The use of concrete is almost always associated with plans for the construction or installation of fixed power structures of one type or another. Moreover, even simple events are accompanied by a complex of technological operations. The reliability and durability of the target operation will depend on the quality of the concrete work.
Varieties of concrete
Concrete is traditionally associated with a cement base, which is quite true, since it is the most common filler for building mixtures. Today, by the way, in this class Portland cement is especially popular, which allows you to erect structures of a high degree of strength.
But in addition to cement, the following mortar fillers are also used in concrete work:
- Silicates. An autoclave method of hardening produces a mixture based on lime. Quite rare, but functional concrete, characterized by insulating qualities.
- Gypsum. Concrete on this filler is suitable for the installation of suspended ceilings, partitions and finishing elements.
- Slag-alkaline fillers. A relatively new and inexpensive component of concrete mortar, which can be used in the same partitions or structures experiencing light loads.
To assess the possibility of using concrete for certain purposes, it will not be superfluous to deal with the bearing capacity of the future design.
For this, there is a classification according to the degree of density:
- Lightweight concrete. The resistance index is 500-1800 kg / m 3 . The basis for the solution is prepared on pumice, expanded clay, tuff and other porous aggregates. Such concrete is not suitable for critical load-bearing structures.
- Heavy. The density due to the combination of limestone, granite and diabase reaches 2500 kg / m 3 , which allows the design of such a solution to be used in the device of internal partitions and screeds.
- Particularly heavy. Fillers for such mixtures are metal chips and iron ore, which leads to a degree of density above 2500 kg / m 3 . Such concrete is suitable for the installation of industrial structures.
General technology of concrete work
The whole workflow can be conditionally divided into two stages with small intermediate operations - this is the preparation and directly laying / pouring the solution. As for the first stage, in each case a mixture of several components is prepared, including the same filler or another binder, sand or gravel (gravel), water and plasticizers (if necessary).
The prepared mixture is mixed with special equipment or, if we are talking about small volumes, with a construction mixer. The second stage of concrete work involves the use of prepared mortar. Again, this may be laying, pouring, spreading the mixture, or spot terminating. But work does not end there. After curing, abrasive treatment of concrete surfaces may be required.
Types of work activities with concrete
The most common works of this kind include the following:
- Foundation device. A wooden or non-removable polystyrene foam formwork is created, into which concrete mortar is poured. In the future, a frozen platform or a system of tape formwork walls will become the supporting foundation of the structure.
- The construction of the columns. Casing pipes are vertically installed around the perimeter of the building, the cavities of which are poured with concrete mortar. Similar designs also serve as a support base.
- The construction of the walls. The most common type of concrete work. The device walls can be performed using a monolithic scheme or masonry blocks. In the first case, a mold for pouring mortar is also pre-mounted, and in the second case, the mixture is used as a binder for bricklaying in particular.
- The device flooring. Screed is also a common way to use concrete mortar. Thus, strong bases for decorative coatings are formed.
Features of winter concrete work
To begin with, it is worth noting that the “winter” for concrete structures is temperature conditions, when the daily average values drop to 5 ° with the possibility of at least one (per day) achievement of 0 ° . Such a regime for the use of concrete mortar is fatal for the reason that in its structure hardening of water crystals will begin, which will create conditions for the formation of pores. In the future, ice particles will thaw, and the porous structure will retain a reduced level of strength. How do concrete work in the winter?
If it is not possible to postpone the construction activities to a more favorable time, then there are two ways out:
- Use frost-resistant additives and plasticizers. Such additives are added to the solution at the stage of its preparation. But it is important to consider that some of these modifiers adversely affect other properties of concrete.
- Maintain optimal temperature during the preparation and placement of the solution. To do this, use heat guns, steam generators, heat purge systems with flue gases, irrigation with hot water, etc.
Work on the device of reinforced concrete structures
This type of work differs from conventional concrete installation activities in that an additional stage of reinforcement integration is introduced into the technological process. Its purpose is determined by the need to strengthen the structure, giving it rigidity and durability. Both concrete and reinforced concrete work are similar in that a mortar is being prepared for them.
But if in the first case the same casting is performed as a self-sufficient procedure, then in the second it is supplemented by the laying of reinforcing bars. It can be metal or fiberglass rods with a diameter of 6-12 mm, which are mounted according to different schemes depending on the requirements of the project.
Completion of work
After laying, the workflow does not end either. Depending on the characteristics of a particular mixture and environmental conditions, the following operations may be required on an arranged structure:
- Shelter of concrete with a moisture-proof material.
- Thermal insulation.
- Watering every 3 hours
- Limitation of possible mechanical damage.
- The introduction of external technological coatings for protection.
- Dehumidification with surface needle rollers to seal the structure.
The simplest and most common advice for those who perform concrete work on the street is to cover the laid screed with polyethylene or a vapor barrier. This is a basic measure of protecting the material from external influences.
Assessment of technical and operational qualities of concrete
Quality control of concrete structures and structures is carried out taking into account the following characteristics:
- Strength. It is determined by how correctly the solution formulation was selected taking into account the ratio of sand, gravel, crushed stone, cement, water and other components.
- Density. It is estimated by the presence of voids in the structure itself. Again, this parameter will depend on the presence of ice and air in its mass.
- Plastic. It is expressed in a property such as mobility. In practice, the ability of concrete to fill the smallest gaps and voids depends on this quality.
- Water permeability. In essence, the resistance of the material to water pressure. The higher it is, the more stable the concrete is in relation to contacts with aggressive aqueous media.
Conclusion
With all the responsibility of using cement mortars, such measures are quite common not only in the professional, but also in the domestic sphere. For example, concrete plastering or tile laying may be associated with concrete work. Another thing is that large-scale operations on the installation of the foundation or pouring screed over a large area will not only require careful preparation, but in rare cases they will do without the use of special equipment. In other words, in each case, an individual approach is needed with a specific flow chart for the preparation, preparation of the solution and its use in accordance with technical standards.