Steel Deck Slab: Price, Advantages and Disadvantages
When it comes to a resistant, safe slab for large environments, the steel deck slab is one of the most interesting alternatives. The structure is composed of a metallic form, associated with a concrete layer and a metallic screen.
Also known as a collaborative or mixed slab, the steel deck makes the construction process faster. After all, its execution is easier than other types of slabs. Also because it does not demand a large number of pilasters or beams. Keep following and find out how the system works!
The system consists almost entirely of galvanized steel sheets. In the form of a trapezoid, these plates have “holes” in each hinge, holes that, later, will facilitate the hydraulic and electrical installation of the property. This is since it will be enough to pass the pipes and electrical wires in these available spaces.
The concrete used for construction, on the other hand, has minimal resistance to compression. The mesh, in turn, is an anti-crack welded mesh. The sheets have small grooves, which favor the adhesion of the concrete to the surface. In addition, there are situations in which it is indicated to add the number of reinforcements in the system, which increases the strength of the structure.
The use of the late steel deck started around the 1950s, in the United States. Considered fast and practical, it started to be used in the country. In Brazil, the option was adhered to in the 1970s by the company Robtek.
In addition to the practicality of the alternative, its diffusion is due to the cost-benefit ratio. The price of this type of slab is not high, and its durability is immense. The parts still offer a system lighter than the weight of many others used by Civil Construction.
This type of resource is indicated for wider slabs. As in the case of industrial environments, hotels, football stadiums and commercial environments. This does not mean, however, that it cannot be used in residential environments. On the contrary: the parts can even work quite well for multi-storey buildings.
As one of the main advantages, the slab withstands fire situations. This for up to 30 minutes. Therefore, in situations like this, there is usually enough time for the individuals to leave before the slab suffers any real shock.
The Brazilian Association of Technical Standards ( ABNT ) does not yet have specific rules on the steel deck. However, in the construction it is necessary to follow some rules of the association. Like NBR 6118, which concerns the Concrete Structure Project – Procedure; the NBR 8800, on the Project for the Execution of Steel Structures and Mixed Structures of Steel and Concrete in Buildings; the NBR 10735, which addresses high-strength galvanized steel sheets; and NBR 14323, responsible for defining the design of steel structures for buildings in fire situations.
Execution of the Steel Deck Slab
A project to use the steel deck slab should start right before construction. This is because it is more interesting to define the material early on, so that it can be installed in a more practical and safe way. The exchange of a slab is also possible, but little more laborious than the first option.
For the execution of the project, it is necessary to obtain some materials. The first is the collaborative formwork, the galvanized metal sheets that are the basis of the entire structure. It is also necessary to have the concrete and steel mesh of the telam type, already mentioned above. The mesh is always positioned on the slab surface, so that it can prevent cracks in the drying of the concrete.
In addition, the work requires negative reinforcement on the supports. Like side finishes, made mainly of galvanized steel sheets. Finally, it is customary to use the solder to fix some steel structures.
For the execution of the project, it is important to hire a company specialized in steel decks. For installation, the molds are taken to the construction site and lifted up to the height that the slab must cover. These plates are then positioned on the beams, of masonry or iron, already assembled. Aligned, they are fixed to the beams with weld points. For fastening to each other, the steel plates receive self-tapping screws or rivets.
Concrete in the execution of the slab
Then, the anti-cracking mesh is positioned on the steel surface. It must be correctly aligned, and cover the entire form. Soon after, the concrete is applied over the area.
This application, however, is done at only one point on the surface. For this, it is necessary to position the concrete launch pump on one of the beams. The concrete will “drain” alone into the tile openings, so it must be prepared a little more softly than usual. These precautions will prevent excessive weight or vibration on the slab, which could hinder its completion.
Afterwards, the concrete must be allowed to dry. The curing time is indicated by the material manufacturer, and must be strictly adhered to. Otherwise, the material may create cracks and create an inferior result than expected.
It is also essential to prevent the mass from accumulating at some point, as this would make part of the structure heavier than the others. According to ABNT rules, the applied concrete must have uniform thickness. The minimum value is 50 mm.
It is also important to pay attention to the moment when drilling holes in the surface. These holes for the passage of hydraulic or electrical ducts. For it to be done correctly, and safely, the process can only take place after the concrete reaches at least 75% resistance. That is, it must be almost completely dry.
At the end of the work, it is possible to use the steel deck slab as a lining, leaving it exposed. Or else cover it with another type of material. If the option is made by the first alternative, the steel of the tiles can be painted before the entire installation. Thus, the inner lining will be more attractive.
Advantages and disadvantages of Slab Steel Deck
The advantages of the steel deck slab are the most diverse. First, there is the speed of execution of the project. This since it is basically composed of only three stages: the installation of the steel sheets, the positioning of the mesh, and the application of the concrete.
Another advantage of the option is the almost total elimination of the struts during concreting. This allows the construction of different pavements to be carried out simultaneously with the preparation of the slab. The metal profiles of the slab are also self-supporting, which makes them a working platform.
The handling of all structures is also made easier. Especially since the parts are considered light and can be handled in a practical way. The slab can also be used for the construction of different materials, such as masonry, concrete, steel or wood.
Finally, the construction with the steel deck generates less debris than other constructions. In addition to facilitating the cleaning and the work of those responsible, the feature is quite good for the environment. After all, the less waste generated, the less waste will be discarded in nature.
As mentioned over time, the trapezoidal shape of steel sheets also offers advantages. This is because the natural spans of the tiles can work for the passage of pipes and electrical installations. Eliminating the need to create holes, the option speeds up work.
Sizing and Composition of the Steel Deck Slab
In Brazil, steel deck sheets are available in three main thicknesses. There is one that has 0.80 mm, 0.95 mm, and 1.25 mm. The length of each “tile” varies, up to 12 meters. This maximum value exists because it is the largest size that a truck can carry.
The concrete of the structure must have a strength equal to or greater than 25 MPa, while its thickness must be at least 50 mm, as explained.
Finally, the dimensioning of the slab wire mesh needs to be defined by the person responsible for the project. With a series of calculations, the professional will analyze the necessary structure. The iron base must withstand the overload and spans of the project. The professional will also consider the design tables provided by the material manufacturers.
In addition to this information, the design of a steel deck slab must make clear the positioning of each steel sheet. It also needs to list the need for complementary reinforcements or reinforcements, as well as any other information for the execution of the plan. Only a very complete project can offer the best results.
Steel deck slab: table
Each manufacturer of materials and execution of the steel deck slab works offers the consumer a different dimensioning table. The information varies especially with the type of components used to produce the construction parts. The data indicate, for example, the thickness of the galvanized steel plates, the maximum allowable span without struts and the method of fixing the parts.
For example, we brought the tables of three large companies in the industry in the country. Starting with Medabil. According to the brand, the dimensions of its steel plates are 903 mm wide, 73 mm high, and four thickness variations (0.65 mm, 0.80 mm, 0.95 mm and 1.25 mm).
Its weight, on the other hand, is around 6.8 kg / m² up to 13 kg / m². In this case, the maximum allowed span without struts is 3.50 meters. The parts are fixed with stud bolt electrofusion welding and/or plug welding.
The molds from Perfilor, on the other hand, are available in thicknesses of 0.80 mm, 0.95 mm and 1.25 mm. Each piece is 840 mm wide, 59 mm high and weighs up to 14.29 kN / m². The maximum space between the gaps, without the need for scores, is 3.40 m. The method of fixing the “tiles” is spot welding on metal supports.
Finally, Metform products are 0.80 mm or 1.25 mm thick. Its width is 820 mm or 915 mm, with a weight ranging from 1.85 kN / m² to 3.97 kN / m². The height of the pieces, in turn, varies according to the slab model. The maximum span without struts allowed varies between 2.8 m and 4.3 m, depending on the thickness of the iron plates. Its fertilization mode is the solder plug next to the metal beams, and rivets between the panels.
Steel deck: maximum span
The maximum span of a steel deck slab consists of the largest space that a support beam and another can have between them. In other words, the space in which the structure can support itself, without new support.
As mentioned, the maximum spans are defined in the tables of each manufacturer of the slabs. They also vary according to the thickness of each mold. Therefore, before construction, it is essential that the professional responsible for the work knows the information in the table well.
Steel deck price: How much does it cost?
In general, the costs with a steel deck slab are lower than the costs with other types of the slab. The final calculation of the work, however, can only be carried out by a specialized company. After all, it will include both material values and payment for labor in the cost. Therefore, the price per square meter can vary from R $ 64.00 per square meter, or R $ 49.66 per linear meter.
Steel deck: suppliers
Steel deck slab suppliers are specialized companies that offer material and labor for construction. They also offer all and any equipment necessary for the execution of the project, such as finishes and wave covers.
To get quality materials and service, do a lot of research on the company before hiring. Check your references, your history, and even your social networks. The opinion of other consumers is usually available on internet pages, and it can facilitate a lot the definition by a company committed and with good execution of works.