In modern construction, most professional activities are associated with the operation of sand-cement or ready-made concrete mortar, made with this binder in mind. The key quality of cement is that when it comes into contact with water, the hydration process begins to form a high-strength stone. The strength class of the powder mixture affects the formation of the characteristics and each operational property of the constructed structure.
Strength of cement pulp
The grade of binder powder is determined by its compressive strength. It learns this value experimentally-a small cube is created from the prepared powder, which is then pressed until it is completely destroyed. Standardized dimensions of test samples and the use of standard technologies under the same conditions make it possible to install powder for class affiliation. According to the quality of strength, such groups of building materials are distinguished (table).
| Strong group | Ultimate compressive strength required, MPa |
| High-strength | from 50 |
| Privates | 30-50 |
| Low-brand products | up to 30 |
In the future, concrete and reinforced concrete parts of the building structure are subject to various negative factors affecting them from the outside during operation:
- mechanical load;
- moisture content;
- temperature spikes, etc.
Moreover, the coefficients responsible for the strength of concrete (compression, stretching, bending) change under this influence.
It is worth noting that the coefficients of compressive strength and flexural (tensile) strength are interrelated. The difference between the first and second increases in proportion to the vintage. For example, for the M400, it is 7: 1, and the M500-8.3:1.
The strength of the binder powder in the concrete mass is directly affected by the volume of liquid and the combination of basic elements with various additives that change the rate of hardening.
Marking of cement (durable type according to GOST)
When classifying binders of the Russian Federation, the regulations of GOST 31108-2016 are used. Due to new designations that are incomprehensible to many, names that are relevant to the outdated GOST 10178-85 can be used. summary tabular information will help you classify the purchased powder to one or another type (these are the most popular ones).
| New designation | Old name |
| 22,5 | M300 |
| 32,5 | M400 |
| 42,5 | M500 |
| 52,5 | M600 |
In accordance with these designations, it is possible to distinguish quite real strength characteristics. In the first case, the result of measuring the load sustained in kg/cm3 is indicated, and in the second – the pressure in MPA.
Powder Powder Testing
The qualitative characteristics of cement powder depend on its structure, represented by various components. Both the composite components and the particles related to the mineral base are important. At the production stage, when evaluating the strength, take into account:
- powder structure;
- minerals included in the product;
- the presence of various additional elements and so on.
Even the manufacturing company can eventually provide different levels of strength indicators, meeting the full range of technological requirements.
During testing, special bars with a volume of (V) 256 . They are kept until completely solidified for 28 days. At the same time, it is necessary to prepare a cement-sand mass from the ratio of 1:3. additional tests are carried out on the 2nd and 7th days, which allows you to more accurately determine the class of powder.
| Class affiliation | Compressive strength (MPa) for aging powder | |||
| 2 days, the slightest | 7 days, at least | 28 days. | ||
| not less than | no more than | |||
| 22.5 N | – | 11 | 22,5 | 42,5 |
| 32.5 N | – | 16 | 32,5 | 52,5 |
| 32.5 B | 10 | – | ||
| 42.5 N | 10 | – | 42,5 | 62,5 |
| 42.5 B | 20 | – | ||
| 52.5 N | 20 | – | 52,5 | – |
| 52.5 B | 30 | – | ||
Designation: H-normalized, B-fast-hard.
The manufacturer is obliged to indicate on the packaging not only the maximum strength index, but also the features of the “vital activity” of the powder in the active phase during steaming. This procedure allows you to check a number of technological indicators much faster. For more than 12 hours, the samples are kept in a common steaming chamber, where they are affected by high temperatures (80 degrees Celsius). The already cooled bars are placed under the press so that the next stage of measurement is performed.
Increase in strength indicators
You don’t have to buy expensive recycled clinker. You can improve the quality benefits of the powder by adding various auxiliary elements to it:
- plasticizers that increase the mobility of concrete mass;
- curing accelerators;
- additives that increase frost resistance and hydrophobizers (moisture resistance);
- complex substances that take into account not only all of the above improvements, but also reduce dust separation.
Using the nuances of choosing a binder powder presented in this article, you can also purchase high-quality building materials that complement the mixed concrete masses-the required amount of sand, crushed stone (gravel), etc.