the molar ratio between said sulfate source that it has a solubility of more than 4 gL-1 and said calcium aluminate mineralogical compounds are between 1, 8 and 8. Most preferably, the setting accelerator and hardening of hydraulic binders according to the present invention is characterized in that -said clinker, is a sulfo-aluminous clinker that contains more than 30% by weight of Yeelimite, preferably from 50% to 70% by mass of Yeelimite, and - said source of sulfates having a solubility greater than 4 gL-1 is of Aluminum sulfate, and said source of sulfates having a solubility of less than 4 gL-1 is gypsum or anhydrite. The present invention also has a cement composition containing a hydraulic binder, a setting and hardening accelerator as described above, and eventually water. The cement composition, according to the present invention, may also contain, in addition to the setting and hardening accelerator of hydraulic binders, and hydraulic binders: fillers, additions, adjuvants, additives or a combination thereof. The present invention uses the term "a" hydraulic binder, but it is evident

for the person skilled in the art that a combination of different known binders, for example of two different Portland-type cements, can perform the same function without substantially modifying the characteristics of the present invention. By "fillers", a finely ground mineral material is designated, of which 85% of its elements have a diameter of less than 80 µm. Fillers are used to optimize the compactness by filling the gaps. By "additive", a finely ground mineral material is designated which has, or is not, a pozzolanic effect. The term "pozzolanic effect" here designates a contribution to the development of mechanical resistances. Additions in general are finely ground and have a diameter of less than 400 µm, in particular, less than 150 µm. The additions can be ground separately from the hydraulic or ground binders together with them. Among the fillings and additions that have a pozzolanic effect, we can mention: blast furnace slags, fly ash and silica fumes. Among the fillers and additions that do not have a pozzolanic effect, we can mention: limestone fillers and siliceous fillers.

By "adjuvant", a substance is designated within the meaning of EN 206.1, and in particular the definition in paragraph 3.1.22: a product added to the concrete during the mixing process, in small quantities with respect to the mass of cement, to modify the properties of fresh or hardened concrete. By "addition", substances or materials are designated that can be added to the cement composition, but which are not additions, fillers or adjuvants such as are described herein. As an example of addition we can mention: the fibers that serve to reinforce the structure (metallic, organic, mineral), the oxides that confer photo-catalytic properties (TiO2), the heavy particles that allow to isolate radiation (mineral particles, in particular , of Iron), the conductive particles of the electricity that allow to shield constructions against the electromagnetic radiations offering cages of Faraday (such as the graphite), thermal conductive particles (metals), particles of changes of phase (PCM: "phase change materials" ) to store heat energy in a structure, or light particles that improve thermal and acoustic insulation (organic particles such as polystyrene or minerals such as vermiculite, perlite, silico-aluminates or molten and blown glass). Preferably, said hydraulic binder is a Portland type binder, chosen from CEM I, II, III, IV or V, preferably a CEM I, more specifically CEM I PM ES. By "PM ES" means a binder having a low content of tricalcium aluminate (C3A), in particular at most 5%, in accordance with standards NF P 15-317 and NF P 15-319. Preferably, the total amount of SO3, which comes from said sulfate source having a solubility of less than 4 g.L-1, contained in said cement composition, is

strictly greater than 5% of the total mass of said cement composition. In this preferred mode, the cement composition according to the present invention contains more sulphate sources having a solubility of less than 4 gL-1, which is possible by obtaining a sulphated hydraulic binder to the maximum of the possibilities of the standard . The EN 197-1 standard (paragraph 9.2.3) imposes a maximum amount of SO3 that varies from 4 to 5% (by mass) depending on 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, preferably still from 0.15 to 0.17. If this mass ratio is less than 0.1, it is likely that the resistance developed in the short term, and in low temperature conditions, will not be sufficient. If this mass ratio is greater than 0.2, it is likely that the resistance developed in the long term, and in high temperature conditions, will not be sufficient. Preferably, the mass ratio between said setting accelerator and hardening of hydraulic binders and said hydraulic binding agent is approximately 0.16. Advantageously, the cement composition defined above is used in a temperature range between approximately 5 ° C and 35 ° C.

In a particular embodiment, said cement composition according to the invention contains, in addition to said setting and hardening accelerator of hydraulic binders and said hydraulic binding agent, one or more adjuvants, in particular superplasticizers, setting retarders; also, in particular, one or more adjuvants chosen among plasticizers, other setting accelerators than those of the present invention (for example nitrates, thiocyanates and / or chlorides), other hardening accelerators than those of the present invention ( in particular, alkali carbonates), aerators (in particular, sodium lauryl sulfates), anti-shrinking agents, anti-bubble or antifoam agents, waterproofing agents (for example calcium stearate), anti-settling agents (in particular, bentonites, attapulgites ), mineral or organic colored pigments, latex (in particular, styrene-butadiene copolymers or vinyl acetate-vinyl versatate or vinyl acetate acrylic monomer), and rheology modifiers (in particular, modified or non-modified polysaccharides modified, preferably diutane gums, xanthan gums, gellan gums, welan gums; and, in particular, retainers of water, preferably starch ethers, cellulose ethers). Advantageously, said cement composition contains, in addition to said setting and hardening accelerator and said hydraulic binder an adjuvant

superplasticizer, in particular, a polycarboxylate. Advantageously, said cement composition contains, in addition to said setting and hardening accelerator and said hydraulic binder, a setting retarder adjuvant, in particular, a polycarboxylic acid, preferably tartaric acid or citric acid. Paradoxically, setting retarder adjuvants may have an interest in the context of the present invention, in particular, in the application of wet-cast concrete. Indeed, this type of application requires precise control of the setting period 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 cement compositions cited above that contain said setting accelerator and hardening of hydraulic binders in a concrete, in particular of a shotcrete, a mortar, in particular a sealing mortar or draft, a coating, a grout or a cement paste. By "slurry" or "cement paste", the addition of water to the cement composition according to the present invention is designated. The distinction between these two denominations is linked to the mass relationship 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. By "coating", a grout or a cement paste is designated, to which some very fine aggregates are added, that is to say, with a diameter between 150 µm and 1 mm (for example fillings). By "mortar", a grout or a cement paste is designated, to which fine aggregates are added, that is, some aggregates whose diameter is between 150 pm and 4 mm (eg sand), and eventually very fine aggregates. By "concrete", a mortar is designated to which aggregates of larger size are added, ie aggregates whose diameter is greater than 4 mm.

As usual, concrete, mortar, coatings, grout and cement pastes are adjuvants. Shotcrete and its applications are the subject of NF P 95-102. Sealing mortars are defined by the NF standard in 1504-6. Draft mortars are defined by NF P 18-821. Advantageously, the present invention relates to the use of a cement composition as defined above, in admixture with fine aggregates, coarse aggregates of a maximum diameter of less than 12 mm, possibly very fine aggregates, water, and possibly adjuvants, for Get a shotcrete.

By "sand", a mixture of aggregates consisting of very fine aggregates, or fine aggregates, or a combination of fine and very fine aggregates is designated. A distinction is made between setting accelerators and hardening accelerators. The setting accelerators act on a term (term of 'stiffening' of the material), while the hardening accelerators act on the mechanical resistances. Consequently, setting accelerators do not necessarily allow high resistance to be obtained in the short term. Within the framework of the present invention, it is convenient to have both characteristics (setting and hardening) to achieve this effect. Preferably, the use of the cement composition as defined above is characterized in that said projected concrete has a setting time of less than 5 minutes, in particular, less than 1 minute, preferably an almost instantaneous setting time. The setting time of the shotcrete made thanks to the cement composition according to the present invention is almost instantaneous after the addition of water, therefore the application of shotcrete according to the present invention is preferably done dry. It is also possible to employ the invention in the wet-cast concrete frame, but that implies the addition of a setting retarder (for example citric acid or tartaric acid). The dry track and the wet track differ essentially by the time the water is added. Dry projection is also distinguished by the absence of kneading itself. The previously homogenized dry mixture is supplied through a tube (by compressed air), to a lance at the end of which the water is added. The water flow rate is adjustable in order to adjust the water content of the project material. A prehumidification of the order of 5% (by mass) can be added upstream to avoid inconvenience due to dust emissions during projection. Advantageously, the present invention relates to the use of a cement composition as defined above, in admixture with fine aggregates, water, possibly with very fine aggregates, and possibly with adjuvants, to obtain a sealing mortar

or draft. The distinction between sealing mortar and draft mortar is maintained and lies in the consistency of the material obtained. The openwork mortar is characterized by a much more fluid consistency than that of the sealing mortar; This higher fluidity can be obtained by increasing the water / dust ratio. The consistency of the mortars is determined according to the NF standard in 1015-3. If the expansion to the shaking table is greater than 200 mm, then the mortar is qualified as fluid (Standard NF in 1015-6 table 1). An openwork mortar has an expansion greater than 200 mm. On the contrary, a mortar

sealing has an expansion less than or equal to 200 mm.

By way of example, a draft mortar having a setting time of approximately 1 to 4 hours can be prepared from a cement composition containing 0.1 to 1% by weight of a setting retarder adjuvant according to the invention. By way of example also, a sealing mortar having a setting time between approximately 1 and 2 hours, can be prepared from a cement composition containing from 0.1 to 1% by weight of a retarder adjuvant of set according to the invention. Among the multiple applications of sealing mortars, we can mention: -sealing of posts, beams, gutters -sealing of doors, windows and minor construction elements -sealing of urban furniture, of signaling elements -sealing of registration boxes on high-traffic roads with restoration of almost immediate traffic. The use of a setting retarder is necessary in this type of applications (draft and sealing) in order to establish the cement composition before setting. Advantageously, the use of the cement composition according to the invention is used in a temperature range between approximately 5 ° C and 35 ° C. The present invention also relates to a concrete or mortar containing the cement composition defined above, and used at temperatures ranging from + 5 ° C to + 35 ° C, characterized in that it has a mechanical resistance to compression at 3 hours greater than 0, 4 MPa, in particular 1 MPa, preferably 2 MPa, and a mechanical resistance to compression at 28 days greater than 30 MPa. The advantageous value of 0.4 MPa is retained within the framework of the present invention to mean that the product has already exceeded the end of setting and that it reached a sufficient level of hardening or sufficient structuring thus preventing it from flowing into the soil. The product is no longer "workable" on its support. I-Materials and methods Standards The definition of the Portland clinker is taught by the European standard EN 197-1. The controls of the mechanical characteristics of the cements were carried out according to the European standard EN 196 paragraphs 1 to 7. 1 - Materials used

1.1 Aggregates Two mixtures of 0 / 8mm aggregates from SOCLI were used; both are screened and

They have four fractions or granulometric sections mentioned in Table 1 (in% by mass):

Wasselonne

Cormeilles

Arena 0 / 0.5

28.88 26.15

0.5 / 2.5 sand

16.41 -

Sand 0,5 / 1,25

- 20.51

Arena 2.5 / 4

21.88 -

Sand 1.25 / 3.15

- 19.15

Gravel 4/8

32.82 34.19

Table 1

5 1.2 Cement / Clinker Portland cement Cements type CEM I 52.5 N PM ES HRC (low C3A content; standards NF P 15.317 and NF P 15.319) from the factories of Beaucaire (Calcia), Gaurain (Calcia) were used , or from St Vigor (Lafarge). Its composition is presented in table 2 (in% by mass).

Factories

C3S C2S C3A C4AF SO3

Beaucaire

75 10 2 14 2.3

Gaurain

55 28 2 12 2.7

St Vigor

55 26 0.5 14.5 2.5

Table 2 Sulfo-aluminous clinker A sulfo-aluminous clinker marketed under the name Alipre (Italcementi, Guardiaregia, Italy) was used in all the following examples, except in example 9.

15 This clinker contains approximately 60% by weight of Yeelimite (calcium sulfoaluminate: C4A3). An experimental sulfo-aluminous clinker containing approximately 30% Yeelimite was also used only in Example 9. This clinker was prepared in the laboratory by high temperature cooking of a crude compound, in particular limestone, clay, bauxite and

20 gypsum which are mixtures of different oxides, in particular, CaO, SiO2, Al2O3, Fe3O2 and SO3. The technique of composing a crude oil based on the mineralogy of the desired clinker is well known to the person skilled in the art (Special Inorganic Cement, Ivan Older, 2000, CRC Press). The main mineralogical phases of these two sulfo-aluminous clinkeres are presented in Table 3 (in% by mass).

C4A3S

C2S C $ C12A7

Alipre

64.2 10.4 2.9 2.4

Experimental clinker

31.6 29 3.2 9.8

Table 3

1.3

Adjuvant Setting and hardening accelerator according to the present invention. The setting of the setting and hardening accelerator comprises sulfate of aluminum (AI2 (SO4) 3 14 to 16 H2O) (Metausel), micronized natural anhydrite (calcium sulfate, Societé Mosellanne d’anhydrite), and alipre sulfo-aluminous clinker. Setting accelerator according to the prior art. A powder setting accelerator was used for dry sprayed concrete marketed by the company SIKA (Sigunit 49AF). Superplasticizer The superplasticizer used is Melflux 2651 F (BASF). It is a superplasticizer from the family of polycarboxylates that comes in powder form. 2 -Method

2.1

Proportions of the constituents Aggregates Several dosages and sands and aggregates were tested: 698, 713, 722 or 726 kg of sands and aggregates per ton of dry formulation. Portland Cement: Several cement dosages were used: 240, 250 or 260 kg of cement per ton of dry formulation. Accelerator: The accelerator / cement ratios indicated in the formulations are mass relations. Superplasticizer: Some formulations contain a superplasticizer. Except specific indication these formulations are dosed at 0.9% by mass of superplasticizer Regarding cement. Water: Two water dosages were used: A / C = 0.45 and 0.385 (mass ratio Water / Cement Portland). These dosages correspond respectively to relationships Water / Total dust = 0.12 and 0.10. By total dust, the set of constituents is designated solids of the cement composition, that is, Portland-type cement, sulfoaluminous clinker, sulfate sources and aggregates (sand and gravels).

2.2 Employment The tests were applied according to the following protocol: Prepare 1.8 kg of a mixture that includes all the accelerator constituents of

hardening, Portland cement and aggregates and / or sands. Introduce this mixture in a 3-liter mixing bowl, mix for 1 minute at small speed (140 rpm with epicyclic (or planetary) train that drives the blade mixture at 1 turn / second) to ensure a good homogeneity of the mixture. Cover the kneading bowl with a waterproof plastic lid, then keep this set for 24 hours in a desired climate environment (temperature, humidity). Knead exactly 1.8 kg of the mixture with water at the desired temperature, mix for 20 seconds at 280 rpm with 2-cycle / second epicyclic train (High Speed). The mechanical resistance tests must be carried out without delay since the setting is done very quickly.

2.3 Chemical and mineralogical analysis

The analyzes of the different chemical compositions, in particular, the different SO3 value determinations of sulfate sources were made by X-ray fluorescence spectrometry (Magix spectrometer, Panalytical). Mineralogical analyzes referring to the different phases of the clinkeres that constitute This hydraulic binder or cement were made by X-ray diffraction (DRX), with a quantification of the mineralogical phases by the Rietveld method (XPERT PRO, Panalytical, EVA and TOPAS software).

2.4 Mechanical characterizations The tests of mechanical resistance to bending and compression according to EN 1961, and of density in the hardened state have been carried out on mortar specimens (dimensions: 4 cm x 4 cm x 16 cm), at different temperatures: -Some specimens are made at 5 ° C and stored in the air at 5 ° C, under 90% H.R. (RH). -Some test specimens are made at 20ºC and stored in the air at 20ºC, under 75% of H.R. - Some specimens are made at 35 ° C and stored in the air at 35 ° C, under 90% H.R.

II. Results The hardening accelerator composition according to the present invention is expressed in percentage by mass of the three constituents: clinker sulfo-aluminous, sulfate source which has a solubility greater than 4 g.L-1 (aluminum sulfate), and source of sulfates that It has a solubility of less than 4 g.L-1 (micronized natural anhydrite). The amounts of Portland cement and aggregates are expressed in kg per ton of fresh concrete The indicated temperature is that at which the samples were prepared and the measurements were make. Compressive strengths (Rc) are expressed in MPa, at 3 hours, 7 days and 28 days,

after the start of kneading. The beginning of kneading 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 samples

5 “functional” (4 x 4 x 16 specimens), that is, they have compressive strengths greater than 0.4 MPa, at 3 hours, and greater than 30 MPa, at 28 days, for operating temperatures ranging from + 5ºC to + 35ºC. However, samples containing a mass percentage in sulfo-aluminous clinker comprised between 25 and 35% of the setting and hardening accelerator according to the

The invention has mechanical compressive strengths (Rc) at 3 hours at 5 ° C of at least 1.46 MPa. The sulfo-aluminous clinker contains approximately 60% Yeelimite C4A3 and approximately 3% C $ (mass%). Example 1: Different proportions of clinker sulfo-aluminous / Aluminum sulfate

Formulation No.

1 (comp.) 2 3 11 (comp.)

CEM Cement I 52.5 N PM ES “HRC” (Gaurin)

260 260 260 260

Wasselone Arena

698 698 698 698

Water / Cement:

0.45 0.45 0.45 0.45

Accelerator / Cement Ratio:

0.16 0.16 0.16 0.16

Sulfo-aluminous clinker (%)

55 25 35 65

Aluminum sulfate (%)

25 55 Four. Five fifteen

Anhydrite (%)

twenty twenty twenty twenty

C $ / C4A3 $ (molar)

2.36 5.18 3.70 1.99

A $ 3 / C4A3 $ (molar)

0.76 3.66 2.14 0.38

5ºC temperature

Rc (MPa) 3 hours:

0.87 2.09 1.46 0.72

Rc (MPa) 7 days

33.90 28.66 35.58 31.57

Rc (MPa) 28 days

40.69 32.30 45.20 42.64

35ºC temperature

Rc (MPa) 3 hours:

8.41 5.42 7.19 11.06

Rc (MPa) 7 days

44.68 52.12 50.30 58.09

Rc (MPa) 28 days

55.84 50.58

Table 4 The accelerator compositions used in formulations 1 (comparative), 2, 3 and 11 (comparative) (table 4) include a constant content of micronized anhydrite (20%), but it varies in sulfo-aluminous clinker content (between 25 and 65%) and consequently in

5 aluminum sulfate (between 15 and 55%). These four formulas allow to see that at low temperature (5 ° C) an increase in the proportion in sulfo-aluminous clinker in the accelerator composition is unfavorable for mechanical resistance at 3 hours. On the contrary, the mechanical resistance at 3 hours and at 5 ° C is improved with an increase in the aluminum sulfate content in the composition of the

10 throttle Example 2: Different sources of aggregates and Portland cement

Formulation No.

3 4 5

CEM Cement I 52.5 N PM ES “HRC” (Gaurin)

260 260

Cement CEM I 52.5 N PM ES “HRC” (St Vigor)

260

Wasselone Arena

698

Cormeilles Arena

698 698

Water / Cement:

0.45 0.45 0.45

Accelerator / Cement Ratio:

0.16 0.16 0.16

Sulfo-aluminous clinker (%)

35 35 35

Aluminum sulfate (%)

Four. Five Four. Five Four. Five

Anhydrite (%)

twenty twenty twenty

C $ / C4A3 $ (molar)

3.70 3.70 3.70

A $ 3 / C4A3 $ (molar)

2.14 2.14 2.14

5ºC temperature

Rc (MPa) 3 hours:

1.46 1.79 2.35

Rc (MPa) 7 days

35.58 31.83 33.58

Rc (MPa) 28 days

45.20

20ºC temperature

Rc (MPa) 3 hours:

2.45 3.12

Rc (MPa) 7 days

34.19 34.48

Rc (MPa) 28 days

35ºC temperature

Rc (MPa) 3 hours:

7.19 7.57 8.73

Rc (MPa) 7 days

50.30 47.88 35.76

Rc (MPa) 28 days

50.58

Table 5 The accelerator used in formulations 3, 4 and 5 (table 5) has a constant composition; It comprises 35% sulfo-aluminous clinker, 45% aluminum sulfate, and 20% micronized anhydrite (mass percentages).

5 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 the mechanical results . It can be seen that the effect of the accelerator used in these three formulations was not modified by the change in the origin of the cement or aggregates.

10 Example 3: Variation of aluminum sulphate content

Formulation No.

7 (Comp.) 10

Cement CEM I 52.5 N PM ES “HRC”

260

CEM Cement I 52.5 N PM ES “HRC” (Gaurin)

260

Wasselone Arena

698 698

Water / Cement:

0.45 0.45

Accelerator / Cement Ratio:

0.16 0.16

Sulfo-aluminous clinker (%)

55 35

Aluminum sulfate (%)

25 53

Anhydrite (%)

twenty 12

C $ / C4A3 $ (molar)

2.36 2.22

A $ 3 / C4A3 $ (molar)

0.76 2.52

5ºC temperature

Rc (MPa) 3 hours:

0.49 2.00

Rc (MPa) 7 days

41.90 34.32

Rc (MPa) 28 days

46.21 35.82

35ºC temperature

Rc (MPa) 3 hours:

2.74 8.19

Rc (MPa) 7 days

45.06 29.02

Rc (MPa) 28 days

52.15 33.80

Table 6 Formulations 7 (comparative) and 10 (table 6) have a mass ratio of sulfoaluminous clinker with respect to the sulfo-aluminous clinker sum and constant anhydrite (0.73). These two formulations differ in their aluminum sulfate content in the composition of the

5 throttle. It is found that an increase in the amount of aluminum sulfate improves the mechanical resistance at 3 hours but is unfavorable to the longer term results (7 days and 28 days). Example 4: Different proportions Clinker sulfo-aluminous / aluminum sulfate

Formulation No.

8 (Comp.) 10

CEM Cement I 52.5 N PM ES “HRC” (Gaurin)

260 260

Wasselone Arena

698 698

Water / Cement:

0.45 0.45

Accelerator / Cement Ratio:

0.16 0.16

Sulfo-aluminous clinker (%)

Four. Five 35

Aluminum sulfate (%)

38 53

Anhydrite (%)

17 12

C $ / C4A3 $ (molar)

2.45 2.22

A $ 3 / C4A3 $ (molar)

1.40 2.52

5ºC temperature

Rc (MPa) 3 hours:

0.75 2.00

Rc (MPa) 7 days

38.36 34.32

Rc (MPa) 28 days

38.12 35.82

35ºC temperature

Rc (MPa) 3 hours:

5.62 8.19

Rc (MPa) 7 days

41.21 29.02

Rc (MPa) 28 days

42.20 33.80

Table 7 The accelerator compositions used in formulations 8 (comparative) and 10 (Table 7) have a close C $ / C4A3 $ ratio (around 2.3), but they are distinguished by their

A $ 3 / C4A3 $ ratio very different. It is found that a high A $ 3 / C4A3 $ ratio favors mechanical resistance to short-term and disadvantages long-term mechanical resistance (in particular, High temperature). These observations correspond to those extracted from example 1. Example 5: Presence of a superplasticizer (Melflux 2651 F)

Formulation No.

12 (comp.) 13 14

Cement CEM I 52.5 N PM ES “HRC”

260 260 260

Cormeilles Arena

698 698 698

Water / Cement:

0.385 0.385 0.385

Accelerator / Cement Ratio:

0.16 0.16 0.16

Sulfo-aluminous clinker (%)

55 25 35

Aluminum sulfate (%)

25 55 Four. Five

Anhydrite (%)

twenty twenty twenty

C $ / C4A3 $ (molar)

2.36 5.18 3.70

A $ 3 / C4A3 $ (molar)

0.76 3.66 2.14

5ºC temperature

Rc (MPa) 3 hours:

1.14 3.65 4.41

Rc (MPa) 7 days

69.8 33.66 42.06

Rc (MPa) 28 days

81.64 58.23

20ºC temperature

Rc (MPa) 3 hours:

7.73 6.11 9.2

Rc (MPa) 7 days

81.08 43.52 73.35

Rc (MPa) 28 days

82.38 86.92

35ºC temperature

Rc (MPa) 3 hours:

18.89 8.19 10.92

Rc (MPa) 7 days

78.24 69.01 35.74

Rc (MPa) 28 days

85.3 36.02

Table 8 All these formulations gave functional samples (4 x 4 x 16 specimens), that is, they presented compressive strengths greater than 0.4 MPa, at 3 hours; and over 30

10 MPa, at 28 days, for operating temperatures ranging from + 5ºC to + 35ºC. Formulations 12 (comparative), 13 and 14 (table 8) are respectively of the same composition as formulations 1 (comparative), 2 and 3 (table 2), with also a

Superplasticizer dosed at 0.9% by mass with respect to cement. It is observed globally that the presence of superplasticizer improves the results concrete mechanics, particularly those at 7 days and 28 days. Example 6: Concrete projected realization in situ in a gallery

Formulation No.

17 18

Ratio (accelerator + superplasticizer) / Cement

0.165 0.165

Sulfo-aluminous clinker (%)

35 35

Aluminum sulfate (%)

Four. Five Four. Five

Anhydrite (%)

twenty twenty

Temperature 14ºC

Rc (MPa) 3 hours:

7.3 13.4

Rc (MPa) 24 hours:

39.6 22.3

Rc (MPa) 7 days

53.5 34.6

Rc (MPa) 28 days

63.4 43.1

Table 9 Table 9 presents the characteristics of projected concrete, according to the present invention, made on samples of 3 tons of concrete used with aggregates from Cormeilles (formulation 17) and Wasselonne (formulation 18). It has been used in both

10 Gaurain cement formulations (CEM I 52.5 N PM ES “HRC”). The tests took place in a gallery at 14ºC and 95% relative humidity. The superplasticizer (Melflux 2651 F) is dosed at 0.5% with respect to cement (mass ratio). The A / C ratio is 0.38. The sum of the accelerator mass according to the present invention and of the superplasticizer mass represents 4.3% of the total mass of the

15 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 formulations called “no

20 functional ”, that is to say that they do not allow 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 + 5ºC to + 35 ° C) within the framework of the present invention. Three formulations were made in order to demonstrate that the source of sulfates having a solubility of less than 4 g.L-1 present in Portland-type cement (table # 2) is not

25 sufficient to allow acceleration of hardening and setting

(formulations without the addition of anhydrite). A final formulation (22) makes it possible to compare the accelerator according to the present invention with a prior art accelerator, Sigunit 49 AF (Sika).

Formulation No.

19 (comp.) 20 (comp.) 21 (comp.) 22 (comp.)

Cement CEM I 52.5 N PM ES “HRC” (Beaucaire)

240

CEM Cement I 52.5 N PM ES “HRC” (Gaurain)

240 240 240

Wasselone Arena

722 726 722 726

Water / Cement

0.45 0.45 0.45 0.45

Accelerator / Cement Ratio

0.16 0.14 0.16 0.14

Sulfo-aluminous clinker (%)

30 30 30

Aluminum sulfate (%)

70 70 70

Anhydrite (%)

0 0 0

C $ / C4A3 $ (moles)

0 0 0

A $ 3 / C4A3 $ (moles)

3.88 3.88 3.88 -

Sigunit 49 AF

- - - 100

5ºC temperature

Rc (MPa) 3 hours

0.60 1.81 - 1.02

Rc (MPa) 7 days

11.69 - - 15.01

Rc (MPa) 28 days

15.61 37.70 - 19.54

20ºC temperature

Rc (MPa) 3 hours

- - 4.11 -

Rc (MPa) 7 days

- - 12.45 -

Rc (MPa) 28 days

- - 12.62 -

35ºC temperature

Rc (MPa) 3 hours

1.72 3.49 - 3.18

Rc (MPa) 7 days

13.46 - - 4.02

Rc (MPa) 28 days

14.09 8.12 - 5.62

Table 10

Formulation 19 (comparative)

The accelerator used in formulation 19 comprises 30% sulfo-aluminous clinker, 70% of aluminum sulfate, and no micronized anhydrite (mass percentages). Formulation 19 uses a Portland cement from Beaucaire. It is observed that the 28-day resistance values are half of those expected. This formulation is considered as "non-functional" since the mechanical resistance 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% of aluminum sulfate, and no micronized anhydrite (mass percentages). Formulation 20 uses a Portland cement from Gaurain and a proportion of accelerator with respect to Portland cement of 0.14. It is observed that the resistance at 28 days is acceptable at low temperature, but too low at 35 ° C. They are less than the required 30 MPa value. Formulation 21 (comparative) The accelerator used in formulation 21 comprises 30% sulfo-aluminous clinker, 70% of aluminum sulfate, and no micronized anhydrite (mass percentages). Formulation 21 is comparable to formulation 19, except for the cement used whose nature varies. Formulation 21 uses a Portland cement from Gaurain. It is observed that the resistance at 28 days is too low at 20 ° C and below the value 30 MPa required. The change in the nature of CEM I does not allow obtaining required results of 30 MPa in compressive strength at 28 days. Formulation 22 (comparative) Formulation 22 comprises a hardening accelerator marketed under the name of Sigunit 49 AF by the SIKA company, instead of the accelerator as presented invention. Formulation 22 uses an accelerator ratio with respect to Portland cement of 0.14. It is observed that the resistance at 28 days is low at low temperature. Resistances They are also much lower at 28 days at high temperature. At 35 ° C, they stabilize very quickly in very low values: of the order of 5 MPa from 7 days.

Claims (1)

1.-Accelerator of setting and hardening of hydraulic binders that include the following mass proportions: 25 to 35% of at least one sulfo-aluminous clinker, -of 45 to 55% of at least one source of sulfates having a solubility greater than 4 gL-1 in water at 20 ° C, and 10 to 20% of at least one source of sulfates having a solubility of less than 4 gL-1 in water at 20 ° C, said clinker containing calcium aluminate mineralogical compounds. 2. A setting and hardening accelerator according to claim 1, characterized in that said calcium aluminate mineralogical compounds contained in said clinker are selected from Yeelimite (C4A3 $), Mayenite (C12A7), mono-aluminate of calcium (CA), tetracalcium alumino-ferrite (C4AF), tricalcium aluminate (C3A), or a combination of several of these compounds; preferably a combination of Yeelimite and one or more calcium aluminate mineralogical compounds. 3.-Setting and hardening accelerator according to claims 1 and 2, characterized in that said at least one source of sulfates having a solubility of less than 4 gL-1 is chosen from the gypsum (CaSO4.2H2O), the anhydrite (CaSO4 ), or a mixture of these. 4.-Setting and hardening accelerator 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 gL-1 is chosen from the aluminum sulfate dodeca-a octadecahydrate ( Al2 (SO4) 3.12 to 18 H2O), tetra-hepta-hydrated iron sulfate (Fe (SO4), 4 to 7 H2O), gypsum (CaSO4.1 / 2 H2O) or a mixture of these. 5.-Setting and hardening accelerator according to any one of claims 1 to 4, characterized in that the molar ratio between said sulphate source having a solubility of less than 4 gL-1, and said calcium aluminate mineralogical compounds, it is comprised between 0.3 and 55, preferably between 0.4 and 12. 6.-Setting and hardening accelerator according to any one of claims 1 to 4, characterized in that the molar ratio between said sulfate source having a solubility greater than 4 gL-1 and said calcium aluminate mineralogical compounds, it is comprised 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 sulfo-aluminous clinker containing more than 30% by mass of Yeelimite (C4A3 $), preferably between 50 and 70% by mass of Yeelimite, and said source of sulfates having a solubility greater than 4 g.L-1 is aluminum sulfate, and said sulfate source having a solubility of less than 4 g.L-1 is gypsum or anhydrite. 8.-Cement composition containing a hydraulic binder, a setting and hardening accelerator according to any one of the preceding claims, and possibly water. 9. - Cement composition according to claim 8, characterized in that said hydraulic binder is a Portland Cement type binder, chosen from CEM I, II, III, IV or V, preferably a CEM 1, more specifically CEM I PMES. 10.-Cement composition according to claims 8 and 9, characterized in that the mass ratio between said setting and hardening accelerator and said hydraulic binder is 0.1 to 0.2; preferably from 0.14 to 0.18, preferably still 0.15 to 0.17. 11. Cement composition according to any one of claims 8 to 10, characterized in that said cement composition contains, in addition to said setting and hardening accelerator and said hydraulic binder, one or more adjuvants, chosen from the superplasticizers, and / or setting retarders. 12. Use of a cement composition as defined in any one of claims 8 to 11, in admixture with fine aggregates, coarse aggregates of a maximum diameter of less than 12 mm, possibly very fine aggregates, water, and possibly adjuvants , to obtain a shotcrete. 13. Use of a cement composition according to any one of claims 8 to 11, in admixture with fine aggregates, water, possibly very fine aggregates, and possibly adjuvants, to obtain a sealing or draft mortar. 14. Use of a cement composition according to any one of claims 8 to 11, characterized in that it is used in a temperature range between approximately 5 ° C and 35 ° C. 15.-Concrete or mortar containing a cement composition according to any one of claims 8 to 11 and used at temperatures between 5 and 35 ° C, characterized in that it has a mechanical resistance to compression at 3 hours greater than 0.4 MPA, in particular, 1 MPa, preferably 2 MPa, and a mechanical compressive strength at 28 days greater than 30 MPa.