Prefabricated reinforced concrete ceiling of the hollow core slabs: the nuances of selection and installation

When building a house before any developer raises the question of choice intermediate floor. The most common type of three floors - wood, monolithic reinforced concrete and precast concrete, mounted from flat hollow core slabs. It is about this kind of overlap, as the most popular and practical for low-rise construction, will be discussed in this material. From the article, you'll learn:

• The different slabs of overlap (PC) of the slabs manufactured by molding formless (PB).
• How to style your slab.
• How to avoid mistakes during assembly.
• How to store the slabs.

How to choose a floor slab Hollow core

At first glance hollow core slabs may seem that they differ only in length, thickness and width. In fact, the technical characteristics of hollow core floor slab is much broader and detail painted in GOST 9561-91.

Hollow core slabs differ from one another according to the method of reinforcement. Moreover, reinforcement (depending on type of plates) may be performed using a pre-stressed reinforcement or without prestressing reinforcement. Most plates are used overlapping with prestressed reinforcement work.

Choosing a floor plate, you should pay attention to such an important time, as the allowable number of sides to lean on the stove. Typically, the floor slab can only rely on the two short sides, but some types of plates allow for bearing on three or four sides. For example:

• PB. Stove provides a bearing on the two sides.
• PK1. Plate Thickness - 220 mm. The diameter of the circular voids - 159 mm. Plate allows a bearing only on the two sides.
• 1PKT. Stove, having similar size, allows a bearing on three sides.
• 1PKK. Board can rely on the four sides;

Also slabs differ in the method of manufacture. For example, often a dispute arises, what to choose - the plate PC or PB.

Andrey164 (User FORUMHOUSE):

It's time to cover the basement floor slabs, but I can not figure out what to choose - the plate PC or PB? At PB better surface finish than that of a PC, but I heard that PB slabs are used only in the cast-frame houses, and the end of such plates can not be loaded wall. Is it really?

Sasha1983 (User FORUMHOUSE):

In fact, the main difference lies in the plate manufacturing methods.

Plates PC labeled (with a thickness of 160 to 260 mm and the standard load capacity of 800 kg / sq.) Is cast in the formwork. PB brand panels (thickness of 160 mm to 330 mm and the standard load capacity of 800 kg / m) manufactured formless method of continuous casting (this allows you to get a smooth and level surface, than the plates PC). Plates PB also called extrusion.

PB slabs, due to prestressing compressed and stretched zones (prestressing reinforcement is done with any plate length), less prone to cracking than PC boards. PC plate with a length of up to 4.2 meters can be produced without prestressed reinforcement and have more free deflection than PB plate.

On request, the PB plate can be cut under a predetermined size (e.g., from 1.8 to 9 meters). Plate can also be cut along the longitudinal and to separate elements, as well as make an oblique cut at an angle of 30-90 degrees, without losing its load-bearing capacity. This greatly simplifies the layout of the floor slab at the construction site and provides a large freedom of the designer, as Box size of the house and load-bearing walls are not tied to the standard sizes of plates PC.

When selecting the PC boards (longer than 4.2 meters) it is important to remember such a feature - these plates are prestressed with special emphasis on the plate ends. If the cut end in a plate, the stopper (together with the cut end of the plate and vertical reinforcement) will not work. Respectively - operating valves will cling to the concrete is only its side surface. This will significantly reduce the ability of the carrier plate.

Although a smooth surface, good geometry, reduced weight and high loading capacity, when choosing plates PB should be noted that moment. Hollow core slabs holes in PC (depending on the width of the plate, with a diameter from 114 to 203 mm) allows to easily pierce a hole in it for sewage riser, 100 mm in diameter. While the size of the hollow openings in the plates PB - 60 mm. Therefore, to break through the through hole in the plate of the brand PB (to prevent damage to fittings) are kindly requested to check with the manufacturer, as it is better to do.

Features mounting slabs

At PB boards (as opposed to PC boards) are no mounting tabs (or have to pay extra for their installation), which may complicate their handling and installation.

It is not recommended to use a "popular" method of PB slabs installation when mounting hooks cling to the end of the hollow hole. In this case, it is likely that the hook will pull out of the hole because of the destruction of the end plate, or just hook soskolznot. This will lead to a drop in the plate. Also at your own risk can be used a method in which in the hollow core slab openings PB inserted scrap (scrap for two on one side of the plate) and for them to cling to the hooks.

ProgC (User FORUMHOUSE):

Mounting plates PB is allowed only with a special soft Chalok or traverse.

Chalkov to pull out from under the plate, laying it, leaving a gap of 2 cm to the adjacent plate. Then already laid slab with a crowbar to move the adjacent plate.

Max_im (User FORUMHOUSE):

I put on a construction site at the plate in such a method. The clearance left in 3 cm. Plates went on a cement-sand mixture 2 cm thick. The mixture acts as a lubricant, and the plate is easily shifted to the scrap required me away.

Also when installing slabs observe the calculated value of the minimum depth bearing plate. the following figures can be used to benchmark:

• brick wall, the minimum depth bearing - 8 cm, the maximum depth of the bearing - 16 cm;
• reinforced - 7 cm, the maximum depth of the bearing - 12 cm;
• gas and foam concrete blocks - a minimum of 10-12 cm, the optimum depth of the bearing - 15 cm;
• steel constructions - 7 cm.

Not advised to tap the floor slab by more than 20 cm, because by increasing the bearing depth, plate begins to "work" as zaschemlonnaya beam. In addition, when laying slabs on walls built of gas and foam concrete blocks, a device reinforced concrete Laying nets, what is told in detail in the article: "Make Laying nets in the house of aerated concrete".

Before installing the seal the ends of the plates is recommended hollow holes. Void are sealed to prevent water from getting inside the plate. It also increases the strength at the ends of the plates (this mainly refers to the plates PC than to PB) for bearing on them bearing walls. Void can be repaired, if you insert them in half brick and "scatter" the gap with concrete. Typically, the voids are sealed to a depth of at least 12-15 cm.

If water still gets inside the plates, it must be removed. For this plate, in the "pustotke" bottom drilled hole through which water can leak out. This is especially important if the slab is already laid on the floor, and the house went into the winter without a roof. Water can freeze in the cold inside the hollow hole (since she has nowhere to flow) and the break plate.

Sergey Perm (User FORUMHOUSE):

I laid on the floor slabs were whole year. Specially drilled holes in the hammer "pustotkah" leaked a lot of water. Drilling is necessary every channel.

Before laying the slabs need to select the crane required duty. It is important to take into account the availability of access roads, the maximum possible boom in crane and allowable under this load weight. And also calculate the opportunity to lay the floor slab is not a single point, and on the two sides of the house.

zumpf (User FORUMHOUSE):

Before ordering crane, I recommend looking on the internet it gruzovysotnye characteristics. It may happen that a maximum outreach of the crane, even 25-ton crane could not "throw" on the second floor of a weight of only 500 kg.

The surface on which the floor slab is placed must be level and free from debris. Before laying plate "stretches out" the cement mixture, the so-called mortar "B", a thickness of 2 cm. This will ensure a reliable engagement with the plates or walls Laying nets. Also before assembly of plates and applying the solution to the wall can be placed reinforcing rod diameter of 10-12 mm.

Such a method would allow mixing to strictly control the verticality of the plates when stacking (as below rod plate does not already fall). In addition, the rod will not allow the stove completely squeeze out from under him grout and go "dry". It is not allowed to put the plate "steps". Depending on the length of the plates, the discrepancy ends must not exceed 8.12 mm.

Serious mistake when laying plates one plate is overlapping of two spans, i.e. plate rests on three walls. Because of this, the plate having an unintended circuit load reinforcement, and under certain adverse circumstances, the plate can break.

If such a layout can not be avoided, to relieve tension on the top surface of the plate, just above the middle partition (wall) is propyl grinder.

After mounting plates made their anchoring and filling rustov (slots remaining after splicing plates with each other) cement.

In PC boards anchor clinging to the mounting lug, then emptiness also is sealed with cement. This will avoid the ingress of water into it and debris.

Another point on which to focus - how to block a flight of stairs between the floor slabs, if they are not to rely on. In this case, the parallel plates may be put two channel, and one across the supply, the edge of the opening, to connect the reinforcing cage, for example in the form of a mesh cell of 20 cm and a diameter of 8 mm rod. Put the formwork and pour monolithic section. Channel bind to the plates overlap is not necessary. In this case, the plates are based on the two short sides and are not subjected to stress from a node supporting the flight of stairs.

How to store the slabs on the site

Ideally, if the slabs were brought to the site, they just need to be installed. If for any reason this is not possible, the question arises: how to store them properly.

For storage of slabs need to prepare in advance solid and smooth area. You can not put a plate on the ground. In this case, the bottom plate can rest on the ground, and because of uneven loading, the weight of the upper plates it fractures.

Plates should be stacked to a maximum of 8-10 units. Moreover, under the bottom row are placed spacers (e.g., from a bar 200x200 mm), and all the subsequent rows are put through a gasket - a board-dyuymovka 25 mm thick. In this napkin must be located no more than 30-45 cm from the ends of the plates, and they should exhibit strictly vertically one above the other. This will ensure an even load on the redistribution plate.

zumpf:

I put the plate "for science" in two stacks of 8 pcs., But did not consider the soil bearing capacity and weight plates. As a result, the gasket-stone completely disappeared into the ground. To lower plate is not cracked, I had for 6 months (until they were laid) to undermine the plate to withstand the necessary clearance between the plate and the ground.

On FORUMHOUSE you can ask questions of overlapping plates. It describes, how to close the span between the floor slabs. You can find out, what to choose - the plate PC or PBAnd read about ribbed monolithic reinforced concrete floorse. The video reveals all the secrets of creating a concrete floor for large unsupported spans.

Discuss the article and read other materials devoted to country life you can on the websiteFORUMHOUSE.

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