In multi-storey and private construction, it is impossible to do without floor slabs, which are of several types: precast reinforced concrete, monolithic and beam. In private and low-rise construction, the procedure of self-reinforcement of floor slabs is often practiced, which, thanks to the tandem “concrete and reinforcement”, have increased strength. In addition, stair steps, reinforced and arched lintels are made in a similar way..
The manufacture of a monolith is not complete without the use of reinforcement, which acts as a binding material in reinforced concrete structures – reinforced slabs, stair steps, reinforced and arched lintels. The process of reinforcing monolithic floor slabs is carried out with the help of reinforcement, which has a cross section of 8 – 14 millimeters, with the condition that the slab differs in thickness up to 150 millimeters. However, the thickness of the reinforcement may vary, depending on the type of product..
Reinforced floor slabs allow you to solve the concept of building truly warm houses. They are used in residential, commercial and industrial construction for the organization of roofs and interfloor horizontal slabs. Slabs of coatings and ceilings allow you to end up with warm interfloor floors, as well as provide reliable protection from the cold of attic rooms and operated attics and the absence of cold bridges.
Reinforced concrete floor slabs, like ordinary concrete, have a specialized marking, and it is recommended to pay attention to it when choosing slabs. Reinforced concrete is marked with marks that consist of letters and numbers. The semantic load of letters indicates the type of plate. For example, PC – floor slabs, PNO – lightweight flooring slabs, or HB – internal flooring. By the numbers that follow the letters (placed with a hyphen), you can recognize the dimensions of the slab: width and length in decimeters.
The most insidious in decoding is the last figure, which means the permissible loads on the floor slab in kilopascals. It is important to remember that any unit that is contained in the last digit means 100 kilograms per 1 square meter of the stove. For example, the number 7 warns you that the maximum loads on the product are 700 kilograms per square meter..
When choosing a concrete slab, you need to pay attention to the fact that these structures can differ not only in size and their markings, but also they are different in structure. Depending on the cross-section, reinforced concrete slabs are divided into 3 types: solid, ribbed and hollow. The most sold and popular in the construction market are hollow core slabs, which they have many worthy advantages..
Such floor slabs have, first of all, a relatively low weight, which simplifies the procedure for their transportation and installation. Also, such plates withstand deformation test better, have excellent heat and sound insulating properties. You should be aware that voids in reinforced slabs come in various shapes: oval, vertical or round.
Due to such differences, reinforced slabs can be selected for specific situations, depending on the natural features and the climate of the area in which you plan to build a house. Useful information when buying reinforced concrete will be the fact that in the case of using floor slabs as only a ceiling or floor, it is worth practicing the reinforcement of ribbed floor slabs, the ribs should go only from one side.
All reinforced floor slabs are recommended for use in coatings and ceilings of residential and public buildings and structures with walls made of aerated concrete blocks, bricks and large blocks. Floor slabs are suitable for buildings with an indoor air humidity of up to 60% and for buildings with a vapor barrier on the inner surface of the walls with an indoor air humidity of up to 75%. The depth of support of floor slabs on load-bearing walls should be taken at least 80 millimeters.
Reinforced plates allow not only to achieve high-quality insulation of the building, but also to speed up the construction process itself, as well as increase sound insulation. The low weight of reinforced slabs and concrete lintels reduces the load on the walls and foundation, allowing you to additionally obtain an economic effect when building a house. The procedure for reinforcing hollow core slabs does not require huge construction equipment such as a crane..
As a result, the structure is very durable, it can withstand colossal stresses and the effects of fire for a long period without problems. For comparison, it is worth making a reservation that a wood floor can withstand a fire effect only for 25 minutes, but monolithic floor slabs – more than an hour.
Construction using floor slabs and huge blocks allows the construction of buildings of any complexity and any size. In the manufacture of monolithic floor slabs, it is possible to overlap a room that has an irregular wall geometry. In this way, even non-standard overlap sizes can be created. A support for such a reinforced floor can be not only walls, but also columns, which makes the layout of the house more free.
If we talk about the components, then the traditional reinforcement scheme for floor slabs looks like this: working rods at the bottom of the slab, working rods at the top, reinforcement that redistributes the load, wire rod supports. The applied drawings may have some differences. But in any case, it is important to correctly calculate the planned load and the required concrete thickness. The thickness is calculated from the proportion of 1:30, so to find out the required concrete thickness, you need to divide the span length by 30 – and you will get the optimal thickness.
If the thickness of the slab is more than 150 millimeters, then the reinforcement in these cases is made in 2 layers, where they are located on top of each other and are connected by wire to each other. The size of the cells should not be more than 200 by 200 millimeters, but also not less than 150 by 150 millimeters. So, for example, if the width between the load-bearing walls is six meters, then the thickness of the reinforced slab should be 0.2 m.
If you deliberately reduce the thickness of the concrete, then the consumption of rolled metal will increase, if the thickness increases, then the costs of concrete will also increase. For the strength of the products, it is advisable to use reinforcement of the same section. Additional reinforcement can be done using rods that have a length of 400-1500 millimeters.
The main loads are on the lower reinforcement, and the upper reinforcement receives a compressive load, which is also perfectly handled by concrete. Remember that the process of reinforcing a monolithic floor slab should be carried out over the entire length of the product, as well as using formwork, which is the most important stage in the installation of the slab. You can even use wood for this – ordinary boards of 50 x 150 millimeters or inexpensive plywood..
The main thing is to firmly and reliably fix the formwork struts, because the weight of the concrete used in this operation often reaches 300 kilograms per one meter of square floor. The only thing that is difficult to do without when installing a reinforced floor slab is telescopic racks. It is a convenient and reliable tool. The stand is capable of withstanding 2 tons of weight, unlike boards, which can be micro cracks or knots.
When installing such a floor, it will be very important to correctly calculate the reinforcement of the floor slabs. For floor slabs at home, it is recommended to use hot-rolled steel reinforcement, which has class A3. The diameter of such a reinforcement is 8-14 mm and depends on the design load..
It is customary to reinforce the slab in two layers. The first mesh is laid at the bottom of the slab, the second at the top. The grids should be located in the middle of the concrete, the protective layer created by the formwork should be at least 15-20 millimeters. The mesh is tied with a knitting wire. Mesh sizes 200 by 200 or 150 by 150 millimeters.
In the mesh, the reinforcement should be solid, without breaks. If the length of the reinforcement is not enough, additional reinforcement must be tied up with an overlap, which is equal to 40 reinforcement diameters. If you are reinforcing the floor with d – 10 reinforcement, then you need to make an overlap of 400 millimeters. The reinforcement joints should be staggered, staggered. The edges of the lower and upper reinforcement in the meshes should be tied together with a U-shaped reinforcement.
The loads on the reinforced concrete slab are transferred from top to bottom and distributed over the entire coverage area. Thus, a similar conclusion can be made: the main working reinforcement is the lower one, which is experiencing tensile loads. The top receives compression loads. In engineering calculations, it is necessary to calculate additional reinforcing reinforcements, but there are general rules.
In the procedure for reinforcing the lower mesh, additional reinforcement is laid between the bearing supports in the middle. When the upper mesh is tied, reinforcements are laid over the supporting supports. Also, additional reinforcement is needed in places where holes and loads accumulate. Additional reinforcement is made with separate whips, which have a length of 400 – 2000 millimeters, depending on the width of the spans. The lower mesh is reinforced between the load-bearing walls in the opening.
The upper mesh must be reinforced over the load-bearing walls. Do-it-yourself reinforcement of floor slabs in the places where they rest on columns is very different from traditional reinforcement, these areas additionally require the creation of volumetric reinforcements.
The floor slab is poured using a concrete pump. When pouring, it is imperative to compact the concrete, for which a deep vibrator is usually used. The process of concrete hardening will be accompanied by its shrinkage, which increases as the concrete dries, and microcracks appear on its surface. Therefore, it is recommended to spill this structure with water within 2-3 days after pouring concrete. It is better to moisten the concrete not with a direct stream, but by spraying..