Concrete. Types of concrete

After planning the site and selecting the project home starts actually building a house, and it begins with the foundation, a house without a foundation can be built except on the rock. But making foundations and the erection of stone walls, etc. requires the most basic knowledge about the different concretes and mortars. So let's forget about the time the main issue of concern to us - building and briefly take a look at some data that will later be useful for you. Depending on the size used concrete aggregate are: - to fine-grained filler - up to 1 cm - on a coarse-grained filler - 1-15, see the density of concrete is divided into four types: - very heavy - more than 2500 kg/m3; - heavy - from 1800 to 2500 kg/m3; - light - from 500 to 1800 kg/m3; - very light - less than 500 kg/m3. The main characteristic during the installation of concrete class is a measure of compressive strength (MPa) (B3, 5, B5 ... B60). Concrete class is a numerical characteristic of any of its properties taken with guaranteed security (usually 0.95). Grade of concrete - numerical characteristic of any property taken by its average value. On the compressive strength, for example, heavy concrete, installed brand 50, 75, 100, 150 ... 600. For conventional reinforced concrete structures in civil and industrial construction usually used concrete grades 200 and 250. Durability of concrete estimate the degree of frost. When frost resistance of concrete are classified in grade P50, P75 ... P300, etc. By type of binder concrete are cement, silicate, gypsum and concrete on inorganic and organic binders. The main types of concrete heavy concrete. Heavy call dense concrete structures, prepared against the cement binder filler. The density of heavy concrete from 1800 to 2500 kg/m3. Porosity of the heavy concrete ranges from 6 to 15%, depending on the kind of aggregates, concrete composition and methods of sealing. Of great importance is the nature of the porosity: large open pores degrade the properties of concrete, small closed (for example, using hydrophobic plasticizers and additives) improves the properties of concrete. Frost resistance of heavy concrete not less than 50 MDE. Frost resistance - depending on the nature and porosity of concrete, type of cement and aggregates. Temperature resistance of heavy concrete is relatively low. It can be used for structures subjected to prolonged heating at temperatures no higher than 200 ° C (strength at the same time reduced by 50%). Shrinkage of heavy concrete, the higher the higher the value of A (water / cement ratio). At the same conditions, if not enough water in the concrete, the concrete mixture is not enough mobile, it will be loosely packed in the form and as a result of the density of concrete will be small. If you used an optimal amount of water (k = 0,3), you can get the optimal composition of the concrete mix. In addition to the brand of cement, the values ??of A used fillers, the intensity of compaction on the strength of concrete to a small extent influenced by other factors. Concrete strength will increase: the replacement of gravel with gravel or sand okatnogo - angled, with an increase in surface roughness of aggregates, with more thorough mixing of concrete mix, while improving the conditions of concrete hardening. High-strength concrete M600 - a kind of heavy concrete. Is derived from the cement high marks, washed sand and gravel through the preparation of rigid or inactive compounds in the forced action mixer. For ukladki smesey and formirovaniya izdely use intensivnoe uplotnenie - obyazatelnoe vibrirovanie. Significant effect in the production of high-strength concrete give plasticizers. Lightweight concrete. For lightweight concrete are concrete, the density of which varies from 500 to 1800 kg/m3. Aggregates for lightweight concrete are porous natural materials (pumice, tuff, limestone-coquina) and artificial (expanded clay gravel, expanded perlite, vermekulit, metallurgical slag). Depending on the volume weight and destination lightweight concrete are classified in insulation - less than 500 kg/m3; constructive insulation - up to 1400 kg/m3; design - from 1400 to 1800 kg/m3. Lightweight concrete on porous aggregates depending on the structure is divided into: normal, in which the intergranular voids of coarse aggregate are completely filled with cement paste and sand, porous, which through the use of gas or blowing agent in the cement stone formed by a set of closed pores malopeschanye in which intergranular voids of coarse aggregate is only partially filled with cement paste or sand; bespeschanye, in which there is no sand and coarse aggregate particles are coated with cement paste. By type of binder used lightweight concrete are cement, lime, cement, lime, slag, silica, etc. In the selection of lightweight concrete on porous aggregates should take into account the fact that the porous filler has a very rough surface, which requires more cement consumption than for the heavy concrete. Porous filler is able to suck out the water, changing the water-cement ratio. It is dangerous not only to excess, but the lack of water, as it leads to a decrease in the strength of hardened concrete. An increase in cement consumption increases the strength of lightweight concrete, but also the concrete becomes more severe, which negatively affects its conductivity. Approximate consumption of cement per 1 m3 keramsit depending on the destination is as follows: for thermal insulation of concrete - up to 175 kg, for construction-insulation - from 175 to 250 and for constructive - from 250 to 400 kg. Used for the manufacture of lightweight concrete panels for walls and ceilings for insulation of floors and ceilings. For the formation of porous lightweight concrete used foaming and blowing agents. Due to the formation of additional pore volume decreases the density and thermal conductivity of porous concrete. Lightweight concrete used in the construction of exterior walls, roofs, as well as for the manufacture of panels and slabs. Cellular concrete - a kind of lightweight concrete. Receive as a result of hardening of expanded (with foam) mixture of binder, water and silica component. Most often as a binder for the cellular concrete (gazopenosilikata) use quicklime ground lime. High frost resistance of cellular concrete is due them, the structure (large number of closed pores filled with air or gas). Due to the large porosity of the cellular concrete have a low thermal conductivity, making them very effective in protecting the device structures. The volume of pores in the cellular concrete is 85% of the total volume of concrete. Indicators of the properties of porous concrete, the higher the smaller the diameter of individual cells (lower thermal conductivity) and the more closed cells (lower water absorption of concrete). By appointment cellular concrete are divided into: thermal insulation - with an average density in the dry state less than 500 kg/m3; construc ¬ no-insulation - with an average density of 500-900 kg/m3; ¬ tional construction - 1000-1200 kg/m3. The main characteristics of aerated concretes ¬ on are the average density and strength: Applied cellular concrete for the manufacture of construction blocks and panels, walls, and re ¬ town, as insulation. In the particular construction of cellular concrete is most often used for otlivaniya melkostenovyh units, who use mainly for the construction of outbuildings (garages, sheds, warehouses). Aerated concrete (also a kind of lightweight concrete) are most likely derived from a mixture of cement paste, ground sand and gazoobrazovatelya (fine powder of aluminum). Aerated concrete blocks used for interior and exterior masonry walls and partitions. For foundation and basement walls (wet mode of operation) Aerated not be used. Above we have listed only the main types of concrete. There are also foam, resistant to chemicals, acid, hydraulic, fire, paroupornye, color and other concretes. For the construction of individual houses, these types of concrete are practically not used. A special place in the building occupied by concrete structures made of concrete and steel reinforcement. Reinforcement increases the bearing capacity in case of tensile or bending forces.