How to make concrete by yourself

Concrete mortar is an important component in the construction of foundations, and the durability of the entire structure depends on its quality. It is not always possible to order a ready mix, so it is advisable to know how to make concrete by yourself. It is important here not only to observe the proportions, but to select the components correctly, otherwise the strength of the solution will not be high enough.

concrete specifications

Strength

Concrete mortar is a mixture of cement, sand, filler and water in certain proportions, which vary depending on the purpose of concrete and cement grade. If necessary, plasticizers are added to the solution. The most important characteristic of concrete is its compressive strength, which is measured in MPa( mega pascal).It is for this indicator that concrete is divided into classes. But the brand of concrete indicates the amount of cement in the solution.

Class of concrete	Average strength of this class, kgs / sq.cm	Nearest concrete grade
B 5	65	M 75
B 7.5	98	M 100
B 10	131	M 150
B 12.5	164	M 150
B 15	196	M 200
B 20	262	M 250
B 25	327	M 350
B 30	393	M 400
B 35	458	M 450
B 40	524	M 550
B 45	589	M 600
B 50	655	M 600
B 55	720	M700
B 60	786	M 800

Concrete grade M100 and M150( B7.5 and B12.5) is most often used as an interlayer for the main foundation, for the manufacture of screeds, concreting tracks. Concrete M200-M350 is most in demand: it is used in the construction of foundations, for the manufacture of screeds, concrete staircases, blind lands. Solutions of higher grades are used primarily in industrial construction.

Plasticity

An important characteristic of concrete is its plasticity. The more plastic the solution, the better it fills the formwork. At low mobility of concrete in the screed or foundation, unfilled areas remain, which leads to gradual destruction of the concrete slab. For standard constructions, concrete with plasticity P-2 or P-3 is used, for formwork of complex shape and in hard-to-reach places it is recommended to use a solution of P-4 and higher.

Water resistance and frost resistance

Water resistance depends on the amount and grade of cement in the solution. The higher the mark, the more resistant the concrete is to moisture. Frost resistance of concrete is achieved by adding plasticizers to the composition. It should be noted that such solutions very quickly seize;if it is wrong to calculate the amount of the mixture or use it at a low temperature, the concrete will turn into a monolithic block directly into the tank.

Concrete components

Cement

Cement fulfills the binding function for all other components of the concrete solution and the strength of the concrete directly depends on its quality. In private construction, the most demanded cement brands M400 and M500.When buying cement, you should know that it loses its quality in long-term or improper storage. Already a month after manufacturing, the binding properties of cement are reduced by 10%, in half a year - by 50%, in a year it is generally not recommended to use. But even fresh cement will become unsuitable for use if it draws damp, so it must be stored in a dry place.

Sand

Sand is the second most important component of a concrete solution. In rare cases, it is replaced by slag, the same concrete is always mixed with sand. It is best to use coarse-grained river sand without various impurities. If only fine fine sand is available, it should not contain clay, earth or silt, which reduces the adhesion of the solution to the filler. Before mixing, sand must be sieved to remove any excess.

Filler

The best aggregate for concrete mortar is crushed stone with dimensions from 5 to 35 mm. Often rubble is replaced with gravel, slightly less often - expanded clay. It is very important that the surface of the aggregate is rough, then its adhesion to cement will be as strong as possible. To compact the mixture, it is necessary to take a filler of different fractions. Like sand, the aggregate must be clean, so it should be poured on a prepared and compacted pad or on a spread tarpaulin.

Additives

To make the concrete frost-resistant, waterproof and other useful properties, plasticizers are used. They ensure the setting of the solution at negative temperatures, increase its plasticity, or, conversely, impart a viscosity. Use them only if it is really necessary, and you should clearly follow the instructions for their use and observe the proportions.

If a thin screed or screed is required on an unstable basis, reinforcing fibers are mixed into the concrete mix. They are made of polyvinyl chloride and polypropylene, the strength is small, but excellent avoid cracking of concrete. In standard foundations and screed reinforcements are not needed.

Solution proportions

To independently produce high-quality concrete, you need to know in what proportions to mix components. The ratio of cement, sand and gravel is most often used as 1: 3: 6;The water is half as low as the total weight of the dry components. It is recommended not to add water all at once, but in several portions, so it is easier to control the density of the solution. The moisture content of sand also has its significance - the more it is, the less water it will take. Measure all components with one container, for example, a bucket. When using containers of different volumes to achieve the necessary proportions will not work.

When mixing, the purpose of the solution should be considered. For the substrate under the screed, scrawny concrete is made without the addition of crushed stone, for the concreting of the tracks and blind areas, medium and fine fractions are used, for the foundation under the house there is a medium-grade crushed stone and high-quality cement. Learn the exact proportions of concrete of different brands will help the table.

Manual mixing method for concrete

Mixing of concrete mortar is performed manually or in a concrete mixer. If you want to fill a large area, the first method is not suitable, because it takes too much time and physical effort. If you need a little solution, it is more convenient to knead it with your hands.

Step 1. Preparation of

To prepare the solution, you need a low wide capacity, for example, a large metal trough, a selection shovel, a bucket and a conventional hoe.

Step 2. Dry mixing

A bucket of cement is poured into the container, then 3 buckets of sifted sand and 5 buckets of crushed stone. Dry ingredients are thoroughly mixed with a hoe. The proportions may be different, depending on the desired brand of solution.

Step 3. Addition of water

If all components are mixed evenly, you can top up the water. First pour 7-8 liters and begin to intensively interfere with the contents of the hoe. This process will require effort, but you need to stir very well. It is desirable to raise the bottom layer and carry out a hoe in the corners where dry lumps may remain. If the solution is very thick and stretches behind the hoe, you need to add some water. Correctly prepared concrete slowly slides off the shovel, does not separate.

There is another version of mixing: first pour water into the container, then pour in the cement.2 buckets of water requires 2 buckets of cement. Stir the cement thoroughly with water and add 4 buckets of sand. Again, it's a good hinder to homogeneity. The last pour crushed stone in the amount of 8 buckets and mix again. Which of the ways is better, there is no one-sided opinion, so it's worth trying both and determining for yourself the most optimal one.

Kneading in the concrete mixer

The cement mixer is installed no further than 40 meters from the working platform, preferably near the sand and gravel. This will allow faster work and facilitate the delivery of the solution. Now you can start mixing:

• in a concrete mixer pour a little less water than you need;
• fill up the required amount of cement;
• add sand and mix for about 3 minutes;
• pour, if necessary, plasticizers and other additives;
• the last pour rubble and mix 10 minutes.
  

  Concrete manufacturing in the concrete mixer

If the resulting concrete is too thick, a little cement is added to the remaining water, mixed well and poured into the concrete mixer. To interfere with the solution for more than 10 minutes is not recommended, otherwise the cement will begin to set. Ready-mixed concrete is poured directly onto the platform or into a wheelbarrow if the concrete mixer is at a distance. It is advisable to pour out the entire solution at once, but if this does not work out, some of the mass is left in the included concrete mixer. Use it as soon as possible.

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