"PREDALLE" Slab Systems

Every designer, architect or engineer, knows the great advantages that the use of PREDALLE in the construction of mezzanines, slabs or roofs means.

The PREDALLE allow to work with many design variants: arches, elements in wedge or of various formats, hollows, integration of beams and brackets, etc.

The system is extremely simple, the PREDALLE is the lower part of the slab, is produced in a precast plant, under strict controls of all the technical aspects, like reinforcements and concrete. The final thickness of the floor is obtained on site by the casting of a layer of concrete to absorb the compression.

The installation of the PREDALLE is very fast, because no formwork is needed (PREDALLE acts as a lost formwork). No heavy lifting systems are required, as the PREDALLE are light. Large surfaces are covered at one time. Reinforcements and metal meshes are reduced to a minimum quantity.

The result is a monolithic, solid slab, with a high resistance to fire and excellent behaviour against the noise.

The PREDALLES are widely used in simple and multifamily housing construction, institutional and commercial buildings (schools, hospitals, offices), and they have a complementary use in infrastructure works (for example to cover spaces between beams in bridges, tunnels, other uses)

PREDALLE CLASSIFICATION:

Depending on the steel reinforced system, we can classify the PREDALLES two big groups

The CLASSIC PREDALLE and the PRESTRESSED PREDALLE.

Other technical aspects allows to classify PREDALLES in: ISOLATED, LIGHT, RIBBED, etc.

1)   THE CLASSIC PREDALLE

TECHNICAL DEFINITION:

The CLASSIC or simply reinforced PREDALLE is a thin plate-shaped element, composed of a layer of concrete, an armature and / or an electro-welded steel mesh, and can incorporate the necessary steel bars for connection with other structural elements and reinforcements.

THE CONCRETE PLATE OF THE PREDALLE:

The concrete plate has different functions. First, it transmits the efforts to the inner reinforcement, which thanks to the concrete coating is protected against the external elements (environment, fire, etc.). The roughness of the upper part of the concrete contributes to the fixation of the casting concrete on site.

THE THIKNESS OF THE PREDALLE:

The thickness of the PREDALLE is variable and ranges from 40 to 150 mm. We could define the standard thickness at 50 mm. The thickness will be defined, among other conditions, by the required steel bars coating, the calculation of the reinforcement, the final thickness of the slab to be build, the constructive details that the project demands and, of course, the local regulations to be applied.

THE WIDTH OF THE PREDALLE:

The width of the PREDALLE varies between 1200 and 2400 mm. The width is generally defined by the precaster and by the equipment used for the production, the possibilities of handling, transport and lifting on site, the customer requirements and the project details. Consideration should be given to the use of "width adjusting" parts of the casting moulds or tables, to optimize the “standard width” and reduce production and construction costs.

The PREDALLE of a standard width guarantee the success and its adaptability to all type of project.

LENGHT AND SHAPE OF PREDALLE:

The length and shape of the slabs correspond to a given project. It is in this context that the PREDALLE are adjusted with their custom design and constitute the strength of the PREDALLE, to which must be added the possibilities of incorporating all kinds of elements, such as:

·        Holes for all kind of installations.

·        Reservations in light weight concrete for future holes.

·        The inclusion of electrical installations (ceiling light boxes, etc.) and other facilities in the production process of the PREDALLE, which allows to accelerate and simplify the assembly process and construction on site.

JOINTS AND UNIONS BETWEN PREDALLES:

The joining systems between different types of PREDALLE are executed by the detail of a joint with chamfer. The shape of this joint will depend on the precaster, the design and, the type of interior finish that you want to give. In general, at these unions or joints, an elastomeric sealant is used, based on polyurethane, high performance type, high humidity curing and mono component, whose advantages are:

·        Being a one-component, ready-to-use sealant, reduces time, effort and need for mixing equipment.

·        Fast drying to the touch and final curing.

·        High elasticity, cures to a solid, durable and flexible consistency with exceptional cut and tear resistance.

·        Excellent adhesion to most primer less building materials.

·        Excellent resistance to aging.

·        Tested in all climates around the world.

 THE QUALITY OF THE CONCRETE:

Both the quality and dosage of concrete can be adapted and adjusted to the demands of the project. Manipulation, loads and the lights to be carried out on precast slabs determine the minimum resistance.

In practice, the resistance characteristics of the concrete used in floor slabs CLASSIC vary between 25 and 30 N / mm2.

THE STEEL REINFORCEMENT OF THE SLAB:

The steel reinforcement from the slab is executed by using high strength steel or structural steel, generally BE500 type with improved adherence through the use of electro-welded mesh, individual bars or a combination of both. The flexibility of the PREDALLE is enhanced given the different possibilities of adaptability to bold projects. The use of stirrups, pins, folded and connections are some of the possibilities of the reinforcement design.

THE REINFORCEMENT STEEL ARMOR:

The greatest innovation of the CLASSIC PREDALLE lies in the steel reinforcement, which performs numerous functions:

·        It gives the PREDALLE the necessary rigidity during handling, transport and the manipulation on site.

·        Ensures, through the roughness of the concrete, the perfect union between the PREDALLE and the cast concrete on site.

·        Acts as a point of attachment during handling.

·        Used as a separator for the upper reinforcement and mesh.

 The steel reinforcement is composed of three elements. The two lower bars are an integral part of the PREDALLE's reinforcement, continuous sinusoidal diagonal reinforcements transfer the stresses to the upper bar and the shear stress between the PREDALLE and in-situ cast concrete. The upper bar keeps the balance of the efforts.

THE COMPRESSION LAYER

From the constructive level, the compression layer is the most important part of the slab plate. It is the active layer of the slab. Once the PRELOSA is in place, the compression concrete is cast on site.

 For the pouring of the concrete it must be taken into account:

·        The Steel reinforcement of joints and connections

On the joints or joints of the PREDALLE, between the reinforcements, small connecting rods will be placed, whose function is that the forged work in monolithic form, and to avoid the appearance of fissures in the layer of compression and in the completion of the inferior face (Interior) of the ceiling.

·        The upper steel reinforcement mesh.

The upper armatures are mounted in all sectors where negative moments must be absorbed. These reinforcements can be mounted on the reinforcements and can serve as stirrups.

·        Supplementary reinforcement

All other reinforcement, indicated in the details of armature assembly, must be considered and installed in its correct position. These additional reinforcements may be necessary for a variety of reasons, for example by the creation of beams incorporated in the slab, to prevent the punching effect of columns, or by the reinforcement of perimeters or edges.

 EQUIPMENTS AND INSTALLATIONS

All types of equipment and installations can be assembled and incorporated into the compression layer, such as electric pipes, heating, drainage pipes, as well as large elements. This allows to avoid the construction of suspended ceilings, with the consequent improvement in free height of mezzanines or the optimization of building heights.

2)   PPRESTRESSED PREDALLE

TECHNICAL DEFINITION:

The PRESTRESSED PREDALLE is a thin plate-shaped element, composed of a layer of concrete, in which the classic reinforcement is replaced by strands or PRESTRESSED wires, which, taking advantage of this technique, increase the loads, the distances between supports and reduction of the arrow, with the same sections of concrete. The characteristics of PRESTRESSED PREDALLE are similar to the classic ones in terms of details of finishes, dimensions and uses. We can define PRESTRESSED PREDALLE as a prefabricated compressed concrete element that forms part of the base or bottom of the section of a slab.

In this type of PRESTRESSED PREDALLE there are no triangular reinforcements, as can be seen in the photo.

COMPOSITION AND MANUFACTURING:

The PRESTRESSED PREDALLE replaces the traditional reinforcement with prestressed steel wires or strands, with a high elasticity limit. The wires or strands are positioned on the fixed production table and tensioned before casting the concrete. Once the concrete has acquired the required resistance, the cables will be relaxed and cut, with the consequent compression of the concrete section.

Step 1: Prestressing of the cables

Step 2: Concrete pouring

Step 3: Relaxation and cut of the wires, and the concrete compression

The PRESTRESSED PREDALLES will be produced with a particularly resistant concrete, type C30 to C37 (compressive strength of 40 Mpa at approximately 28 days)

For demoulding, a minimum curing time of 6 to 12 hours (depending on the type of concrete used and the climatic conditions of temperature and humidity) must be available. To increase productivity, curing acceleration systems are usually used by the implementation of hot water or steam heating circuits on the production tables.

Demoulding is performed once the resistance of the concrete has been verified by laboratory tests. Mobile cranes or gantry cranes are used for demoulding. It is transported to a storage yard.

Transportation to site is done by truck, so it is very important to verify the dimensions of the elements that we are going to produce and the local transport regulations.

For more information please contact: [email protected]