In the construction of buildings that have many floors, it will take a very long time and money.
Besides that, it can also require a lot of workers to be able to complete work quickly and on time. In the construction of a building, a very high level of efficiency is needed, if it is not done, it can make costs very swell. In addition, it is also necessary to pay attention to the strength of the material used so that the building can stand firmly and can support the weight of the building above it.
For buildings that have many floors, the strength of each floor will be a matter of concern because it is very dangerous if the floor is not strong enough to withstand the loads above it, but also must be made in a fairly short time.
Hollow Core Slab
A hollow core slab is a method used to make concrete floors for multi-story buildings. In the construction of the floor of a multi-story building conventionally a lot of work is carried out, starting from the initial work, namely working, after which iron is given or often called reinforcement, after which casting is done.
To accelerate it can be given a concrete slab material that has a cavity inside which is commonly called a precast hollow core slab. This HCS can be used in various buildings to be built, which can be in the form of houses, apartments, shopping centers or malls, offices, hotels, parking buildings, hospitals, schools, and others. This HCS can be used for buildings that have a steel structure or buildings that have a concrete structure.
Advantages of Hollow Core Slab
This hollow core slab will be used faster when casting conventionally. Just put the HCS, after that it is given iron or reinforcement, after which the spell is cast. This activity will be faster because the formwork will be passed faster. The advantages of HCS itself are as follows:
- HCS has a lighter load when compared to ordinary concrete slabs. Because of the cavities created in the HCS.
- This Will result in a larger room (from the floor to the next floor) because the dimensional structure is reduced.
- Installation is easier and saves time and even saves money.
- Does not require scaffolding so that the floor below can finish immediately.
- Does not require a formwork system.
- The surface is neat and flat so that the bottom surface can immediately become a ceiling for the floor below.
- Minimizes the risk of earthquake hazards.
Disadvantages of hollow core slab
The most well-known disadvantages of hollow core slabs are:
- Hollow core slabs require more consideration when being shipped. If not very much secured, harm can happen.
- Since they are precast, they are hard to reinforce or fix when harm happens.
- Difficulties with making associations between the precast parts may happen when hollow core slabs are utilized.
- The plan isn’t appropriate for more modest structures and may not be applied for two-way structures due to the restricted board size.
- The pieces of hollow core slabs are weighty and require extraordinary apparatus (cranes) to lift and move them around without harm.
- The joints between the boards are costly.
- The establishment of the boards requires unique abilities and information; it is impossible by anybody.
Now, you know the advantages and disadvantages of Hollow Core Slab, but do you know the types of concrete slabs. Here are some concrete slabs you must know.
Other types of concrete slabs: Advantages and Disadvantages
Executed directly on site, in situ molded slabs involve intermediate-term production processes given the curing time required by concrete; they do not require specialized labor, and they can take very different forms depending on the formwork.
1. Solid Slab
Fully formed in the construction process, with thicknesses that normally vary between 7 and 15 cm, its execution is carried out from a casting that will constitute the mold in which the concrete is poured onto a metallic reinforcement.
Commonly used in small to medium-sized constructions – residential and commercial -, the molds are filled with concrete working in conjunction with the metal reinforcement, according to the heights defined by the structural calculation previously carried out. This system allows, in addition to traditional designs, three-dimensional formats, and fluid shapes. It also has a high degree of resistance to cracks and fissures.
Due to a large amount of material used in the formwork, which is later discarded, there is a high cost in the total value of the work and a greater generation of waste. It should also be noted that since a greater volume of concrete is required and, consequently, a greater weight, the other elements of the structure must also be reinforced, leading to an increase in the material used in the structure.
2. Slab without beams
The slabs without beams are those that support directly on columns. They can be solid, made of reinforced or prestressed concrete, or incorporate another material to form ribbed slabs. They can have capitals of various shapes, square or circular, to avoid punching.
Despite not being used as frequently, compared to other systems it has a great advantage as it allows covering large spans. Due to the absence of beams, which generate discontinuity in the execution of the formwork, it allows a simpler execution, especially compared to other slabs molded in situ, such as ribbed slabs.
Despite allowing large spans to be covered, the main drawback of this system is the cost of the work, since the slabs here require a greater thickness and, consequently, high consumption of both concrete and steel materials, which that in many cases can make its application in the project unfeasible in economic terms. In addition, this system requires specialized labor for its execution.
Structurally, as they do not have beams, the slabs are subject to a high risk of punching shear where, depending on the level of stress that exists between the support and the plane of the slab, the column can pierce it. Faced with this danger, in addition to increasing the thickness of the slab, two possible solutions can be adopted: increasing the dimension of the column, which also generates an increase in material and some cases a disproportion with the project; or even, the execution of a capital. Generally, this last solution is the one most adopted by builders and architects.
3. Ribbed Slab
This type of slab is made up of a tensioned area, made up of nerves or ribs, and a layer of concrete that takes the compression. The space between the ribs can be left empty or elements such as ceramic blocks, aerated concrete, or EPS (polystyrene foam) can be placed, which do not contribute to the final loads. The main function of these elements is to lighten the weight of the structure by eliminating the concrete in the tensile zone, improving the efficiency of the system. The slab has a “T” shaped section, with a concrete layer that receives the compression forces and ribs in which, together with the metallic reinforcement inserted in them, receive the traction forces.
If the distance between the ribs were greater than one meter, the system would be a grating
Compared to the solid slab, this system presents a greater economy, allowing covering larger spans and providing greater design freedom on its surface. For spans greater than 7 meters, it is worth investing in the possibility of using this system. In the case of plants of square proportions, ribs are used in both directions. In the case of very rectangular plants, the use of the ribs is indicated only in one direction, is always arranged in the direction of the smallest light.
Due to the need for precision in the elaboration of the ribs and the placement of the reinforcement, this system requires specialized labor. Also, it requires a greater volume of material for the execution of the formwork. Structurally, they increase the height of the constructions, and due to their design, they present a greater difficulty in the compatibility with other architectural elements such as the building’s installations, both electrical and hydraulic.
The process of the work, involves great care and attention in the concreting, requiring maximum attention in the process of vibrating the concrete.
Produced through industrial processes, these types of slabs are carefully designed to be strong and lightweight. The structural calculation is very precise and involves strict quality control for the materials used. As you can see below, their greater resistance and dimensional regularity make them excellent options for various types of constructions.