Concrete preparation technology - proportions and materials
It is impossible to imagine the world around us without modern architecture. It should be remembered that concrete is, without exaggeration, the main material used in construction.
A similar material was used in Ancient Egypt. When using cement for different purposes, it is important to use the correct concrete proportions to suit the application. Let's talk about making concrete by hand.
Concrete - what is it? The physical properties of concrete will be determined by what it is made of and how it is made. In order to understand this as best as possible, it is important to pay attention to its components.
This element can be considered the main one in the process of making concrete. The legislation provides that its quality must comply with GOST 31108-2003, TR-166-94 and SNiPu 2. 03.
11-85. In order to make sure that the cement is of good quality, it is required that it meets certain conditions. Here are some of them:
- The fineness of grinding should be from 350 to 380 square meters per 1 kilogram. It can differ from the prescribed norm, but no more than 10%.
- The solution after a couple of hours should show the first signs that it begins to set.
The process should end after 4-5 hours.
The density of the cement mixture must be such that the water content in it does not exceed 26%.
The use of aggregates
In this role, sand, gravel or their combinations are used, which will perform the following functions:
It should be noted that construction sand is different from the standard one.
The difference will consist in the form of a huge number of its grains of sand - in building sand they are round in shape and approximately equal in size. Moreover, there is a little clay in its composition, which will provide an increase in its level of plasticity. In the role of large-sized aggregate, gravel, granite chips and crushed stone are most often used. A crumb of granite is used in the production of the most durable concrete grades (for example, M500), but for M350 and those that are weaker, crushed stone and gravel are used.
This component can be called the second most important, and here pure water is used.
True, its required amount is determined taking into account the water absorption by cement and depending on the composition and the presence of special additives.
The use of additives
The use of additional components in the manufacture of concrete has the following objectives:
The need for the use of plasticizers and additives is determined by the specific application of concrete.
In the construction industry, this material is used at every step. Not just walls are made of it, but even load-bearing beams. Where an increased degree of strength is needed, reinforced concrete is used, in which metal pins are inside in order to increase strength.
This material has a large number of areas of application:
- Construction of facilities in the oil or even gas industry.
- Application in the mining industry.
- Design use.
- Military industry.
- Performance of repair work.
- In the construction of buildings and structures.
The specific properties of concrete will depend on how it was made by the manufacturer or made in-house.
To prepare concrete in a concrete mixer (or with your own hands), you need water, cement, sand and gravel. The proportions are required in the solution. To do this, take the following concrete composition:
All this needs to be stirred. This composition is determined approximately, since the numbers may change for various reasons. This can be influenced by:
Concrete mixtures, depending on the characteristics of the composition, can have different properties. The basis for their production will be the use of water and cement, and as a result of their interaction, a cement stone appears.
But when using it, problems arise. He, as it hardens, may begin to deform. Cement stone can shrink at least 0.2 cm per meter. The curing process is extremely complex, and internal stresses usually appear in various places, which create cracks in the cured material.
Usually they are not visible due to their microscopic size, and their presence greatly reduces the strength of the concrete masonry. In order to make the material much stronger, different additives are used (crushed stone, expanded clay and sand). The additives will absorb most of the stresses that appear before shrinkage.
Designations of different concrete grades are made in the form of the letter M and a number. For example, M75 or M1000.
The figure will be characterized by the compressive strength of the concrete. The higher it is, the stronger the material. Resistance will be noticeable in the hardened material, which occurs at 28 days. This indicator is measured in kg per square centimeter. For example, if you take the M300 brand, then the considered value is 300 kg per square centimeter.
The other parameters are also used:
- If you plan to use this composition at a low temperature level, then the degree of its resistance to frost (F) will be of great importance. To determine it, it is required to carry out the maximum probable number of complete cycles of freezing and thawing of solid concrete. The larger this value, the higher the resistance of the material to frost.
- Another feature is that water can flow into the concrete under the influence of pressure. The higher the pressure level is needed for this, the more water-resistant the material (W).
It is measured on a scale from 1 point to 20. If this indicator is from 17 or more, then this concrete can be used in the construction of dams or hydroelectric power plants.
- Indicator (P) will characterize the properties of the uncured mixture. He talks about how easily this mixture takes the required form. The most plastic mixtures are P 1 and P 2 .
The average level, as a rule, P 3 -P 5 . Usually the M350 has this plasticity. Such mixtures can be used to fill complex formwork. But the curing time of such concrete will be increased.
- A parameter such as (B) is an indication of the strength level of the cured mixture by points.
This dimension is associated with parameter (M). M100 will correspond to B7. 5, and M350 - B35.
The characteristics of the concrete used must necessarily correspond to the type of tasks performed.
The proportions of concrete preparation are important, and the material itself is used in construction everywhere.
But for each work, a certain brand is required:
This brand is used to create road-type surfaces.
The strength of the material must correspond to the work being performed.
Preparation of the mixture
When mixing the concrete, proceed as follows:
When using a concrete mixer, it is required to fill in the required amount of cement and add water. Then the mixture is mixed and crushed stone and sand are poured. Further, if there is not enough water, it needs to be topped up. Then turn on the device and prepare the mixture.
Concrete for the base
In order to make the cement mixture for the foundation, the following must be prepared:
Concrete composition for the foundation, the proportions of the parts will be discussed in more detail later. A concrete mixer is required only when you need to make a huge amount of cement mortar. in order for the mixture to obtain the desired consistency, it is required to correctly calculate the amount of components - sand, cement, water and large-sized filler As a rule, the weight amount of water is taken on the basis that it is half of the cement used.
Concrete proportions in buckets or even by weight can be used. As a rule, the M300 or even M350 brand is used for the foundation, and the proportions in this case:
Water needs 1/2 liter. For example, 10 kg of cement requires 18 kg of sand and 37 kg of crushed stone. Although M300 and M350 are the most popular solutions, it is nevertheless acceptable to use other brands of cement. In this case, it will be necessary to use other proportions:
6 to 7.
2 to 2. 7.
But more durable cement, grade M450, requires a ratio of 1 to 1. 1 to 2. 5.
If we consider the required ratios not in terms of weight, but in terms of volume, then you can find out about the proportions of concrete per 1 cubic meter, the table is presented below. Shown here for concrete are proportions in parts by concrete and by weight. It is required to distinguish between the brands of cement and concrete that are obtained as a result. It is generally accepted that for concrete of a certain strength, it is required to use cement, which has twice the rate.
Mortar for building a house
For this, M100 solution is usually used, which is made in a hard consistency.
For stairs or paths, you can use the same cement, but make concrete out of it more plastic. If the house is built on damp ground, then M150 grade cement is used. If you make a strip foundation, or build an unloaded part of the building, then M200 or even M250 is perfect. Having made the solution more plastic, you can use it when arranging a septic tank, cesspool or sump. The base of a residential building will be reliable and durable if it is made of cement grade M300, while using a fraction of 2-4 cm as a coarse-grained filler.
M450 and M500 are usually not used in the construction of a private residential building. They have increased strength characteristics and are required for those cases when high reliability requirements are imposed on buildings.
When preparing the composition, you can apply the proportions for the constituent components by weight or taking into account the volume. With the second method, there is no need to weigh the initial components. The work requires the use of a suitable cement grade and mortar preparation method.
it is important to observe the proportions of the components of the solution. in this case, correctly selected and manufactured concrete will be durable and strong.
( 2 marks, average 3.5 from 5 )
Posted By: Work Style |11, Nov 2020
Posted By: Work Style |11, Nov 2020
Posted By: Work Style |10, Nov 2020
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Posted By: Work Style |05, Nov 2020