Cement is a hydraulic binder in the group of binders, one of the two main groups of building materials. In all its varieties, cement can harden both in air and in an aqueous environment. There are also air binders, which include mortar and building plaster. Binders are powdery materials that are mixed with water and form a plastic mass, which in turn hardens after a certain period of time.
The other main group of building materials, besides binders, are inert materials. These include sand, stones, wood, metal, bricks, etc. Inert materials represent the essence of the building structure and make it complete, while binders bind them together and turn buildings into stable and safe engineering structures.
Cement is one of the most widely used building materials because it is of fundamental importance. It is familiar even to people who have never worked in construction.
As we have already noted, cement is a mineral binder that has been known to mankind for a long time and is still used for construction purposes today. Cement is used for the production of mortars and concrete products, concrete and reinforced concrete structures.
WHAT IS UNDERSTOOD BY CEMENT IN CONSTRUCTION PRACTICE?
In construction practice, cement is understood as the so-called Portland cement, since it is the most widely used type of cement. Portland cement is a hydraulic binder - when mixed with water, it forms a plastic mass, which hardens after aging and has the ability to increase and maintain its strength. The durability of the resulting product and the relatively low costs of its production are a prerequisite for the widespread use of cements in construction.
Cement has no independent (individual) application, but it is an important starting component for the production of many composite materials based on it: mortars, various types of concrete, dry building mixes. The properties of these new materials directly depend on and are formed on the basis of the properties of cement - from the mixing of the starting ingredients to the subsequent bonding and formation of cement stone.
WHERE DOES THE NAME PORTLAND CEMENT COME FROM?
Cement was first patented by the Englishman Joseph Aspdin in 1824, and the name "Portland cement" is due to its gray color, which strongly resembled the color of the rocks near the British city of Portland. Nowadays, cement and its varieties are the basis of modern construction. With its help, concrete and reinforced concrete structures are made for all types of construction - residential and public buildings, industrial buildings and facilities, as well as transport and hydraulic facilities. Cement concrete has been perhaps the most common building material for almost a century, and there is a high probability that this trend will not change in the current 21st century.
HOW IS CEMENT MADE?
Portland cement is obtained by co-grinding Portland cement clinker and gypsum (up to 5%). Often in practice, mineral additives such as trass, volcanic tuffs, granulated blast furnace slag, limestone, thermal power plant ashes or microsilica powder are added to achieve certain goals. Clinker, which is the main raw material for cement production, is obtained by roasting a finely dispersed mixture of limestone and clay and other materials - marls, pyrite cinders, blast furnace slag and others. The technological process of cement production consists of four main and sequentially implemented stages:
1. Preparation of raw materials and raw material mixture, including extraction, crushing and grinding of raw material components, homogenization and correction of the raw material mixture.
2. Firing the mixture to obtain cement clinker and its cooling, preparation for burning the firing fuel.
3. Cement production – joint grinding of clinker, gypsum and additives.
4. Cement storage, packaging and shipping.
Portland cement clinker is the main component of cement (with a content in cement between 50 and 100%). For the production of clinker, natural rock materials are mainly used, which after crushing and grinding form the raw material mixture. Typically, this mixture has approximately the following composition: 70% limestone, 20% marl and bottom ash, 10% corrective additives - mainly iron-containing material, sand. The raw materials required for production are extracted in open quarries.
WHAT ARE THE METHODS FOR PRODUCTION OF CEMENT?
Depending on the method of preparation of the raw material mixture, there are mainly two methods for the production of cement – wet and dry. In the wet method, the grinding of limestone, clay and corrective additives takes place in ball mills with the addition of a significant amount of water, resulting in an aqueous suspension (sludge). In the dry method, the grinding and homogenization of the raw material mixture takes place in a dry state. Each of these two methods has its pros and cons.
TYPES OF CEMENT
Portland cement from regular production in cement plants cannot always meet the requirements for the production of concrete and reinforced concrete products and structures. Due to these more specific requirements, special properties are added to the properties of the cements used for making concrete with the help of various additives.
Pozzolanic Portland cement: obtained by the joint grinding of Portland cement clinker, trass (20-40%) and natural gypsum. It is distinguished by: higher water consumption than Portland cement (28-35%); slower increase in strength at an early age; high water resistance and water impermeability; lower frost resistance. It is used for concrete and reinforced concrete elements located under water or in high humidity, which are not subject to freezing.
Slag Portland cement: a product of the joint grinding of Portland cement clinker, granulated blast furnace slag (20-50%) and natural gypsum. Slag Portland cement is characterized by high water resistance, water impermeability and frost resistance. This type of cement is also used in concrete and reinforced concrete structures located under water or in high humidity, but unlike pozzolanic cement, slag Portland cement is also suitable for structures subject to freezing.
Rapid-setting cement: this type of cement is obtained by very fine grinding of Portland cement clinker, active mineral additive and gypsum. The tricalcium aluminate content is slightly higher than that of Portland cement. This cement hardens quickly at an early age and releases more heat than Portland cement. It is suitable for concrete and reinforced concrete elements for prefabricated construction, for concreting in winter conditions, and also for strengthening works.
Alumina /aluminum/ cement: the raw materials for its production are limestone and bauxite (aluminum ore). The main mineral obtained is monocalcium aluminate. It hardens very quickly, reaching standard strength on the third day. As with fast-setting cement, significantly more heat is released when the concrete mix is mixed. For this reason, it is also recommended for work in winter. Alumina cement is mainly used for restoration work in emergency situations - after natural disasters.
White and colored cements: among the requirements for the production of white cement are that the raw materials for it do not contain large amounts of iron trioxide and manganese oxide and that the grinding of the clinker is carried out with very hard alloy steel bodies. Colored cements are obtained by coloring white cement or Portland cement. The application of these cements is for mosaics, decorative plasters, panels, facing slabs.
Sulfate-resistant Portland cement: obtained by co-grinding Portland cement clinker with a certain mineral composition and gypsum (SO3≤3.5%). Sulfate-resistant Portland cement is used for the manufacture of concrete and reinforced concrete structures exposed to increased sulfate ions in an aggressive environment. It is also recommended for concrete located in the conditions of the variable zone of hydraulic and other facilities, where they are subjected to periodic wetting and drying, freezing and thawing.
Low-temperature cement: obtained by co-grinding Portland cement clinker with a certain mineral composition, mineral additives and gypsum (SO3≤3.5%). The requirement for the mineral composition of Portland cement clinker is that the alite content should not exceed 50%, and the tricalcium aluminate content should not exceed 5%. Low-temperature cement, in addition to reduced heat release (exothermy), is also characterized by slow strength growth at an early age, increased sulfate resistance and reduced frost resistance. Its use is recommended for the manufacture of large-sized (massive) concrete and reinforced concrete parts and structures such as large-sized foundations of tall buildings, concrete dam walls and others.
WHAT DO WE OFFER?
With us you can find cements from the brands DEVNYA CEMENT, SIKA, BORO, TERAZID.
The prices are very affordable.
