PROCESS AND SYSTEM FOR LAYING TRACKS FOR UNDERGROUND, RAILWAY AND TRAMWAY LINES

Abstract

The present invention relates to a process and to a system for laying tracks for ballastless railway and tramway lines, both in tunnel and in surface.

Description

FIELD OF APPLICATION

The present invention relates to a process and to a system for laying tracks for ballastless railway and tramway lines, both in tunnel and in surface. In particular, the proposed system has important evolutions with respect to the traditional systems of anti-vibrating permanent way with tanks÷floating, and not floating, prefabricated slabs.

Hereinafter in the description, under the term “railway and tramway line” an underground, railway and tramway line will have to be meant indistinctly.

BACKGROUND

The ballastless permanent way systems are installed with the purpose of implementing railway superstructures capable of guaranteeing performances in terms of safety and running comfort, maintaining the parameters of geometric quality of the track over time, reducing the direct and indirect costs linked to the maintenance activities, moreover to make possible the resolution of particular problems connected to specific applications in tunnel, in station and other types of work of art.

Systems of Known Art and Disadvantages Thereof

The systems of known art with tanks—prefabricated, floating and not floating, anti-vibrating slabs—provide the laying of artifacts made of ordinary or pre-stressed concrete, with important weight-mass and frequently thickness.

These artifacts are then laid on site on continuous or discrete supports involving the intrados of the tanks-slabs.

In case of discrete supports (used only for the anti-vibrating floating solutions) the laying of tanks-slabs and of the elastomeric discrete supports is implemented dry without possibility of altimetric adjustments (required in relation to the inevitable construction irregularities of the laying bed). Altimetric (and planimetric) adjustments of the upper surface of the rails are then guaranteed in a second phase with laying—by using mortars-bedding grouts on site—sleepers (monoblock, double-block with or without gauge spacer, made of cap, cao, wood, plastics, iron, equipped with or not equipped with under-sleeper elastomeric plates and rubber shoes) housed in compartments existing in extrados to the tanks-slabs.

There are also solutions which provide the use of direct fastening elements implemented on site which provide altimetric adjustments by laying mortars-bedding grouts on site placed below the permanent way metal plate (solutions used, however, even for not prefabricated solutions).

In case of continuous supports (mainly used for the not floating and not anti-vibrating solutions) the laying of the tanks-slabs (and in case of the elastomeric continuous supports) takes place with laying mortars-bedding grouts on site in intrados to the just mentioned artifacts, with possibility of altimetric adjustments (required in relation got the inevitable construction irregularities of the laying bed). In these cases, often one does without using sleepers, the tanks-slabs being equipped in extrados with gauges and inserts for the installation of the fastening elements of the rails.

Generally, these systems are equipped with stoppers (having different positions and types) having the purpose of contrasting the (both transversal and longitudinal) loads in the track bed. These components—in case of the floating and anti-vibrating solutions—should not prevent the tanks-slabs from moving freely vertically (floating freedom of tanks-slabs). The most used position is the one aligned with the (central) track. Solutions with laying of stoppers made of steel-rubber on the flanks of the (side) tanks-slabs are used—less frequently.

The most significant disadvantages of the just described systems of known art with tanks-prefabricated slabs can be summarized as follows:

• • For the discrete solutions the altimetric adjustment during laying is extremely limited [from minimum adjustments of the order of (−5)+(+10) mm to maximum adjustments of the order of (−20)+(+20) mm] and then often not compatible with the usual laying bed construction techniques. This aspect involves both the use of more expensive laying bed construction solutions, and the presence of several construction non-compliance to be removed during construction (with costs and time which not always can be pre-defined and are compatible with the infrastructure construction).
  • For the continuous solutions the adjustment during laying is limited by the reduced thickness of mortars or resins, generally lower than 3 cm. In order to obtain adequate levels of altimetric adjustment the use of important volumes of grouts, but this involves both high costs and time and the use of components (grouts) which often—if not suitably selected and tested (reasonably feasible for reduced volumes)—could involve deterioration in time not compatible with the commercial duration of the track, as already highlighted in previous experiences with mixed cement-asphalt products. Moreover, —in case of high thicknesses of grouts—the use of electro-welded reinforcement meshes could be required.
  • The implementation of the intermediate layer with thicknesses so as to obtain adequate adjustment levels involves the use of materials which have a resistance development time not compatible with the ordinary interruptions of the railway operation for track renewal work.
  • The use of side stoppers, in certain lay-outs of the line, has problems of space which not always can be solved easily.
  • In many solutions of known art there is the presence of elastomeric components characterized by high values of dynamic stiffening (meant as ratio between the static stiffness—mobilized by the gravitational loads moving along the track—and the dynamic stiffness—mobilized by the dynamic phenomena of interaction track+vehicle and of contact wheel+rail), the reduction thereof would guarantee better performances of the track system (both in terms of settlements of the upper surface of the rails, and of the capability of attenuating the vibrations).
  • The construction time often are not compatible with the construction and/or renewal programmes; it appears necessary to reduce to the minimum terms the procedures on site, by privileging prefabrication and pre-assemblies in factory or off-line.

A drawback of the use of prefabricated platforms is linked to the fact that the layouts can vary along their development, it is possible to have straight tracts, curved tracts or planimetric connections with variable curvature and the prefabricated platforms cannot be adapted to the peculiarities of each infrastructure tract. On the contrary, the prefabricated platforms are produced with determined parameters of plan, length, width, orientation of the seats for housing the tracks, etc. For this reason, often it happens that the platforms assembled in series do not support perfectly the course of the layout to be followed.

SUMMARY OF THE INVENTION

The object of the present invention is then to solve the problems nowadays left unsolved in the known art, by providing a modular system for laying tracks for railway and tramway lines. This is obtained through a module as defined in claim 1 and a system as defined in claim 20.

Additional features of the present invention are set forth in the depending claims.

The present invention, by overcoming the problems of known art, involves several and evident advantages.

The ballastless permanent way system and the process according to the present invention are specifically studied to be able to perform installations both on the occasion of renovation work performed with daily (day and night), punctual (weekends) or total interruptions of the railway traffic, and in construction work of new lines. The particularities of the system together with the use of specific laying equipment and machineries allow a high installation speed by guaranteeing the quality of the geometric parameters of the track and of the performance features of the system both in the temporary phases and in the definitive phases.

In particular, the present invention allows to lay tracks both for underground lines and for railway and tramway lines.

Conceptually the railway and tramway solutions are wholly analogous to the underground ones as to operation scheme, assembly mode and type of used components. The sizes of some components, the masses of the massive floating portions and the pitch of the track supports change, varying from 750 mm for the underground and tramway solution up to 600 mm for the railway solution.

Moreover, the system according to the present invention can be installed on any foundation of the railway and tramway line, in terms of layout (see straight stretches and curves with possible superelevation of the external rail) and in terms of infrastructure (see tunnel, cutting, grade, embankment, viaduct).

The system—after suitable dimensioning and selections of the single components described hereinafter and both in the field of the floating and not floating solutions—is capable of adapting to any operating condition, going from the solutions for tramways and undergrounds, to the solutions for high-speed railways.

The ballastless permanent way system according to the invention is characterized as modular, as several configurations can be provided to be adopted depending upon the technical and operating installation conditions, for example in case of installation in renewal interventions performed during daily interruptions of circulation (<24 h), or in case of installation in renewal interventions performed during punctual (36/56 h) or total (>56 h) interruptions of the circulation, or in case of installation in interventions for the construction of a new line.

The system modular conception makes possible further subsequent developments without altering the base features thereof.

The system design is completed by the development of technological solutions which make possible the installation thereof with high qualitative standards, implementation speed and laying reliability.

Interventions for replacing the traditional permanent way can be performed in tunnel, in station on viaduct or on embankment.

In tunnel the system can be installed on the existing bed, both it is made of concrete, super compacted or of the filling-in of the tunnel invert. The line operator should have to check preliminarily the structural stability and the absence of deforming phenomena. In case the system resting plane is constituted by the filling-in of the tunnel invert, the material constituting the filling-in should be characterized in advance by means of a survey plan, cognitive investigations, geometrical reconstructions and on-site tests. The layer should appear compact, without the presence of infiltration water and capable of guaranteeing adequate bearing capacity, on the contrary it should have to be removed and re-constituted.

In station, the system can be used as solution in case of reduced thickness of the permanent way package, especially at underpasses and moreover for keeping clean and decent the seat.

On bridges or viaducts, the prefabricated slab, installed on an intermediate layer having a minimum thickness of 10 cm, does not involve increased loads to the structures. By considering a track with traditional permanent way with an average distance between the paraballast walls of 4.6 m, therefore there is a permanent project load higher than 60 kN/ml, the system according to the invention has a finished weight lower than 25 kN/ml.

On existing embankments, the system installation assumes the laying bed preparation with interventions to be planned depending upon each specific application. The ballastless permanent way system can be used on embankment with a variable thickness (min. 10 cm) of the intermediate layer for dividing the loads on the resting plane, depending upon the specific installation, in particular with regard to respect of gauges at intersections with works of art/overpasses, by reducing the thickness of the permanent way package with respect to the traditional system.

Other advantages together with the features and the use modes of the present invention, will result evident from the following detailed description of preferred embodiments thereof, shown by way of example and not with limitative purposes.

To this purpose the figures of the enclosed drawings will be referred to, wherein:

FIG. 1 is a schematic view in axonometry of a prefabricated slab used in the present invention;

FIG. 2 is a plan view of a slab according to the present invention, prepared for a curve tract;

FIGS. 3A to 3D show the pre-stressed reinforcements used in implementing a slab according to the invention;

FIGS. 4A to 4C show the loose reinforcements used in implementing a slab according to the invention;

FIGS. 5A to 5B show dimensional aspects and/or aspects for arranging a slab according to the invention;

FIGS. 6A to 6B show the use of a TPE strap according to the invention;

FIGS. 7A and 7B show anti-vibrating solutions applied to a slab according to the invention;

FIGS. 8A and 8B show the supporting devices applied to a slab according to the invention;

FIG. 9 shows, by way of example, a section of tunnel with tunnel invert equipped with a ballast system;

FIGS. 10A to 10D show trains which can belong to a laying system according to the invention;

FIG. 11 shows a detail of the train used for removing pre-existing tracks;

FIG. 12 shows a section of tunnel with tunnel invert after the excavating step according to the present invention;

FIGS. 13A and 13B show the steps for laying slabs according to the invention;

FIGS. 14A and 14B show the topographic references used for the plano-altimetric adjustment of the laid slabs;

FIGS. 15A and 15B show a railway tract equipped with temporary tracks and a detail of the temporary junctions implemented according to the invention, respectively;

FIG. 16 shows a detail of a train for casting an intermediate layer according to the invention;

FIGS. 17A to 17C show the implementation of horizontal stabilizing elements according to the invention;

FIGS. 18 to 21 describe, by way of example, the steps of a laying process di according to the invention; and

FIG. 22 shows the implementation of a carriageable surface on a railway tract laid according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The ballastless permanent way system according to the present invention is of the type with prefabricated slabs, laid on the resting plane by means of an intermediate layer to be implemented on site.

With reference to FIG. 1, it shows by way of example and schematically the base element of the system, a prefabricated plate 1 (slab) the manufacturing and installing methods thereof are devised to minimize the use of the adjustments of the fastening system, by leaving them available for possible corrections during operation. FIG. 1 shows by way of example the rails (even if without fastenings) in the final position.

The slab 1 and its manufacturing process are already set forth, for several aspects, in the International patent application PCT/IB2020/058309, in the name of the same Applicant.

The curvature of the geometrical elements of the project track centre is constant at the straight lines and the circular curves and variable at the planimetric connections.

The management of the position of the fastening elements inside the prefabricated element is particularly important with the purpose of following at best the curvature of the rails.

The prefabricated element is produced by means of a formwork with variable geometry, specifically devised and implemented to allow the suitable positioning of the fastening elements with a minimum radius equal to 150 m.

Depending upon the position on the plate, the fastening elements in pairs:

• • rotate to search for the direction radial to the curve of the project layout;
  • translate to put in the correct geometrical position.

FIG. 2 shows an example of slab for the installation in curve.

Some additional technical features, specifically provided for the present invention, applicable to the slab according to the manufacturing process already set forth in the patent application Nr. PCT/IB2020/058309, will be described hereinafter.

Each one of the following features could be provided, depending upon the specific project requirements, alone or in combination with the other ones.

Slab Reinforcements

The prefabricated slab 1 according to the present invention is made of prestressed concrete in the two main directions by means of post-tensioned sheathed wires 11, 12, anchored to the threaded ends by means of metal plates 15 and locking nuts 16.

FIGS. 3A, 3B and 3C show the arrangement of the plan and heading pre-stressing reinforcement. FIG. 3D is an enlargement of the detail in the circle of FIG. 3A.

To reinforce the side portions of the plate, analogously with the mono-block sleepers, the pre-stressing reinforcement is integrated with on-board loose reinforcement 17, preferably with diameter of about 8 mm, as illustrated in the subsequent FIGS. 4A, 4B, 4C.

The stressing state thereto the plate is subjected during the step of re-activating the circulation, further makes advantageous the introduction of loose reinforcements, above all with respect to the punching check in the areas adjacent to the on-board supports, constituted by two lower and upper meshes having diameter of 8 mm with variable pitch.

Slab Dimensions

The subsequent FIGS. 5A and 5B are a plan view and a cross section of a slab 1 according to the invention, respectively.

According to the present invention, the external sizes of a slab are preferably about 2.45 m×4.75 m.

The thickness S of the plate is preferably comprised between about 201 mm and about 215 mm, with a thickness S′ of about 240 mm at the fastenings.

The reduced thickness of the plate allows its use by replacing the traditional permanent way even for solving problems linked to gauge adjustments or reduced ballast thickness.

The minimum distance between the rail base and the plate extrados surface, outside the fastening areas is so as to allow to perform aluminothermic welding, and to allow to perform aluminothermic welding, preferably equal to about 60 mm.

The side walls of the slab 1 preferably can be tilted with respect to the vertical, by an angle α comprised between +5° and −5°.

Prearrangements

In particular, as it can be seen in FIG. 5A, the plate 1 according to the invention advantageously can provide some prearrangements, in particular:

• • Through-holes 22 from the extrados to the intrados having the diameter of about 105 mm for casting the underlying intermediate layer;
  • Two compartments 21 along the longitudinal axis of the slab 1, preferably at the second and penultimate spacing, with sizes of about 278×345 mm for implementing the stoppers;
  • An additional possible service compartment in the centre of the slab to allow to implement a well accessing to underlying water discharge pipes.

It is to be meant that each one of the technical data provided sofar (equipment and/or dimensioning) could be adapted depending upon the specific project requirements.

Slab Treatment

In order to allow to replace the prefabricated element damage after an exceptional event and the reconstitution of the track continuity, the intrados surface of the prefabricated can be treated in the factory with a product having high-penetrating power, applied directly on the concrete surface by making it not adherent to the products thereof the intermediate layer is made. Thanks to its composition, the product succeeds in penetrating by capillarity in depth, by protecting the concrete from degradation phenomena, by creating a hydrophobic effect which drastically reduces the absorption of water and chlorides by preventing the corrosion of the reinforcing rails. Moreover, the product avoids degradation due to the action of freeze-thaw even in presence of de-icing salts. The treatment increases the durability of the prefabricated element.

Alternatively, especially in case of anti-vibrating configuration, described hereinafter, the function of insulating the plate from the intermediate layer can be performed by an under-plate elastomeric mat.

On the side surfaces a trapezoidal profile 30 can be conveniently applied, to be extracted before the removal of the prefabricated element.

Strap

With reference to FIGS. 6A and 6B, in the separation area between slab and on-site casting a strap 31 is fastened which guarantees the system sealing.

To this purpose a strap 31 made of TPE is used for the sealing and elastic waterproofing of joints; it is a special elastic strap with high longitudinal and lateral extension, thin and with high toughness, consisting of a tape made of thermoplastic elastomer on support made of non-woven fabric made of polypropylene, generally used for example for the elastic waterproofing of joints of tunnels and road works or sealing joints for hydraulic works.

Anti-Vibrating Configuration

With reference to FIGS. 7A and 7B, a possible configuration of the slab 1 with capability of filtering vibrations is illustrated. Such configuration provides the use of an elastomeric mat 35, 35′, with thickness preferably of about 25 mm, to support the prefabricated element and in case the installation of an additional mass 36 in the gauge internal area. Such mass 36 for example can be implemented by means of plates made of concrete solidarized to the slab.

The use of the elastomers and the system mass increase allow to obtain the typical performances of a permanent way with capability of filtering vibrations (for example: natural frequency in vertical direction comprised between 18 and 20 Hz for freight trains and passenger trains, settlements in vertical directions lower than 2.5 mm for trains with axial weight up to 225 kN and lower than 3.3 mm for trains with axial weight higher than kN).

Supporting Systems

The prefabricated element according to the present invention is provided with supporting systems consisting of mechanical devices allowing the adjustment of the plano-altimetric position.

With reference to FIG. 5A, each slab 1 preferably is arranged—through relative through-holes 20—for the installation of fourteen mechanical supports 40, 3+3 positioned at about 190 mm from the side edge and additional 4+4 at about 660 mm.

FIG. 8A shows a partial cross section of the slab, with an installed support 40. FIG. 8B shows a section of the slab 1 therefrom four supports 40 are visible.

With reference to FIG. 8A, each supporting device 40 consists of a screw 41 preferably M39 which transfers the load to the resting plane by means of a dividing plate 44. The slab 1 is supported by a steel plate 43, preferably with sizes of about 160×160 mm and thickness of about 15 mm.

The supports 40 could be used in number and configuration according to the different modes, depending upon the load to be sustained.

For example, with the purpose of supporting construction site trains up to 200 kN/axis running at speed not higher than 15 km/h, 3+3 supports 40 in temporary mode could be used.

Additionally, in compliance with the law with reference to the load train LM71, 7+7 supports 40 could be used.

Laying Procedure

The system with slabs according to the present invention can be used advantageously in different types of interventions, for example:

• • Intervention on renewal occasion on net interruption of 5 hours;
  • Intervention on total interruption (operativity in 24 hours);
  • Intervention on punctual interruption of 48 hours;
  • New construction intervention.

Hereinafter the main operating steps are described, with reference to the type of intervention on renewal occasion, allowing a description of all steps which can be provided according to the present invention. It is to be meant that only some of these steps are common even to other intervention types.

By way of example, a detailed description of the operating steps for the intervention case in single-track tunnel with tunnel invert (FIG. 9) will be provided.

For implementing the process according to the present invention, a laying system was specifically devised comprising a plurality of apparatuses, for carrying out the different process steps.

In particular different trains were supplied:

• • a train for the removal and loading of the existing track spans (FIG. 10A);
  • a train for excavating and removing the existing ballast, as far as platform plane (FIG. 10B);
  • a train for launching the slabs, with handling portal and end-on launching wagon (FIG. 10C);
  • a concreting train for the production of concrete on the place of use, to be used for completion casting on site (FIG. 10D).

According to the invention, within the tract being processed there are construction site activities which can be grouped in the following operating steps:

• • laying of slabs
  • On-site casting
  • Laying of definitive rails

Laying of Slabs

Within the tract involved by such step, within the interruption under examination, the following activities are performed:

Track Removal

With reference to FIG. 11, then, one proceeds sequentially to demolish the existing permanent way package.

For the removal, the loading of the track spans and their positioning on the flat wagons are performed by means of cranes 113 and portal 112 placed on the slab launching train 110.

Excavation as Far as Platform Plane

With reference to FIG. 12, after the removal of the existing track spans, the ballast excavation is started as far as the platform plane, through the train 120 of FIG. 10B, thereafter one could proceed with laying the central tube for water removal, the possible adjustment of the bed for the subsequent launch of the prefabricated slabs.

Slab Launching

The prefabricated slabs are transported on the launching site through the slab launching train 110, consisted of flat wagons whereon the same are placed.

The handling of the slabs, from the flat wagon as far as the gripping point of the launching train 110, is performed through a mobile portal 112 (FIG. 13A).

The positioning of the latter in the railway seat through a crane system 113 (FIG. 13B) follows.

At this point a system plano-altimetric adjustment is performed through the temporary supports, FIG. 14A, 14B.

For positioning the slabs on the tunnel side wall topographic references are installed in advance with pitch of 3 m low rope side, with respect thereto the laying and check printout showing the design DO and HO are exported. By using a laser distance meter, equipped with inclinometer, it is possible to detect the distances Dr and Hr and perform in real time the required corrections. For checking the progressive laying, the topographic references placed on the slab are used, with respect thereto the distance Dp from the references on the side walls is defined.

With reference to FIGS. 15A and 15B, during launching the prefabricated slabs are laid with pre-installed temporary rails having length equal to the pitch of the slabs (4.8 m). The rails are jointed therebetween through temporary junctions which will be removed upon the laying of definitive rails.

The laying of temporary rails is performed so that the temporary junctions 61 of the rails result to be at the centre of the first spacing of each slab 1, wherein under the term spacing the region between two consecutive fastenings along the laying longitudinal direction is designated. The junctions 61 are of the rested type and they are implemented with four-hole jaws.

The junction resting is performed by interposing between rail base and slab extrados a shaped element 62 so as to support the rail base and the under-rail plate.

On-Site Casting Execution

With reference to FIG. 16, the on-site casting performs the function of dividing and transmitting the loads, recovering the irregularities of the resting plane and, suitably reinforced, constituting the system foundation.

Such step is performed in the tract wherein the slabs were laid and plano-altimetrically adjusted.

Within the involved tract, the following activities are performed:

• • preparation of concrete;
  • arrangement of the stoppers;
  • casting of intermediate/foundation layer.

Stoppers

With reference to FIGS. 17A, 17B and 17C, the task of contrasting the actions acting in the truck bed, both longitudinal and transversal thereto, is assigned to horizontal stabilizing elements (stopper).

The stoppers consist of two retaining elements (278×345 mm), made of reinforced concrete with reinforcements 70, 71, obtained at two rectangular compartments 21 aligned with artifact 1 at the second and penultimate spacing. The reinforcements 70 consist of “omega”-like bars and casting is implemented contemporary to the implementation of the intermediate/foundation layer.

Concrete

The intermediate layer 50 is implemented with concrete with average thickness of 10 cm, in case the on-site casting constitutes the foundation, this is suitably reinforced and it has a thickness higher than 10 cm, hereinafter the material performance features are reported.

• • Capability of filling up the space between intrados slab and resting plane, thus capability of flowing in the space between the mentioned horizontal surfaces spaced 10 centimetres apart;
  • Slump Flow SF1/SF2 Class, with flowing time t500 (i.e., time for reaching an expansion of 500 mm) comprised between 10 and 15 s;
  • Shrinkage due to limited drying;
  • Quick development of the resistances.

The concrete is produced with an automatic concreting system, installed on the concreting train, equipped with inert storage hoppers provided with electronic weighing balances, cement storage silos provided with electronic balances, mixer provided with a waiting hopper with horizontal agitator against grout sedimentation, conveyor belt, water dosing system, additive dosing system. A helical cavity pump, with progressive adjustment of flow and pressure, is used for casting.

To implement the intermediate/foundation layer a concrete with specific features for the particular use conditions has been developed.

The concrete used for the present invention is of self-levelling type and it is produced by using normal Portland cement (PC) with the addition of calcium sulphoaluminate-based cement (with formula 4CaO·3Al₂O₃·SO₃, abbreviated as CSA). These are accompanied by compounds generally existing in the Portland cement (calcium sulphate CaSO₄·2H₂O) and calcium hydroxide (Ca(OH)₂).

CSA matrix, after combination with mix water, results to be much resistant thanks to the packaging of needle-like crystals of Ettringite (chemically, a trisulphoaluminate tricalcium hydrate: 3CaO·Al₂O₃·3CaSO₄·32H₂O), whose interweaving creates a mechanical interlock which offers a better resistance to the possible propagation of cracks (crazing).

PC matrix is different since the resistance arises from the attraction forces due to capillary phenomena, of Van Der Waals, with chemical bond and others, between the thin plates or foils of C—S—H gel, formed by poorly crystalline calcium hydrated silicates, produced by the cement hydration reactions, in particular by the hydration of the silicates existing in the clinker.

Sulphoaluminous clinker, Portland cement and micronized calcium sulphate, dosed in suitable percentage, in case together with fluidifying and retardant additives, allow to obtain formulations the setting time thereof can be adjusted by varying the mixing ratio, even depending upon the environmental temperature. Thanks to optimization of the ratio between PC and CSA, the concrete according to the present invention is characterized by a quick development of the performances, by controlled shrinkage and optimum resistance to the aggressive environments, in particular to the sulphatic ones.

Advantageously, the concrete developed by the inventors is characterized by a shrinkage due to limited drying and by a quick development of the resistances. The product, even if it guarantees a workability preservation time of 30 minutes, in fact, is able to develop resistances higher than 5 MPa within two hours from casting. Moreover, the CSA-based concrete is able to develop a moderate hydration heat and has a reduced carbon-footprint.

Therefore, the present description refers to:

• • Concrete comprising a binding blend of Portland cement and calcium sulphoaluminate-based cement (CSA);
  • A process for the production of concrete as defined in the present description and in the claims, comprising at least a hydration passage of a Portland cement and calcium sulphoaluminate-based cement (CSA).
  • The use of concrete as defined in the present description and in the claims, for implementing the foundation of railway slabs, in particular prefabricated railway slabs.
  • A process for implementing the foundation of railway slabs comprising at least the following passages:
    • preparation of concrete according to any one of the herein described embodiments;
  • casting of said concrete between the intrados surface of said slabs and a platform plane.

In the present description, under the term “clinker” the base component for the production of cement is meant, so called from the name of the kiln in which the backing process takes place. The raw materials used for the production of clinker are minerals containing silicon oxide (SiO₂), aluminium oxide (Al₂O₃), iron oxide (Fe₂O₃), generally existing in clay, calcium oxide (CaO), and magnesium oxide existing in carbonate rocks.

The present description relates to a concrete particularly advantageous in terms of rheological and mechanical properties, in particular characterized by a shrinkage due to limited drying, by a quick development of the resistances, as well as by an excellent resistance to aggressive environments, for example the sulphate environments.

Therefore, a first aspect relates to a concrete comprising a binding blend of Portland cement and a calcium sulphoaluminate-based cement (CSA).

The combination of Portland cement and CSA cement represents the “blend of the binder”, that is the concrete element which, by reacting with water and by hardening, will create the characteristic monolithic product having hard consistency.

The Portland cement is the product of an industrial process mainly consisting of baking in kiln natural earth (clinker) containing a blend of silicates and aluminates, and in the subsequent mill grinding in presence of small amounts (generally between 4 and 8%) of chalk (CaSO₄ 2H₂O) or anhydrite (CaSO₄).

Several types of Portland cement can be used for implementing concrete, which include traditional Portland cement and/or limestone Portland cement.

In the reaction with C₄A₃S (main constituent of CSA cement), the calcium hydroxide is required. To this purpose it is possible using Portland cement or a derivative thereof, for example CEM II limestone cement or other derived Portland cements provided that they can provide such hydroxide to the extent required.

Under the term “calcium sulphoaluminate-based cement” (CSA), in the present description, cement is meant, comprising or consisting of calcium sulphoaluminate clinker, or a cement wherein the active mineralogical phase from the hydraulic point of view is a phase consisted of calcium sulphoaluminate synthetized starting from raw materials such as bauxite, anhydrite and limestone. The CSA cement used for the preparation of concrete according to the present invention can be obtained by using any one of the methods known in the art. By pure way of example, the CSA cement can be produced by means of baking of bauxite, anhydrite and limestone in rotating kilns at the temperature of about 1300° C. The main constituents of this cement are: Dicalcium Silicate (CaO SiO₂), Dihydrate chalk (CaSO₄ 2H₂O) and/or Anhydrite (CaSO₄), Ye'elimite (4CaO·3Al₂O₃·CaSO₄). The content of Ye'elimite in CSA cement can vary from 35 to 65%.

The concrete set forth by the present description comprises dicalcium silicate (CaO—SiO₂ or C₂S) and calcium sulphate in one of the anhydrous, hemihydrate or bihydrate forms, or combinations thereof.

The hydration of the binding blend of Portland cement and CSA cement involves the formation of ettringite, that is trisulphoaluminatetricalcium hydrate (3CaO Al₂O₃ 3CaSO₄ 32H₂O). The packaging of needle-like crystals of ettringite forming after the combination of CSA matrix with mixing water, is capable of forming a mechanical interlocking which offers a better resistance to the possible propagation of cracks (crazings).

As previously mentioned, in the matrix of Portland cement, the resistance instead originates from the attraction forces due to capillary phenomena, of Van Der Waals, of chemical bond and others, between the thin plates or foils of C—S—H gel, formed by poorly crystalline calcium hydrated silicates, produced by the hydration reactions of cement compounds, in particular by the hydration of the dicalcium and tricalcium silicates existing in the clinker.

In a preferred embodiment, the concrete is characterized by a weight ratio of Portland cement with respect to the calcium sulphoaluminate-based cement varying from 90:10 to 65:35, preferably said ratio is equal to 75:25 or equal to 80:20.

An embodiment in particular relates to a concrete wherein said Portland cement is present in an amount comprised between 65% and 90% by weight, and said calcium sulphoaluminate-based cement is present in an amount comprised between 10% and 35% by weight with respect to the total weight blend of Portland cement blend and CSA cement.

In a preferred embodiment, said Portland cement is present in an amount comprised between 75% and 80% by weight, and said calcium sulphoaluminate-based cement is present in an amount comprised between 20% and 25% by weight with respect to the total weight of blend of Portland cement and CSA cement.

The binding blend of Portland cement and CSA cement has a total weight comprised between 250 and 500 kg/m³, preferably equal to 400 kg/m³.

The concrete, preferably comprising a blend of Portland cement and CSA cement according to any one of the previously described embodiments, is preferably characterized by a volume mass comprised between 2250 and 2400 kg/m³.

According to an aspect, the concrete comprises, apart from the binder blend according to any one of the previously described embodiments, even one or more additives selected among: fluidifying agents of various effect level, for example normal fluidifying agents, superfluidifying agents or hyperfluidifying agents, (suitable for the summer or winter season) retardant, accelerating agents, deaerating agents, expanding agents, shrinkage reducers.

Not limiting examples of retardant and accelerating additives include the citric acid, the tartaric acid, the lithium carbonate and the calcium oxide.

Preferably, the concrete according to any one of the previously described embodiments comprises citric acid.

The citric acid can be used in the concrete in an amount comprised between 0.1 and 0.5% by weight with respect to the total weight of the binding blend, preferably in an amount equal to 0.3%.

The use in the concrete of accelerating agents containing chlorides to the extent higher than 0.1% with respect to the total weight of cement is excluded.

The herein described concrete further comprises a blend of inert materials, more properly known as “aggregates”, that is natural granular material of mineral origin subjected to mechanical processing thereafter, depending upon the size, the fine aggregate (whose maximum size is ≤4 mm) and the big aggregate (whose upper size is >4 mm) are obtained, commonly used in the constructions and the properties thereof are specified in UNI EN 12620. The aggregates constitute the backbone of the conglomerate, the cohesion thereof is guaranteed by the cement-based binder blend.

Aggregates with reduced volume mass can also be used, such as for example expanded clay, vermiculite and perlite, and/or combinations thereof.

The quality and the granulometric composition of the aggregates are important for the good success of the final conglomerate.

Aggregates suitable to be used for the production of concrete according to the present invention are the aggregates commonly used for the constructions made of reinforced concrete, then having a typical maximum diameter of the aggregates commonly used for such constructions, provided that they are capable of providing a self-levelling concrete to be cast in a space with limited height.

The blend of aggregates usable for the preparation of the invention concrete preferably consists of the fine aggregate, in particular sand, and of the big aggregate, designated as “aggregate 4/8” according to the standard UNI EN 12620 (or an aggregate with the percentage passing by mass from 0 to the 20% at the sieve of 4 mm and from 80 to 99% at the sieve of 8 mm).

According to an aspect, said blend of aggregates comprises the big aggregate, in particular aggregate 4/8, in an amount equal to 45% by weight with respect to the total weight of the blend of aggregates and comprises sand in an amount equal to 55% by weight with respect to the total weight of the blend of aggregates.

Even the filler, a very thin material, most part thereof passes at the sieve 0.063 mm, can be added in an amount varying between 50 and 170 kg/m³, preferably equalling to 150 kg/m³. The presence of filler is useful to adjust the technological properties of the blend.

According to an additional aspect, the concrete according to any one of the herein described embodiments comprises water in an amount comprised between 140 and 190 l/m³.

A preferred embodiment relates to a concrete consisting of:

• • Portland cement: 70%
  • CSA: 30%
  • Total binder 400 kg/m3
  • Water 176 l/m³
  • Superfluidifying additive 2%
  • Retardant (Citric acid) 0.3%
  • Filler 150 kg/m3
  • Sand 55%
  • Aggregate 4/8, 45%

A second preferred embodiment relates to a concrete consisting of:

• • Cement Portland: 75%
  • CSA: 25%
  • Total binder 400 kg/m3
  • Water 176 l/m³
  • Superfluidifying additive 2%
  • Retardant (Citric acid) 0.3%
  • Filler 150 kg/m3
  • Sand 55%
  • Aggregate 4/8, 45%

A third preferred embodiment relates to a concrete consisting of:

• • Cement Portland: 80%
  • CSA: 20%
  • Total binder 400 kg/m3
  • Water 176 l/m³
  • Superfluidifying additive 2%
  • Retardant (Citric acid) 0.3%
  • Filler 150 kg/m3
  • Sand 55%
  • Aggregate 4/8, 45%

As previously mentioned, the concrete set forth by the description is of “self-levelling” type, also defined as self-compacting (Self compacting concrete or SCC), it is namely a cement conglomerate which apart from having a high fluidity, in the fresh state, has even a high resistance to segregation since it results to be capable of compacting due to the effect of its own weight without the supply of external energy (mechanical vibration).

The rheological and/or mechanical properties of concrete can be determined and/or quantified by using one/or any one of the standard techniques and methods known in the field. Some of the most widespread equipment for evaluating the rheological properties of the self-levelling concretes, recognized by UNI EN Standard and by the European Guidelines, include Abrams cone (Slump-flow), V-funnel like shape (V-funnel), or the L-like box (L-box).

Abrams cone is generally used to perform a spreading test and a test of the concrete spreading time. The test consists in inserting the concrete within the Abrams cone rested upon a smooth plate with a plane surface and, subsequently, in lifting it by letting the concrete to flow, actuating a chronometer when the same is lifted.

The test by means of Abrams cone allows to determine:

• • the “slump-flow” (d_f), or the final diameter of the concrete cake after the same has ceased to flow, which is the average of two orthogonally measured diameters;
  • the time required so that the concrete cake reaches a diameter (spreading) equal to 500 mm (t₅₀₀).

The slump-flow measurement is proportional to the material flowing capability in absence of obstacles: the higher is the value of d_f, the higher is the material deformability, i.e. its capability of reaching areas distant from the point of inserting the concrete into the formwork. Based upon the value of d_f the European Guidelines and UNI EN 206-9 standard, with the test method of UNI EN 12350-8 standard, divide the self-levelling concretes, relatively to the slump-flow measure, into three classes:

• • SF1, spreading diameter in mm: 550-650;
  • SF2, spreading diameter in mm: 660-750;
  • SF3, spreading diameter in mm: 760-850;

According to an aspect, the concrete has a class of Slump Flow of SF1/SF2 type, a flowing time t₅₀₀ comprised between 10 and 15 seconds and a spreading diameter comprised between 550 and 750 mm.

The concrete is further characterized by a quick development of the resistance. The resistance development can be measured according to UNI EN 12390 standard.

Advantageously, the concrete according to any one of the previously described embodiments is capable of developing short-term resistances, preferably a resistance equal to at least 5 MPa within two hours from casting and it guarantees a workability of at least thirty minutes.

Thanks to its optimum rheological and mechanical properties, the concrete set forth by the present description is suitable to implement most part of the conventional applications, such as the implementation of vertical structures, supporting walls, pillars. The authors of the present invention have found that the herein described concrete results to be particularly suitable for laying slabs and in particular for laying prefabricated railway slabs (or plates), i.e. for the implementation of an intermediate/foundation layer for prefabricated railway slabs.

The present invention, then, further relates to the use of a concrete according to any one of the previously described embodiments for implementing the foundation of railway slabs, such as prefabricated railway slabs.

The intermediate/foundation layer performs the function of dividing and transmitting the loads and of recovering the irregularities of the resting plane. In the procedure for laying the railway slabs, the concrete foundation casting is performed in the tract in which the slabs are laid and adjusted plano-altimetrically. In particular, the casting of said concrete is performed to form an intermediate layer between the intrados surface of said slabs and a platform plane. The optimum rheological properties of the concrete set forth by the invention allow it to fill-in the space between intrados slab and resting plane and then to flow between the two horizontal surfaces.

The present description further relates to a process for the concrete production according to any one of the previously described embodiments, comprising at least a passage of hydrating a blend of Portland cement and CSA cement.

Said passage can be performed by using any one of the techniques and/or of the procedures known to a person skilled in the field.

Preferably, said production process further provides a passage for adding citric acid to the cement blend, in an amount preferably equal to 0.3% with respect to the total weight of the binding blend, useful to modulate the setting time of the blend.

According to an aspect, the herein described concrete production process can include the use of an automatic concreting system, equipped with inert storage hoppers provided with weighing electronic balances, cement storage silos provided with electronic balances, mixer provided with waiting hopper with horizontal agitator against sedimentation of grout, conveyor belt, water dosing system, additive dosing system. For casting a helical cavity pump with progressive adjustment of range and pressure can be used.

According to an aspect, a concreting train, equipped for the concrete production as well as for casting the foundation supporting the slabs, could be used.

According to an aspect, the concreting system can be provided with electric-electronic apparatus for commanding and controlling manually and automatically (even remotely) the system as well for recording all parameters necessary for the product qualitative control.

According to an aspect the concreting train can be provided with a system for managing and controlling the temperature of the product components.

According an aspect of the present invention heating serpentines within casting can be used.

The present description also relates to a process for laying tracks for ballastless railway and tramway lines on prefabricated slabs comprising at least a step of casting an intermediate or a foundation layer made of concrete between the intrados surface of the slabs and a platform plane, wherein said concrete is any one of the previously described concretes.

The invention further relates to a process for implementing the foundation of railway slabs comprising at least the following passages:

• • preparation of concrete according to any one of the previously described embodiments; and
  • casting of said concrete between the intrados surface of said slabs and a platform plane.

In any point of the description and claims the term “comprising” can be replaced by the term “consisting of”.

Examples are reported herebelow, having the purpose of better illustrating the compositions described in the present description, such examples are in no way to be considered as a limitation of the previous description and of the following claims.

EXAMPLES

Examples of concrete composition and corresponding experimental data are reported.

Example 1

• • Portland cement: 70%
  • CSA: 30%
  • Total binder 400 kg/m3
  • Water 176 l/m³
  • Superfluidifying additive 2%
  • Retardant (Citric acid) 0.3%
  • Sand 55%
  • Aggregate 4-8, 45%

	Spreading	Rc, MPa	Rc, MPs	Rc, MPa
a/c	0 min/30 min	2 h	5 h	10 h
0.44	760/700	12.65	15.70	17.55

Example 2

• • Portland cement: 75%
  • CSA: 25%
  • Total binder 400 kg/m3
  • Water 176 l/m³
  • Superfluidifying additive 2%
  • Retardant (Citric acid) 0.3%
  • Sand 55%
  • Aggregate 4-8, 45%

	Spreading	Rc, MPa	Rc, MPs	Rc, MPa
a/c	0 min/30 min	2 h	5 h	10 h
0.44	740/720	6.45	15.8	17.30

Example 3

• • Portland cement: 80%
  • CSA: 20%
  • Total binder 400 kg/m3
  • Water 176 l/m³
  • Superfluidifying additive 2%
  • Retardant (Citric acid) 0.3%
  • Sand 55%
  • Aggregate 4-8, 45%

	Spreading	Rc, MPa	Rc, MPs	Rc, MPa
a/c	0 min/30 min	2 h	5 h	24 h
0.44	740/690	7.00	17.55	22.50

The prefabricated slab, in the phase of implementing the intermediate layer, is preferably sustained by fourteen temporary supports 40 and it continuous to be sustained even in the re-activation phase, then the case will never happen in which the intermediate/foundation layer 50, in the concrete maturation phase, is required to sustain the prefabricated element 1. The activities to implement the intermediate/foundation layer 50 in any case should end at least two hours before the transit of the first train.

Hereinafter the plate-intermediate/foundation layer maximum contact pressures are evaluated. As to the concrete compressive strength value, the value which the product succeeds in widely reaching within two hours from the blend packaging is taken as reference.

Calculation model assumption:

• • 1. For the blend constituting the concrete, a maturation level is considered so that the material resistance is taken equal to fc=5 Mpa;
  • 2. The background coefficient was calculated by considering for the intermediate layer the elastic module corresponding to fck=5 Mpa, obtained by multiplying the elastic module after twenty-eight days for the ratio pcc (t)=(fcm (t=2 hours)/fcm(t=28 days))0.3 and thus Ecm(t)=17870 Mpa;
  • 3. The considered loading cases relate to the operation condition and result to be as follows:
  • a) Structural permanent loads (own weight slab+own weight additional mass);
  • b) Carried permanent loads (own weight track);
  • c) Vertical variable actions deriving from the railway traffic (load model LM71) The maximum contact pressure which is reached considering the envelope of the loading conditions at SLU is equal to 0.26 Mpa.

The reached safety factor FS=fc/σ acting=5/0.26=19.23.

Laying of Definitive Rails

Such phase is performed on tracts in which the laying of the slabs and the casting of the intermediate layer were performed.

Inside the involved tract, within the interruption under examination, the following activities are performed:

• • Discharge of definitive rails on the use place and recovery of the temporary rails (FIGS. 18, 19);
  • Installation, welding and fastening of rails (FIGS. 20,21);

Ballasted—Ballastless Transitions

The transition areas between ballastless permanent way and ballasted permanent way have preferably to be implemented so as to have a vertical deformability of the track as uniform as possible, with a gradual variation of the global stiffness of the structure.

To this purpose it is preferable to plan tracts with length at least equal to V[m/s]×0.5[s] and the maximum variation of the vertical settlement, under the real transiting loads, has not to exceed 0.5 mm.

In the plan of the transition tracts the following solutions can be used, to obtain graduality in the track stiffness variation:

• • Use of fastening systems with several values of vertical stiffness;
  • Use of elastic mats under sleepers;
  • Use of elastic mats under ballast;
  • Prosecution of the stiff base layer below the ballasted track;
  • Use of resins as treatment to limit the ballast elasticity;
  • Use of additional rails to increase the distribution of the loads.

The plan of the transition areas depends upon the function of the extreme stiffnesses to be connected, then it depends upon the installation conditions of the ballastless track and upon the features of the ballasted track to be connected in terms of stiffness of the fastening systems, type of sleepers, thickness of the ballast, stiffness of the bed.

At the end of the working one proceeds with the detection of the laid tract and to the tamping of the connecting ramp between laid tract and existing track.

Carriageable Grid

The slab system according to the present invention can further be made carriageable. With reference to FIG. 22, a grid preferably of pultruded elements made of fibreglass 10 is assembled on the prefabricated element 1 by implementing a carriageable plane the surface thereof can be implemented depending upon the specific needs of each installation. The grid has sizes so as to guarantee the passage of a 18000-kg-weighing fire truck in case of fire. The pultruded profiles 10 made of GFRP (Glass Fibre Reinforced Polymer) are extremely stiff and light, they are not subjected to corrosion and guarantee the thermal insulation.

Electromagnetic Compatibility

The system of ballastless permanent way Overail provides the possibility of implementing prefabricated elements the closed electric circuits of reinforcements thereof are avoided by using not metallic reinforcements. To this purpose, special prefabricated plates are implemented with reinforcements made of FRP—Fiber Reinforced Composite and the reinforcements of stoppers are made of the same material, it is reinforcement, bars, stirrups and mesh developed suitably for reinforcing structures made of concrete.

This type of product is used in installations of permanent way systems in which the feature of radio transparency has fundamental importance for the functionality of the systems and the transportation safety. The product results to be insulating and insensitive to electric fields or electromagnetic waves.

The used reinforcements are of two types:

• • bars of RWB type made of GFRP, implemented according to a production process which does not provide any milling of the bar to obtain the improved adherence;
  • mesh made of monolithic GWN-FRP, having mesh 150/150 and thread diameter 8, wherein warp and weft are produced continuously with polymerization of the composite which takes place downstream of the cycle.

For reinforcing the stoppers, the on-board reinforcements and those for the local reinforcement arranged in the pre-stressed plates, the used RWB bars are equipped with the minimum mechanical features shown in the following table:

TABLE 1
Mechanical features of Rockworm bars
Bar	ffk	Ef	εfk	Af
diameter	(MPa)	(MPa)	(—)	(mm2)
14 mm	755	40000	0.0188	153
10 mm	830	40000	0.0208	78

For the mesh reinforcement arranged in the prefabricated plate the used “GWN-FRP” mesh is provided with the minimum mechanical features shown in the following table:

TABLE 2
Mechanical features of GWN-FRP mesh
Bar		ffk	Ef	εfk	Af
diameter	Mesh	(MPa)	(MPa)	(—)	(mm2)
8 mm	150 × 150	700	35000	0.0200	78

For all provided steel reinforcements: on-board reinforcements, localized reinforcements, C-like elements, “L”-like elements and closed stirrups not subjected to specific sizing, one proceeds with the replacement with analogous element of GFRP by increasing the diameter from diameter 8 mm to diameter 10 mm.

The present invention has been sofar described with reference to preferred embodiments thereof. It is to be meant that each one of the technical solutions implemented in the preferred embodiments herein described by way of example, could advantageously be combined differently therebetween, to create other embodiments belonging to the same inventive core and however all within the protective scope of the herebelow reported claims.

Claims

1. A prefabricated slab for implementing layouts of ballastless railway and tramway lines, with substantially rectangular shape, with a longitudinal direction (L) corresponding to the direction (B) of laying tracks, and a transverse direction (T) orthogonal thereto, made of prestressed concrete both in the longitudinal direction (L) and in the transverse direction (T) by means of a primary reinforcement implemented with post-tensioned, sheathed wires, anchored at respective threaded ends (P) by means of metal plates and locking nuts, said slab further comprising a loose reinforcement, consisting of bars arranged to form a mesh embedded in cement,said slab having a thickness varying, depending upon the longitudinal and transverse sections, between about 200 mm and about 240 mm.

2. The prefabricated slab according to claim 1, wherein said onboard loose reinforcement bars have a diameter of about 8 mm.

3. The prefabricated slab according to claim 1, wherein said primary reinforcement and loose reinforcement are made of non-metallic materials.

4. The prefabricated slab according to claim 1, wherein the external sizes of a slab are about 2.45 m×4.75 m.

5. The prefabricated slab according to claim 1, further comprising at least a through-hole from the extrados to the intrados, with diameter of about 105 mm, for casting the underlying intermediate layer.

6. The prefabricated slab according to claim 1, further comprising at a compartment, open to the intrados, along the longitudinal axis of the slab for housing corresponding horizontal stabilizing elements.

7. The prefabricated slab according to claim 6, comprising two compartments for housing corresponding horizontal stabilizing elements, each one with sizes of about 278×345 mm, at the second and penultimate spacing of the slab.

8. The prefabricated slab according to claim 1, comprising a plurality of through-compartments from the extrados to the intrados for housing corresponding supporting devices each one comprising a mechanical device allowing to adjust the plano-altimetric position of the slab.

9. The prefabricated slab according to claim 8, comprising fourteen through-compartments, 3+3 thereof positioned at about 190 mm from the longitudinal side edges of the slab and additional 4+4 at about 660 mm from said longitudinal side edges.

10. The prefabricated slab according to claim 8, wherein said each supporting device comprises a screw M39 which transfers the load to a resting plane through a distribution plate and a steel plate, with sizes of about 160×160 mm and thickness of about 15 mm to support the slab.

11. The prefabricated slab according to claim 1, wherein the intrados surface of the slab is treated with a product having high penetrating power, applied directly on the concrete surface by making it not adherent to the products thereof the intermediate layer is made and by protecting the concrete from degradation phenomena, creating a hydrophobic effect which drastically reduces the absorption of water and chlorides by preventing the corrosion of the reinforcing rails.

12. The prefabricated slab according to claim 1, comprising a strap made of thermoplastic elastomer fastened in the separation area between slab and on-site casting.

13. The prefabricated slab according to claim 1, comprising a trapezoidal profile (30) applied to the side walls to be extracted before the removal of the prefabricated element.

14. The prefabricated slab according to claim 1, comprising an elastomeric mat fastened on the intrados surface, with thickness optionally from 6 mm to 25 mm.

15. The prefabricated slab according to claim 1, comprising an additional mass made integral with the slab, optionally implemented by one or more concrete plates.

16. A system for laying tracks for ballastless railway and tramway lines on prefabricated slabs, comprising: a train for launching the slabs, equipped with handling portal and wagon for end-on launching the slabs; anda concreting train equipped for the production of concrete and for casting an intermediate or foundation layer, supporting the slabs.

17. The system according to claim 16, wherein said prefabricated slabs have substantially rectangular shape, with a longitudinal direction (L) corresponding to the direction (B) of laying tracks, and a transverse direction (T) orthogonal thereto, made of prestressed concrete both in the longitudinal direction (L) and in the transverse direction (T) by means of a primary reinforcement implemented with post-tensioned, sheathed wires, anchored at respective threaded ends (P) by means of metal plates and locking nuts, said slabs further comprising a loose reinforcement, consisting of bars arranged to form a mesh embedded in cement, and said slabs having a thickness varying, depending upon the longitudinal and transverse sections, between about 200 mm and about 240 mm.

18. The system according to claim 16, wherein said train for launching the slabs comprises flat wagons whereon the slabs are placed.

19. The system according to claim 18, wherein said train for launching the slabs comprises a mobile portal for handling the slabs, from the flat wagon to a gripping point of the launching wagon.

20. The system according to claim 16, wherein said train for launching the slabs comprises a crane system for positioning the slabs in the railway seat.

21. The system according to claim 16, further comprising a train equipped for the removal and loading of spans of pre-existing track.

22. The system according to claim 16, further comprising a train for excavating and removing a pre-existing ballast.

23. A process for laying tracks for ballastless railway and tramway lines on prefabricated slabs according to claim 1, comprising the following steps: launching of the slabs and laying thereof in sequence on a platform plane, said slabs being laid with pre-installed temporary rails;plano-altimetric adjustment of each launched slab, by comparison with topographic references pre-installed along the railway and tramway line;junction of said temporary rails to form continuous temporary tracks;casting of an intermediate or foundation concrete layer between the intrados surface of the slabs and said platform plane;removal of said temporary tracks;installation of definitive rail tracts; andwelding of said definitive rail tracts to form definitive tracks.

24. The process according to claim 23, further comprising a step of removing pre-existing tracks.

25. The process according to claim 23, further comprising a step of excavating a pre-existing ballast, as far as a platform plane.

26. The process according to claim 23, wherein the laying of rails is performed so that said temporary junctions of the rails result to be at the centre of the first spacing of each slab.

27. The process according to claim 23, wherein said temporary junctions are of the rested type and implemented with four-hole jaws.

28. The process according to claim 23, comprising a step of arranging horizontal stabilizing elements below each slab to be laid, preceding the step of casting the intermediate layer, so that said horizontal stabilizing elements result at least partially embedded in the intermediate layer.

29. The process according to claim 23, wherein the concrete of said intermediate layer has a composition so as to guarantee a workability of at least thirty minutes, and development of short-term resistances, preferably a resistance equal to at least 5 MPa within two hours from casting.

30. The process according to claim 23, comprising a step of implementing transition areas between ballastless permanent way and ballasted permanent way to obtain a maximum variation of the vertical settlement not higher than 0.5 mm, and/or and a tamping connecting between the laid tract and the existing track.

31. The process according to claim 23, performed with a system comprising: a train for launching the slabs, equipped with handling portal and wagon for end-on launching the slabs; and a concreting train equipped for the production of concrete and for casting an intermediate or foundation layer, supporting the slabs.