Concreting of various structures. Concreting of frame structures

TO category:

Laying and compaction concrete mix

concreting various designs

Massive structures and foundations

To reduce material, labor and monetary costs and the duration of construction, the construction of monolithic foundations and massive structures must be carried out by industrial methods, i.e., transfer most of the construction processes to workshops and factories and comprehensively mechanize the rest of the processes performed in construction. Therefore, formwork and reinforcement are produced, as well as the concrete mix is ​​prepared in a centralized manner. In addition, to reduce the amount of work at the facility, formwork and reinforcement elements are enlarged, if possible, and when using load-bearing reinforcing cages combined into armored formwork blocks.

Monolithic foundations and massive structures or blocks are most often concreted in a collapsible formwork made of prefabricated unified elements or in spatial block forms. When concreting large arrays, large formwork panels with an area of ​​up to 30 m2, installed by cranes, are used.

When laying in monolithic foundations and blocks, the concrete mix is ​​​​served using one or more types of mechanization: in buckets by construction cranes, concrete trucks and dump trucks along overpasses or directly into the formwork, belt concrete pavers and conveyors, concrete pumps, and sometimes overhead cranes in buckets.

The choice of methods of mechanization concrete works depends on the location of the concrete plant or plant for the preparation of the mixture, the design of the foundation or array (volume, width, height, saturation with reinforcement and embedded parts).

When choosing a concreting method, the minimum number of overloads of the concrete mixture is provided when it is moved to the place of installation.

For concreting hard-to-reach places foundation or block, as well as to distribute the concrete mixture over the area of ​​​​the structure, vibration chutes and belt concrete pavers are used. When pouring concrete mix into reinforced structures from a height of more than 2 m, vibrating chutes, inclined trays and trunks are used, and at a height of more than 10 m, vibrating trunks are used.

The concrete mixture in unreinforced and low-reinforced massifs and foundations is compacted using IV-78, IV-79, IV-80 manual vibrators. Concrete, as a rule, in horizontal layers 0.3-0.4 m thick. Concrete in large arrays is compacted with deep vibrators IV-90, assembled in vibration packs, rearranged by cranes. At the same time, the thickness of the compacted concrete layer reaches 1 m. With dense reinforcement, vibrators with a flexible shaft IV-66, IV-67, IV-47, IV-75 are used.

If the concreting process is organized correctly, the work of concrete workers is reduced to only a partial distribution of the concrete mixture and its compaction with vibrators.

In hydraulic engineering construction, when concreting large non-reinforced blocks, electric vibration laying machines are used based on the M-663B small-sized electrified tractor. The tractor is equipped with a vibrating package consisting of four IV-90 deep vibrators, or a blade for distributing the concrete mixture. Estimated productivity of the tractor when compacting the concrete mixture is 60 m3/h. From one block to another, the tractor moves under its own power or is rearranged by a crane.

On fig. 54 shows the concreting of a block of a hydraulic structure using a small-sized electrified tractor equipped with a blade and an electric tractor equipped with a vibration package. The concrete mixture is delivered to the place of laying by a concrete truck with a capacity of 5 m3.

The upper surface of the foundations is compacted with a vibrating screed or surface vibrators, and then smoothed with a rule to the level with the upper edges of the guides or special lighthouse boards.

Foundations designed for static load can be concreted intermittently, but with the obligatory processing of working joints.

Massive foundations that perceive dynamic loads, as well as massive hydraulic structures, are concreted in separate blocks, the dimensions and location of which are provided for in the project. Each block is concreted without interruption.

Foundation slabs up to 250 mm thick with single reinforcement are compacted with IV-91 surface vibrators during concreting. Foundation slabs with double reinforcement and slabs with a thickness of 250 mm or more - with internal vibrators.

Rice. 54. Concreting of the block with the help of small-sized electric tractors M-663B

Embedded parts (for example, anchor bolts, slotted structures) are installed immediately before concreting using carefully calibrated conductors (Fig. 55), which are fixed to special frames remaining in the concrete. During the laying of the concrete mixture, the design of the conductors must exclude the possibility of deviation of the embedded parts from the design position. The threads of the bolts installed in the conductors, together with the nuts, are lubricated with oil and wrapped with roofing paper.

Rice. 55. Conductor for installing anchor bolts:
1 - movable clamp, 2 - holes for fastening retractable racks of the conductor, 3 - clamps for fixing anchor bolts

To reduce the consumption of cement, it is advisable to place individual stones, called "raisins", with a particle size of more than 150 mm into concrete. The largest size of the “raisin” stone should not exceed Uz smallest size a block or mass concreted without interruption. For "raisins" stones without cracks are selected. It is impossible to use stones with a smooth (rounded) surface due to their poor adhesion to concrete. When erecting massive structures made of lightweight concrete on porous aggregates, laying "raisins" is not allowed.

Before laying, the stone is thoroughly cleaned and washed with a jet of water under pressure. The distance between the stones to be laid must allow the use of a deep vibrator, i.e. it must be at least 20 cm. In this case, there will be a sufficient layer of concrete around each stone. Stones should also not come into contact with reinforcement and embedded parts. The distance from the stone to the formwork must be at least 30 cm.

Reducing the consumption of cement when using "raisins" leads to a decrease in the heating of concrete from exothermy (heat release during setting and hardening of cement), which is of great importance, especially at high rates of construction of massive concrete structures.

Underlayment under zero

The concrete underlying layer (preparation) is arranged for concrete, asphalt and other floors. Rigid concrete mixtures are usually used for the underlying layer.

With dense soils, the concrete mixture is placed in the underlying layer directly on the planned soil, with weaker soils - on the crushed stone layer rammed into the soil. In case of weak soils, the underlying layer of concrete is sometimes reinforced with a mesh of reinforcing steel.

Before concreting the underlying layer, beacon guide boards are installed, which are nailed to stakes driven into the ground. Beacon boards are placed at a distance of 3-4 m from one another, and the upper edge of the board should be at the level of the surface of the underlying layer.

The concrete mixture is laid into the underlying layer and the floor covering in strips 3-4 m wide, separated by beacon boards. The strips are concreted through one. Intermediate strips are concreted after concrete hardening in adjacent strips. Before concreting the intermediate lanes, the lighthouse boards are removed.

In the concrete underlying layer, longitudinal expansion joints are arranged every two strips and transverse expansion joints every 9-12 m along the length of the strips (Fig. 56), which divide the concreting area into separate slabs ranging in size from 6X9 to 8X12 m. In addition, in each slab between adjacent concreting strips form working seams.

The side faces of the strips, forming a longitudinal expansion joint, are coated with hot bitumen with a layer of 1.5-2 mm before laying the concrete mixture in an adjacent strip adjacent to the face treated with bitumen. The side edges of the strips in the working seam are not coated with bitumen.

A transverse expansion joint is formed using a metal strip 80-100 mm wide and 4-6 mm thick, buried in the concrete underlying layer by 30 mm of its thickness. The strip is left in concrete for 20-40 minutes, after which it is carefully removed. The resulting groove after the final hardening of the concrete mixture is thoroughly cleaned and poured with bitumen or cement mortar.

Rice. 56. The location of the seams when concreting the underlying layer: I-V - concreting zones in the order of laying the concrete mixture;, 1-25 - the order of concreting individual slabs

Concrete mixture for concreting the underlying layer is fed to the place of laying, usually in concrete trucks. It is compacted with a vibrating rail, which is a metal beam (Tavr, rail) 4.1 m long, in the middle of which one or two electric motors from the IV-91 surface vibrator are mounted. The screed is moved along the lighthouse guide boards or along the surface of previously concreted adjacent lanes. In small rooms (up to 100 m2), the mixture is compacted with IV-91 surface vibrators.

Concrete floor coverings are made single-layer or double-layer. Single-layer coatings with a thickness of 25-50 mm are laid on the base along beacon rails and compacted with a vibrating rail or a surface vibrator.

When laying the concrete mixture in two layers (underlying layer and clean floor), the lower layer is compacted with a surface vibrator IV-91. Upper layer they are laid before the concrete mix begins to set in the lower layer and compacted with a vibrating screed moving along the beacon boards.

At the end of the work shift, in places where it is planned to finish laying the concrete mix, the board is placed on the edge, after which the last portion of the concrete mix is ​​laid and vibrated along the edge. If there is no partition, it is impossible to install a vibrating screed at the edge of the laid layer, since in this case the edge of the layer will creep.

In cramped places (between columns, foundations for equipment, the top of which is located above the floor level), the concrete mixture is smoothed with a trowel (Fig. 57, a) on a long handle or a trowel (Fig. 57, b).

Cement milk, protruding to the surface of the underlying layer or coating during compaction of the concrete mixture, is removed with a light scraper with a rubber band (Fig. 57, c).

Rice. 57. Hand tool for smoothing concrete surfaces:
a - trowel, b - wooden trowel, c - scraper with a rubber band to remove cement milk, d - ironing board, d - rubberized tape, e - trowel

Rice. 58. Machine SO-103 for grouting and leveling concrete surfaces:
1 - trowel disc, 2 - removable wheels, 3 - control handle, 4 - switch, 5 - cable, 6 - electric motor, 7 - auxiliary handle for machine repositioning

The surface of a clean concrete floor some time after laying on the concrete that has not yet hardened is rubbed using a SO-103 machine (Fig. 58) or SO-89. The machine has a trowel disc 1 with a diameter of 600 mm, which is driven by an electric motor 6 with a power of 1.5 kW. The disk makes 1 rpm, leveling and smoothing at the same time concrete surface gender. Machine weight 100 kg. Productivity 40 m2/h. The machine is serviced by one worker. The machine is equipped with a removable pair of wheels 2 to move it.

For small amounts of work, the surface of the concrete floor is finally finished with an ironing board (see Fig. 57, d) or a tarpaulin rubberized tape (see Fig. 57, e) 300-400 mm wide, the ends of which are attached to the rollers that serve as handles. The length of the tape should be 1-1.5 m more than the width of the strip to be concreted.

30 minutes after the end of concreting, the workers smooth the compacted concrete with a tape. By this time, a thin film of water appears on the surface of the concrete, which the workers drive off by rubbing the surface with light longitudinal and transverse movements of the tape. Workers after 15-20 minutes return to the smoothed layer and finally smooth the concrete with shorter movements of the tape.

Approximately 30 minutes after this, the concrete is processed from the bridge with a metal trowel, exposing grains of gravel (crushed stone), which creates good abrasion resistance of the concrete surface. If high abrasion resistance is not required, then for concrete preparation, a cement floor is arranged from a layer cement mortar cooked on coarse sand.

To give the floor an increased density, ironing of the concrete surface is used: mechanical - with the help of a SO-YUZ trowel or manual - with steel trowels (see Fig. 57, c). Ironing consists in the fact that dry and carefully sifted cement is rubbed with a steel tool into the surface of wet concrete until an even sheen appears on it. If the concrete has already dried up, then before adding cement, the surface is moistened with water until saturation.

Walls and partitions

Walls and partitions in a collapsible formwork are concreted without interruption in sections with a height of not more than 3 m.

When supplying a concrete mixture from a height of more than 2 m, link trunks are used. Thin walls and partitions with a thickness of less than 15 cm, where it is impossible to use trunks, are concreted in tiers up to 2 m high, while on one side the formwork is erected immediately to the full height. Reinforcement is attached to this formwork. The second side of the formwork is first erected to the height of one tier, and after concreting the tier, the formwork of the second tier is mounted, etc. The concrete mixture is compacted with deep or external vibrators. Concreting is resumed at the next highest section of the wall or partition only after the construction of the working seam.

If it is necessary to concret without working joints sections of walls and partitions with a height of more than 3 m, it is necessary to arrange breaks in work for the concrete mixture to settle. The duration of breaks should be at least 40 minutes and not more than 2 hours.

When concreting the walls of tanks for storing liquids, it is necessary to continuously lay the concrete mixture to the entire height in layers no higher than 0.8 of the length of the working part of the vibrator. In exceptional (emergency) cases, it is allowed to arrange a working seam with subsequent careful processing of its surface. The joints of the walls and the bottom of the tanks are carried out in the places provided for by the project.

In large tanks, the circumference is divided into sections by vertical seams and concreted in sections, but it is better to concrete such tanks continuously around the entire circumference.

Ironing is used to make the surfaces of the bottoms and walls of tanks more water resistant.

The walls in the vertically sliding eat (movable) formwork begin to be concreted, filling the form with concrete mixture to half its height, in two or three layers, compacted with vibrators. The laying of two (three) layers of concrete mixture around the entire perimeter should take no more than 3.5 hours. Then the formwork is torn off and lifted (continuously) at a speed of 30-60 cm / h until the formwork is filled with concrete mixture to its full height.

Subsequently, the concrete mixture is laid into the mold continuously in layers of 200-250 mm, not reaching its top by 50 mm. Typically, the layers of the laid concrete mixture are taken in height no more than 200 mm in thin walls (up to 200 mm thick) and no more than 250 mm in other structures. The next layer in height begins to be laid only after the previous one is laid to a predetermined height along the entire perimeter of the formwork.

For the preparation of a concrete mixture, Portland cement of a grade of at least 400 is used with the onset of setting no earlier than 3 hours and the end of setting no later than 6 hours. The water-cement ratio should be no more than 0.5 for areas with a harsh climate and 0.55 for other areas.

The grain size of coarse aggregate should be no more than / e of the smallest cross-sectional size of the concreted structure, and for densely reinforced structures - no more than 20 mm.

The concrete mix is ​​fed into the mobile molds by buckets or concrete pumps. When filling the corners of the forms, shovels and buckets are used.

The concrete mixture is compacted with flexible shaft vibrators or manually bayoneted with screws (metal rods). In order to avoid damage to the underlying layers of concrete, do not rest the vibrating tip against the formwork or reinforcement.

The rate of laying the concrete mix is ​​determined by the most favorable working speed of lifting the forms, which excludes the possibility of both adhesion of the laid concrete to the formwork and its slipping upon exiting the forms. At this speed, the concrete released from the formwork is hard to the touch, but the marks from the formwork panels on it are easily smoothed out. Its compressive strength is approximately 0.8-1 MPa.

With sliding formwork, breaks in concreting lasting more than 2 hours should not be allowed. With longer breaks, it is necessary to continue slowly raising the forms until a visible gap appears between the concrete and the walls of the formwork. Before resuming concreting, the surface of the hardened concrete in the joint must be treated according to the rules set out in § 11.

The surface of the walls concreted in the sliding formwork is rubbed immediately after the concrete leaves the molds, using special scaffolds suspended from the molds. Concrete is rubbed with steel floats without adding mortar, only slightly wetting it with water with a brush. At the same time, shells are sealed and defects in concreting are corrected.

In case of dry winds or an outdoor temperature of 30 ° C and above, protective aprons are made from tarpaulin, burlap from the formwork visor to the platform flooring. The results of the survey and acceptance are recorded in the work log.

Walls in a horizontally sliding (kat y -whose) formwork during the construction of structures of great length (retaining walls, tunnels, collectors, conduits and other structures being erected open way) are concreted in tiers. Concrete mixture prepared on Portland cement grade not less than 400 with the beginning of setting not earlier than 1 hour and the end of setting no later than 6 hours is laid continuously over the entire height of the formwork board, not reaching the top of the boards by 50-70 mm. The formwork is moved horizontally to the next position after the laid concrete has gained the required stripping strength.

columns

Columns with cross-sectional sides from 0.4 to 0.8 m in the absence of intersecting clamps are concreted without interruption in sections not more than 5 m high, freely dropping the concrete mix directly from the container into the formwork. When lowering the concrete mixture from a greater height, link trunks are used.

Columns with cross-sectional sides less than 0.4 m and columns of any section having intersecting clamps that cause the concrete mixture to separate when it falls, are concreted without interruption in sections not more than 2 m high. In this case, the concrete mixture is fed through windows arranged in the side walls formwork. The concrete mixture is compacted with deep or external vibrators. The sections following in height are concreted only after the construction of the working seam.

With a higher height of the sections of the column, concreted without working joints, it is necessary to arrange breaks in concreting for the concrete mixture to settle. The duration of the break should be at least 40 minutes and not more than 2 hours.

For strict observance of the thickness of the protective layer in the columns, special gaskets are used, made of cement mortar and attached to the reinforcement bars before concreting with a knitting wire embedded in the gaskets during their manufacture.

The formwork of high columns is mounted only on three sides, and on the fourth it is built up during the concreting process. If beams and girders with dense reinforcement are located above the columns, which does not allow the columns to be concreted from above, then it is allowed to concrete them before installing the reinforcement of the beams adjacent to them.

Columns, as a rule, are concreted to the full height of the floor without working joints. Working seams can only be arranged at the level of the top of the foundation A-A (Fig. 59, a) or at the bottom of the runs and beams B-b.

Rice. 59. Location of working joints when concreting columns:
a - a column supporting a ribbed floor, b - a column with crane beams, c - a column of beamless ceilings, d - a rack and a frame crossbar; 1 - floor trusses, 2 - crane beams, 3 - consoles for crane beams; A-A, B-B, C-C, G-D - the position of the working seams

In the columns of industrial workshops, working joints can be arranged at the level of the top of the foundation A - A (Fig. 59, b), at the level of the top of the crane beams B - B or at the level of the bottom of the consoles (ledges) B-B supporting the crane beams. In columns of beamless floors, joints can be made at the level of the top of the foundation A - A (Fig. 59, c) and the bottom of the capitals B - B. The capital should be concreted simultaneously with the floor slab. Frame structures they are erected with a break between concreting columns (pillars) and crossbars of frames, arranging working seams at the bottom or top of the bevel (haft) Г-Г (Fig. 59, d).

Floors and individual beams

Ceilings (beams and slabs), monolithically connected with columns and walls, are concreted not earlier than 1-2 hours after concreting the columns and walls due to the need for initial settlement of the concrete mixture laid in them.

Beams (girders) and slabs of ribbed floors are concreted, as a rule, simultaneously. Beams, arches and the like similar designs at a height of more than 80 cm, they are concreted separately from the slabs, arranging working seams 2-3 cm below the level of the bottom surface of the slab, and if there are haunches in the slab, at the level of the bottom of the slab haunch.

To form a protective layer in beams and girders, special gaskets made of cement mortar are used, on which reinforcement is installed. Concrete workers, while concreting, lightly shake the reinforcement with metal hooks, making sure that under the reinforcement a protective layer concrete of required thickness.

Rice. 60. Location of working joints when concreting ribbed slabs in a direction parallel to secondary ones! (a) and main (b) beams:

In beams and girders, the concrete mixture is laid in horizontal layers 30-50 cm thick, depending on the type of vibrator used. If the beams are heavily reinforced, then deep vibrators IV-75, IV-66 are used during concreting. In runs and beams large sizes the concrete mixture is compacted with IV-67 or IV-79 vibrators. At the intersection of the reinforcement of the purlins and beams, if it is impossible to use vibrators, the concrete mixture is compacted by bayonet.

The concrete mixture is placed into the slabs along the lighthouse rails, which are installed on the formwork in rows every 2-2.5 m and attached to the bosses located on the formwork. The upper plane of the rail is placed at the level of the top of the slab. After removing the rails and bosses, the recesses remaining in the slab are filled with concrete.

Vibrators for compacting the concrete mixture are selected depending on the thickness of the slabs and the type of reinforcement (Table 9).

They level and smooth the surface of the plate with a CO-103 trowel, and for small amounts of work - with a rule and trowels.

When concreting flat slabs, the working joint can be placed anywhere parallel to the smaller side of the slab. When concreting ribbed floors in a direction parallel to the secondary beams, as well as individual beams, the seam is arranged within the middle third of the span of the beams (Fig. 60, a), and when concreting in the direction parallel to the main beams, within two middle quarters of the span of the beams and plates (Fig. 60, b). At the supports, working seams cannot be arranged, since subsequently cracks may appear in the seams. In beams and slabs, the working seams must be vertical, therefore, in the designated places of concreting breaks in the slabs, slats are installed according to the thickness of the slab, and in the beams - shields with cutouts for passing reinforcement.

Arches and vaults

Arches of great length are divided along the length into separate sections of concreting by working seams perpendicular to the generatrix of the arch. The concrete mixture is placed on each section of the arches and vaults simultaneously on both sides from the heels to the lock (from the supports to the middle), which ensures the preservation of the design shape of the formwork throughout the entire period of concreting.

Rice. 61. Location of shrink
seams in the arch: 1 - heels of the arch, 2 - shrinkage seams, 3 - castle strip; /, //, III - order of concreting

If there is a danger of bulging, i.e., raising the formwork at the lock (key) of the vault or arch during concreting of the side parts, then the non-concrete section of the formwork in the lock is temporarily loaded (for example, with sandbags). With steep vaults, sections near the supports are concreted in a double-sided formwork, and the second (upper) formwork is installed with separate panels along the course of concreting.

The gaps between the strips (shrinkage joints) 2 (Fig. 61), which are approximately 300-500 mm wide, are concreted after the main concrete shrinkage occurs in strips II and III, that is, five days after their concreting. Shrink seams concreted with an inactive concrete mix, which is vibrated. Puffs of vaults and arches with tension devices are concreted after tightening these devices.

In the vaults, the concrete mixture is compacted with IV-91 surface vibrators, and in case of thick reinforcement, it is preliminarily worked out with IV-66, IV-67 or IV-79 vibrators.

The timing and procedure for circling arches and vaults are established by the construction project.

Tunnel lining

Tunnel linings are most often concreted in parallel with the tunneling. In this case, the speed of erection of the lining is approximately equal to the speed of tunneling.

Parallel tunneling and concrete work reduces general term tunnel construction, but with small cross-sectional dimensions of the tunnel, it causes significant difficulties and inconveniences, especially when transporting rock from the face to the portals and transporting concrete mix and other materials from the portals to the face. For this reason, in tunnels of a small cross-sectional area with single-track traffic, built in solid rocks, the lining is erected after the tunneling of the entire tunnel or its section between intermediate additional faces is completed.

The tunnel lining is concreted either continuously over the entire cross section of the working, or in a certain sequence along separate parts contour. In the latter case, two solutions are possible: first, the tunnel tray is concreted, or, conversely, the vault and walls.

The vaults of the tunnels are concreted simultaneously from two sides - from the heels to the castle in radial layers. The castle is concreted in inclined layers along the vault, and the formwork is laid as the concrete is poured in short sections from round to round. Lock working seams are made radial.

Concrete mixture for lining tunnels is usually prepared outside the tunnel in a concrete plant located near the portal. In short tunnels at the portal, a concrete pump (or pneumatic blower) is installed, which supplies the concrete mixture through concrete-water directly behind the formwork.

With a long tunnel, the concrete mixture can be delivered from the portal in dump trucks or trolleys 9 (Fig. 62) to the pneumatic blower 5, which delivers the mixture beyond the formwork I-IV.

Due to the fact that the mixture separates along the way, it is preferable to prepare it in the tunnel itself, if its dimensions allow. In this case, a concrete train is located in the tunnel, consisting of a concrete pump or pneumatic blower, a concrete mixer and a mobile conveyor. Aggregates and cement measured in required quantities, are brought to the concrete mixer in trolleys. The use of a mobile concrete train makes it possible to use a short length concrete pipeline when concreting the tunnel lining and simplify the concreting process.

For the formwork, the concrete mixture is fed from the end or through hatches in the formwork using a concrete pump or pneumatic blower. In the side walls of the tunnel and the tray, the concrete mixture can also be fed by tipping trolleys using distribution chutes.

The concrete mixture is compacted layer by layer with deep vibrators through the windows provided in each formwork section, or with external vibrators attached to the formwork. At the end of concreting and the concrete reaching the required strength in one area, the section of the resilient formwork is moved to next section, and all operations are repeated.

If the walls of the tunnel lining are concreted after the erection of the vault, then before concreting, the formwork from the lower surface of the toes of the vault is removed and the surface is thoroughly cleaned. Concrete the walls in horizontal layers while building up the formwork to a height not reaching the heel of the vault by 40 cm. The space between the fifth vault and the adjacent wall is filled with a rigid concrete mixture and thoroughly compacted. Previously, pipes are laid at the junction for subsequent injection of cement mortar, which ensures the density of the junction seam.

Sometimes, when concreting tunnel linings, in addition to the usual method of laying the ready-made concrete mixture behind the formwork, separate concreting is used, which consists in sequentially placing coarse aggregate in the lining, and then cement-and-sand mortar. This method is found in the construction of hydraulic tunnels, for example, in two-layer lining structures, when laying the outer layer of the lining of a small thickness behind its first (inner) layer, erected from precast concrete or steel shell.

Coarse aggregate (most often gravel) must be well compacted by vibrating or laying it under pressure with gravity blowers before the solution is injected into it. Then, under pressure, a solution of high mobility is injected, sufficient to fill all the smallest gaps between the grains of coarse aggregate. Injection starts from the bottom of the lining.

Separate concreting is especially effective in cases where the supply of a concrete mixture by a concrete conduit into a narrow gap in the behind-pipe space is difficult even for the length of one section. inner shell, additional processing a deep vibrator of the laid mixture is not feasible, and external vibrators may not provide the necessary compaction. When the solution is injected, it simultaneously fills small pores and cracks in the rock.

When erecting the outer layer of the lining by separate concreting, there is no need for subsequent injection of the solution behind the lining.

Concrete flooring is a durable and reliable element, which is indispensable during the construction multi-storey buildings and structures. Installation of a monolithic ceiling does not require lifting mechanisms, which saves on equipment and additional labor costs. The use of interfloor partitions in the construction reduces the time for work and allows you to build structures with your own hands. Making concrete floors is an easy process, but to make the material High Quality with its main advantages, you should follow the sequence of work and calculate the main parameters of the building element.

Purpose

Concrete floors are one of the main building elements in the construction of buildings. They are designed to connect:

• basement with rooms;
• the first floor with the second;
• roofs with a house.

They are also used for horizontal screeding of buildings and structures.

Cover requirements

The following requirements are put forward for concrete floors:

• the presence of the necessary strength;
• must not contain deformations and must have rigidity and a long service life;
• an important property in a concrete floor is its maximum fire resistance, water resistance and the inability to penetrate air;
• the concrete structure between the floors must have sound and heat insulation.

Kinds

There are the following types of concrete floors:

• attic;
• basement;
• interfloor.

Concrete flooring also happens:

• hollow, which is often used in construction, where interfloor overlap is required for houses made of concrete, blocks and bricks;
• ribbed, used in the manufacture of the roof of industrial buildings, where there is no heating of the premises;
• monolithic, which is a reinforced concrete element and is characterized by increased strength, is used in the construction of buildings and structures with a large number of storeys.

Materials and tools for manufacturing

When working with concrete floors prepare with their own hands the following tools and materials:

• concrete pump;
• capacity;
• buckets;
• jack;
• building level;
• plywood with moisture resistance property;
• boards;
• steel fittings;
• wire;
• concrete mortar or components for its preparation by one's own hands: sand, water, cement and various additives to increase the strength of the mortar.

How to calculate parameters?

When working with concrete floors, it is important to purchase high quality materials. making building mix, which will be used to fill the structure, use concrete grades 250 and 400, which include heavy fillers. To make partitions with your own hands, it is important to thoroughly calculate the main parameters of the material. The calculation is based on a comparison of two main properties:

• strength of the reinforcing structure;

Plate calculations are based on the following indicators:

• intensity of constant loads;
• efforts in sections with a large load;
• axle stiffness.

Payment monolithic floors consists of defining their individual components. First you need to make a formwork from plywood of great thickness, then install it from steel rods tied with wire. The calculation of partitions is carried out by special computer programs and designers.

The definition of strength is obtained from factors such as: load and strength.

To find out the maximum bending of the slab, use the following data:

• design resistance of reinforcement and concrete;
• fittings A400 C class.

The definition of parameters includes the following calculations:

• working reinforcement area;
• required moment of resistance;
• the maximum moment in the section of the beams.

Formulas and constants are in the collection to building codes and rules.

Formwork device for overlapping

Formwork construction technology includes the installation of plywood on horizontal supports. To choose the right amount of materials, you need to know the area and volume of the planned floor. The thickness of the structure depends on the possible loads and the dimensions of the span. Thus, the formwork is made of increased strength without allowing deformations, so that it can bear the weight of reinforced concrete for a long time.

When choosing boards for formwork, you should pay attention to their strength and thickness. Before installation, the structure is measured by the construction laser level span height and floor bottom. During installation homemade racks adjusted in length to the height of the structure on which the first layer of the beam will be built.

It is important to observe the distance, which should be more than one cubic meter. Place racks on the floor flat surface and high strength. After that, the transverse beam is laid in increments of about half a meter and then the formwork is installed. After mounting the formwork, check the top of the structure for horizontality using the building level.

When using boards instead plywood sheet, they are laid to each other without gaps and a moisture-proof material is laid on top. On all edges of the formwork, boards are installed, which are fixed at the corners of the structure so that they do not deform from the solution.

When installing the formwork yourself, it is important to remember a few rules:

• eliminate the formation of holes, cracks through which the mortar can flow out of the concrete during the pouring process;
• check the strength of the jacks installed under the formwork;
• moisture-resistant plywood is used for the construction of formwork;
• formwork should be as strong as possible, because the quality of the structure being built depends on it;
• formwork should be installed both over the area and around the perimeter of the room, which will protect against leakage of the concrete mixture.

Reinforcement

Partitions between floors need reinforcement, which can be started after the formwork has been installed. Reinforcement of structures is carried out with reinforcement in one or two layers per formwork. A reinforcing mesh measuring twenty by twenty centimeters is installed, while the first row is laid on a protective layer, which ensures uniform distribution of the concrete mixture under the reinforcement.

If necessary, connect the reinforcing elements, an overlap of at least seventy centimeters should be made. To maintain proportion, should be installed on top of the first row reinforcing mesh the second layer with the same step (twenty centimeters), only while ensuring perpendicularity. At the intersection of the reinforcing bars, they are fixed steel wire and a special hook designed to connect the reinforcement. In the manufacture of a two-layer frame based on segments of reinforcing bars, a similar sequence is carried out for the first layer and the second is laid, while maintaining a distance between layers of at least three centimeters.

Construction of monolithic columns, beams and ceilings

The most massive structures erected in monolithic reinforced concrete are columns with a section of 0.4 × 0.4 m - 0.6 × 0.8 m, beams and slabs with a span of 6 - 18 m. Depending on the required bearing capacity they can be weakly and strongly reinforced. Structures with dense reinforcement are concreted with a mixture with a cone draft of 6 ... 8 cm and aggregate size up to 20 mm, with weak reinforcement - with a mixture with a cone draft of 4 - 6 cm and aggregate size up to 40 mm.
The authorship of this article belongs to the blog -,. The use of resource articles is allowed only if you set an active backlink to the author's blog.

Technological schemes for concreting columns up to 5 m high (a) and more (b), with thick reinforcement of beams (c), formwork scheme with a removable shield (d): 1-formwork, 2 - clamp, 3 - tub, 4 - vibrator with flexible shaft 5-receiving funnel, 6-link trunk, 7-hinged vibrator, 9-pockets, 10-removable shield

Columns up to 5 m high are concreted continuously to the full height. The concrete mixture is loaded from above using a bucket or a flexible trunk of a concrete pipeline manipulator and compacted with deep vibrators. If the height of the columns is more than 5 m, the mixture is fed through funnels along the trunks, and compacted with mounted or deep vibrators. When using deep vibrators in the formwork, the concrete mixture is compacted and fed. Sometimes, to supply the concrete mixture, the formwork of the columns is performed with removable panels, which are installed after the first tier is concreted.

Beams and slabs, monolithically connected to the columns, are concreted not earlier than 1 ... 2 hours after the completion of the concreting of the columns. Such a break is necessary for the precipitation of concrete laid in columns. A movable concrete mixture with a cone draft of 6–8 cm is laid in densely reinforced beams. Beams with a height of more than 0.8 m are concreted separately from the slabs with a horizontal working joint at the level of the bottom of the slab. Floor slabs are concreted in a direction parallel to the main or secondary beams. In this case, the concrete is fed towards the concreting. When concreting slabs with a reinforced frame, light portable shields are laid on top, serving as a workplace and preventing deformation of the reinforcement.

A critical stage in the construction of buildings is the installation of floors. Overlaps are arranged from the bottom up or from the top down. In the first case, they are erected with a delay from the concreting of the walls by 2 ... 3 floors; immediately after concreting the walls to the height of the floor, after concreting the walls to the entire height of the building. After the walls are erected on 2 ... 3 floors, the concrete acquires strength, which makes it possible to build a ceiling. Now the future house is not afraid of anything, in turn, the craftsmen who make high-quality repairs of plastic windows can even climb out onto the cornices - all structural details are reliable and will not threaten to collapse.

For the installation of ceilings, collapsible formwork from panels is used. small size. Formwork panels are installed on sliding crossbars located on telescopic racks. Racks rest on the ceiling of the underlying floor. After installing the shields, the ceiling is reinforced and then concreted. To ensure a monolithic interface between the floor and the wall, horizontal grooves (cavities) are left in the walls during concreting, into which the floor reinforcement is passed. After the floor concrete acquires stripping strength, the formwork is dismantled: first, the telescopic racks are loosened, then the crossbars are removed one by one and the formwork panels are torn off. Similarly, the floor is concreted immediately after the walls are erected to the height of the floor.

If the ceiling is concreted after the walls have been erected to the entire height of the building, then collapsible formwork is often used complete with supporting elements in the form of telescopic racks, crossbars, brackets.

a - on telescopic scaffolds, 6 - collapsible and adjustable complete with telescopic racks, c - using beams and brackets, d - on suspended scaffolds; 1 - crossbars, 2 - flooring boards, 3 - slab for the junction of the ceiling and the wall, 4 - telescopic racks, 5 - ceiling of the underlying floor, 6 - metal pipes, 7 - brackets, 8 - beams, 9 - formwork on suspended platforms

The formwork consists of a set of unified elements: panels of various sizes: flat, angular, curvilinear. Set of flat and corner shields allows you to assemble formwork blocks for concreting floor cells with dimensions of 4.2 ... 7.2 m in length and 2.7 ... 7.2 m in width. Formwork panels are placed on crossbars with telescopic racks and jacks. Formwork, depending on the width of the slab, can have two, three or four telescopic props with inclined or vertical support at the corners of the junction of the slab with the wall.

The formwork of the floor is supported on the erected walls with the help of brackets. To do this, when concreting, lay in the walls metal tubes, through the holes of which the bolts for fastening the brackets are passed. Crossbars with telescopic struts are laid on the brackets, and beams along them, on which formwork panels are placed. Verify the position of the formwork with screws located on telescopic racks. For stripping, the screws of the telescopic racks are lowered down, the beams with shields are torn off from the concrete. Then the formwork is dismantled and installed in a new place.

Concreting of floors after erecting the walls of the building to the full height is carried out from top to bottom using suspended scaffolds on rigid suspensions (d). FROM inner sides walls install hooks or brackets, on which wooden or metal beams. Formwork is supported on beams on suspended scaffolds. After reconciliation of the design position, the formwork is reinforced and concreted. When dismantling the formwork, first remove support beams, then the brackets, tear off the formwork from the concrete and lower it for the installation of the underlying floor. The concrete mixture is fed through holes in the walls (window or door openings), as well as through technological openings left in floor slabs (for example, elevator shafts). In some cases, prefabricated reinforced concrete floors are used, which are pre-stored in the form of a package at the level of the first floor and, after the walls have been erected, are installed accordingly. top floor to the bottom.

a - from bottom to top; b - from top to bottom; c - in a cyclic way; 1 - tower crane; 2 - tub; 3 - ceiling formwork; 4 - sliding formwork; 5 - concrete pump

The intensification of the construction processes of the considered types of structures is determined by the optimal set of mechanization tools and the appropriate selection of the technological properties of concrete mixes. The use of chemical additives makes it possible to: increase workability and thereby reduce labor costs for the distribution and compaction of mixtures; use concrete pumping transport complete with manipulators; shorten the cycle of curing, especially in the early stages of curing, which ensures the rhythmic operation of the complex for the construction of structures. The use of vacuum technology in the construction of floors contributes to the improvement of the physical and mechanical properties of concrete and accelerated strength development.

My blog is found by the following phrases
.
.
.
.
.
.

For concreting densely reinforced columns with a cross section of 0.6X0.6 m or less, a concrete mix with a cone draft of 6-8 cm and an aggregate size of up to 20 mm is used. With weak reinforcement and a larger section of the columns, the cone settlement can be reduced to 4-6 cm, and the fineness can be increased to 40 mm. If beams and girders with thick reinforcement are located above the columns, which makes it difficult to supply the concrete mix to them from above, it is allowed to concrete the columns before installing the beam reinforcement. Before concreting the columns, it is necessary to clear the joints and lay a layer of greasy cement mortar 3-5 cm thick.
Columns up to 5 m high with cross-sectional sides up to 0.8 m, without intersecting clamps, are concreted continuously to the full height. The concrete mixture is carefully loaded from above and compacted with internal vibrators lowered into the formwork on ropes.
If the height of columns of large cross-section exceeds 5 m and they do not have crossed clamps, the concrete mixture is fed through funnels along the trunks, and it is compacted with mounted or internal vibrators.
High and densely reinforced columns with crossed collars are concreted through windows in the formwork and special pockets. The mixture is vibrocompacted using mounted vibrators. Columns, regardless of their height, section and reinforcement, should be concreted continuously to the entire height of the floor.
Working seams are recommended to be arranged along the upper edge of the foundation, i.e. in section A-A, at the bottom of the runs and beams in section B-B. In columns of industrial structures, working joints are located at the top of the foundation, at the level of the top of the crane beams or at the level of the bottom of the consoles.
In columns with beamless ceilings, working joints should be arranged at the level of the top of the foundation and at the bottom of the capitals, in the coatings along the line of junction with the walls.
Beams and slabs, monolithically connected with columns and walls, are concreted not earlier than 1-2 hours after the completion of concreting columns and walls. Such a break is necessary for the precipitation of concrete laid in columns and walls.
The main beams, girders and floor slabs should be concreted at the same time so that the number of working joints is the smallest. With a beam height of more than 0.8 m, they are concreted separately from the slabs with a horizontal working seam at the level of the bottom of the slab.
A movable fine-grained concrete mixture is placed in densely reinforced beams. Individual beams and girders must be concreted continuously. The mixture is loaded into the formwork from buckets, and compacted with internal vibrators.
Ribbed floors are concreted in a direction parallel to the main or secondary beams (girders), taking smallest front concreting. The mixture is fed at several points along the front. The best way this condition is met by the supply of the mixture by a crane. Concrete must be delivered towards concreting. In the presence of double reinforcement of the slabs and a small diameter of the reinforcement, in order to avoid its deformation, light portable shields are laid on top of the meshes.
The mixture in the slabs is compacted with platform vibrators with a slab thickness of up to 0.25 m and internal vibrators with a greater thickness. Concrete is vibrated especially carefully at the junction of slabs to beams and columns, as well as in places with dense reinforcement.
The slabs are concreted over the lighthouses. Their surface is leveled and smoothed with trowels and rules. Working seams in flat slabs are arranged anywhere, but always parallel to their smaller side. In ribbed floors, concreted parallel to secondary beams, as well as in separate beams, working seams are arranged in the middle third of the span of these beams.
When concreting in a direction parallel to the main beams, the working seam is arranged within the two middle quarters of the span of the main beams and in the middle of the slabs. The working seams must be vertical, for this, boards are installed in the slabs, and shields with holes for the passage of reinforcement are installed in the beams.
Frames are recommended to be concreted continuously. If this cannot be done, then a cross-sectional weld is allowed. Concreting of high (more than 5 m) and densely built worlds of nth pillars is carried out through windows or in tiers with formwork build-up. The mixture is compacted using internal or mounted vibrators.

The process of installing a monolithic foundation beam is divided into three main types of work (as with any other reinforced concrete structure):

1) knitting of reinforcing cages and beam meshes (reinforcement),
2) installation of beam formwork and
3) beam concreting.

Such a beam got its name due to the fact that it rests on the foundations and serves as the basis for the outer walls of the building (or for the basement, when columns perceive the load from the walls).

Reinforcement of a monolithic beam (Bm).
Initially, we prepare reinforcing bars of the required length and diameter (as per the drawing). We knit spatial frames from them (working longitudinal reinforcement and clamps made of smooth reinforcement (A-I), which provide the required position of the working rods). The bonded frames must be of such length that the bearing (supporting part) of each side of the beam on the foundation is at least 150 mm.

Before installing the finished frame in the required (design) position, check that the reinforcing bars are free of rust. It is unacceptable. If necessary, treat the fittings with a rust preventative (e.g. “Antirust”).

Also make sure that a protective layer of concrete is provided on all four sides of the monolithic beam (15 ... 25 mm). The photo shows that special protective layer retainers (“high chairs”) are placed under the lower rods of the frame.

So, the reinforcement of the foundation beam is completed. After the final check of the dimensions and strength of the knitting of the frames, we proceed to the next stage.

Reinforced concrete beam formwork installation.

The main tasks are to provide correct geometry(height, width, length of the beam), position in plan and reliability of the formwork. Our beam has a modest height of 300 mm, so we used sheets of ordinary laminated plywood.

Formwork fastening should be such that the laid concrete does not violate the geometry of the beam (does not swell in the lower, upper section or in the middle). In this we will be helped by strands (you can use ordinary smooth reinforcement of 6 diameters), bars and self-tapping screws.

With a high beam height, I recommend putting side struts in increments of a couple of meters. It is better to be safe once again than to let the concrete break the formwork and pour out (thus causing a lot of trouble). Do not forget that 1 m3 of concrete weighs 2.65 tons.

It remains on the formwork to make level marks to which we will lay concrete. Very practical solution is the twisting (drilling) of self-tapping screws at the desired height every 0.5 ... 1 m. They will show us the level of concrete (the top of the monolithic beam).

Smoothly, we approached the main stage, for which the two previous ones were completed.

Foundation beam concreting.
In other words, laying the concrete mixture into the formwork.

Having ordered a mixer with concrete (concrete mixer truck), make sure that the equipment can easily drive to the right place. If this is impossible to ensure (for example, there are ditches and pits around), then prepare a long tray in advance, along which the concrete will move from the barrel to the structure.

When concreting the foundation beam, the main thing is to vibrate (pierce) the laid mixture well in order to exclude the formation of voids in the body of the structure. Voids inside the beam will weaken its strength and bearing capacity.

Concrete laid to the required level (in height) remains to be smoothed out - to remove irregularities along the upper edge (bumps, pits). We are waiting for the complete solidification of the concrete mixture (usually a day is enough) and remove the formwork. Dismantling of the formwork is recommended to be carried out after three days. During this time, under normal conditions, concrete gains 50% of its strength. And the construction will gain 100% of its strength in 28 days.