When considering such a concept as cement grades, one should be guided by official regulatory documents, among which GOST 30515-97 can be noted, 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 brands of cement have different levels of compressive strength, different setting speeds (quick setting and normal hardening), different setting times - there are mixtures that begin to harden in less than 45 minutes, and there are slow setting (more 2 hours).
Each grade of cement must meet a number of criteria, including: a certain material composition, thickening time, compressive strength, self-stressing, cement paste density, linear expansion, the content of required chemicals (chlorine ion, sulfur oxide, oxide magnesium), water separation, heat dissipation and other characteristics.
You can learn about the composition of the cement mixture by itsname. A detailed breakdown of the characteristics of cement is given in the above GOST, as well as in GOST 10178-85. If the name begins with PTs, then these are cement grades based on Portland cement clinker, and if on ShPTs, then we have Portland slag cement with a high content of slag mass (more than 20%).
After the full or abbreviated name are numbers in hundreds, which mean compressive strength. Portland cements are characterized by values of 600, 550, 500, 400, for Portland slag cements - numbers from 500 to 300. The name also indicates the maximum number of additives from D0 (no additives) to D20 (additives - 20%). There may be an indication of rapid hardening (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 PC550-D5-B-PL is a Portland cement with a compressive strength of 550, with 5% additives, quick-hardening and plasticized.
When erecting a building, it is very important that the work of the zero cycle be performed with high quality. Particular attention should be paid to the foundation, which is often made of concrete. Concrete is a mixture of cement, sand and gravel. The brand of cement for the foundation must have a sufficiently high compressive strength (400-500), and the higher this number, the less the amount of other materials can be. For example, for grade 400 cement, the remaining materials are taken in the proportion 1\3\3, and for grade 500 cement - 1\4\4, respectively.
Cement is a materialwhich absorbs water very well, which undoubtedly affects its properties - it eventually loses its declared strength. Therefore, when choosing brands of cement for construction work, you need to look at the date of manufacture and specify the storage conditions, because. cement grade 400 loses 10% of its strength in a month of storage, and in half a year it can lose 30% of this characteristic and become grade 280 cement.
