Concrete is a very common building material. Its main components in most cases are cement and sand. A variety of structures of buildings and structures, including responsible ones, are poured from the mortar of this variety. And of course, the preparation of the concrete mixture must be carried out with strict observance of all the required technologies.
Requirements
Cement mortar is supposed to be prepared in such a way that concrete subsequently has a given strength. Quality material of this type should:
- maintain its uniformity during transport and formwork;
- have the consistency necessary for the construction of a particular structure;
- be easy to fit.
Basic components of concrete
When preparing a concrete mix, the following three types of ingredients are always used:
- sand as filler;
- cement as a binder;
- water as a sealer.
Also, in some cases, plasticizers can be added to concrete. The cheapest and most popular of them is lime. Sometimes more expensive polymer compounds can be used to increase the elasticity of such solutions.
Crushed stone is also often used in the preparation of concrete mix. This material makes the finished structure more durable and saves on cement, which is known to be quite expensive on the market today.
Varieties
There are only two main types of concrete - ductile and rigid. The first type of mortar fits well into the formwork and is compacted under the action of its own weight. It is these concretes in construction that are most popular. Rigid mixtures contain little water in their composition. At the same time, they add a lot of crushed stone or gravel. Finished structures made of such concrete are more durable than plastic ones. But at the same time, solutions of this variety are not very convenient in laying. When erecting various kinds of structures, such concrete has to be subjected to vibration, vibration stamping, vibro-rolling. In addition, such solutions are usually quite difficult to prepare. Dosages when mixing them must be observed as accurately as possible. Otherwise, such a mixture can dramatically change its properties for the worse.
Where it can be prepared
Most often this type of mortar is mixed in concrete plants and delivered toconstruction site with special vehicles. The material prepared in this way is usually of excellent quality. In some cases, concrete can also be prepared directly on the construction site using special mobile equipment. This is how cement mortars are made, for example, when erecting private low-rise buildings, owners of suburban areas.
GOST
When preparing mortars based on cement, of course, the requirements of GOST must be observed first of all. Only in this case, the finished structures will be strong and durable. Regulates the procedure for the manufacture of concrete mixtures in Russia GOST 7473-2010. This document, among other things, indicates the permissible parameters for the separation of mortars, deviations in their workability, etc.
Basic ways of preparing concrete
Purely technologically, the operation of mixing cement mortar is nothing complicated. The only thing is that when performing such work, dosages should be observed exactly. According to the requirements of GOST 7473-2010, for example, errors in this regard should not exceed 2% for water, cement and additives and 3% for aggregates. If this rule is not observed, the structure erected from the solution will not be too strong and durable. And this, in turn, of course, will negatively affect the quality of the entire building or structure as a whole.
There are only two main methods for preparing concrete mixes:
- mechanized;
- manual.
The first technology can be used both when mixing mortar at the factory and at the construction site. The second method is used, of course, mainly by the owners of suburban areas when building any structures with their own hands. No equipment is used in this case. Mixing is done using most often ordinary garden tools.
Mechanical kneading technology, in turn, can be:
- fully automated;
- simple.
In the first case, all operations in the manufacture of concrete mortar are performed using special equipment. It is this method of kneading that is used in factories.
A simple technology for the mechanical preparation of concrete mix involves loading the ingredients manually. In this case, the actual mixing of the components is carried out using equipment. This technique is also quite often used by the owners of suburban areas in the self-construction of concrete structures.
Equipment
Concrete mixers are, of course, used as the main equipment for mixing cement mortar. Such machines for the preparation of concrete mix can have different sizes and capacities. On the market today there is inexpensive and at the same time not too dimensional equipment of this type, designed specifically for owners of suburban areas and small developers.
Standard manual loading mechanical kneading technique
The technology of mixing mortar in concrete mixers of different capacities and dimensions is usually the same. When using such equipment, in order to obtain high-quality material, it is important first of all to follow the order of loading the ingredients.
Standard concrete mixing technology in this case is as follows:
- crushed stone and sand are loaded into the bowl of the concrete mixer;
- these ingredients are thoroughly mixed;
- cement is poured into the mixer, after which the concrete mixer is turned on for several minutes;
- water is poured into the bowl.
Auto kneading technology
The procedure for supplying ingredients in the preparation of concrete mortars at factories is the same as when mixing at construction sites with manual backfilling of components. At the first stages, in this case, sand and gravel are also laid in the bowl. After mixing, cement is added to them. Then the mixer is turned on again until a homogeneous mass of dry ingredients is obtained.
The methods of automatic and simple preparation of concrete mix differ only in the way of adding water. In factories, a dry, homogeneous mixture of cement, sand and gravel is first poured with 70% of the prescribed proportion of the mixing agent. Next, the concrete mixer is switched on for 1 min. Then the rest of the water is poured into the solution.
Is it possible to break the batch order
It is desirable to put the ingredients into the concrete mixer mixer in exactly the sequence that was indicated above. Otherwise, the mixture may later, for example, contain lumps. In addition, a violation of the order of operations during preparation can lead to the fact that the solution will not have the consistency that is needed.
If, for some reason, the concrete at the construction site was mixed incorrectly and turned out to be of poor quality, you can try to correct the situation without wasting time. In the presence of lumps, the solution must be thoroughly mixed again in a mixer. If the concrete turned out to be liquid, sand and cement should be added to it. If the mixture is too thick, thin it out with a little water. All these operations should be carried out as soon as possible. The cement mortar retains its performance characteristics no more than 2-2.5 hours after preparation.
Hand kneading technology
This technique allows you to get not as high-quality as when using a concrete mixer, but still quite suitable for the construction of not too heavily loaded structures. Inventory in this case is usually used like this:
- shallow trough;
- chopper and shovel;
- buckets;
- garden cart;
- garden hose.
Actually, the method of preparing the concrete mixture in this case is as follows:
- sand and gravel are poured into the trough;
- thoroughly mix thesedry ingredients;
- add cement to the trough and again mix everything until smooth;
- pour water into a trough and knead everything again.
The cement mixture is kneaded using this technique, most often using a hoe. It is believed that preparing a solution with such a tool is easier than with a shovel. At the final stage, the cement is transferred to buckets and poured into the formwork.
Materials for the production of concrete mix: quality requirements
Ingredients for the preparation of mortars of this type are selected depending on the specific purpose of the latter. For pouring loaded structures, only high-grade cement (for example, M400 or even M500), coarse river sand and high-quality crushed stone are usually used. To prepare the plaster mortar, a less expensive and high-quality binder is used. At the same time, fine quarry sand is used.
In any case, cement for the preparation of concrete mixtures should be used exclusively fresh. During storage, this material usually absorbs water and, as a result, loses the quality of the binder. Sand must be sifted before preparing solutions. Such material, both river and quarry, may contain dirt, debris, organic residues.
Like sand and cement, crushed stone is usually prepared before mixing the mortar. Such material in some cases may be pre-distributed into fractions. It is believed that the addition of such stones to the mixture of different, butnot the same size, improves its quality.
There are certain requirements for the water intended for the preparation of the concrete mixture. It should not contain too many minerals. And of course, the water for the solution should be used exclusively clean without organic impurities and debris.
