The proportions of concrete mix is perhaps the most important criterion for the quality of a future material. Compliance with the correct formulation and method of preparation of the solution have a decisive influence on the characteristics of the resulting concrete stone, so each competent builder must understand the rules for preparing a mixture for concreting.
Composition and components
First, we want to remind you what concrete is and what components it contains. This may seem superfluous, but an understanding of the role of each ingredient will help prevent common mistakes during the preparation of the mixture.
So, concrete is called artificial stone, prepared by mixing the binder with fillers. We will not go into the theory and classification, we say only that we are considering a particular case of concrete - cement concrete. This material requires the following components:
|Concrete component||Description and Purpose|
|Cement||The main binding substance of concrete is Portland cement or slag cement. This substance reacts hydration with water, as a result of which it is observed to harden and form a cement stone, which ensures the setting of all other ingredients into a single structure.|
|Sand||Sand is a fine aggregate, the main function of which is to prevent cracking of the cement stone in the process of hardening due to the redistribution of internal stresses and the creation of a durable frame. Also sand saves cement, reducing its consumption.|
|Rubble||Crushed stone plays the role of coarse aggregate, which also participates in the distribution of loads and prevents the appearance of cracks. Provides basic cement savings and reduces the cost of concrete|
|Water||Water необходима для гидратации цемента и получения камня. Также она выступает в качестве несущей среды, в которой происходит равномерное перемешивание и распределение всех компонентов смеси по объему раствора|
In addition, the composition of modern concrete mixes include various additives:
- accelerators and retarders,
- antifreeze additives,
- water repellents, etc.
Note! It should be borne in mind that the inclusion of chemical additives must be done very carefully, with the calculation of the dosage and according to the rules of mixing. Otherwise additives can spoil the concrete.
In most cases, Portland cement is used for civil engineering.
This material is 78 - 80% calcium silicates, which give it unique properties:
- fast hardening;
- quite high activity;
- good adhesion with fillers;
- moisture and frost resistance.
In some cases, for example, when working in hot weather, slag cement is used. For the construction of certain types of hydraulic structures and military facilities, special types of cements are used, which provide maximum strength, water resistance and frost resistance.
Note! For the preparation of concrete with their own hands most often used Portland cement brand M500 or M400, but not lower. The use of higher grades is inexpedient, since their price will be too high, and the excessive strength of the resulting concrete will not bring tangible benefits.
When choosing and buying cement, you should carefully look at the quality and condition of the package. If its integrity is broken, there are traces of moisture, efflorescence or stains on the surface - such a product should not be purchased. It is also important to pay attention to the date of manufacture of the material: the highest quality powder is considered to be produced at least a month ago, but no later than two.
Also, do not save on quality.
Do not buy:
- discounted goods;
- mixed with other brands;
- crumpled or dirty.
It is also important that the packaging should indicate its parameters:
- the amount of impurities
- type of.
Note! The amount of impurities is indicated in the marking after the numerical strength index. For example, M500-D20 indicates that there is up to 20% of impurities in the composition of the cement, choose a material with the amount of impurities from 0 to 20%, that is, the marking will be M500-D0 or M500-D20, but not higher.
Water и заполнители
For the preparation of concrete using ordinary fresh water. The instruction and the SNiP do not impose any special requirements on it, so you can follow the simple rule: if the water is suitable for domestic needs, then it can also be used for concrete.
Sand use medium and coarse fractions (1 - 5 mm), but the best material is a mixed and matched fractional composition, which presents particles of different sizes. Usually used material of two types - river and career, and the river is considered to be of higher quality.
Note! The sand must be washed with clay, dust and silt inclusions, as well as from organic impurities. Otherwise, the quality of concrete will noticeably suffer.
Crushed stone is used medium (5 - 20 mm), sometimes fine (proportions of concrete for the floor may require small marble chips, pouring into complex and densely reinforced forms is also no exception). Granite rubble and gravel are considered to be the most qualitative, however, other varieties are often used.
Tip! If possible, mix the average crushed stone with fine, this will increase the density of concrete and its strength.
The use of additives for concrete is a delicate matter. Calculate their number, and even more so to ensure the correct dosage and add in the conditions of the construction site is not so easy. Therefore, we do not recommend abusing chemistry unless absolutely necessary or with the guidance of a professional.
Recipes and proportions
The grades of concrete and the proportions of the components are directly related. To obtain a given brand, it is necessary to follow the formula as accurately as possible, which is given in the regulatory documents: GOST 7473-94, SNiP 5.01.23-83, as well as in some compilations and extracts.
We have simplified this task for you and presented the most relevant ratios of concrete ingredients:
The amount of water is usually selected based on the desired consistency. Water-cement ratio is an important parameter for a concrete mix, however, it is impossible to withstand it exactly in conditions of self-preparation at the construction site.
Note! It is considered successful that this ratio of water to cement is observed: 0.6–0.9, while 0.5– 0.7 is ideal.
The composition of the solution may vary depending on its purpose. For different mobility and plasticity use such ratios:
Note! When dosing components by volume, dry powders should be used, pour them without tamping and slides. It is advisable to pre-weigh the bucket of sand, cement and gravel, then, in accordance with the obtained values, adjust the data tables and translate them into buckets.
The proportions of concrete determine its quality and brand identity. The video in this article will help you choose the right components and prepare a concrete solution in a building site.