- Portland cement is the most popular type of cement in construction. It is made from portland cement clinker, gypsum and special additives. Clinker is obtained from limestone, clay and additives by firing.70-80% of finished Portland cement consists of calcium silicates, the rest falls on gypsum( adjusts the setting speed) and corrective additives. Portland cement is made of grades M400-M600, used to create reinforced concrete structures, mortars, asbestos-cement and other materials. Not suitable for the construction of structures subject to the influence of sea water;
- white Portland cement is made on the basis of gypsum, diatomite and clay-sandy rocks with a minimum content of coloring matter. The result is a composition with high strength, resistance to weathering and rapid setting. Available only two brands M400 and M500.Often the composition is used for external finishing works, as it has an aesthetic appearance and is not subject to the formation of cracks. Used for the manufacture of decorative elements( statues, columns), in the organization of self-leveling floors, in road construction, in the finishing of facade works. On the basis of white Portland cement, is made of colored formulations ;
- sulphate-resistant portland cement is produced on the basis of portland cement clinker and gypsum. The composition has a lower content of calcium aluminates, which ensures resistance to sulfates. Cement can be without additives or have additives in the form of granulated slag. Mark M400 and M500.Used in the creation and construction of structures that will be operated under the influence of saline water. Such cement is used in the manufacture of piles, bridge supports, in the arrangement of external elements of hydraulic structures;
- pozzolanic portland cement is obtained from portland cement clinker, gypsum and additives of sedimentary origin, some of which are 20-30%.The composition is resistant to fresh and sulphate-containing waters, water-tight. Among the minuses low frost resistance and low speed of solidification. Used in pouring foundations and laying basements of industrial and civil buildings, in the construction of subways, mines, canals, sluices, water pipelines;
- slag cements is a group of cements that includes slag Portland cement( SHPC) and lime-slag cement( CIP) .The first is obtained on the basis of Portland cement clinker, gypsum and blast furnace slag, part of which is 21-60%.The composition has a slow increase in strength, increased resistance to aggressive media, but is not resistant to temperature extremes. Used in hydraulic engineering construction. IHTS is obtained from a mixture of slag with lime( its part is about 30%), small additions of gypsum and Portland cement are allowed. The composition slowly hardens, the most resistant in fresh and sulphate waters, can be used for the manufacture of low-quality concrete, in mortars for plaster and masonry;
- quick-hardening Portland cement , as the name suggests, is distinguished by rapid strength in the first hours of hardening. Such properties are explained by the exact selection and dosage of special additives. As a result, the composition already after 3 days reaches the tensile strength, which accelerates the process of production of reinforced concrete structures;
- aluminous cement is also characterized by a high rate of hardening and curing. Made on the basis of bauxite or alumina with the addition of limestone. According to the alumina content, ordinary( up to 55% alumina), high-alumina( up to 65%) and high-purity high-alumina cements are isolated. The compositions have high resistance to fire, corrosion and a rapid increase in strength. Such cement has been used in emergency operations, high-speed construction and winter concreting;
- Expanding Cements is a group of cements that are characterized by an increase in volume during hardening. A similar effect is achieved by passing the reaction between the powder and water, resulting in the formation of calcium hydrosulfonic aluminum, a substance capable of binding a large amount of water. In the group of expanding cements, waterproof, straining, gypsum-alumina compounds and expanding Portland cement are distinguished. Consider all of them separately;
- Waterproof Expandable Cement is made from gypsum, high alumina cement and calcium hydroaluminate. The composition begins to set after 4 minutes, and after 10 minutes the curing process is over. It is used in underground and underwater construction, for repairing cracks and when creating monolithic structures from individual precast reinforced concrete elements;
- is used in Portland cement clinker, lime, alumina slag and gypsum stone. The structure relatively quickly hardens, is waterproof. Used in concreting pool bowls, the production of pressure pipes;
- gypsum alumina expanding cement is made from alumina blast furnace slags and gypsum. The composition is set within 4 hours, the expansion ends in 3 days. Cement is characterized by high frost resistance, durability and deformation resistance. With it, carry out waterproofing work;
- Expanding Portland Cement is a blend of Portland cement clinker, slag with a high content of alumina, gypsum and mineral additives. Depending on the composition, the expansion is from 0.3 to 2.5%.The expansion period is long, so the volume is filled evenly. Used in the construction of pavements and repair of hydraulic structures;
- grouting cement is used only when plugging oil and gas wells in order to isolate them from groundwater. Produced from clinker and gypsum;
- hydrophobic cement , in addition to gypsum and clinker, has oleic acid or other hydrophobic substances that allow you to create a waterproof film on the surface of the dried cement. Such cement is ideal for foundations;
- magnesia cement is characterized by the content of magnesium oxide, thereby increasing the elasticity of the composition, its resistance to aggressive substances. It is used at arrangement of floors;
- waterproof non-shrinkable cement is obtained on the basis of alumina cement, gypsum and hydrated lime. The structure quickly grabs and is not afraid of water;
- Acid-resistant quartz cement is a product of the mixing of quartz sand, sodium silicofluoride and liquid sodium glass. The composition is resistant to aggressive substances, but loses its strength in water;
- cement with surface-active additives has increased mobility and is used when working on complex from an architectural point of view of objects.
Contents
- №1.The main types of cement
- №2.Brand cement strength
- №3.Marking of additives in cement
- №4.Marking on the speed of gaining strength
- №5.What else could be in the marking of cement?
- №6.What to look for when choosing a cement?
- No. 7.The best cement manufacturers
Cement is used everywhere: from laying the foundation to the arrangement of brickwork and work on interior decoration. Such a wide and even immense scope of use of cement led to the emergence of materials with different composition and characteristics. You can not just buy the first available cement and start work - first it is important to make sure that the composition corresponds to the task. When going to the hardware store, it is important to know the theoretical foundations, so it's time to figure out how to choose cement, find out which brands and types of cement exist, where certain compositions are used, and what to take into account when choosing.
№1.The main types of cement
Cement called inorganic binders. The cement powder in contact with water forms a plastic mass, which quickly sets and forms a stone-like body. Often used for the manufacture of concrete and mortars. The composition of cement can vary greatly. Accordingly, the properties and scope of use will be different.
Today such basic types of cement are manufactured:
№2.Grade cement by strength
The most important characteristic of cement of any kind is its strength. This indicator is determined experimentally: a solution of cement and sand is prepared in a ratio of 1: 3, a sample is created in the form of a parallelepiped with sides of 40 * 40 * 160 mm. The resulting sample is subjected to a gradually increasing load. The experiment is slightly different only for some types of cement.
The data obtained during laboratory studies are reflected in the stamps. If the sample can withstand a load of 300 kg / cm2, then this is the brand M300, 500 kg / cm2 - M500, etc. Stamps are designated by the letter M and the subsequent index from 200 to 600 in increments of 50 or 100. The higher the grade, the more durable the composition before us, and the more durable and high-quality concrete it will turn out:
- for the foundation use cement of the brand M400-M500;
- for finishing works suitable cement M200-M300;
- cement brand M600 called the military, it has high strength, is much more expensive than the M500 and is used in the construction of bunkers and other military facilities.
Today, next to the classifications of cement according to grades of strength, a division into strength classes has appeared. If the mark is an average indicator, then the class is more accurate and provides a 95 percent guarantee of compliance with the specified data. Strength classes vary from 30 to 60:
- 52.5 - cement withstands a pressure of 52.5 MPa, corresponds to cement grade M600;
- 42.5 corresponds to cement M500;
- 32.5 corresponds to cement M400;
- 22.5 corresponds to cement M300.
№3.Marking of additives in cement
In addition to the mark of strength, on the packaging you can see the labeling of the percentage of various additives in cement. This indicator is denoted by the letter D, followed by a numerical indicator in percent. For example, cement D20 means that it contains 20% of additives. The higher the amount of additives, the lower the price of the composition.
№4.
Acquisition Rate Marking The time during which cement reaches its maximum strength is another important measure of composition. In some cases it is required that it hardened instantly, in others, on the contrary, excessive speed of gaining strength will only damage. According to this parameter, the cement is divided into the following types:
- CEM V - normal hardening cement with a compressive strength of 32.5 MPa;
- CEM IV is a normal hardening pozzolanic cement with a strength of 32.5 MPa. The composition may contain silica, pozzolana( 21-35%);
- CEM III - normal hardening slag Portland cement with a slag content of 36-65% and strength up to 32.5 MPa;
- CEM II differs in different curing rates, which depend on the amount and composition of additives;
- CEM I - cement with the highest setting speed. On the following day, the strength already reaches 50% of the design.
№5.What else could be in the marking of cement?
In the characteristics of the composition, following the designation of the cement grade and percentage of additives, there may be various abbreviations indicating the specific qualities of the cement:
- SS is a sulfate-resistant cement;
- GF - hydrophobic cement;
- B - quick-setting cement;
- PC - Portland cement;
- BC - white cement;
- H - normalized cement, which is produced from clinker, having a normalized composition;
- PL - plasticized cement with high rates of frost resistance;
- VRTS - cement with a high setting speed and expansion during hardening.
№6.What to look for when choosing a cement?
The demand for cement is enormous, which has given rise to the emergence of many unscrupulous manufacturers, who often mix additives into cement that greatly reduce the quality of the finished composition. In order not to make a mistake when choosing cement and to buy a really high-quality product, you need to know something about how good cement looks and what properties it should have:
- cement is sold in bags and in loose form. It is better to take cement in bags, because it is protected from external influence, it retains its qualities longer, and you can always find out information on the composition, production date, characteristics of the cement and its manufacturer on the bag's packaging. Bags are usually made of two layers of paper, the inner one protects the cement from getting wet. By the way, the absence of any information on the packaging is also a sign that you may have low-quality material;
- if you buy cement in bulk, and it is packaged in bags, then it is better to check carefully the shelf life of on each, as in the total mass you can sell the stale goods. Cement activity after 6 months from the date of production decreases several times;
- can also be used to test the freshness of cement by testing. It is enough to hit the bag - the sensations should not resemble a blow to the stone. The cement in the corners of the bag is the first to harden, so they also do not interfere with checking. Naturally, if the production date is not on the package at all, then it is better not to take such a product;
- cement must be stored in a dry and well ventilated area, otherwise it will quickly harden;
- The color of high-quality cement is gray, more precisely from light gray to dark gray and even greenish. Dark and swamp shades are not allowed. A good cement should crumble in the hand, and when squeezed, do not wrinkle into a ball;
- fineness affects the hardening process. The smaller the fraction of particles, the faster the composition will harden and the higher its price. Too small fraction increases water consumption, so ideally it is better to take cement, where fractions from 40 to 80 microns meet;
- does not prevent from assessing the composition and characteristics of cement. This is easy to do, but in advance it is necessary to prepare sodium bicarbonate water( suitable for Borjomi) or sodium bicarbonate. Gas must be released from the water. Further, we use it for kneading cement paste and forming a cake with a diameter of 15 cm from it. In the center it should be thicker( 5 cm), to the edges - already( 1 cm).High-quality cement should start setting no later than in 10 minutes, and the thickened part will noticeably heat up. If the seizure does not occur even within 30 minutes, then the composition of low quality is in front of you.
Types of counterfeit bags using designations similar to the extent of confusion with the trademarks of JSC "Eurocement Group"
№7.The best cement manufacturers
Cement producers in the world and Russia a lot. Before buying, it is better to read reviews about the products of a specific company, and we will focus on at the largest enterprises, , whose cement is guaranteed to meet all standards:
- Lafarge is a French company that is the largest cement manufacturer in the world. In Russia, there are several factories of the company; product quality is at its best;
- Cemex is another major player in the global cement market. The first factories appeared in Mexico, and today the company's enterprises operate on all continents. Products are widely represented in Russia;
- HeidelbergCement is a German company whose products since 2006 have been widely represented in the domestic market. The company operates several cement plants in Russia;
- Eurocement Group is the largest domestic cement manufacturer. He began operations in 2002, and today the company includes 16 factories throughout Russia. In terms of price and quality, this is one of the best deals on the market;
- Novoroscement OJSC is the second largest domestic cement manufacturer in terms of production. Products are widely represented in different regions of the country;
- Sibirsky Cement JSC is a large enterprise providing a full production cycle for cement production. It is among the five largest domestic cement producers.
Finally, let us once again emphasize the need for packaging information on the brand of cement, its properties, production date and contact information of the manufacturer.
