Portland cement: technical characteristics and application
Currently, Portland cement is rightfully recognized as the most common type of cementitious cementitious binder. It is made from carbonate rocks. Often it is used in the manufacture of concrete. Today we will look in detail what technical characteristics are inherent in this material, as well as how it can be applied.
What it is?
Before considering the characteristics and features of such a material as Portland cement, it is worth figuring out what it is.
Portland cement is a type of cement., which is a special hydraulic and binder. To a greater extent it consists of silicate calcium. This component takes about 70-80% percent of such a cement composition.
This type of cement mortar is popular all over the world. He got his name from the island, which is located on the coast of Great Britain, since rocks of Portland have exactly the same color.
Advantages and disadvantages
Portland cement has strengths and weaknesses.
For a start, it is worth considering what advantages this material has:
- It should be noted the excellent strength characteristics of Portland cement. That is why it is most often used in the manufacture of monolithic reinforced concrete structures and other similar objects.
- Portland cement is frost resistant. He is not afraid of low temperatures. In such conditions, the material is not subjected to deformation and is not covered with cracks.
- This material is waterproof. It does not suffer from contact with moisture and moisture.
- Portland cement can be used even when building a foundation in difficult soil conditions. For such conditions a sulfate-resistant solution is used.
- There are several varieties of Portland cement - each buyer can choose the best option for themselves. You can purchase quick-hardening or medium-hardening composition.
- If you have purchased really high-quality Portland cement, then you should not worry about its subsequent shrinkage and deformation. After mounting it does not form cracks and other similar damage.
Portland cement has few disadvantages. As a rule, they are associated with low-quality solutions, which are now in store a lot.
Among them are the following:
- During its full hardening, poor quality material is subject to deformation. This must be considered when working. All shrink seams should also be considered.
- This solution can not be called environmentally friendly, as in its composition, in addition to natural, there are many chemical components.
- Care should be taken to work with Portland Cement, since contact with it can cause chemical burns and irritation. According to experts, in conditions of long contact with this material it is possible to earn lung cancer.
Unfortunately, today, many buyers are faced with poor-quality solutions of Portland cement. This product must comply with GOST 10178-75. Otherwise, the mixture may not be as strong and reliable.
In the composition of modern Portland cement there is lime, gypsum and special clinker clay, which has undergone special processing.
Also this type of cement is complemented by corrective components that improve the technical characteristics of the solution:
- provide him with the proper density;
- determine one or another speed of solidification;
- make the material resistant to external and man-made factors.
The production of this type of cement is based on calcium silicates. To make the setting setting, gypsum is used. Portland cement is produced by burning (by a special formula) a specific mixture with a large amount of calcium.
In the production of Portland cement can not do without carbonate rocks. These include:
- a piece of chalk;
Also often in the manufacturing process is often used such a component as marl.It is a combination of clay and carbonate rocks.
If we consider the process of manufacturing Portland cement in detail, we can conclude that it consists in grinding the necessary raw materials. After that, it is properly mixed in certain proportions and fired in kilns. At the same time, the temperature mode is kept at 1300-1400 degrees. In such conditions, firing and melting of raw materials is provided. At this stage, the product is obtained, called clinker.
To obtain finished products, the cement composition is crushed again.and then mixed with plaster. The resulting product must pass all checks to confirm its quality. Proven and reliable composition always has the appropriate certificates of the desired sample.
In order to result in high-quality Portland cement, use several ways to create it:
The most commonly used dry and wet production methods.
This production option involves the creation of Portland cement with the addition of a special carbonate component (chalk) and a silicone element - clay.
Iron supplements are often used:
- pyrite cinder;
- sludge converter.
Care must be taken to ensure that the moisture level of the silicone component does not exceed 29%, and clay - 20%.
Wet this method of manufacturing durable cement is called, since the grinding of all components occurs in the water. At the same time, a charge is formed at the outlet, which is a water-based suspension. As a rule, its humidity varies in indicators from 30% to 50%.
After this, the sludge is directly fired in the kiln. At this stage carbon dioxide is released from it. The clinker balls that have appeared are carefully ground until they turn into a powder, which can already be called cement.
Components such as lime and clay are used for the semi-dry manufacturing process. According to the standard scheme, these components are crushed and dried. Then they are mixed, crushed again and adjusted with the help of various additives.
At the end of all stages of production, clay and lime are granulated and calcined. It can be said that the semi-dry method of production hardly differs from the dry one. One of the differences between these methods is the size of the crushed raw materials.
The dry method of manufacturing Portland cement is rightly recognized as the most economical. Its distinctive feature lies in the fact that all stages of production apply raw materials that are exclusively in a dry state.
One or another cement manufacturing technology directly depends on the physical and chemical properties of the raw materials. The most popular is the production of material in particular rotating furnaces. In this case, components such as clay and lime should be used.
When the clay and lime are completely crushed in a special crushing machine, they are dried to the desired state. The level of humidity should not exceed 1%. As for the grinding and drying, they are carried out in a special separator machine. Next, the resulting mixture is transferred to cyclone heat exchangers and remains there for a very short time - no more than 30 seconds.
This is followed by a stage in which direct firing of the prepared raw material is carried out. After that, it is transferred to the refrigerator. Next, the clinker “moves” to the warehouse, under the conditions of which it will be carefully ground and packed.In this case, the preliminary preparation of the gypsum component and all additional elements, as well as the future storage and transportation of clinker, will take place in the same way as with the wet method of manufacture.
Otherwise, this production technology is called combined. With it, the sludge will be obtained by the wet method, and after that the resulting mixture is freed from excess moisture using special filters. This process should occur until the moisture level is 16-18%. After that, the mixture is transferred to roasting.
There is another option for mixed-mix cement production. In this case, provides for the dry preparation of raw materials, which is then diluted with water (10-14%) and subjected to subsequent granulation. It is necessary that the size of the granules was not more than 15 cm. Only after this, they start firing the raw material.
What is different from simple cement?
Many consumers are wondering what is the difference between Portland cement and ordinary cement.
It should immediately indicate that clinker cement is one of the subtypes of the classic solution. As a rule, it is used in the production of concrete, and that, in turn, is indispensable in the construction of monolithic and reinforced concrete structures.
First of all, the differences between the two solutions are in their appearance, performance and properties. So, Portland cement is more resistant to the effects of low temperatures, as it contains special additives. At simple cement, these characteristics are much weaker.
Portland cement has a lighter color than that of ordinary cement. Due to this characteristic, the dye is significantly saved during construction and finishing works.
Portland cement is more popular and in demand than regular cement, despite its chemical composition. It is his experts recommend to use in construction work, especially if they are large-scale.
Types and characteristics
There are several types of Portland cement.
- Quick-drying. This composition is supplemented with minerals and slag components, therefore, it completely hardens during the first three days. Due to this feature, the exposure time of the monolith in the formwork is significantly reduced.It is worth noting that in the process of drying quick-drying portland cement, it increases its strength characteristics. Marking of quick-drying mixtures - M400, M500.
- Normally hardening. In the composition of such Portland cement there are no additives that affect the curing time of the solution. In addition, he does not need fine grinding. Such a composition should have characteristics consistent with GOST 31108-2003.
- Plasticized. The composition of this Portland cement has special additional components, called plasticizers. They provide cement with high mobility, increased strength properties, resistance to different temperature conditions and minimal moisture absorption.
- Hydrophobic. Such Portland cement is obtained by introducing components such as acidol, milonap and other hydrophobic additives. The main feature of hydrophobic Portland cement is a slight increase in setting time, as well as the ability not to absorb moisture in its structure.
Water from such solutions evaporates very slowly, so they are most often used in arid areas, where the stone should harden gradually so as not to lose strength.
- Sulfate resistant. Sulfate-resistant type of portland cement is used to obtain high-quality concrete, not afraid of low temperatures and frost. This material can be used in the construction of buildings and structures that are experiencing the effects of sulphate water. Such cement prevents the formation of corrosion on structures. Grades of sulfate-resistant Portland cement - 300, 400, 500.
- Acidproof. The content of this Portland cement is quartz sand and sodium silicofluoride. These components are not afraid of contact with aggressive chemicals.
- Aluminous. Aluminous clinker cement is characterized by a composition in which alumina is present in high concentration. Thanks to this component, this composition has a minimum time setting and drying.
- Pozzolanic Pozzolanic cement is rich in mineral additives (of volcanic and sedimentary origin). These components occupy about 40% of the total composition. Mineral supplements in pozzolanic portland cement provide higher water resistance. However, they do not contribute to the formation of efflorescence on the surface of the already dried solution.
- White. Such solutions are made from pure lime and white clay. In order to achieve a greater whitening effect, clinker goes through an additional process of cooling with water. White Portland cement is most often used in finishing and architectural work, as well as color. It can also be the basis for a colored solution of Portland cement. Marking this composition - M400, M500.
- Slac Portland cement. This kind of portland cement is used for the manufacture of heat-resistant concrete. Such material has a low coefficient of frost resistance, so it is so often used in the construction of not only ground, but also underground and underwater structures.
A characteristic feature of slag Portland cement is that it contains a high content of the smallest metal particles due to the addition of blast furnace slags.
- Cementing. Special cementing Portland cement is most often used in the cementing of gas and oil wells. The composition of this cement is mineralogical. It is diluted with quartz sand slag or limestone.
There are several varieties of this cement:
- low hygroscopic;
- Slag alkaline. Such Portland cement has additives from lye, as well as ground slag. There are compounds in which there are clay components. Slag alkaline cement is grasped in the same way as regular Portland cement with a sandy base, however, it is notable for its increased resistance to negative external factors and low temperatures. Also, this solution has a low moisture absorption.
As you can see, the technical and physical properties of different types of Portland cement are very different from each other. Thanks to such a wide choice, it is possible to choose a mortar for both construction and finishing works in any conditions.
All varieties of portland cement are distinguished by their markings:
- M700 is a very durable composition. That it is used in the manufacture of high-strength concrete for the construction of complex and large structures. Such a mixture is not cheap, so it is extremely rarely used for the construction of small structures.
- M600 is a composition of increased strength., which is most often used in the production of critical reinforced concrete elements and complex structures.
- M500 - also has high durability. Due to this quality, it can be used in the reconstruction of various buildings that have suffered serious accidents and destruction. Also, the composition of the M500 is used for laying pavements.
- M400 - is the most affordable and common. It differs in quite good parameters of frost resistance and moisture resistance. It is possible to use M400 clinker for the construction of buildings for any purpose.
Scope of application
As mentioned above, portland cement is an improved type of cementitious mortar. The specific technical characteristics of this material directly depend on the type of filler. So, quick-drying Portland cement with markings 500 and 600 boasts rapid hardening, so it is mixed into concrete for the construction of massive and large-sized structures, and they can be ground and underground. In addition, the compositions are often referred to in cases where the fastest possible curing is required. Most often, this need arises when pouring the foundation.
Portland cement with marking 400 is rightfully recognized as more common. It is universal in its application. It is used to create powerful monolithic and reinforced concrete parts, which are subject to increased requirements for strength. This composition lags slightly behind Portland cement brand 500, but it is cheaper.
Sulfate-resistant cementitious compound is often used to prepare mixtures involved in the construction of various structures that are under water. This advanced portland cement is indispensable in such conditions, since underwater structures are especially susceptible to the harmful effects of sulphate water.
Cement with a plasticizer and a marking of 300-600 increases the plasticity properties of the solution, and also increases its strength characteristics. Using such Portland cement, you can save about 5-8% of the binder, especially if you compare it with a simple cement.
Special types of portland cement are not often used for small scale construction works. This is due to their high cost. And not every consumer is well acquainted with such compositions.Still, Portland cement, as a rule, is used in the construction of large and important objects.
When not to apply?
Portland cement provides ordinary concrete with special properties and strength properties, which makes it very popular in construction work (especially large-scale). However, such a solution cannot be used in flowing river beds, saline bodies of water, as well as in water, which has a high content of mineral substances.
Even a sulfate-resistant type of cement will not cope with its main functions in such conditions, as it is designed to operate in static and temperate waters.
Portland cement is more complex in its composition than the usual solution.
Working with such materials, you should listen to the advice and recommendations of specialists:
- To harden the solution as soon as possible, it is necessary to select the suitable mineralogical composition of the cement, as well as apply special additives. Often in such cases refer to electric heating or heat-wet processing.
- Apply nitrates of sodium, potassium and ammonium to slow down the hardening. Uh
- It is necessary to take into account the setting time of the cement paste. The beginning of this process takes place no sooner than in 30-40 minutes, and completion - no later than 8 hours.
- If portland cement is planned to be used for the construction of the foundation in complex soil conditions, then experts strongly recommend choosing a sulphate-resistant solution, which has a high content of mineral components.
- For the decoration of the floor is ideal color or white Portland cement. Using this solution, you can create beautiful mosaic, tile and breccia-like coatings.
- Portland cement is not uncommon. It can be bought at almost any hardware store. It must be properly prepared for work. To do this, you need to take 1.4-2.1 water for every 10 kg of cement. To calculate the exact amount of fluid required, you need to pay attention to the degree of density of the solution.
- Pay attention to the composition of Portland cement. If it contains various additives to improve moisture-resistant qualities, then the frost-resistant characteristics will decrease. If you select cement for a humid climate, then the usual solution will not work for you.It is better to buy slag Portland cement.
- Color and white clinker mixtures must be transported and stored in special containers.
- Today in the shops sold a lot of fake clinker. Experts strongly recommend that when buying to get acquainted with the certificates of quality of goods, otherwise the cement may be of poor quality.
The process of obtaining portland cement can be viewed below.