FR2796065A1 - REINFORCED MATERIAL BASED ON HYDRAULIC BINDER, ESPECIALLY CONCRETE, CORRESPONDING COMPOSITION AND PROCESS FOR PREPARATION - Google Patents

Abstract

The invention concerns a hardened reinforced material based on a calcium silico-aluminate hydraulic binder. The binder contains ground clinker grains based on calcium phosphates, said grains being coated, after the binder and the grains have been hydrated, with hydroxyapatite fibres and being distributed substantially homogeneously within the hydrates of the hydrated binder. The grains have a cohesive interface with the hydrates wherein the fibres coating the grains and the hydrates are closely mixed. The clinker preferably comprises 10 wt. % of tetracalcium phosphate, at least 5 wt. % of hydroxyapatite and between 0.5 and 5 wt. % of free lime. The invention is applicable to a cement composition and a reinforced concrete.

Description

The present invention relates to a hardened reinforced material based on a calcium silico-aluminate hydraulic binder, a cementitious composition, a reinforced concrete and a process for preparing such a reinforced material or concrete.

In what follows, the standard abbreviated notation is used: C for CaO, P for P205, HAp for hydroxyapatite, of the formula Calo (P0 4) 6 (OH) 2, substituted or not, H 2 for H 2 O S for SiO 2.

These ratings will be systematically used later, unless explicitly stated otherwise.

A technique often used consists of reinforcing concretes by means of exogenous micro-reinforcements such as, for example, Wollastonite (CS).

To obtain satisfactory mechanical properties, a sufficient quantity of these micro-reinforcements must be used, which has repercussions on the costs as well as on the dependence on the sources, both in geographical terms (some sources being inactive) and commercial (suppliers).

Moreover, to reinforce certain materials, such as, for example, dental cement or cement for prosthesis, it is known to use a mixture of pure tetracalcium phosphate synthesized and other suitable constituents, by hydration. The hydrated tetracalcium phosphate has the property of generating hydroxyapatite and CH-Portlandite, according to reaction 3 (C4P + H) -> -> PAH + 2CH.

The addition of the C4P-mixed components is necessary since C4P alone would not provide a satisfactory reaction rate. This technique, however, requires precise preparation of the mixture and requires the handling of several products. In addition, it is not suitable for the preparation of concretes or other materials based on a silico-aluminate calcium hydraulic binder.

The invention relates to a hardened reinforced hardened base material based on a hydraulic silico-aluminate calcium binder, having improved mechanical properties, and may have in particular good flexural and compressive strengths. The invention more specifically relates to such a material comprising a micro-self-mineral developed in situ, providing a high degree of cohesion and good adhesion with the matrix formed by the hydraulic binder.

The reinforced material of the invention can, by combining the inorganic micro-self-backing in situ and exogenous micro-reinforcements, such as for example wollastonite (CS), to obtain a performance gain greater than that obtained by the addition of a larger quantity of exogenous micro-reinforcements, which represents an economic and strategic advantage. Indeed, the reinforced material is economical because it reduces the amounts of exogenous micro-reinforcements and is strategic because it reduces the dependence on sources of these exogenous micro-reinforcements.

The reinforced material of the invention may also allow a robust formula by the combination of exogenous micro-reinforcements and the mineral micro-self-backing, in which the optimum mechanical properties of the reinforced material are relatively stable with respect to variations in the microparticles. reinforcements in situ and ex situ.

The invention applies in particular to a reinforced concrete that can have, thanks to the presence of the micro-self-resilient mineral, a gain of more than 40% on the bending strength and about 15% on the compressive strength.

The reinforced material of the invention may furthermore be obtained by a process that is easy to implement, involving a good reproducibility of the hydration as well as a satisfactory rheology and durability and a slight sensitivity to variations of a few percent of the constituents used. . The invention also relates to a cementitious composition and a process for preparing a reinforced material or a concrete according to the invention.

The invention thus relates to a hardened reinforced material based on a silico-aluminate calcium hydraulic binder.

According to the invention the binder contains crushed clinker grains based on calcium phosphates, these grains being covered, after hydration of the binder and the grains, with hydroxyapatite fibers (HAp) and being distributed in a substantially homogeneous manner within the Hydrates of the hydrated binder. These grains have with the hydrates a cohesive interface in which the fibers covering the grain and the hydrates are intimately mixed.

The term clinker usually refers to the product of the baking of components at the exit of the furnace, before grinding, but we also understand by this term the crushed product.

Surprisingly, a very effective reinforcement of the material is thus obtained by means of a product based on calcium phosphates, whereas the use of pure C4P would be inefficient because of the slow hydration thereof and that the addition to C4P of known constituents for other types of materials than those based on a calcium silico-aluminate hydraulic binder would not be adapted to the situation and have the drawbacks mentioned above.

The cohesive interface between the crushed clinker grains and the hydrates of the hydrated binder leads to a good adhesion of the micro-self-support, which makes it possible to obtain the very favorable mechanical properties of the reinforced material. The improvement of the mechanical properties is explained by the fact that the clinker grains have a function of hydrate organization, which can allow a reduction of defects or voids in the material and a radial orientation of the hydrates around the grains.

Preferably, the clinker of calcium phosphates before hydration comprises by weight: # at least 10% of tetracalcium phosphate (C4P), # at least 5% of hydroxyapatite (HAp), and # between 0.5% and 5% of lime free (C).

Such a clinker makes it possible to obtain astonishing performances and, used independently of any other constituent, produces a very effective mineral micro-self-support. It constitutes a reactive clinker making it possible to manufacture in situ hydroxyapatite fibers.

This clinker can have the following advantages: - good reactivity; kinetics and progress of the reaction, - good reproducibility of the hydration, - satisfactory rheology and durability, - easy manufacture to be carried out, - reproducibility of the manufacture of the product, and - low sensitivity to variations of a few percent of the constituents used to make this product.

The introduction of the clinker in a cementitious composition based on calcium silico-aluminate hydraulic binder makes it possible to create, after mixing with water, a very cohesive matrix and a good adhesion of the fibers to the matrix.

<B> It </ B> then offers the advantages traditionally obtained with tetracalcium phosphate: - low consumption of water necessary for hydration, - chemical stability of hydroxyapatite fibers, including at high pH (above 12 , 5).

But, compared to the use of pure C4P, this clinker considerably improves the reactivity and cohesion force produced by hydration (mechanical resistance). The significant acceleration of the hydration kinetics of clinker compared to pure C4P can be explained by the following factors: - presence of HAp seeds already contained in the clinker: seeding effect and also the recovery of C4P grains at a rate of higher rate of progress, - presence of free lime which rapidly hydrates in CH, which also produces germs for CH.

The presence of the calcium released by the hydration of the calcium silico-aluminate hydraulic binder slows down the degree of progress of hydration of the clinker, but does not preclude obtaining the reinforced material of the invention, insofar as hydration clinker grains occurs early enough compared to that of the hydraulic binder.

In addition, it is found that this clinker of the invention makes it possible to generate quasi-amorphous fibers of HAp (1 to 4 #Lm), whereas with pure C4P, the size of the hydroxyapatite fibers is generally less than 1 μm. because of higher supersaturations with respect to hydroxyapatite. In the presence of the hydraulic binder, the HAp fibers have a smaller size, for example less than 2 μm in the presence of Portland cement. This decrease is explained by the addition of calcium, which leads to greater supersaturations with respect to hydroxyapatite.

Preferably, the clinker also comprises tricalcium phosphate (C3P) or a solid solution C3P-C2S, in an amount at most equal to 25% by weight.

The C3P-C2S solid solution is obtained in a system containing silica.

In a preferred embodiment, the clinker comprises by weight: at most 75% of tetracalcium phosphate (C4P), at most 50% of hydroxyapatite (HAp), and at most 25% of tricalcium phosphate (C3P); of a solid solution C3P-C2S.

Preferably, according to another definition of the calcium phosphate clinker before hydration, it comprises a distribution of mineralogical phases such as during hydration at 20 C milled clinker with a fineness of 25 #tm for 50% by weight of passing through the sieve (d50 = 25 μm), with equal masses of water and clinker, the heat flux released as a function of time has: - a first initial exothermic peak and a second exothermic peak observed before 1 h 30 from the beginning of the hydration, and a progress rate of the hydration reaction at least equal to 30% at the end of the appearance of this second exothermic peak.

The reactivity of such a clinker is particularly good, particularly in comparison with pure tetracalcium phosphate. This clinker may be of the type defined previously by its mineralogy, and it is moreover advantageously in accordance with the preceding definitions.

The calcium phosphate clinker has a particle size of preferably between 5 μm and 200 μm for 50% by weight of sieve pass.

In a preferred embodiment, the reinforced material according to the invention is a concrete.

The clinker of the reinforced material of the invention is advantageously obtained by the following manufacturing method: a raw material is prepared from a source of phosphate and a source of calcium adapted to the desired mineralogy, and a cooking of this raw material with at least one temperature stage having a level and duration suitable for obtaining this clinker.

According to different forms of implementation, the raw material includes already purified products or natural ores. In an advantageous form of implementation, the raw is a stoichiometric raw vis-à-vis the CIP C4P report.

Preferably, the temperature stages comprise an upper stage having a level of between 1300 ° C. and 1500 ° C. and a duration of between 0 h 30 and 15 hours.

In a particularly advantageous embodiment, the upper plateau has a level of about 1400 C and a duration of about 3 hours.

Another particularly advantageous form, using or not this upper bearing, is such that cooking comprises: a first rise at 600 Clh up to 900 ° C., an intermediate bearing of 1 hour at 900 ° C., a second rise at 600 Clh to the upper bearing, - the upper bearing, - cooling to 1000 Clh up to 1100 C, and - air quenching or slow cooling.

In a preferred embodiment, the raw material is obtained by means of a mixture of CaCO3 and calcium phosphate. The raw material is then advantageously obtained using a mixture of CaCO 3 and CaHPO 4. This mixture may in particular be homogenized by the wet route.

The invention also relates to a cementitious composition (a) based on a mixture of crushed calcium phosphate clinker and calcium silico-aluminate hydraulic binder intended for producing a hardened reinforced material according to the invention. The milled clinker and the hydraulic binder are such that the kinetics of hydration of the clinker is faster than the kinetics of hydration of the hydraulic binder.

Thus, the micro-self-relief produced by the milled clinker is created before the setting induced by the hydraulic binder, which makes it possible to give the clinker its full effectiveness.

This composition is advantageously obtained by mixing or co-grinding.

Advantageously, the hydraulic binder consists of a Portland cement, a composite cement and / or an aluminous cement. The setting produced by the cement then often takes place between 2 and 3 hours from the beginning of the hydration. The clinker used makes it possible to obtain hydration kinetics faster than that of cement.

In order of preference, the clinker in the cementitious composition (a) represents by weight dry cement: # between 2% and 50%, # between 5% and 15%, and # about 7%.

The invention also relates to a reinforced concrete consisting of a hardened cementitious matrix obtained by the hydration of a cementitious composition according to the invention. In a first preferred embodiment, the reinforced concrete of the invention further contains: # granular elements; pozzolanic reaction elements having an elementary particle size of at most 1 μm, preferably at most 0.5 μm; at least one dispersing agent; and satisfying the following conditions: (1) the weight percentage of water E relative to the cumulative weight of the cementitious composition and the pozzolanic reaction elements is in the range 8-24%; (2) all of the components have a grain size d75 of at most 2 mm, preferably at most 1 mm, and a grain size d50 of at most 200 μm, preferably at most 150 pm.

By size of the grains d75 and d50 is meant the sieve sizes respectively, the passer of which respectively constitutes 75% and 50% of the total volume of the grains.

In a second preferred embodiment of the concrete of the invention, it contains in addition to the cementitious composition (a): (b) granular elements; (c) pozzolanic reaction elements having an elementary particle size of at most 1 μm, preferably at most 0.5 μm; (d) constituents capable of improving the toughness of the matrix chosen from acicular or platelet elements having an average size of at most 1 mm, and present in a volume proportion of between 2.5 and 35% of the cumulative volume of the granular elements (b) and pozzolanic reaction elements (c); (e) at least one dispersing agent; and satisfying the following conditions: (1) the weight percentage of water E relative to the cumulative weight of cement (a) and elements (c) is in the range 8-24%; (2) all of the components (a), (b), (c) and (d) have a grain size d75 of at most 2 mm, preferably at most 1 mm, and a grain size d50 of at most 200 μm, preferably at most 150 μm.

Condition (2) applies to all solid constituents (a), (b), (c) and (d) combined, excluding fibers, and not for each separately.

The tenacity of the cementitious matrix is obtained by adding to the cementitious composition elements (d) of average size of at most 1 mm, preferably at most 500 μm, in acicular form or in the form of platelets. . They are present in a volume proportion in the range 2.5-35%, in particular in the range 5-25% of the cumulative volume of granular elements (b) and pozzolanic reaction elements (c).

These elements, given their function of improving the toughness of the matrix, will be referred to below in the description reinforcing elements.

Their size, their nature, their shape, their chemical composition, their geometric properties, the results obtained and their possible surface treatment with the nature of these treatments and their corresponding compounds are described in the international patent applications of Applicants PCTIFR98 / 02552 and PCT / FR99101145.

Preferably, in the first or the second embodiment, the concrete also comprises metal and / or organic fibers.

In a third preferred embodiment, the concrete, in which metal fibers are distributed, contains in addition to the cementitious composition (a): (b) granular elements; (c) pozzolanic reaction elements having an elementary particle size of at most 1 μm, preferably at most 0.5 μm; (d) constituents capable of improving the toughness of the matrix chosen from acicular or platelet elements having an average size of at most 1 mm, and present in a volume proportion of between 2.5 and 35% of the cumulative volume of the granular elements (b) and pozzolanic reaction elements (c); (e) at least one dispersing agent: and satisfying the following conditions: (1) the weight percentage of the water E relative to the cumulative weight of the cementitious composition and the pozzolanic reaction elements (c) is included in the range 8-24%; (2) the metal fibers have an individual length I of at least 2 mm and a ratio II0, <I> 6 </ I> being the diameter of the metal fibers, of at least 20; (3) the ratio (R) between the average length (L) of the fibers and the grain size d75 of all the components (a), (b), (c) and (d) is at least 5 preferably at least 10; (4) the amount of fiber is such that its volume is less than 4% and preferably 3.5% of the volume of the concrete after setting; (5) all components (a), (b), (c) and (d) have a grain size d75 of at most 2 mm, preferably at most 1 mm, and a size of d50 grain of at most 200 Nm, preferably at most 150 pm.

In a fourth preferred embodiment of the concrete, in which organic fibers are distributed, it contains in addition to the cementitious composition (a): (b) granular elements having a maximum grain size (D) of at most 2 mm, preferably at most 1 mm; (c) pozzolanic reaction fines having an elemental particle size of at most 1 μm, preferably at most 0.5 μm; (e) at least one dispersing agent, and satisfying the following conditions: (1) the weight percentage of water relative to the cumulative weight of the cementitious composition (a) and the pozzolanic reaction elements (c) is between 8 and 25%; (2) the organic fibers have an individual length I of at least 2 mm and a ratio 1I6, <I> 0 </ I> being the diameter of the organic fibers of at least 20; (3) the ratio (R) between the average length (L) of the fibers and the maximum gain size D of the granular elements is at least 5; (4) the amount of organic fibers is such that their volume is at most 8% of the concrete volume after setting. In a fifth preferred embodiment of the concrete, in which organic fibers are distributed, it contains in addition to the cementitious composition (a): (b) granular elements having a maximum grain size (D) of at most 2 mm, preferably not more than 1 mm; (c) pozzolanic reaction fines having an elemental particle size of at most 1 μm, preferably at most 0.5 μm; (d) constituents capable of improving the tenacity of the matrix chosen from acicular or platelet elements having an average size of at most 1 mm, and present in a volume proportion of between 2.5 and 35% of the cumulative volume of the granular elements (b) and pozzolanic reaction elements (c); (e) at least one dispersing agent; and satisfying the following conditions: (1) the weight percentage of water relative to the cumulative weight of the cementitious composition (a) and elements (b) is between 8 and 25%; (2) the organic fibers have an individual length I of at least 2 mm and an II0 ratio, <I> 0 </ I> being the diameter of the fibers, of at least 20; (3) the ratio (R) between the average length (L) of the fibers and the maximum grain size (D) of the granular elements is at least 5; (4) the amount of fiber is such that its volume does not exceed 8% of the concrete volume after setting.

Advantageously, the concrete according to the fourth or fifth preferred embodiment has in direct traction a ductility, expressed in terms of ductility coefficient 8, of 8> 1.25.

Preferably, the toughness of the cementitious matrix is at least 15 μm 2, advantageously at least 20 μm 2.

The tenacity is expressed either in terms of stress (stress intensity factor: Kc) or in terms of energy (critical energy rate: Gc), using the formalism of the Linear Mechanics of Breaking.

In the second, the third or the fifth preferred embodiment, the components (d) for improving the toughness are advantageously wollastonite.

The addition of wollastonite (ex-situ reinforcements) in combination with milled clinker (in-situ reinforcements) has the advantage of producing more robust formulas in terms of mechanical properties insofar as the optimal performances are less sensitive to the quantities clinker and / or wollastonite, without degrading performance.

The hydraulic binder of the cementitious composition (a) is advantageously a Portland cement such as CPA Portland cements PMES, HP, HPR, CEM I PMES, 52.5 or 52.5R or HTS (high silica content). This can also be advantageously a compound cement or an aluminous cement.

The granular elements (b), the fine pozzolanic reaction elements (c), the water / cement weight ratio, the dispersing agents (e) and any additives, with their properties, their quantities and the technique for measuring the sizes of the particles, are described in the international patent applications of the Applicants PCT / FR 98/02552 and PCT / FR 99I01145. The matrix may contain other ingredients provided that these do not disturb the expected performance of the concrete.

The concrete according to the first preferred embodiment advantageously has a flexural strength of between 18 and 26 MPa. That according to the second preferred embodiment advantageously has a flexural strength of between 23 and 26 MPa.

The invention also relates to a method for preparing a reinforced material according to the invention or a concrete according to the invention, in which is added to the hydraulic binder crushed clinker based on calcium phosphates.

The invention will be better understood and illustrated with the aid of particular embodiments and implementations that are in no way limitative, with reference to the appended figures in which: FIG. 1 represents a histogram giving the mineralogy of a clinker used for a method for preparing a reinforced material according to the invention, obtained with an upper temperature step of a duration of 3 hours and as a function of the temperature of this stage; FIG. 2 represents a histogram of the mineralogy of a clinker used for a preparation process according to the invention, obtained with an upper temperature level equal to 1400 ° C. and having a duration of 3 hours or 15 hours; - Figure 3 shows the reactivity, in the form of the heat flow (in mW / g) as a function of time (in minutes) during a hydration at 20 C, pure C4P and two clinkers used for the preparation process a reinforced material obtained with an upper temperature step of 3 hours and respectively worth 1300 C and 1400 C, for a grinding corresponding to d50 = 25 gym; FIG. 4 shows the reactivity, in the form of the heat flux (in mW / g) as a function of time (in minutes) during a hydration at 20 ° C., of two mixtures of a Portland cement of the CPA-CEM type. 1 52.5 (High Silica HTS cement) and a clinker obtained with an upper temperature level of 3 hours of 1400 C; FIG. 5 is a photo obtained by TEM micrograph showing the interface between the HAp generated by the hydration of a clinker grain and the hydrated calcium silicate (CSH) generated by the hydration of calcium silicates in a reinforced material according to the invention; FIG. 6 gives the compressive strength Rc (in MPa) of two concretes respectively without and with exogenous micro-reinforcements (wollastonite), reinforced according to the preparation method of the invention by means of a milled clinker, according to the quantity of this clinker (in grams compared to 2000 g of cement); FIG. 7 represents two curves giving the three-point flexural strength Rf (in MPa) of two concretes respectively without and with exogenous micro-reinforcements (wollastonite), reinforced according to the preparation method of the invention by means of a clinker ground, depending on the quantity of this clinker (in grams compared to 2000 g of cement); FIG. 8 shows in the form of a histogram the tenacity (in JIm2) for a concrete comprising exogenous micro-reinforcements consisting of 20% of wollastonite and for three concretes without exogenous micro-reinforcements but reinforced by the process for the preparation of the invention by means of a milled clinker having different contents of the milled clinker.

Calcium phosphate clinker is manufactured, for example, as follows.

In a first step, a stoichiometric mixture is made with C4P in CaCO3 and wet homogenized CaHPO4.

In a second step, this mixture is dried at 90 ° C. in an oven. In a third step, a muffle furnace is baked in a crucible of Pt. This third stage comprises the following phases: - rise to 600 Clh up to 900 C, - step of 1 hour at 900 ° C, - rise at 600 C / h to a higher temperature value, - higher temperature range to higher temperature value, - cooling to 1000 C / h up to 1100 C and - air quenching or slow cooling .

The clinker mineralogy thus obtained depends on the level and duration of the upper temperature stage. Preferably, the upper tier has a level between 1300 C and 1500 C and a duration between 0 h 30 and 15 hours.

The main constituents present in the clinker formed are as follows: C, HAp, a.C3P, PC3P (the latter two constituents are particular crystallographic forms of C3P) and C4P. These phases are respectively referenced 1 to 5 in FIGS. 1 and 2. The reactions in progress for a level of the upper temperature stage of between 1200 and 1500 C are essentially as follows:

     Clinker mineralogy was thus obtained for a duration of 3 hours and levels of 1200 C, 1300 C, 1400 C and 1500 C of the upper temperature plateau (Figure 1), the percentage by weight of each phase. (axis 12) being given in the form of a cumulative histogram as a function of the temperature in C (axis 11). The histogram bars corresponding to the temperatures 1 200, 1 300, 1 400 and 1 500 C are respectively referenced 41 to 44. The bar 44 is not strictly speaking a clinker, but a reference product containing pure C4P. The mineralogy of a clinker formed with an upper temperature level equal to 1400 C and a duration of this stage equal to 15 hours was also obtained. The results appear in a histogram giving the percentage of each phase (axis 12) as a function of time (axis 13, in hours), and showing the bar 45 corresponding to these manufacturing conditions at the side of the bar 43 associated with a level of 1400 C and 3 hours of the upper temperature range (Figure 2).

To obtain the desired clinker, cooking conditions are defined which make it possible to produce, by weight, in the clinker: at least 10% of C4P, at least 5% of HAp, and between 0.5% and 5% of C.

In the examples shown, these conditions are verified by bar 43 (upper temperature level of 1400 C and 3 hours) and (to an insignificant amount regarding the percentage of C4P) by the bar 42 (upper temperature step of 1,300 C and 3 hours).

With regard to the reproducibility of the syntheses, it is found that: - for a plateau of 3 hours, the reproducibility is very good at 1500 C and, below 1500 C, the percentage of the different phases varies by 3% according to the cooking, and - with a bearing of 15 hours, the reproducibility is very good at 1400 C and 1500 C.

In a fourth step, the clinker obtained is milled, advantageously with a fineness of 25 pm for 50% by weight of sieve pass (d50 = 25 gm). This milled clinker makes it possible to carry out reactivity measurements, in which the progress of the hydration reaction of the milled clinker at 20 C, with equal masses of water and clinker, is followed. Thus, the flow of heat released (axis 16, in mWlg) as a function of time (axis 15, in minutes) was drawn (Figure 3) for three products corresponding, respectively, to the bars 44 (pure C4P), 43 (upper level temperature of 1400 C and 3 hours) and 42 (upper temperature level of 1300 C and 3 hours). The curves obtained, respectively referenced 20, 21 and 22, make it possible to follow the progress of the hydration, in particular by the observation of the exothermic peaks.

The curve (pure C4P) has a first steep exothermic peak for the first few minutes, then negligible heat release until about 100 minutes from the start of hydration. Slow heat growth with slow growth and decay then occurs, defining a "second exothermic peak" 60.

For curves 21 and 22 (clinkers at 1400 ° C and 1300 ° C respectively), we also observe first exothermic peaks respectively referenced 51 and 52 during the first minutes, but also second exothermic peaks. respectively referenced 61 and 62, having high values of. heat flux released relative to the curve 20 (of the order of 15 mWlg) and appearing much earlier than for curve 20, these second peaks culminating at times close to 60 minutes from the start of hydration.

It is noted that the level of C4P consumed is worth, respectively for curves 20, 21 and 22: after 50 minutes: 5, 15 and 20%, and after 300 minutes: 10, 65 and 75%.

Thus, it is verified that pure C4P has a low degree of advancement and, in particular, kinetics that are too slow compared with that of Portland cement (the onset of setting of Portland cement being close to 2 hours). In contrast, clinkers corresponding to bars 42 and 43 have a significantly accelerated hydration kinetics compared to pure C4P.

We have investigated the reproducibility of the reactivity of clinker manufactured with an upper temperature level of 1400 C and 3 hours. On ten firings, variations in the following ranges were observed: - intensity of the first peak 51: 40 to 42.5 mWlg, - intensity of the second peak 61: 12.5 to 17.5 mWlg, - time at the summit of the second peak 61: 60 to 75 minutes. Thus, the kinetics of hydration of the clinker is relatively insensitive to variations of a few percent of the constituents for making it.

In an alternative embodiment, instead of seeking to achieve a specific clinker mineralogy, it is ensured that the clinker has a desired reactivity. Thus, advantageously, the clinker comprises a distribution of mineralogical phases such that, during a 20 C hydration of clinker milled at d50 = 50 μm, with equal masses of water and clinker, the heat flux released as a function of time represents a first initial exothermic peak and a second exothermic peak observed before 1 h 30 from the start of hydration, and a progress rate of the hydration reaction of at least 30% at the end of the appearance of this second exothermic peak. These conditions are verified by the clinkers associated with the bars 42 and 43 (FIG. 3).

A preferred embodiment is that associated with the bar 43 (upper temperature stage of 1400 C and 3 hours): - good reproducibility of cooking despite a fairly short plateau, - good reactivity: kinetics and advancement of the reaction, good reproducibility of hydration and satisfactory rheology and durability.

This clinker is that which has been used in cementitious compositions, in the following examples. In these examples, the milled clinker was added to a Portland cement.

According to two examples of implementation in which the cement used is of the CPA-CEM 1 52.5 (HTS) type, the following are respectively mixed: # 1.6 g of HTS and 0.4 g of clinker, and # 0.4 g of HTS and 1.6 g of clinker. The reactivity obtained during the hydration of these mixtures is respectively represented by curves 71 and 72 (FIG. 4), giving the heat flux (mWlg, axis 16) as a function of time (in minutes, axis 15). The two curves 71 and 72 respectively show exothermic peaks 81 and 82, corresponding to the hydration of the cement, approximately 9 hours after the start of the hydration. An inflection of curvature is also visible on the curve 72 at a point 83, a little more than 2 hours after the beginning of the hydration, this inflection corresponding to the second exothermic peak of the hydration of the clinker.

It is thus observed that there is no strong interaction of clinker C4P on the hydration of Portland cement, whatever the percentage of this clinker: the phosphate ions are not accumulated in the aqueous phase. The formation of CH during the hydration of clinker C4P accelerates the hydration of Portland cement a little.

On the other hand, the calcium released by the hydration of the Portland cement decreases by approximately 15% the degree of progress of the hydration of clinker C4P. However, the second step in the hydration of the C4P clinker (second exothermic peak) occurs before the second stage of hydration of the Portland cement during which the setting takes place: so we obtain clinker grains of C4P coated with microparticles. autoreactive surface reactors of HAp, before setting Portland cement.

The reaction interface between a clinker grain coated with HAp fibers is CSH hydrates of Portland cement can be observed on a TEM micrograph. It is thus possible to see, in FIG. 5, a hydrated grain (lower part of the Figure), the reaction interface and the hydrates (upper part of the Figure). The size of the hydroxyapatite fibers is less than 2 μm. In addition, the hydrated C4P clinker grains are distributed in the CSH hydrated binder homogeneously: the gap has an area where HAp and CSH are intimately mixed on less than 0.1 μm. This reactive and cohesive interface leads to good adhesion of micro-self-reinforcements. The clinker defined above is thus advantageously used for the reinforcement of concretes, by the conjugate hydration with calcium silicates, C4P of cementitious compositions. Preferentially, C4P clinker is simply added to the formula of reinforced concrete powders such as those described in international applications PCTIFR98102552 and PCTIFR99101145.

In the following examples, non-fibrated matrices corresponding to BPR (composition 1311) and DUCTAL (composition B2) formulations were used, as indicated in Table I below. The values mentioned are proportions by weight relative to the mass of cement.

<B><U> TABLE <SEP> I </ U></B>
<tb><U> Formulation <SEP> of <SEP> concretes <SEP> used </ U>
<tb> B1 <SEP> B2
<tb> Cement <SEP> 1 <SEP> 1
<tb> Smokes <SEP> of <SEP> Silica <SEP> (MST) <SEP> 0.325 <SEP> 0.325
<tb> Flour <SEP> of <SEP> quartz <SEP> (C500) <SEP> 0.3 <SEP> 0.3
<tb> Sand <SEP> 1.43 <SEP> 1,248
<tb> Wollastonite <SEP> (NYAD <SEP> G) <SEP> 0 <SEP> 0.2
<tb> Superplasticizer <SEP> 0.06 <SEP> 0.06
<tb> E / C <SEP> 0.225 <SEP> 0.225 The silica fumes used are of the MST (Micro Thermal Silica) type, the quartz flour is of the C500 type sold by the company SIFRACO and the wollastonite is of the type marketed under the name NYAD G.

The addition of increasing amounts of a clinker C4P decreases spreading, without the latter being too weak to ensure a good implementation. The decrease in the spread due to the addition of CS (wollastonite) in formulation B2 adds to the decrease induced by the addition of C4P. The results obtained in the spreading tests are given in Table II which follows. This spread was measured after one minute of vibration with respect to an initial cone of 10 cm diameter made with an ASTM cone.

<U> TABLE <SEP> II </ U>
<tb><U> Etching <SEP> (in <SEP> mm) <SEP> in <SEP><SEP> Function of <SEP><SEP> Addon of <SEP> clinker <SEP> C4 </ U > P
<tb> Adding <SEP> of <SEP> clinker
<tb> C4P <SEP> (in <SEP>%) <SEP> 0 <SEP> 3% <SEP> 7% <SEP> 10% <SEP> 15%
<tb> B1 <SEP> 300 <SEP> 300 <SEQ> 285 <SEQ> 260 <SEP> 260
<tb> B2 <SEP> 270 <SEP> 270 <SEP> 270 <SEP> 265 <SEP> 245 The percentage of clinker added is expressed relative to the mass of cement. The compressive strength Rc (in MPa, axis 92) was measured (FIG. 6) as a function of the amount of clinker C4P added (in grams relative to 2000 g of cement, axis 91) in concrete formulations B1 (curve 101) and B2 (curve 102). It is observed that curves 101 and 102 respectively increase to maxima 105 and 106 greater than levels 103 and 104 obtained in the absence of clinker C4P, and then decrease. The maxima 105 and 106 are obtained for about 140 g of clinker, that is to say approximately 7% by weight relative to the cement. For this optimum value, the gain is close to 14% for the formulation B1 and 3% for the formulation B2. Beyond 10%, the addition of clinker C4P is no longer beneficial. The three-point flexural strength Rf (in MPa, axis 93) was also measured (FIG. 7) as a function of the addition of clinker C4P (axis 91), for formulation B1 (curve 101) and B2 (curve 112). ).

For the curve 111, an increase is observed up to a maximum 115 corresponding to about 140 g of clinker (ie 7% of the cement), or a gain of 48.5% compared to the level 113 obtained in the absence of the clinker. The resistance Rf then decreases regularly.

With regard to the curve 112, an increase in resistance is observed up to an upper level 116 of between approximately 50 g and 200 g of clinker (ie between 2.5% and 10% relative to the cement), then a steady decrease. The bearing 116 corresponds to a bending gain of about 13% compared to the level 114 obtained in the absence of clinker.

Thus, for both flexural and compressive strength, the addition of C4P clinker is beneficial for less than 10% of cement and is optimized for an addition of about 7%.

In addition, the combined use of clinker and wollastonite micro-reinforcements (B2) does not alter or slightly alter the maximum values obtained for the resistors, but has the advantage, for flexural strength, of making the formula more robust.

It was also compared (FIG. 8) the tenacity (J / M2 # axis 94) of several reinforced concretes, which respectively correspond to: # the formulation B2 above without addition of clinker C4P (bar 120), and # of the formulations B1 with additions of clinker C4P respectively corresponding to 7% (bar 121), 15% (bar 122) and 25% (bar 123) by weight of cement.

It is thus observed that the increase in tenacity is less for concrete B1 with clinker C4P than in formulation B2, but that the performance is similar for a 7% addition of clinker C4P. These results show the advantages provided in terms of flexural and compressive strength by the addition of clinker C4P, and the interest of the additional addition of wollastonite to make the formulas more robust.

In an alternative embodiment, instead of adding the C4P clinker to concrete, it is used in substitution of cement or quartz flour. The best mechanical performance, however, is obtained by adding clinker C4P.

Claims (24)

<U> CLAIMS </ U> 1. Reinforced reinforced material based on a silico-calcium aluminate hydraulic binder, characterized in that said binder contains crushed clinker grains based on calcium phosphates, which grains are covered, after hydration of said binder and said grains, of hydroxyapatite fibers (HAp) and are substantially homogeneously distributed within the hydrates of said hydrated binder, the grains having with said hydrates a cohesive interface in which the fibers covering said grain and said hydrates are intimately mixed. 2. Reinforced material according to claim 1, characterized in that the clinker of calcium phosphates before hydration comprises by weight: # at least 10% of tetracalcium phosphate (C4P), # at least 5% of hydroxyapatite (HAp), and # between 0.5% and 5% free lime (C). 3. Reinforced material according to claims 1 and 2, characterized in that the clinker of calcium phosphates before hydration comprises tricalcium phosphate (C3P) or a solid solution C3P-C2S in an amount of at most 25% by weight. 4. Reinforced material according to one of claims 2 or 3, characterized in that the calcium phosphate clinker before hydration comprises by weight: # at most 75% of tetracalcium phosphate (C4P), # at most 50% of hydroxyapatite (HAp), and # at most <B>% </ B> tricalcium phosphate (C3P) or a solid solution C3P-C2S 5. Reinforced material according to any one of claims 1 to 4, characterized in that the clinker of calcium phosphates before hydration comprises a distribution of mineralogical phases such as during a hydration at 20 C milled clinker with a fineness of 25 pm for 50% by weight of sieve pass (d50 = 25 Nm), with equal masses of water and clinker, the heat flux released as a function of time has a first initial exothermic peak and a second exothermic peak observed before 1 h 30 from the beginning of the hydration and a rate of progress of the hydration reaction at least equal to 30% at the end of the appearance of said second exothermic peak. 6. reinforced material according to any one of claims 1 to 5, characterized in that the clinker of calcium phosphates with a particle size preferably between 5 and 200 pm for 50% by weight of sieve pass (5 pm <d50 < 200 μm). 7. Reinforced material according to any one of claims 1 to 6, characterized in that it is a concrete. 8. A cementitious composition based on a mixture of crushed calcium phosphate clinker and calcium silicoaluminate hydraulic binder for producing a hardened reinforced material according to any one of claims 1 to 7, wherein said milled clinker and said hydraulic binder are such that the hydration kinetics of the clinker is faster than the hydration kinetics of the hydraulic binder. 9. Cementitious composition according to claim 8, characterized in that the hydraulic binder consists of a Portland cement, a composite cement and / or an aluminous cement. 10. Cementitious composition according to claim 9, characterized in that said clinker represents between 2% and 50% by weight of the dry cement. 11. Cementitious composition according to claim 10, characterized in that said clinker represents between 5% and 15% by weight of the dry cement, and preferably about 7%. 12. Reinforced concrete consisting of a hardened cementitious matrix obtained by the hydration of a cementitious composition according to any one of claims 9 to 11. 13. reinforced concrete according to claim 12, characterized in that it further contains: # granular elements; pozzolanic reaction elements having an elementary particle size of at most 1 μm, preferably at most 0.5 μm; at least one dispersing agent; and satisfying the following conditions: (1) the weight percentage of water E relative to the cumulative weight of the cementitious composition and the pozzolanic reaction elements is in the range 8-24%; (2) all of the components have a grain size d75 of at most 2 mm, preferably at most 1 mm, and a grain size d50 of at most 200 μm, preferably at most 150 pm. Reinforced concrete according to claim 12, characterized in that it contains in addition to said cementitious composition (a): (b) granular elements; (c) pozzolanic reaction elements having an elementary particle size of at most 1 μm, preferably at most 0.5 μm; (d) constituents capable of improving the toughness of the matrix chosen from acicular or platelet elements having an average size of at most 1 mm, and present in a volume proportion of between 2.5 and 35% of the cumulative volume of the granular elements (b) and pozzolanic reaction elements (c); (e) at least one dispersing agent; and satisfying the following conditions: (1) the weight percentage of water E relative to the cumulative weight of cement (a) and elements (c) is in the range 8-24%; (2) all of the components (a), (b), (c) and (d) have a grain size d75 of at most 2 mm, preferably at most 1 mm, and a grain size d50 of at most 200 μm, preferably at most 150 μm. 15. Concrete according to any one of claims 12 to 14, characterized in that the concrete also comprises metal and / or organic fibers. 16. Reinforced concrete according to claim 12, wherein are distributed metal fibers, characterized in that it contains in addition to said cementitious composition (a): (b) granular elements; (c) pozzolanic reaction elements having an elementary particle size of at most 1 μm, preferably at most 0.5 μm; (d) constituents capable of improving the toughness of the matrix chosen from acicular or platelet elements having an average size of at most 1 mm, and present in a volume proportion of between 2.5 and 35% of the cumulative volume of the granular elements (b) and pozzolanic reaction elements (c); (e) at least one dispersing agent: and satisfying the following conditions: (1) the weight percentage of the water E relative to the cumulative weight of the cementitious composition and the pozzolanic reaction elements (c) is included in the range 8-24%; (2) the metal fibers have an individual length I of at least 2 mm and a ratio II0, <I> 0 </ I> being the diameter of the metal fibers, of at least 20; (3) the ratio (R) between the average length (L) of the fibers and the grain size d75 of all the components (a), (b), (c) and (d) is at least 5 preferably at least 10; (4) the amount of fiber is such that its volume is less than 4% and preferably 3.5% of the volume of the concrete after setting; (5) all components (a), (b), (c) and (d) have a grain size d75 of at most 2 mm, preferably at most 1 mm, and a size of d50 grain of at most 200 μm, preferably at most 150 μm. Reinforced concrete according to Claim 12, in which organic fibers are distributed, characterized in that it contains in addition to said cementitious composition (a): (b) granular elements having a maximum grain size (D) of at most 2 mm, preferably at most 1 mm; (c) pozzolanic reaction fines having an elemental particle size of at most 1 μm, preferably at most 0.5 μm; (e) at least one dispersing agent, and satisfying the following conditions: (1) the weight percentage of water relative to the cumulative weight of the cementitious composition (a) and the pozzolanic reaction elements (c) is between 8 and 25%; (2) the organic fibers have an individual length I of at least 2 mm and a ratio II0 where 0 is the diameter of the organic fibers of at least 20; (3) the ratio (R) between the average length (L) of the fibers and the maximum gain size D of the granular elements is at least 5; (4) the amount of organic fibers is such that their volume is at most 8% of the concrete volume after setting. Reinforced concrete according to claim 12 in which organic fibers are distributed, characterized in that it contains in addition to the cementitious composition (a): (b) granular elements having a maximum grain size (D) of at most 2 mm, preferably at most 1 mm; (c) pozzolanic reaction fine elements having a unit particle size of at most 1 Nm, preferably at most 0.5 μm; (d) constituents capable of improving the tenacity of the matrix chosen from acicular or platelet elements having an average size of at most 1 mm, and present in a volume proportion of between 2.5 and 35% of the cumulative volume of the granular elements (b) and pozzolanic reaction elements (c); (e) at least one dispersing agent; and satisfying the following conditions: (1) the weight percentage of water relative to the cumulative weight of the cementitious composition (a) and elements (b) is between 8 and 25%; (2) the organic fibers have an individual length I of at least 2 mm and a ratio II0 where 0 is the fiber diameter of at least 20; (3) the ratio (R) between the average length (L) of the fibers and the maximum grain size (D) of the granular elements is at least 5; (4) the amount of fiber is such that its volume does not exceed 8% of the concrete volume after setting. 19. Concrete according to one of claims 17 or 18, characterized in that it has in direct traction a ductility, expressed in terms of ductility coefficient 8, of â> 1.25. 20. Concrete according to any one of claims 12 to 17, characterized in that the toughness of the cementitious matrix is at least 15 Jlm2, preferably at least 20 JIm2. 21. Concrete according to any one of claims 14, 16 or 18, characterized in that the constituents (d) for improving the toughness are wollastonite. 22. Concrete according to claim 13, characterized in that it has a flexural strength of between 18 and 26 MPa. 23. Concrete according to claim 14, characterized in that it has a flexural strength of between 23 and 26 MPa. 24. A method of preparing a reinforced material according to any one of claims 1 to 7 or a concrete according to any one of claims 12 to 23, according to which is added to the hydraulic binder said crushed clinker based on phosphates of calcium.