Cement grades: old and new GOST, transcript

For more than fifteen years, a standard has been in force that more fully describes the composition and characteristics of cement. According to the new standard, cement grades are designated by Roman numerals, and the number and type of additives, compressive strength class and hardening speed are also indicated. In general, the new label contains complete information for an informed choice of binder.

Grades of cement according to GOST 31108

The new standard was developed in 2003 to harmonize the current labeling with that adopted in the EU countries. At the moment, the latest version from 2016 is operational. As usual, the action of the previous standard is not canceled – both work in parallel.

Name and material composition

In a new way, cement grades are determined by their material composition. The marking contains three Cyrillic letters – CEM and Latin numbers behind them. In Latin numerals, the composition is encrypted:

• The abbreviation CEM I stands for Portland cement. It cannot contain additives. It consists only of ground baked clinker and technological additives in an amount of not more than 5% by weight.
• CEM II – Portland cement with mineral additives. The mass fraction of additives is from 6% to 35%. According to the number of additives is divided into two groups:
  • group A with a content of 6% to 20%;
  • group B says that additives are introduced from 21% to 35%.
    

• If you see CEM III – this is Portland slag cement. This grade contains from 36% to 65% of slag ground into dust. By the number of additives, there are three subtypes:
  • A — from 6% to 20%;
  • C — from 21% to 35%;
  • C — from 36% to 65%.
• Pozzolanic cement is designated CEM IV. It is an additive of volcanic origin. It is usually produced in those places where this mineral is mined.
• Marking of composite cement CEM V. This brand of cement may contain several types of additives: slag, ash and limestone.

Cement from CEM II to CEM V can have subtypes depending on the additives. They are denoted by the Latin letters A, B and C. After the designation of the group, they put a slash, followed by a letter indicating the type of additive, then through a dash the letter that encodes the additive itself. For example, CEM N/A-I. If there are several additives, their designation is indicated through a dash, and the whole group is taken in brackets: for example: CEM IV / A (P-Z-Mk).

Additives in the composition

Additives and designation of concrete grades with them are in the table. As you can see, CEM I is made only from crushed clinker with a small amount (no more than 5%) of technological substances. The second group of Portland cement has the most modifications and varieties.

Portland slag cement and lower grades of cement also have additives, but there are much fewer variations. All additives and additives in the labeling are displayed in capital letters:

• Ш – granulated slags;
• Mk – microsilica;
• P – pozzolana;
• D — gliege;
• C — ash;
• C – burnt slate;
• And limestone.

Pure Portland cement – CEM I, always comes without additional components, since, by definition, it cannot have them. Consider a few examples of marking other brands of cement. If we see CEM II / V-Sh. This means that we have Portland cement of the second type, that is, with additives. This is indicated by the letters that come after the slash. The letter “B” indicates that the amount of additives is more than 21%, and the letter “Sh” indicates that slag was used. The inscription CEM III / C denotes Portland slag cement with the addition of burnt shale. In general, the way of decoding the marking is probably understandable.

Compressive strength class

In the new standard, the composition should indicate the compressive strength that this brand of cement is able to give. According to GOST, there are only three values:

• 22,5 N;
• 32,5 N;
• 42,5 N;
• 52,5 N.

Strength is checked for 2, 7 and 28 days. Almost all cements are checked 7 days after mixing, and CEM III (Portland slag cement) is checked after 2 days. According to the hardening rate, the brand of cement can be:

• normally hardening – denoted by the letter H after the compressive strength class;
• slow-hardening – M;
• fast hardening B.

All this information is displayed in the label. For example: CEM III / V-Sh 32,5M. Denotes Portland slag cement with additives of type B – granulated slag, compressive strength 32,5 M, slow-hardening.

What does the brand of cement according to the old GOST mean

There are more types of cement in the old standard. All of them are shown in the table. The two most popular brands are ShPC and PC. Accordingly, slag Portland cement and ordinary. Marking is simple – after the abbreviation is a three-digit number. This is a brand that indicates the compressive strength in kilograms per square centimeter (kg / cm²). For example, PC 400, ShPC 300, PC 500. PC 550, 600 and 700 are much less common and used. They are used for special construction conditions.

In the marking of Portland cement, the brand is followed by the letter “D”, which stands for “additives” and then a number from 0 to 20. The figure indicates the percentage of additives, respectively, D0 is no additives, D20 is 20%. As an additive, granulated blast-furnace slag is usually used. For example, PC 400 D15. He says that there are 15% slag additives in cement.

By definition, there is more slag in the ShPTs. According to GOST, it contains from 21% to 85% of this substance and therefore the SPC cannot withstand more than 300 kg / cm². This is the cheapest brand of existing cement, which is used for the manufacture of low-grade concrete – M100, 150 or 200. And then, if you look at the recommendations, M200 cement is recommended for preparing a mortar of the M400 brand, and acceptable grades are M300 and M500. Nevertheless, Portland slag cement is used in everyday life – for screeding, if its high strength is not required, for pouring concrete preparation when laying the floor on the ground.

In the private sector, the most common brand of cement is PC 400. It is optimal in strength. From this cement, you can make a solution from M200 to M350. It is these brands that are most widely used. Higher ones are used for multi-storey and special construction.

Compliance with the old and new cement markings

There can be no exact match, since the new standard gives a more complete breakdown of the composition. It can only be compared in terms of strength and the total number of additives.

If we compare by the number of additives, we see the following picture.

• Those grades of PCs that have a zero amount of additives (D0) or no more than 5% of them correspond to a new brand of cement – CEM I. That is, PC400 D0 to D5 and PC500 D0-D5 will both be labeled CEM I. But it will only continue to stand a different number that indicates the compressive strength class.
• All Portland cement produced according to the old standard with more than 5% additives will be classified as type 400 according to the new marking. That is, PC 10 D500 or PC 20 D20 is equivalent to CEM II. Since, according to the old GOST, the amount of additives is not more than XNUMX%, then all brands will belong to subtype A.
• Slag Portland Cement ShPTs is re-designated as CEM III.

We figured out the correspondence between the types of concrete according to the old and new markings. In any case, with the most popular brands. And the correspondences of old brands and new ones in terms of strength are as follows:

• M300 corresponds to 22,5 N;
• M400 – 32,5 N;
• M500 – 42,5 N;
• M600 — 52,5 N.

Now you can give an exact correspondence between old and new brands of cement using examples:

• PC400 D5 — CEM I 32,5
• PC400 D15 — CEM II/A-Š 32.5
• PC500 D0 — CEM I 42,5
• PC500 D20 — CEM I/A-Š 42.5
• ŠPC 300 — CEM III 22,5

Not so difficult. The new brands indicate a more accurate composition and the amount of additives that affect performance. The curing speed may also be indicated. In general, if you know the decoding, it is more convenient to select the right brand.