Concrete is a building material that is often used for a variety of jobs. This is not only the construction of foundations, but also the construction of fences, buildings, the implementation of ceilings, fillings for the floor.
The scheme of preparation of concrete mix.
Concrete will be of high quality only if it is prepared correctly, otherwise the structure will not gain the necessary strength. In order for the concrete mixture to acquire the necessary properties, it is required to strictly observe all proportions. Compositions may vary in concrete grade, the presence of plasticizers and other additives.
Features of concrete mixing
To prepare concrete in a concrete mixer correctly, it is necessary to observe certain proportions. The conditions are not too complicated, but they are important for obtaining a quality mixture suitable for working with certain materials and structures.
Proportion of concrete mass.
Concrete in a concrete mixer is prepared in compliance with the following requirements:
- Equipment should be put only on a flat platform. If required, wooden boards should be enclosed, taking into account the fact that they must withstand the weight of the concrete mixer and the mixture kneaded in it. If possible, the concrete mixer is placed on the finished concrete site. These are optimal conditions for work.
- In the course of mixing, in no case can one put a shovel or hands into the blade of the equipment, bend over the open drum. There are certain labor safety rules that should be strictly followed. It is necessary to use special protective gloves.
- To make concrete of excellent quality, it is necessary to comply with all requirements. The solution should not stick to the walls, and freely move away from them. To do this, even before the start of work, the walls of the equipment on the inner side are lubricated with a mixture consisting of water, cement, fine aggregate.
- Only half of the fillers are loaded into the mixer drum at the time of the initial setting. After that, water is poured. A large filler in the remaining amount and cement should be added gradually, the portions for this should be small. It is this simplest rule that provides excellent mixing quality: the solution is homogeneous and perfectly kneaded.
- If small equipment is used, the tab is made differently. First you need to fill the sand, then add a small part of rubble, cement. Next, the dry ingredients are mixed, then part of the water is poured, and the mixture is already mixed with the liquid. After you can add the remnants of the mass of rubble.
Advanced mixing options
Scheme for determining the plasticity of a concrete solution.
It is important to know the following features of the manufacture of the composition:
- To make the composition, you need a concrete mixer with an inclined special axis. It is required to observe a duration of 2 minutes during the mixing process, and for a normal horizontal axis, 1 minute is sufficient. In this case, the counting time for mixing starts from the moment the complete addition of the ingredients and the first kneading are carried out. You can not retain the mixture, because its quality will be extremely low.
- If the time for kneading takes a long time, then the water will gradually evaporate, and this will cause the plasticity to decrease, the solution will not be as good.
- Next you want to test the mixture, its readiness. To do this, slightly tilt the drum, pour a small amount of the mixture into a wheelbarrow or a metal container. The back of a spade needs to make several test rows of concrete. After that, the surface should be inspected. If it is flat, smooth, then the quality is excellent, the combs should keep their shape and not fall off. If the composition is not ready, it is necessary to continue mixing.
- After each kneading it is necessary to clean the drum. To do this, it poured about a bucket of water so that the remnants of the solution moved away from the walls. Water can be used to knead further batches of concrete.
Variants of proportions of concrete for concrete mixers
Scheme fillers for concrete mix.
When deciding how to make concrete using a concrete mixer, attention must be paid to the fact that the proportion largely depends on the type of cement used, the type of concrete required at the outlet, and the required volume. These are important conditions, since the quality of the solution must be high, otherwise its strength will not be sufficient for the work.
Any proportion of concrete involves the use of certain ingredients, without which mixing will not be possible. The main components are:
- Binder - cement of the chosen brand.
- The filler, which are fine sifted sand, large crushed stone or gravel.
- Lime can be used to improve styling if the compositional requirements allow the addition of this component.
- Special additives that give concrete mix certain properties. These are aerating substances, various plasticizers.
When mixing the mix for making tiles, you can add special pigments that provide a different shade. The color intensity is excellent if the dosage is clearly defined. There are special substances that do not fade in the bright sun, different bright and saturated colors.
Concrete preparation in a concrete mixer: proportions.
Each of the ingredients has certain functions. For example, water gives viscosity to the resulting solution, and the fillers used are necessary for strength. The quality of the mixture depends largely on what brand of cement is used.. The best is to use this proportion:
- cement - 2 parts;
- sand cleared, river - 8 parts;
- crushed stone - 4 parts;
- water - 1 part.
The grade of the solution, which depends directly on the brand of cement, also matters. For example, if you need to get concrete M250, you will have to take cement brand M400. And for concrete M350 should take cement M500. The amount of water for mixing the future solution should not exceed ½ of the total volume of the poured cement.
When choosing ingredients, one should pay attention to the concrete mixer that will be used for work.
Gravity models are distinguished by a large range of containers, which can yield from 60 to 500 liters per batch. For the equipment of forced action, small volumes are almost not used.Back to table of contents
Proportions of concrete
The process of making concrete.
Various recipes are used for the manufacture of concrete mix, but if a concrete mixer is used, the proportions will be different from the usual manual mixing. It is necessary to correctly calculate the amount of water so that the solution is plastic, but not too liquid or hard. The stiffness parameters depend on the purpose for which the concrete will be used.
The following proportions are used to prepare the concrete solution:
For a class of concrete B7,5 marks 100:
- the mass composition of the solution in kilograms (cement / sand / crushed stone) - 1 / 4.6 / 7;
- volume per 10 liters of cement (sand / gravel) - 41/61;
- the amount of concrete, the total for 10 liters of cement (in liters) - 78.
For the class of composition B12,5 mark 150:
- mass composition of the solution in kilograms (cement / sand / crushed stone) - 1 / 3.5 / 5.7;
- volume per 10 liters of cement (sand / gravel) - 32/50;
- the amount of mortar total per 10 liters of cement is 64.
For the class of composition B15 mark 200:
- the mass composition of the solution in kilograms (cement / sand / crushed stone) - 1 / 2.8 / 4.8;
- volume of 10 liters of cement (sand / gravel) - 25/42;
- the amount of mortar, the total for 10 liters of cement - 54.
For the class of composition B20 mark 250:
- mass composition of the solution in kilograms (cement / sand / crushed stone) - 1 / 2.1 / 3.9;
- the volume of 10 liters of cement (sand / gravel) - 19/34;
- the amount of the resulting solution, the total for 10 liters of cement - 43.
For a class of solution B30 brand 400:
- the mass composition of the solution in kilograms (cement / sand / crushed stone) - 1 / 1.2 / 2.7;
- volume per 10 liters of cement (sand / gravel) - 11/24;
- the amount of concrete, the total for 10 liters of cement - 31.
During the choice of proportion, attention must be paid to what concrete will be used for. It is important to immediately determine whether the concrete is kneaded for conventional fencing or for foundations in areas with difficult conditions.
Concrete is a versatile building material that is mixed on the basis of cement, sand, rubble and water. In this case, the amount of water is often determined not by a recipe, but on the basis of what properties it is necessary to impart to the mixture. It is necessary to follow the recipe unquestioningly, but do not forget that individual circumstances are possible.