The present invention relates to the field of the realization of pavements. More particularly, the present invention relates to a hydraulic composition for the production of roadways, particularly for pavement repairs. The term reconstruction, operation of public works of removing all or part of the wearing course of a roadway and replace it with a new surface. It is known to build roads based on asphalt, such as bitumen-serious. The asphalt has the advantage of quickly acquire from its compaction resistance to compression. Thus, the asphalt is often used for rehabilitation of a road. However, under certain constraints creep or shearing, the asphalt can be subjected to the degradation mechanisms, especially rutting wearing course of the road. These stresses are caused by the support and the friction wheel on the road, especially during braking phases, acceleration and cornering. Thus, rutting is especially prominent on the pavement roundabouts where the trajectory is curved and wherein the braking and acceleration phases are more important. Furthermore, rutting on roadways performed based asphalt is even more marked than at higher temperatures, the viscosity of the asphalt tends to decrease with increase in temperature. Thus, the use of asphalt allows rapid repair of a floor, but may require a relatively higher maintenance frequency compared to the use of other materials, including concrete. It is known to make concrete pavement including pavement roundabouts, to alleviate the rutting problem related to the use of asphalt. Fresh concrete is transported from the concrete plant to the construction site using truck mixers. The fresh concrete can then be poured on the floor in a formwork and then spread and compacted using a vibrating beam. Alternatively, the fresh concrete can be poured into the hopper of a slipform paver or the hopper of a finisher. The finish of the tread layer is made, for example by scanning to create a surface state in which adhesion is compatible with the vehicle traffic on the roadway. According to professional recommendations cited in the book "Concrete pavements - Technical Guide 2000, LCPC / SETRA," a road can be reopened to traffic when its compressive strength is at least 20 MPa, as determined by method test described in DIN EN 12390-3 of April 2012. The currently used concretes reach a compressive strength of at least 20 MPa after a few days. Accordingly, currently used concrete cause a downtime of the road up to several days against a day to the asphalt. It is known to use concrete fast setting for the construction of buildings. These concretes or mortars fast-setting hydraulic binders are using quick setting and hardening. Concretes using such binders in their compositions, once implemented, acquire high mechanical strength in the short term. These concretes are fluid or self-compacting concrete (or self) and a workability of a minimum time to a maximum of two hours. They preferably have a compressive strength of at least 1 MPa at 4 hours after mixing for the fluid concrete and at least 1 MPa 5 hours after mixing for self-compacting concrete (or self), and at least 12 MPa 24 hours after mixing. The workability of fluid concretes is measured by the slump flow value with the Abrams cone or value of "slump" according to the test method described in the standard NF EN 12350-2 dated of April 2012. This test method allows to classify the concretes according to several classes of sagging from S1 to S5 according to the value of the sag. It is estimated that concrete is fluid when the value of the sag is at least 150 mm, preferably at least 180 mm, which corresponds to the sag class S4. The workability of self-placing (or self) is generally measured from the spreading diameter or "slump flow," according to the test method described in the standard EN 12350-8 dating from November 2010. This test method allows to classify the concretes according to several classes of spreading ranging from F1 to F6 depending on the value of the diameter spreading. It is estimated that self-compacting concrete is (or self-compacting) when the value of this spread is greater than 620 mm (and in general less than 800 mm), which corresponds to the spreading class F6. The consistency of the fluid or self-placing (or self) does not allow their implementation on a roadway. In particular, such fluid concretes or compacting (or self) are incompatible with the use of a slip forming machine or the use of a finisher. Moreover, it is not possible to give a slope to these fluids or self-placing (or self). Thus, the desired objective of the present invention is to formulate a hydraulic composition ready for use with a non-fluid consistency in the droop classes S1, S2 or S3 suitable for implementation on site, maintained for at least the first 90 minutes, and to achieve a compression strength of at least 20 MPa 24 hours after mixing at 20 ° C, preferably 18 hours after mixing at 20 ° C or 14 hours after mixing to 20 ° C, a strength of at least 20 MPa 24 hours after mixing at 10 ° C, and a strength of at least 20 MPa 12 hours after mixing at 30 ° C. The term "ready to use" hydraulic composition delivered fresh requiring no changes in its composition at the site. In particular the additives are incorporated at the time of preparation of the hydraulic composition in the concrete plant and not on site. The development of such a hydraulic composition is rendered all the more difficult it is to achieve accelerated hydraulic composition and thus with limited workability. To this end, the present invention relates to a hydraulic composition for the production of roadways, particularly for the renovation of roadways, comprising: - a hydraulic binder comprising a cement, - from 0.18% to 0.35% of a superplasticiser, percentage expressed as dry weight relative to the cement, said superplasticiser comprising a branched polymer having at least one pendant chain having a terminal function of the phosphonate or phosphate, and - from 0.25% to 2% of a setting accelerator, percentage expressed as dry weight relative to the cement, said setting accelerator comprising a calcium salt, said hydraulic composition having a weight ratio water / cement equal or greater than 0.38 and strictly less than 0.45. Such hydraulic composition overcomes the rutting problem related to the use of asphalt. Indeed, the concrete is not subject to degradation mechanisms such as rutting. Moreover, concrete pavements have several other advantages over asphalt pavements, particularly in terms of resistance to rutting, durability and maintenance costs. A hydraulic composition generally comprises a hydraulic binder and water, optionally aggregates and optionally additives, for example other than those described above. The hydraulic compositions include both compositions in the fresh state and in the hardened state, e.g., a cement grout, a mortar or a concrete. The aggregates used in the compositions of the invention include or sand and gravel defined according to standard EN 12620-A1 June 2008. By the term "hydraulic binder" is meant according to the present invention any compound having the property of hydrating in the presence of water and the hydration of which allows to obtain a solid having mechanical characteristics. The hydraulic binder may be a cement according to the standard "cement" NF EN 197-1 of April 2012. A cement typically includes a clinker and calcium sulfate. The clinker may particularly be a Portland clinker. A Portland clinker is obtained by clinkering at high temperature of a mixture comprising limestone and, for example, clay. For example, a Portland clinker is a clinker as defined in EN 197-1 standard of April 2012. Portland clinker is generally co-ground with calcium sulfate to give a cement. Calcium sulfate used include gypsum (calcium sulfate dihydrate, CaS0 4 .2H 2 0), hemihydrate (CaS0 4 .1 / 2H 2 0), anhydrite (anhydrous calcium sulfate, CaS0 4 ) or a mixture thereof. The gypsum and anhydrite exist naturally. It is also possible to use a calcium sulfate that is a byproduct of industrial processes. Cement is such a type of Portland cement CEM I according to the standard "Ciment" NF EN 197-1 dated April, 2012, preferably belonging to strength class 42, 5N, 42, 5R, 52, or 52 5N , 5R according to the same standard. The cement may also be a type of cement, CEM II, CEM III, CEM IV or CEM V according to the same standard. The cement may also comprise at least one mineral addition. The mineral additives are, for example, dairy (eg as defined in EN 197-1 standard of April 2012, paragraph 5.2.2), pozzolans natural or artificial (eg as defined in EN 197-1 standard of April 2012, paragraph 5.2.3), fly ash (eg as defined in EN 197-1 April 2012 paragraph 5.2.4), calcined shale (eg as defined in the standard EN 197-1 April 2012, paragraph 5.2.5), mineral additives based on calcium carbonate, for example limestone (by such as defined in the standard EN 197-1 2012 April, paragraph 5.2.6), silica fume (eg as defined in EN 197-1 April 2012 5.2.7 ) metakaolins or mixtures thereof. Thus, the invention relates to a hydraulic composition comprising a hydraulic binder comprising a cement, a superplasticizer specific whose proportion is defined in a range determined by dry weight relative to the cement, an accelerator comprising a calcium salt which is defined in proportion a range determined by dry weight relative to the cement, and having a water / cement ratio also defined in a specific range. The combination of the various components of the hydraulic composition in the various ranges claimed as well as a Water / Cement determined possible to confer to the hydraulic composition resulting in a non-fluid consistency subsidence classes S1, S2 or S3 suitable for its implementation implemented on site, maintained for at least the first 90 minutes, and having a compressive strength of up to at least 20 MPa 24 hours after mixing at 20 ° C, preferably 18 hours after mixing at 20 ° C or 14 hours after mixing at 20 ° C, a strength of at least 20 MPa 24 hours after mixing at 10 ° C, and a strength of at least 20 MPa 12 hours after mixing at 30 ° C. Therefore, the use of such a hydraulic composition greatly reduces the downtime of the road compared to current concrete solutions. Moreover, this time to the floor of unavailability approaches the downtime caused by the asphalt solution. A consistency in the slump class S1 allows the application of the hydraulic composition to the floor by a slipform paver or a finisher. A consistency in the slump class S2 or S3 allows the application of the hydraulic composition to the floor using a vibrating beam. These different implementing devices can get a good solid surface but also impart a sloping concrete pavement, which is not possible with a fluid concrete. Such consistencies and such workability include obtained through the use of specific admixtures, including a superplasticizer. The superplasticizer is present in the hydraulic composition in amounts which can range from 0.18% to 0.35% by dry weight relative to the cement. The expression "superplasticizer" means a high water reducing admixture that constant consistency helps reduce over 12% the amount of water necessary for the realization of concrete. A superplasticizer has a fluidifying action in so far as, for the same amount of water, the workability of the concrete is increased in the presence of superplasticizer. The superplasticizer used in the hydraulic composition of the invention comprises a branched polymer having at least one pendant chain having a terminal function of the phosphonate or phosphate. The terminal function of the phosphonate or phosphate of at least one pendent chain superplasticizer allows the pendant chain of gripping of the cement grains. More specifically, the superplasticizer comprises at least one organic compound (I) which is an organoaluminum compound (I) soluble or dispersible, comprising at least a amino-di group (alkylene) and at least a polyoxyalkylated chain or at least one salt of compound (I), said compound (I) having the formula: ta-o (V<» ft J »? font*/ }y i in which : • R is a hydrogen atom or a monovalent hydrocarbon group, saturated or not, having from 1 to 18 (inclusive) carbon atoms and optionally one or more hetero atoms: preferably, R is a hydrogen atom or a hydrocarbon group monovalent, saturated or unsaturated, having from 1 to 4 carbon atoms; • 50% to 100% of the Ri are ethylene, 0 to 50% of R i are propylene and 0 to 5% of the other optional Ri are similar or different and represent an alkylene such as butylene, amylene, octylene or cyclohexene, or an arylene such as styrene or methylstyrene; these Ri optionally contain one or more heteroatoms; • Q is a hydrocarbon group having from 2 to 18 (inclusive) carbon atoms and optionally one or more heteroatoms; preferably Q is a group hydrocarbon having from 2 to 12 (inclusive) carbon atoms, more preferably 2 to 6 (inclusive) carbon atoms, even more preferably is ethylene or propylene; • A is an alkylidene group having 1 to 3 (inclusive) carbon atoms: preferably A represents methylene; • Rj are similar or different and may be selected from: • Group A-P03H2, A having the above meaning, • and the group: wherein B denotes an alkylene group having from 2 to 8 (inclusive) carbon atoms: preferably, B is ethylene or propylene, and A has the abovementioned meaning; • "n" is an integer from 20 to 250, inclusive; • "r" is the number of groups (RO (R i -O) n] groups carried by all the Rj; • "q" is the number of [R-0 (R-0) n] groups carried by Q; • the sum "r + q" is not more than 3; • "y" is an integer equal to 1 or 2. Preferably, the superplasticizer used in the present invention does not include a carboxylic vinyl monomers as illustrated by the following examples do not allow to obtain a good consistency of the hydraulic composition. According to one aspect of the invention, the number of pendant chains is less than or equal to three. The hydraulic composition further comprises a setting accelerator comprising a calcium salt. According to one aspect of the invention, the calcium salt comprises calcium nitrite, calcium nitrate or mixtures thereof. The calcium salt is present in the hydraulic composition in amounts which may vary from 0.26% to 2% by dry weight relative to the cement. The hydraulic composition may also include other additives to hydraulic composition, including an air entraining agent, a thickening agent, a timer, an inerting clays, for example one of those described in the NF EN 934-2 of August 2012, EN 934-3 October 2012 or EN 934-4 of August 2009. The inerting of the clays are compounds that reduce or prevent the damaging effects of clays on the properties of hydraulic binders. The inerting clays include those described in WO 2006/032785 and WO 2006/032786 Furthermore, the skilled person is able to select different values ​​for each component in each range claimed according to the desired characteristics of the hydraulic composition and the climatic conditions. Thus, the higher the proportion of superplasticizer is large in the range claimed, more sag increases and therefore the hydraulic composition tends to a slump class S3. Similarly, the more the accelerator is large proportion in the range claimed, and the hydration of the hydraulic composition is early thereby obtain faster compressive strengths. Of course, the rapid acquisition of resistance to compression is achieved at the expense of workability. Similarly, an increase in the water / cement ratio will tend to delay the acquisition of these resistors in favor of workability. It is also known that an increase in temperature accelerates the hydration process of a hydraulic composition and thus reduces its workability. Thus, a temperature increase during the preparation of the hydraulic composition can be compensated by increasing the proportion of superplasticizer and decreasing the proportion of accelerator. Conversely, a decrease in temperature during the preparation of the hydraulic composition can be offset by the decrease in the proportion of superplasticizer and increasing the proportion of accelerator. Furthermore, pavement for concrete must also meet specific requirements, including in terms of their exposure to the environment as is specified in the standard EN 206-1 dated December 2012. In particular, a floor subjected to freeze / thaw cycles must include a minimum of 4% of occluded air. Thus according to one aspect of the invention, the hydraulic composition comprises from 0.001% to 0.1% of an air entraining agent, the percentage being expressed by dry weight relative to the cement, and preferably from 0.001% to 0, 06%. The presence of air-entraining agent in the proportions cited allows to incorporate a minimum of 4% of occluded air in the hydraulic composition according to the region in which the concrete is to be cast so as to satisfy the requirement of the NF EN 206-1 dated December 2012. At first, having to obtain short-term high resistance contradicts the normative requirement of having to incorporate minimum 4% entrained air to withstand the freeze / thaw cycles. The present invention can manage the tradeoff between the amount of entrained air required by the standard EN 206-1 from December 2012 and the compressive strength of the hydraulic composition. The presence of an air entraining agent also possible to impart to the hydraulic composition a good resistance to peeling due to gel in the presence of deicing salts. Air-entraining agents are admixtures that drive and stabilize a large number of micro air bubbles uniformly distributed in the mass of the hydraulic composition and remaining after hardening of the hydraulic composition. Unlike air bubbles occluded air bubbles intentionally driven are extremely small (10 to 500 μηη). These bubbles are not intimately connected and are uniformly distributed in the paste, the paste being defined as the hydraulic binder mixture, water and air. In one aspect of the invention, the air entraining agent comprises a fatty acid sulphonic, carboxylic fatty acid or mixtures thereof. Carboxylic fatty acid leads to faster air a sulfonic fatty acid. However, the amount of air entrained by a saturated fatty carboxylic acid beyond a certain amount of entrained air. A sulfonic fatty acid is more soluble than a carboxylic fatty acid, allowing it ultimately can lead to higher amount of air that can be driven by the carboxylic fatty acid. A floor can also be classified according undergone vehicle traffic. This classification is defined in the standard "cement concrete pavement" NF P98-170 dating from April 2006 and is based on the estimated number of HGVs per day and direction of travel on the road. According to the traffic class of the roadway, gravel is crushed preferably used to increase adhesion between the tires of the vehicle and the road rather than rolled gravel. In both cases a surface treatment to increase the adhesion between the vehicle tires and the roadway may be envisaged, for example by grooving, by scanning, shot peening. Examples illustrating the invention without limiting the scope of protection, will be described below. While the invention has been described in connection with particular embodiments, it is obvious that it is not limited and it includes all the technical equivalents of the means described and their combinations. EXAMPLES In the following different examples, percentages are percentages by weight. The designation D / d as defined in the NF EN 12620 + A1 is specified in the various tables for sand and gravel used. Example 1: Selection of the superplasticizer and definition of the components of the hydraulic composition consistency tests on a hydraulic composition were carried out at 20 ° C with five different superplasticizers, such as: - 1 superplasticizer sold under the name Optima 203 and comprising polymers of the chemical family of polyalkoxylated polycarboxylate (PCP), - 2 superplasticizer sold under the name Advaflow 450 and comprising polymers of the chemical family of PCP, - 3 superplasticizer sold under the brand 135 Omega, and mainly comprising polymers of the chemical family of PCP, - 4 superplasticizer sold under the brand Optima 100 and belonging to the chemical family of phosphonate. The superplasticizer is a branched polymer having at least one pendant chain having a terminal function of the phosphonate or phosphate. The hydraulic composition used to test each of these four superplasticizers included cement from cement plants Teil, mineral addition with a specific surface area of limestone filler 0.8 m 2 per gram and from the quarry Beatus, aggregates from Career paw and Brefauchet and a four superplasticizers test. The amount of the components used for each of the four tested hydraulic compositions is summarized in Table 1 below, unless otherwise specified values ​​are expressed in kilograms per cubic meter of hydraulic composition: hydraulic composition Cl C2 C3 C4 Le Teil cement CEM 1 52.5R 416.7 416.7 416.7 416.7 Filler Saint smug 52.91 52.91 52.91 52.91 Sand 0/4 Limp 766.9 766.9 766.9 766.9 4/6 Limp 187.1 187.1 187.1 187.1 Gravel 6/10 Limp 187.8 187.8 187.8 187.8 11/22 Brefauchet 661,6 661,6 661,6 661,6 superplastifiant 1 4,68 superplastifiant 2 5,03 Superplastifiants superplastifiant 3 4,38 superplastifiant 4 3,24 Water efficient 175175175175 Rapport E / C 0.42 0.42 0.42 0.42 Paste volume (L / m3) 328 328 328 328 Superplasticizer (% dry / L) 0.22% 0.30% 0.22% 0.21% Table 1: Formulas are différenl hydraulic compositions tested The percentage shown in the last line of Table 1 indicates the proportion by dry weight of superplasticizer used in the hydraulic composition. These tests were carried out according to the following procedure: - introduction of sand and gravel into the mixer, - implementation of the mixer road - introduction in 30 seconds of prewetting water equivalent to 5% of the mass of granulate, this quantity of water being cut off on the amount of mixing water, - kneading for 30 seconds - rest for 4 minutes - Mixer stopped, introduction of the cement and optionally the filler in 1 minute, - mixing for 1 minute, - introduction in 30 seconds the mixing water including the admixture while maintaining kneading, - mixing for 2 minutes, - Stop the mixer. The mixer used is brand Pemat ZK50HE model. It comprises an eccentric movable blade which rotates at 60 rev / min into a vessel which also rotates in the same direction 40TR / min. The differential speed between the eccentrically movable blade and the tank creates shear. The shear is amplified by a fixed blade fixed to the edge of the tank and returns the product to the eccentrically movable blade. The slump measurements were then carried out according to DIN EN 12350-02 April 2012. The press used is the 3R Quantris brand and model. The results of these tests were summarized in Table 2 below, the values ​​being expressed in cm: Table 2: Slump test results with many superplasticizers These results have shown that hydraulic compositions C1, C2 or C3 have poor maintenance of rheology. This poor maintenance of rheology does not ensure consistency compatible with use on a roadway. Only the hydraulic composition C4 using 4 superplasticizer sold by Chryso under the trade name of Chryso ® Fluid Optima 100 exhibited a sag 90 min and even at 120 min is closest to the starting substance to 5 min, which gave to the hydraulic composition consistent with the desired consistency consistency of objectives for use on a roadway. This superplasticizer is sold in liquid form. The specifications provided by the manufacturer specifies that the amount of superplasticizer dry matter for this is equal to 31% ± 1 .5%. From this superplasticizer, several other hydraulic composition formulas were performed. Example 2 Formulations of wasted witnesses The tests of Example 2 were intended firstly to define a range of values ​​for the proportion of superplasticizer in the hydraulic composition, but also aimed to the other to define a range of values ​​for the accelerator calcium salt type and for the water / cement ratio. The hydraulic compositions made using different cements and fillers and various aggregates. The cements used come from the Lafarge cement Teil for the type of CEM I 52.5R, from Le Havre to Lafarge cement type CEM I 52.5N and the Lafarge cement plant Kujawy in Poland for EMC type of cement I 42.5R. The technical characteristics of each of these cements are summarized in Table 3 below: Cement 1 Cement 2 Cement 3 CEM I, CEM I 52.5 52.5 CEM I 42.5 N CE CP2 R CE CP2 R NF NF Kujawa Cement: Le Havre Le Teil Poland Snaring the mono 63.10 62.40 59.30 Belite 15,10 17,20 14,80 Ferrite 9,00 7,50 10,40 Aluminate Cubic 6.60 4.30 3.10 Aluminate Mineralogical composition ortho 0.80 0.10 2.20 (Wt%) Lime CaO 0.40 0.50 0.30 Portlandite Ca (OH) 2 0.40 0.00 2.00 Periclase 0.50 0.00 0.20 Quartz 0,00 0,20 0,20 Calcite 0,90 3,20 4,20 Gypsum 1, 90 1, 10 0,30 Added (% by mass) Se mi -hydrates 1, 10 0,80 3,00 Anhydrite 0,20 2,60 0,00 Free CaO (wt%) 0.85 0.52 2.14 K20 Soluble 0,32 0,14 0,44 soluble alkali (% mass) Na20 Soluble 0,08 0,11 0,08 chemical composition of the Si02 20.14 20.42 19.17 clinker (wt%) 5.19 4.40 4.82 AI203 Fe203 2,78 2,42 3,17 Chemical composition of CaO 65.06 65.50 63.39 clinker (wt%) MgO 1 ,21 0,92 1 ,24 K20 0,36 0,15 0,57 Na20 0.16 0.17 0.23 S03 3,01 3,55 3,11 Ti02 0.23 0.20 0.30 Mn203 0,09 0,05 0,08 P205 0.20 0.07 0.12 Value