What is cement and how to put stress in a word?

Today it is difficult to imagine a construction area in which cement is not needed. It is used absolutely at all stages of erection and interior decoration of any structure. Despite the development of technology, no material has been found so far that could show itself better than cement. In this article we will learn more about what cement is. After all, many know how it looks and where it is applied, but do not represent what is hidden behind this gray powder, which hardens when drying out. Also, we will deal with the question of how to correctly place the stress in the word cement.

History

Before we understand what cement is, let's look into history. This material is known to mankind since ancient times, but before its opening, people also built. For bonding stone blocks, they used lime, gypsum, clay and even egg whites. All of the listed materials slowly hardened and were not sufficiently reliable. Then the builders began to mix the components: clay, crushed stone and volcanic ash were added to the lime. In combination with water, this mixture gave the desired effect. It was used in ancient Rome.

In the Middle Ages, builders also used lime in a mixture with clay. But the mixture was pre-burned. This was the first cement. The word, translated from Latin, means "broken stone". In fact, it is, because the frozen mixture is really hard as a stone. The correct stress in the word cement is put on the second letter "e", and nothing else. Experiments on this material lasted quite a long time. As a result, in the 19th century, an ideal proportion of components was found, which made it possible to achieve maximum reliability. Also, the optimum calcination temperature of limestone and clay was established, in which the lime-oxide compound is the most durable. It was 1450 degrees. Since then, cement has become very tightly integrated into the construction industry.

What is cement: composition

Modern cement is a clinker powder into which fillers and modifying additives are introduced. In dry form it is a loose, homogeneous mass of gray color. When water is added, an astringent paste-like composition is obtained which is well applied to rough surfaces. After solidification of the mixture, a strong bond is obtained, which in density can be compared with a stone. That's why artificial stones are made from cement.

Now let's look at the cement composition in more detail . When clay with limestone is heated to a temperature of about 1450 degrees, their structure changes. As a result, clinker granules are formed. They add gypsum and grind the mixture to a loose state. From the point of view of chemistry, the composition of the finished cement is as follows: 67% CaO (calcium oxide); 22% SiO ₂ (silica); 5% Al ₂ O ₃ (alumina); 3% Fe ₂ O ₃ (iron oxide); And 3% of concomitant substances. The production of cement is a very complex and time-consuming process that requires the availability of special equipment and the observance of specific technological conditions.

Make

We have already learned what cement is and how to put stress in the word cement, now we will get acquainted with the main characteristics of this miraculous material. The main characteristic of this product is its brand. It is indicated by the letter "M", and the corresponding numerical value. The figure shows the maximum load (in kilograms) that can sustain 1 cm ^{2 of} cement. In simple terms, it means the weight that cement can withstand without breaking down. For example, if this weight is 400 kilograms, the material gets the M400 grade. Let's analyze the main brands of cement.

M400 . As you have already understood, the strength of such cement is 400 kg / cm ² . This is the most common and universal brand. It is used in all kinds of construction and finishing works. This can be: the erection of buildings, monolithic construction, the production of concrete slabs and blocks, as well as the manufacture of staircases, reinforced concrete rings, and other products.

M500 . Such cement has a strength of 500 kg / cm ² . It is characterized by fast hardening and high strength. This brand is used in the monolithic construction of high-rise structures, for the manufacture of load-bearing elements and other cases where higher strength is required.

The strength of cement for compression is also called activity. Based on its measurements, the material is assigned the appropriate mark. The activity of cement depends on: the strength of clinker granules, the degree of grinding, and the presence of additives.

Types and additives

What is cement and what brands does it have, we already know, but how else is it classified? In addition to grades, cements are also divided into species, each of which is distinguished by a special combination of individual components (additives). For example: fast-hardening, sulfate-resistant, plugging, and so on. Each of the species is designed for certain jobs. For example, for the construction of a pool, cement, on which brick is placed, will not work.

Composition of additives is indicated on the package together with the brand. It is indicated by the letter "D", followed by the percentage of additives. For example, if the package says "D10" means, in this type of cement contains 10% of additives. Next come the symbols denoting the properties of these additives. In the end, the cement marking looks like this: "M400D10PTs". In this case, "PC" means ordinary Portland cement. Consider what other characteristics determine the quality of cement.

Density

The lowest density is observed in freshly prepared cement. Its individual particles repel each other under the action of electrostatic forces. In the process of transportation and storage, these forces are weakened, the material is caked and compacted. The density is also affected by the degree of grinding of the clinker. In the calculations, the average density of the material is set at 1300 kg / m ³ . However, in practice, this indicator depends on the conditions of storage of cement.

Specific and volumetric weight

The specific weight (in construction practice) is, in fact, the same density. This concept is used to make the right proportion of cement mortar. Depending on the state of the mixture, the specific gravity may differ. The fresh cement powder has a density of the order of 1000 kg / m ³ , and the density of the caked powder can reach 1500 kg / m ³ .

The volume weight is another identity concept of density. It is used to calculate how much cement is obtained from one kilogram. For example, in a bag weighing 50 kg, contains 0.04 cubic meters of material, if its density is 1300 kg / m ³ .

Shelf life

Despite the fact that cement is an inorganic material, its shelf life has a clear framework. Under normal conditions, in unsealed packing, cement is stored for only 2 months. If you put it in a sealed package, then you can extend this figure to a year. Of course, the old cement can be used, but its strength characteristics will not be the same.

In this case, the higher the brand of cement, the faster it loses its properties. For example, the material of the brand M500, after monthly storage in conditions of high humidity, will have the properties of the brand M400, and so on.

Bags with cement are recommended to be stored in dense cellophane packages, at a height of not less than 0.3 meters from the floor. In special bags, the material is stored much longer than in loose form.

Freezing time

The properly prepared solution sets and hardens for several hours. In the summer, the full hardening of cement takes only 2-3 hours, and in winter it will take much more time. At zero temperature, the solidification of the solution can take up to 20 hours. To accelerate or slow down the process of solidification, additives are introduced into the solution.

Fineness of grinding

The higher the degree of particle size reduction, the faster the solution will harden, and the more reliable it will serve in the future. The fineness of grinding depends on the quality and characteristics of the equipment used in cement plants. The optimal particle size is 40-80 μm.

Strength class

In regulatory documents, the term "brand of cement" has been transformed into a "strength class". Tests of the material for compliance with its strength of a class are conducted in factory laboratories. At the same time, modern equipment and progressive methods of analysis are used.

In the laboratory, the fineness of grinding, the density of the aqueous solution and the timing of the setting of the cement are measured. In the solidified samples, also determine the bend in the bending and compressive strength.

Certification

Certification of cement was earlier carried out in accordance with GOST 10178085, 30515 97. However, recently the majority of large enterprises have already passed to GOST 31108-2003, which was adopted in 2004. The document specifies more stringent requirements to the quality of cement and the criteria for its testing. These standards fully comply with European quality standards.

Cement and concrete

Consider another problem that arises as often as an incorrect accent in the word cement. How to properly name the material, we have already figured out, and how does it differ from concrete? Many people think that these are identical concepts. In reality, of course, no. Concrete is called frozen cement mortar. It includes cement, fillers and water. Sand is the most commonly used filler. Sometimes also used: gravel, screenings, slag, expanded clay and the like. Until the point of solidification, the cement slurry is a mobile mixture. In order not to cause confusion and temptation to deceive the sellers of construction shops, remember what accent in the word cement is correct and how this material differs from concrete.

Conclusion

So, we have figured out what cement is. The importance of this material in modern construction is difficult to overestimate. Nevertheless, many people who are far from this industry do not even know what this useful material consists of and blush when the children ask them about it. Now we know what cement is and how to put stress in the word cement.