How and from what cement is made: cement composition, marking of mixtures and their scope of application

A key component of strong, long-lasting structures, cement is a material used extensively in construction. It is the binding agent in concrete that enables the construction of both modest sidewalks and enormous skyscrapers. We can better appreciate cement’s significance and the variety of uses it fulfills if we are aware of how it is made and the different compositions it comes in.

Cement is first made from a mixture of raw materials, including sand, clay, and limestone. Clinker is the product of heating these materials to extremely high temperatures in a kiln. The finished product, known as cement, is made by grinding the clinker into a fine powder and then mixing it with additives like gypsum. In order to guarantee the quality of the cement, this complex process needs to be done precisely.

There is no one-size-fits-all type of cement; instead, there are several types and mixtures that are ideal for distinct uses. These mixes are frequently identified by unique codes and numbers that represent their contents and intended applications. Certain cements, for example, are made to withstand harsh environmental conditions, while others are made to set quickly for last-minute repairs.

Builders and homeowners can choose the right materials for their projects by knowing the various types of cement and how to use them. To ensure longevity and performance, the right type of cement must be chosen whether building a new home, fixing a road, or creating decorative elements.

What is cement made of — the main raw material

Solid minerals are the raw materials used in cement production, and these are the locations of cement plants.

Clinker, the result of firing rocks together, is made from carbonate stones and clays.

The following types of amorphous or crystalline limestone belong to the first category of mineral formations, which is consumed in greater quantities:

• chalk – a soft white rock, consists of calcium carbonate with an admixture of magnesium, metal oxides and quartz grains;
• marl – a natural mixture of 50-75% calcite derivatives with 25-50% silicate clay formations, well suited for the production of cement clinker;
• shell rock is limestone from the shells of marine animals, its variety metamorphosed by pressure at high temperature is called marble;
• dolomite — in addition to calcium carbonate CaCO3, contains a magnesium component: MgCO3.

Clay rocks such as loess, clay shales, and loams are what contribute silicates to clinker. Alumina, iron, silicon, and waste from metallurgical plants are alloying additives used in the technology to give cement unique properties and lower production costs.

What is cement clinker

This product is the result of sintering two rocks, 25% clay and 75% limestone, at a temperature of 1450 °C. Clinker is discharged from the kiln as granules with an Ø of 10–60 mm.

Each manufacturer’s calcined crushed stone may have a different chemical makeup, but the following is an average breakdown expressed in percentages:

• CaO – 67;
• SiO2 – 22;
• Al2O3 – 5;
• Fe2O3 – 3.

Portland cement is made up of more ingredients than just kiln-crushed stone. The granules are ground into a fine powder by adding up to 6% calcium sulfate CaSO3, which is present in gypsum or gypsum rock, to the clinker in order to slow down the setting time of the finished product.

Ball mills are used to grind the ingredients, and pneumatic transport is used to pump the finished product into multi-ton silos.

State standards, GOST 30515-2013 for general technical conditions and GOSTs 10178-85 and 31108-2003 for Portland cements intended for construction, govern the production of cement. For particular types, separate standards have been created.

Main characteristics of the product

Indicators of cement density are as follows: compaction = 1400-1700 and bulk = 900-1100 kg/m³. Values of true specific gravity approach 3 t/m³. The quality of the binder powder is assessed using a number of technical factors, including:

1. Grinding fineness — determines the activity of the cement: the smaller the particles, the larger the surface they cover in one layer. Control measurements are performed by scattering on a sieve with a cell of 80 μm.
2. Water requirement — the amount of moisture required to hydrate the cement and impart plasticity to the dough. Excess water in the solution leads to the formation of pores and cracks, reducing strength.
3. Frost resistance is the ability of products based on cement powder to withstand repeated freezing and thawing without destruction. The required indicator is achieved by special additives when mixing the solution.
4. Setting time – depending on the consistency of the mixture is in the range of 0.7-10 hours. The indicator also depends on the amount of gypsum added to the clinker during grinding.
5. Strength is determined by the destruction of a sample made from cement from each batch of the released solution. The age of the cubes is set by the standard – 28 days.

For all volumes shipped by the cement plant, quality certificates are filled in, in which the listed characteristics are entered. Consumers independently carry out incoming inspection to confirm the integrity of the supplier.

What is a cement grade

Portland cement’s grade, which is determined by testing cubic samples with a 10-cm edge for compression, is a measure of its strength. What makes up the fill-in solution for the forms? One part powdered binder Three parts pure quartz sand.

The mass is combined, water is added, and it is then allowed to solidify for 28 days. At the same time, six to ten metal forms are poured.

Six samples are chosen at random from among them and crushed in a press. On the basis of four cubes that collapsed under the highest load, the arithmetic mean pressure is determined. The cement grade in accordance with GOST 10178-85 will be indicated by values expressed in kg/cm². In MPa, stress is displayed using the metric system of units in accordance with GOST 31108-2003. The cement strength class is in charge of distribution in this case.

It turns out that the strength characteristics are evaluated using both the old and new classifications at the same time. Grades M200, M300, M400, M500, and M600 in digital format. The hardness class values that correspond are B15, B22.5, B32.5, B42.5, and B52.5.

The main ingredients of cement, which is used in construction, are limestone, clay, silica sand, and shells. Clinker is created by heating these materials and then ground into a fine powder. Cement composition varies, and various mixes, or "markings," are made for particular applications, like general construction, high-strength projects, or needs requiring quick setting. Choosing the proper cement for any building project requires an understanding of these mixtures and their uses.

Cement marking

Only a small portion of the data encoded in the complete marking regarding the characteristics of the manufactured cement is represented by the designations given to the Portland cement strength indicators.

Under circumstances where standards bearing prior designations are used concurrently, starting in 2003. Numerous codes contain the same data.

Using the language of both standards, cement producers attempt to communicate information about the characteristics and quality of their products.

What does the marking of cement by the type of additives mean

To enable the use of cement in special-purpose concretes, additives are added to the binder mineral substance in addition to the primary components. Special property information is included in the product marking. Additives and powder are letter-encrypted:

• PC – Portland cement without improving additives;
• SHPC – slag is added in an amount of ≥20% during clinker grinding, the product is called slag Portland cement;
• PPC – pozzolanic cement, used for concreting in flooded conditions (pozzolans are products of volcanic activity: ash, tuff, pumice);
• SPTS, SSPTs, SSShPTs – sulfate-resistant binders, anticorrosive;
• B – fast -hardening powder;
• BC – white sequence; The clinker for its production is made of kaolin and light limestone;
• G – rapidly snapping clay -means powder, raw materials components for firing are carbonate rocks and bauxite;
• GF – hydrophobic cement for concrete products in water;
• Pl – plasticized, ensures the convenience of laying the solution even at low temperatures;
• WRC – moisture -proof expanding cement, hardens in any environment.

In the GOST 10178-85 marking The letter and percentage D0, D5, D20 denote the number of additives. The standard by which the product is made is indicated at the end of the cipher. As an illustration, consider PC 400-D20-B-T-TP GOST 10178-85 Portland cement, which has a strength of 400 kg/cm² and 20% additives in a fast-hardening, plasticized form.

Deciphering cement labeling according to new standards

According to GOST 31108-2003, product information is coded using a system that groups different types of cement into five categories, each represented by a Roman numeral. The first three characters come from the powder’s name, CEM.

Features indicating the manufacturing features are present in each association:

• I – Portland cement without additives, consists of 95-100% cement clinker;
• II – this group is divided into subclasses A with additives of 6-20% and B – 21-35%. Here are also pozzolanic cements containing
• III – slag Portland cement with a slag content of 36-65%;
• IV – pozzolanic cement with an additive of 21-35%;
• V — composite powder, including 11-30% slag and pozzolan within the same limits.

The designations of the additives are as follows: I stands for limestone, Z for fly ash, MK for microsilica, K for composite additive, G for glyage, Sh for slag, and P for pozzolan. The strength class number is then shown, with the letters H for normal hardening time and B for fast setting coming next. Slag Portland cement CEM III/A 32.5N GOST 31108-2003 is one example. It can be understood as follows: With a strength of 32.5 MPa and a slag content of 36–65%, cement is typically hardening.

An intricate process using raw materials like limestone, clay, and other minerals results in cement, a basic component of construction. Cement is made by grinding finely ground ingredients, blending them, and heating them in a kiln to create clinker, which is subsequently ground into fine powder. Building strong and long-lasting structures requires cement, which undergoes this transformation process that gives it its binding properties.

Different types of cement with distinct properties and applications can result from variations in its composition. For example, Portland cement, which is widely used in general construction, is well-known for its strength and versatility. Specialized mixes, like sulfate-resistant or fast-hardening cement, are designed to meet specific requirements and improve performance in particular conditions. Comprehending these variances aids in choosing the appropriate cement type for various projects, guaranteeing best outcomes.

A standardized system called cement marking tells you the mixture’s composition and intended use. These markers assist engineers and builders in selecting the right kind of cement for their particular needs. When constructing a high-rise building, paving roads, or adding decorative elements, being aware of the markings guarantees that the cement will function as required, enhancing the structure’s longevity and safety.

Cement has a wide range of applications, from large-scale infrastructure projects to residential buildings. Because of its versatility and dependability, it is essential to modern construction. Builders can create better built environments by making informed decisions based on their understanding of the composition, manufacturing process, and significance of cement markings. With this knowledge, professionals can fully utilize cement, which promotes efficiency and innovation in the construction sector.

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