from monolithic concrete and reinforced concrete
Training questions:
Composition of complex concreting process.
Decking. Classification. Types of formwork.
Reinforcing products. Mounting of fittings. Stress reinforcement.
Preparation, transportation, packing, compacting of concrete mixtures. Special methods for processing concrete mix.
Concreting of structures. Curing. Stripping. Correction of defects ..
Question 1 . Composition of complex concreting process.
By the method of execution, the concrete and reinforced concrete structures are divided into prefabricated, monolithic and prefabricated-monolithic structures.
Erection of monolithic concrete and reinforced concrete structures requires integrated process , including: formwork , reinforcement of structures , concrete concreting , concrete curing in concreted structures , decapitation , correction of defects , surface finishing of finished structures .
Question 2. Decking. Classification. Types of formwork.
Decking - temporary auxiliary structure, serving to give the required shape, geometric dimensions and position in the space of the erected structure (or part thereof).
In accordance with the materials used in the construction of the formwork, it is customary to classify the formwork on: wooden ; metal ; polymeric ; reinforced concrete ; reinforced cement ; tissue , combined .
The frequency of application is: individual formwork; wrapped formwork; fixed formwork .
Shaped formwork At least 50 cycles of concreting can be used. In the group of wrapped forms, the following are most widespread: collapsible-rearrangement , volume-rearrangement , sliding , self-elevating formwork , horizontally movable , lifting and moving ,
pneumatic .
Collapsible and adjustable formwork consists of separate shields and supporting elements: ribs, fights, screeds, etc. At the height of the shuttering boards support forests consisting of racks, burrs and braces.
Volume-rearrangement (tunnel) formwork consists of spatial metal U-shaped sections, from which the formwork unit is assembled for the width of the room. The side panels serve as the inner formwork of the monolithic walls, and the upper ones serve as the deck deck. Fully assembled formwork is installed in the design position with the help of a crane. For removal, the formwork is folded and rolled onto the next position or on the scaffold.
Sliding formwork . The main elements of the formwork are shields, jack frames, working floor, scaffolding, jacks and jack bars.
Shaping boards cover the concrete structure on the outer and inner contours. The shields are tapered. Hydraulic and electromechanical jacks are used to lift sliding formwork.
The formwork is constantly moving, in case of breaks in concreting the formwork is transferred to the "step in place" mode.
Fixed formwork After concreting the basic structure remains and works together with the structure. Formwork is made of reinforced concrete, reinforced concrete plates, metal sheets, of expanded polystyrene.
Construction of reinforced concrete structures
The device of concrete and ferro-concrete construction allows the construction of a building or structure directly on the construction site.
To create such a structure it is necessary to fill in the frame structure, formwork, the prepared mixture.
Such designs are now increasingly used due to the fact that they can be used both for the construction of small and large-sized objects.
Reinforced concrete structures have a number of undeniable advantages:
1. Such reinforced concrete structures have no seams, which gives them increased resistance and strength. This feature makes it possible to use them as a foundation for a building under construction, including a large one, whose foundation is under heavy loads.
2. The absence of seams also guarantees a higher level of sound and heat insulation.
3. The structures erected from this type of structures are more resistant to seismic activity.
Often when building objects, a combination of monolithic and prefabricated structures is used.
Monolithic structures have significantly less weight, which significantly reduces construction costs.
The cost of building concrete and reinforced concrete structures is based on several factors-the complexity of the structure being constructed, the size of the building, the operating time and the cost of the materials used.
The construction of monolithic foundations has become widespread due to such important indicators as reliability, high demand and long service life. Usually the foundation is monolithic learn finance online construction of block and brick houses, the erection of buildings with multi-ton reinforced concrete structures, as well as on complex ground. Such a foundation perfectly copes with the enormous loads of the above-ground part of the building and prevents the appearance and development of deformation processes in the bearing and enclosing structures of the structure.
According to the method of the device, monolithic foundations can be of the following types:
Ribbon foundation.
It is a continuous reinforced concrete strip, made along the entire perimeter of the structure. The finely stripped monolithic ribbon foundation is inherently a rigid horizontal frame that provides high stability to houses of logs and logs on the heaving grounds. The deepened band foundation monolithic is used for the construction of buildings with stone walls, as well as for the organization of basement floors, cellars and garages under the house.
The column foundation.
The construction of the communicating monolithic pillars. Such pillars are installed in the corners, under the intersections of the walls and all supporting structures of the house. Empty space between the pillars is filled with crushed stone or sand, which is covered with a layer of reinforced concrete on top. This design is used in the construction of light buildings.
Solid foundation is monolithic.
It is laid on difficult subsidence grounds for the entire building area, which allows to reduce and evenly distribute the pressure transmitted by the building. Also, this type of foundation monolithic suitable for construction on any ground, even mobile and puchinistyh. The whole structure of the foundation does not allow the destruction of the building, assuming the deformation of the soil.
According to the technology of making a monolithic foundation, concrete and reinforced concrete are distinguished. When constructing a concrete base, concrete grade 50 is used. In order to reduce the consumption of cement, rubble stones can be added to it, but the strength of the concrete foundation is not reduced. When the concrete foundations of monolithic structures are used, formwork is used, and in the event that the walls of the excavation play the role of the formwork, it is waterproofed.
Ferroconcrete monolithic foundations are reinforced with rods, frames or nets. They perfectly withstand vertical and lateral loads and are characterized by a high degree of reliability and moisture resistance, so they are used in multi-storey construction.
We offer customers services for the calculation and installation of monolithic foundations of belt, columnar and continuous types. All work on laying the foundation is carried out using the latest technologies and using modern technology, which allows to guarantee high quality of work and optimal terms for their implementation.
The bearing base of construction is considered to be a monolithic reinforced concrete skeleton, which consists of vertically arranged columns, as well as from diaphragms of rigidities, united by floor-to-ceiling monolithic slabs. Thanks to this design, it is possible to save on building materials and energy resources. Moreover, the design with high reliability potential allows the use of the most modern construction methods.
The walls in the resulting buildings are self-supporting. This is a great advantage, providing low weight and acceptable volumes.
So, thanks to the device of concrete structures and reinforced concrete structures of monolithic type, the mass of all load-bearing parts is several times less than the mass of buildings made of bricks for the same number of floors. At the same time, there is the possibility of free planning of the location of premises and their destination, as well as the right to talk about a new architectural turn of facade solutions while maintaining all the requirements for reliability and comfort.
The most laborious process in the structure of monolithic concrete and cast-in-situ reinforced concrete structures is reinforcement work, of which 50% how to lower student loan interest rate all technology of monolithic construction is being built. 70% of the reinforcement articles are made manually on the site of the construction site. This is due to the fact that each building or building project requires its own unique reinforcement products. Reduce labor costs and construction time can be due to a partial transfer of production of blanks in the reinforcement shop or the corresponding manufacturing workshops. As a rule, several specialized brigades are required that divide the manufacture of reinforcement between each other on a horizontal and vertical basis, that is, some masters prepare reinforcement for vertical structures, others for horizontal ones.
No less labor-intensive in monolithic construction are considered works with formwork. This is due to the fact that there is a lack of technological developments, necessary and reliable tools, and the quality of its individual components leaves much to be desired.
Nevertheless, reliable construction companies can easily cope with the installation of concrete and reinforced concrete structures, applying the right technology and carefully following all the necessary standards and requirements. Having in the team of highly qualified experienced specialists, the companies guarantee the execution of works impeccably, in accordance with the agreed terms.
Reinforced concrete is a tandem of steel and concrete with their pluses and minuses. However, being a pair, they form an incredibly strong material, actively used in different directions of construction. In spite of the fact that the concrete itself is rather fragile, it perfectly copes with compression loads, and steel rods are easy to bear stretching. Due to the exclusive complementarity of two different but at the same time unique materials, reinforced concrete is still indispensable ace check and cash in construction.
Objects that are performed in compliance with production technologies and the installation itself are irreproachable.
In the assembly of prefabricated reinforced concrete structures, it is important to control the quality of the joints, the connections on which the structure depends is how strong. At any stage of the ongoing work, it is important how accurate markup is. In the case of violations, there may be skewed or other problems associated with incorrect distribution of the load. Decent, reliable organizations always have the necessary skills, materials, equipment of appropriate quality and a license that gives the right to carry out one or another type of activity.
Construction of reinforced concrete structures
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At present, when building buildings and structures, monolithic construction is gaining in popularity. This is the erection of structural elements from a concrete mix and steel reinforcement using special forms (formwork) directly in the design position.
An absolutely rigid frame with various types of enclosing structures is created. For many years preference was given to prefabricated construction in our country. Although it can be noted that in the 30s - the time of the development of constructivism - there was an experience of monolithic construction. Then there was a time of "brick", panel construction was very actively promoted, and only the last 10 years one can say that monolithic construction has taken its rightful place.
Advantages of monolithic construction in front of other technologies are as follows:
The pitch of the bearing structures in case of monolithic construction does not matter. In the team - all designs have dimensions that are multiples of a certain module; the technology of the structures performed at the plant does not allow changing the form of the tooling quickly. Therefore, architects and designers were tied to certain standard sizes and, as a consequence, they are limited in making design decisions.
Monolithic buildings are lighter than brick ones by 15-20%. The thickness of walls and ceilings is significantly reduced. Due to the simplification of the weight of structures, the material consumption of foundations decreases, and their device is cheaper.
The production cycle is transferred to the construction site. In the prefabricated housing construction, the products are manufactured in the factory, they are brought to the site, they are mounted. In the manufacture of prefabricated structures, tolerances are applied at all technological stages, which lead to additional labor costs in finishing the joints. If the monolithic construction is conducted according to a well-developed scheme, the erection of buildings is carried out in a shorter time.
Monolithic construction provides a virtually "seamless" design. Thanks to this, the heat and soundproofness indicators increase. At the same time, the designs are more durable.
The use of modern shuttering systems in monolithic construction significantly enhances its processability. Timing, quality of erection of structures is largely determined by the formwork used.
Modern shuttering systems can be classified according to various criteria.
On the field of application and specific tasks: for walls; for overlapping; columns; annular walls with a variable radius; tunneling; one-sided.
By design features: frame; beam.
By the installation method: stationary; self-elevating; lifting and rearing; lifting, non-removable.
In size: large-panel; small-piece.
On the materials used. For the manufacture of elements of formwork, various materials are used: steel, aluminum, wood, plastic.
The variant of a rigid monolithic frame with efficient enclosing structures is today the priority direction in housing construction.
The use of technology for the erection of monolithic buildings makes it possible to erect buildings of different purposes, of different storeys, using a wide range of materials as enclosing structures. The monolithic framework can be of three types:
with bearing longitudinal walls;
with bearing transverse walls;
with overlaps on the supporting columns.
The technology of concreting the structure is chosen taking into account the type of construction, its location on the building or construction, climatic conditions, availability of energy resources, etc.
Foundations and arrays, depending on the volume, depth of their heights and other features, can be concreted using the following technological schemes: unloading the mixture from the vehicle directly into the formwork from the ground or a mobile bridge or overpass, using vibrating feeders, vibration excavators, concrete pumps or buckets with the help of cranes .
In the foundations with sides of the cross section of the columnar 0.4-0.8 m, the height of the free fall of the concrete mixture is allowed up to 5 m, with sides larger than 0.8 m - 3 m. Concrete high sub-columns with a cone draft of 4-6 cm should be slow and even with some interruptions (1-1.5 hours) to exclude the extrusion of concrete laid in the steps through their upper open facets.
The foundations that absorb dynamic loads are concreted continuously.
Task 1.
Determine the amount and complexity of formwork, reinforcement, concrete, and formwork during the erection of monolithic foundations.
Initial data: working drawings (Fig. 5.1., 5.2.), ЕНиР сб.4 вып.1. The weight of the grid is C-1 -360 kg, the weight of the frame is K-1 -180 kg.
When calculating the volume and complexity of work units of measurement of reinforced concrete works are accepted in accordance with ENIR:
Laying of concrete mix - in m3;
Installation of the bar reinforcement - in t;
Installation of reinforcing cages - in pcs .;
Formwork device - in sq. M. m formwork adjacent to the concrete structure;
The device of support timbering formwork - in pog.m rack;
Dimensions of the building in digital axes 144 m., In letter axes 18 m.
Shallow formwork for the foundation of foundations.
The erection of monolithic structures is a typical example of a complex construction process. The complex of works includes the processes of manufacturing and installation of formwork, the manufacture and installation of reinforcement, the preparation, transportation and laying of the concrete mix, disassembly of the formwork (decking). In this case, the formwork and reinforcement are referred to as preparatory works.
Fig.5.1. Foundation plan
Fig. 5.2. Sizes of foundations.
Progress of the task.
It is more convenient to calculate the amount of work in a tabular form at the same time as the definition of labor intensity. The calculated scope of work is recorded in a table. The volume of a regular truncated pyramid is determined by the following formula:
|
Name of works |
Scope of work |
Time norm, people * hour |
Labor intensity, people * h |
Composition of the link according to ENIR |
||
|
Formwork | ||||||
|
Reinforcement work | ||||||
|
Concrete works | ||||||
|
Shuttering work | ||||||
Task 2.
Design the flow organization for the installation of monolithic reinforced concrete foundations.
Initial data.
Concreting is carried out at an average daily temperature of + 14 ° C. Formwork under this temperature can be made after holding the concrete for 48 hours. The rhythm of the stream is 1 day.
Concreting of stepped foundations is carried out in three steps. First, the lower steps are concreted, then the sub-column to the nest generator and then the top of the sub-column. Concrete mixture is delivered to the construction site in dump trucks and unloaded in the overturning buckets with a capacity of 1.2 cubic meters. (the mass of 1 m 3 of concrete is 2.4 tons), each bucket with concrete is fed to the work site by a crane. (Figure 5.3.).
Fig. 5.3. scheme for feeding concrete mix to the place of installation
Progress of the task.
The reinforcing mesh of reinforced concrete foundations can be laid only after installation of the first basement formwork and in all cases prior to the installation of the upper ledge formwork. Therefore, formwork and reinforcement work in this case will have to be carried out by one complex link consisting of shutters and fittings. Thus, the construction of the foundations will use three links (three groups of workers):
1 - shutters with reinforcing bars;
2 - concrete workers;
3 - decalcers.
In the process of production of reinforced concrete works, the construction object is divided into longlines and seizures.
The smallest number of seizures on which workers, machines, or technological processes are simultaneously occupied when building monolithic reinforced concrete structures can be expressed by the formula:
,
(5.2.)
where N is the minimum number of captures;
P - the number of separate groups of workers (shutters, reinforcement workers, concrete workers, decollers);
t b - duration of hardening (aging) of concrete before decking, day;
k-rhythm of flow, day.
Dependence between the terms of work, the total number of seizures and the time of hardening of concrete can be expressed by the following formula:
, (5.3.)
where T - the period of performance of the works at the facility, day;
t p - duration of stay of all groups of workers on each capture, day;
After determining the minimum number of seizures, the minimum deadline is calculated.
Not always the minimum terms of work justify the cost of funds for the organization of the construction process, the payment of work of workers, machinery and machinery, vehicles. The practice of the construction industry determined that for the productive and convenient work of the shutters, fitters and concrete workers, when installing separately foundations, 25-30 square meters are sufficient. m with the length of the shuttering board up to 6 m. That is, if the size of the grip is more or less than the recommended one, you need to perform the adjustment by decreasing or increasing their number, by working in several threads.
It is necessary to determine the number of cranes used when rearranging the formwork, mounting reinforcing mesh, concreting, as well as the necessary number of workers.
,
,
,
,
where K o, K a, K b, K p - the number of shutters, rebars, concrete workers, decappers.
The number of workers must be adjusted in accordance with the requirements of ENIR.
After determining the number of links, cranes and the duration of all operations, a schedule is drawn up in the form of a linear and in the form of a cyclogram. (See the figure)
If there are more links than the foundations on the seizure, then it is necessary to organize these works (device formwork) in two shifts.
Concrete work must be carried out in two shifts, in order to reduce the necessary number of cranes for feeding concrete from the dump truck to the excavations.
The need for workers is displayed on the labor movement graph. This schedule is based on the schedule of work. Its values are determined by the sum of the number of workers in each shift.
For each link of concrete workers it is necessary to provide the number of deep vibrators required for production. The number of deep vibrators is determined by the replaceable capacity of concrete workers, referred to the productivity of the vibrator. The crane is selected for the required lifting capacity at the maximum (required) boom reach. The rate of crane production is determined by ENR. It also determines the time spent by the crane to install reinforcing mesh. According to the total output of the crane, their required quantity is determined.
The projected rate of performance is determined by the following formula:
,
(5.3.)
where П р.вып. - projected compliance with the norm;
Т р - normative labor intensity, person;
Prod. - the accepted duration of work;
n p is the number of workers in the link.
Practice has determined that the maximum overfulfillment of norms is 20%.
Under the arrangement of reinforced concrete and simply concrete structures, it is supposed to perform reinforcement work, shuttering, as well as work on laying concrete mixes.
The company "Basalt" performs time-consuming and massive work on the installation of concrete and reinforced concrete structures.
Reinforcement work
This type of work has a specific nature, which is due to factors such as assembly at different heights, the complexity of the outlines of monolithic structures made of reinforced concrete, as well as a considerable volume in comparison with prefabricated structures. In addition, the fixture must work closely with concrete workers and many other workers. Reinforcing concrete and reinforced concrete monolithic constructions mean working with manual arc welding.
As you understand, these works are quite complex, not everyone can handle them, but only a true master and a highly specialized specialist. The fixture harvests the reinforcement products in a special workshop, also assembles and installs the frames, assembles and assembles the reinforcement and formwork units.
Formwork
This type of work is aimed at the creation of special form-formwork. These devices serve to give concrete and reinforced concrete structures the necessary dimensions and outlines. It should be noted that formwork can be made of a variety of materials, including wood, metal, reinforced concrete.
Wooden formwork is short-lived, but cheap to manufacture.
Metal formwork can be used many times, which makes them more economical than wooden ones.
Reinforced concrete formwork is used for concreting on an industrial scale.
To give strength to formwork, they are fixed with special bolted and wire ties. The design of concrete and reinforced concrete structures is part of the overall construction project, therefore all shuttering work is carried out in strict accordance with the working drawings.
Laying of concrete mixes
To this stage of work proceed after the reinforcement packing. After that, you can safely proceed to receive, distribute and compact concrete in the structure. The construction of concrete and reinforced concrete structures does not forgive errors, so if deformations and displacements arise, the laying of the mixture stops until all the inaccuracies are eliminated.