Just as, for example, granite is composed of certain natural minerals and cement clinker is a system of several artificial minerals formed by firing the raw mix. But unlike granite separate parts clinker is impossible to distinguish with the naked eye, as clinker is composed of fine-grained crystalline and amorphous phases. Approximate mineralogical composition of Portland cement clinker: 1. Tricalcium silicate (alite) - 3 CaO x SiO2-40-65%; 2. Dicalcium silicate (blanches) - 2 CaO x SiO2-15-45%; 3. Tricalcium aluminate-3 CaO x Al2O3-4-12%; 4. Chetyrehkaltsievy alumina ferrite-4 CaO x Al2O3 x Fe2O3-12-25%. The total content of alite and Belita typically ranges from 70-80%. Consequently, in Portland cement clinker quantitatively dominated by calcium silicates. Therefore, the cement at one time called silicate. In addition to these important minerals in the clinker in small quantities and other alyumoferrity aluminates and calcium, and calcium ferrite. Along with the crystalline phases in the clinker is an amorphous substance in the form of non-crystallized glass (6-10%). In small quantities (no more than 5%) in the clinker contains magnesium oxide, magnesium carbonate as is almost inevitable natural impurity in the limestone. The clinker is sometimes found free calcium oxide (1%) as a result of incomplete burning of clinker, that is errors in the technology of burning. Finally, the clinker can be compounds (1-2%) formed by alkali oxide-sodium oxide and potassium. These oxides are transformed into clinker from raw materials and ash solid fuel. Knowing the properties of clinker minerals, in particular the amount of heat in contact with water, and mineralogical composition of clinker, can be a first approximation to identify the main features of the cement produced from this clinker. Tricalcium silicate (alite) is chemically very active in the reaction with water. This is evidenced by the magnitude of the heat during hydration, especially during the first three days. He has the ability to quickly harden and hardening develops greater strength. Therefore, a high content of tricalcium silicate is important for the quality of cement. High-quality and early-strength cement should contain a large number of alite. Dicalcium silicate (blanches) is significantly less active, as indicated not only the heat of hydration, but the slow pace of heat: for the three days allocated only 10% of the total heat of hydration. Hardens it very slowly. But for several years with the strength of favorable conditions for hardening steadily increases. Tricalcium aluminate is the most active clinker minerals, he has the greatest heat, with three days to devote at least 80% of the heat of hydration. Tricalcium aluminate quickly hardens. However, the hardening of the product has low strength. Chetyrehkaltsievy alumina ferrite largest heat by reaction with water occupies an intermediate position between the tricalcium and dicalcium silicate. Chetyrehkaltsievy alumina ferrite hardens considerably slower than the tricalcium silicate, but faster than dicalcium. Strength is also higher than the product of hydration of dicalcium silicate. The above brief description of clinker minerals give some idea of the impact of their quantitative content in the clinker on the properties of the cement. So, if you want to fast-hardening cement, right, for example, in the manufacture of precast concrete products and structures to accelerate their production, then apply the clinker with a high content of tricalcium silicate and tricalcium aluminate. These minerals in the sum must be at least 65-70% by weight of clinker. For concrete work in the winter too convenient cement with a relatively large amount of tricalcium silicate and tricalcium aluminate. This cement has a high-heat. Therefore concrete in any structure, protected from heat loss, can successfully harden and at negative temperatures. The construction is often required with moderate-heat cement is mainly for massive concrete hydraulic structures. It is known that when a large heat release hardening cement concrete greatly expanded in the inner parts of the array and less in the outer, which are naturally cooled by air or water. Volumetric strain arising from uneven expansion and contraction of concrete, causing cracking and often leads to accidental destruction of buildings. Therefore, in the massive concrete structures (eg, waterworks) shall not apply cements, characterized by high heat. For a moderate-heat cement clinker should contain a relatively small amount of tricalcium silicate and tricalcium aluminate. The properties of cement in addition to these major clinker minerals is also influenced by it contains magnesium oxide, calcium, potassium and sodium. In a properly constructed and cooled clinker large part of the free crystalline magnesium oxide (periclase) is dissolved in the glassy phase in the form of very small crystals, small crystals of the same, moreover, are in finely ground cement, hydrated in time to the stage where the cement had not yet solidified. During this period, an increase of individual components of cement does not cause mass destruction, to maintain some plasticity. So modern technology almost completely eliminates the harmful effect of magnesium oxide in the cement when its content in the clinker and 5%. Free calcium oxide present in normal clinker, as indicated, in small quantities and, moreover, in the form of very small particles. The smaller the particle, the faster they are hydrated. Under such conditions, the process of hydration of free lime in concrete is usually not dangerous. Alkali oxides are present in the clinker in various chemical compounds, such as potassium aluminate K2O x Al2O3. If the stone concrete aggregate has opaline silica, ie water silicon dioxide (SiO2 x nH2O) in an amorphous form, the presence of alkali oxides in the cement can cause destruction of the concrete. The contents of these oxides in the clinker is on average about 0,5%. The reasons for this failure are as follows. Alkali oxides react with silicon dioxide, located in the stone aggregates in an active, active reactive form, forming a water-soluble silicates of potassium or sodium. They in turn interact with calcium hydroxide cement to form calcium salts, thereby reducing the strength and durability of cement stone layer, located on the border with the grain filler.