When carrying out construction work, the choice of a particular grade of concrete is usually determined by the characteristics of a particular project. If the construction is not so large-scale as to create a detailed project, then the choice of the type of concrete mix may well be entrusted to the builders. But if you do not fully trust their professionalism, try to independently understand the features of construction technology, in particular, how you can determine the grade of concrete.
Necessary
- - concrete samples;
- - wooden planks;
- - a hammer;
- - sclerometer.
Instructions
Step 1
Check out the existing types of concrete and their purpose. The easiest way to find out the brand of concrete sweep is to familiarize yourself with the factory markings. The concrete markings usually contain numbers (for example, m-200). They mean the average compressive strength of the material, expressed in kgf / cm2. To check how the concrete meets the declared characteristics, a compression method using a special press is used. In addition to the indicated marking, such a parameter as "concrete class" is used in construction. If the grade uses average strength, the concrete class reflects the strength with the so-called guaranteed security.
Step 2
To check that the concrete used meets the required parameters, take a sample from the material when unloading the material. Cast a few cubes from the concrete with an edge length of about 150 mm. Use a mold made from wood planks of the correct size for casting. When taking a sample, it is not recommended to dilute the mixture with water. Sample concrete directly from the mixer pan.
Step 3
Moisten the mold to keep the wood from taking up a lot of moisture from the mixture. Then fill the box with concrete. Using a piece of rebar, make a series of indentations in the mixture so that cavities (empty spaces) form in the filled sample. In this case, excess air will come out, and the mixture will thicken a little. For additional compaction, lightly tap the sides of the mold with hammer blows. Place the samples prepared in this way in a room with medium temperature and high humidity, such as a basement.
Step 4
After 28-30 days, submit concrete samples aged under the specified conditions to an independent laboratory. The examination will issue a conclusion on what the concrete grade actually is, indicating compliance with the declared parameters. Keep in mind that the test can be carried out earlier, since concrete has intermediate stages of hardening (3, 7 and 14 days). Within a week, the mixture in the sample gains about 70% strength.
Step 5
If you want to speed up the procedure, use non-destructive methods to determine the grade of concrete and its characteristics. For this, a shock pulse test is carried out with a special device (sclerometer). Equipment for such concrete “tapping” is also available in specialized laboratories.
