When considering such a concept as cement grades, you need to focus on official regulatory documents, among which can be noted GOST30515-97, which divides all cements into special and general construction. Cement mixtures can have different bases (ferritic, aluminous or Portland cement clinker) and contain various mineral additives.
It is also worth noting that different grades of cement have different levels of compressive strength, different hardening rates (quick-hardening and normal-hardening), different setting times - there are mixtures that begin to harden in less than 45 minutes, and there are slow-setting (more than 2 hours).
Each brand of cement must meet a number of indicators, including: a specific material composition, thickening time, compressive strength, self-stress, cement paste density , linear expansion, the content of the required chemicals (chlorine ion, sulfur oxide, magnesium oxide ), water separation level heat dissipation and other characteristics.
You can find out about the composition of the cement mixture by its name. A detailed interpretation of the characteristics of cement is given in the above GOST, as well as in GOST10178-85. If the name begins at the PC, then these are cement grades based on Portland cement clinker, and if at the ShPC, then we have slag Portland cement with a high content of slag mass (more than 20%).
After the full or abbreviated name, there are numbers in hundreds, which mean compressive strength. Values of 600, 550, 500, and 400 are typical for Portland cement, and figures from 500 to 300 are typical for Portland cement slag. The name also indicates the maximum number of additives from D0 (no additives) to D20 (additives - 20%). May indicate fast curing (B), plasticization and hydrophobization of the cement mixture (PL, GF), the manufacture of cement from clinker with a normalized composition (H) and a link to the corresponding GOST.
For example, cement grade PTs550-D5-B-PL is Portland cement with a compressive strength of 550, with 5% additives, quick-hardening and plasticizing.
When constructing a building, it is very important that the work of the zero cycle be performed efficiently. Particular attention should be paid to the foundation, which is often made of concrete. Concrete is a mixture of cement, sand and gravel. The cement grade for the foundation must have a sufficiently high compressive strength (400-500), and the higher this number, the smaller the amount of other materials. For example, for cement grade 400, the remaining materials are taken in the proportion 1 \ 3 \ 3, and for cement grade 500 - 1 \ 4 \ 4, respectively.
Cement is a material that absorbs water very well, which undoubtedly affects its properties - over time, it loses its declared strength. Therefore, choosing cement grades for construction work, you need to look at the date of manufacture and specify storage conditions, as cement of brand 400 loses 10% of strength in a month of storage, and in half a year it can lose 30% of this characteristic and become cement of brand 280. For such cement, more additives will be needed, however, it cannot be guaranteed that the foundation in this case will be of the required strength.