What is cement made of?

The word cement is familiar to everyone. Even those who have never been involved in construction know that cement is needed for mortar in brickwork, that it is the main component of reinforced concrete products. However, few people know what cement is made of.

Cement is ubiquitous. It is used not only in the construction of all kinds of buildings. You cannot do without it when carrying out restoration and repair work. There is no substitute for cement yet. This justifies its relevance.

The building material is based on inorganic binders. Cement is essential in the production of panel boards. Plaster and masonry mortars are made from it. In the composition of concretes, one of the main places is assigned to cement.

Basically, cement is a fine powder. The main feature of the powder mass is that when interacting with water, it gradually begins to harden. The process of interaction of two components (cement and water) ends with the formation of a solid mass, similar in hardness to natural stone.

A strong structure is formed with excess moisture. The reaction takes place both in the open air and in water. After hardening, the cement retains its strength for a long time.

The physical characteristics of cement depend on several factors.

The most significant are:

• types of additives;
• the degree of grinding;
• composition.

The fineness of the grind of the cement affects the strength and the time required for hardening. Fine grinding provides greater strength and faster curing.

To determine the fineness of grinding, a special sieve with the smallest cells up to 80 microns is used. When preparing a mortar from too finely ground cement, more water is required. This disadvantage is eliminated by mixing particles of different sizes: large and small. Dust grains of 80 microns are considered large, and small - 40 microns.

Cement has the following properties:

• strength;
• corrosion resistance;
• frost resistance;
• water demand;
• setting time (hardening).

This indicator depends on the brand. Determine the strength properties by performing compression tests. Experienced blank is kept under load during the lunar month - 28 days. After testing the sample, the cement is assigned an appropriate designation. Strength is measured in MPa.

Reinforced concrete products under the influence of water and other liquid media begin to corrode. The negative impact is eliminated in several ways. For example, you can change the composition, add hydroactive materials to the powder mixture. The presence of specific substances prevents the occurrence of harmful chemical reactions.

Corrosion resistance increases with the use of polymer additives. As a result, microporosity is reduced, and the durability of products is increased.

Pozzolanic cement has the greatest corrosion protection.Therefore, it is used for the construction of structures operated in high humidity conditions.

One of the main indicators of the quality of cements is the ability to repeatedly freeze and thaw a concrete product.

The cement stone contains micropores that contain water. When freezing, water can increase in volume by 8%.

In construction, cement without additives is not used. Components are added to different grades that give the cement the ability to resist temperature changes.

In the process of making concrete, air-entraining additives are included. The smallest air bubbles are distributed evenly inside the concrete body, which solves the problem associated with water freezing and its expansion.

This is the amount of water, expressed as a percentage, that is required to obtain the optimum consistency of grout.

In a solution of the nominal density of water, as much as the cement can hold in itself. For example, in Portland cement, this value is in the range of 22-28 percent.

Better concrete is obtained from cement with a low water demand.than the one with a high rate. In the first case, the products are resistant to temperature extremes. In the second, concrete has increased porosity and is not at all suitable for construction. Such cement is used for the production of reinforced concrete fences or drainage structures.

This is the time period corresponding to the change in the physical properties of the cement slurry from the state of plasticity to the formation of a stone.

A solution that does not solidify too quickly, but not very slowly, is considered ideal. The setting time is regulated by the presence of a certain amount of gypsum in the material. The larger volume of gypsum provides faster setting. While a decrease in its content contributes to a longer solidification of the solution.

According to the standard, under normal conditions, Portland cement begins to set after three quarters of an hour. The hardening process should be completed in 10 hours.

Cement is made at specialized enterprises. Cement factories are built in close proximity to the source materials extraction sites.

Raw materials for its production are obtained from natural rocks:

• fossils of the carbonate type;
• clay materials.

Carbonates have an amorphous or crystalline structure, which determines the effectiveness of the interaction of the material with other components during the firing process.

Carbonate rocks include:

• chalk;
• marl (marly limestone);
• limestones, including shell rock;
• dolomite-type rocks.

Clay materials are sedimentary rocks. Possessing a mineral base, they are endowed with plasticity, and with excessive moisture they can increase in volume. Clay materials are used in the dry production method.

Clay rocks include:

• clay;
• loam;
• clay-based shale;
• loess.

In addition to raw materials, corrective additives are used in the production of cement.

They are obtained from fossils, which include:

• apatite;
• alumina;
• fluorspar;
• silica.

The additives introduced according to a certain technology improve the quality of the described material.

The composition of the cement depends on the required characteristics, which are determined by the grade assigned to the material.

The most popular Portland cement consists of:

• 60% lime;
• 25% silicon dioxide;
• 10% iron and gypsum oxides;
• 5% aluminum (alumina).

In different brands, the percentage of raw materials is different, as is the composition itself. For example, slag Portland cement contains slag. Quantitative proportions can also vary with the peculiarities of the chosen technology for the manufacture of building material.

For any brand of cement and for any method of its production, limestone and clay remain unchanged components. Moreover, limestone is always three times more than clay. This ratio contributes to the production of high-quality clinker, from which cement is made.

In industry, the following components are used for the production of cement:

• clinker;
• gypsum;
• special additives.

Clinker is the most important component of cement. It determines the strength properties of the final material. The clinker enters the production process in the form of granules. The diameter of the granules varies between 10-60 mm. The heat treatment of the component is carried out at a temperature of about one and a half thousand degrees.

The amount of gypsum is determined by the set hardening period. In the basic version, gypsum in the form of a powder is included in the cement in a volume of 6%.

First, limestone and clay are mixed in a 3/1 ratio. The mixture is then fired at a high temperature. As a result, the starting material for the production of cement is formed. It is called clinker. Granular clinker is sent to ball mills for grinding.

There are three ways to make cement.

Depending on the manufacturing technology, it can be:

• wet;
• dry;
• combined.

The differences lie in the methods of preparing the feedstock.

In accordance with wet technology, chalk is used instead of lime. It is mixed with clay and other ingredients with the addition of water. The result is a charge with a moisture content of 30 to 50 percent. The batch is converted into clinker balls during firing.

Dry technology shortens the manufacturing process, since the two operations (drying and grinding) are combined into one. The resulting charge becomes powdery.

At different enterprises, the combined method is used in different ways. In some cases, a dry batch is first obtained, and then moistened. In others, they use not a wet, but a semi-dry method with a low humidity not exceeding 18%. Firing is performed in both cases.

There are many different variations of cement. The most famous is Portland cement.

Other material options are quite popular:

• slag;
• pozzolanic;
• aluminous;
• expanding.

Portland cement is produced in several grades: 400, 500, 550, 600. Mortars are made from M400 cement.

White Portland cement is characterized by a fine grinding. The composition includes low-iron clinker, gypsum and dolomite additives. Differs in high strength and resistance to atmospheric precipitation. White Portland cement products have an aesthetic appearance. It is used in the manufacture of self-leveling floors, decorative elements, as well as in the construction of roads. It is the basis for colored cements.

Portland sulfate-resistant cement is used in the manufacture of piles, supports for bridges, hydraulic structures, wherever there is repeated moistening and drying of structures, where structures are subjected to freezing and thawing.

The main purpose of slag cements is to create concrete products for structures located under the ground and under water.

Pozzolanic cements are needed in the construction of dams, river hydraulic structures, various underground communications, as they are endowed with resistance to the effects of fresh water.

Alumina ones are not afraid of sea waters, therefore they are part of reinforced concrete products in contact with saline waters. Can be used for urgent plugging of wells, including oil wells; when concreting in winter; for fixing cracks in rocks.

It is possible to prepare cement at home if it is possible to reach a high temperature for firing. Perhaps the most that can be obtained by an artisanal method is cement grade M 200. You will need chalk and kaolin in a ratio of 3 to 1. About 5% of gypsum powder should be added to the fired and crushed substance - and the cement is ready.

Even when everything you need is found, it is hardly worthwhile to engage in the production of cement on your own. Before starting work, answer yourself the question about the appropriateness of the process. It is unlikely that your work and the costs incurred will pay off. Most likely, it is more profitable to simply buy a bag of ready-made cement.

When choosing cement for certain needs, remember that there are many varieties. The right choice at the initial stage of work will guarantee the durability of the building. You should not always give a choice to higher and more expensive brands. The strength of the product will not increase from this, and the costs will not be justified.

See the video below for the cement production process.