An overview of phase composition and quality phase of clinker

Short formula in cement chemistry and chemical simplification of nomenclature typically used to refer to oxides. The following abbreviations are used. This is how ordinary characters do not confuse the elements in cement chemistry.

A12O3 - A CaO - C CO2 - c

Fe2O3 - the F H2O - H K2O - the K

MgO - M Na2O - SiO2 of N - S

SO3 - s

Alit..Trehkaltsievy silicate - is the main component of Portland cement clinker consists of C3S, which contains a number of other oxide impurities, about 2% MgO, along with this A12O3, Fe2O3, TiO2, etc. Standards interstitial impurities depend, inter alia, on the composition of the starting material, the firing temperature and the cooling mode. The content of oxides influences the quality of the clinker, for example, increasing the proportion of CaO increases, generally cement strength. At a temperature of less than 1250 ° C C3S at very slow cooling can break down into CaO and C2S, especially if you set a reducing environment during the combustion of fuel. Tricalcium silicate as the main component is largely determines the quality of the cement, particularly with the increase in the strength of hydration and final mark. Tricalcium silicate forms large crystals with a transverse dimension and a diameter of about 1-10 microns. Often crystals of tricalcium silicate overgrown with application dicalcium silicate inclusions and phase of clinker Glass. Under the polarizing microscope they appear (by etching with CDTA) in the characteristic light yellow color (see Figure 1.2). In wet storage (water contact) there is a typical corrosive edges alite (see Figure 1.2 on the left below) to arise in alite crystals. Figure 1.3 shows a partial exemption of clinker belite phase under the scanning electron microscope [5, 25,26, 27]. Bleaches, occurrence of melt at a temperature preferably in the solid state, in the clinker lime standard high belite is formed only in minor amounts. In belite strength increase is slow, however, after a long time, it reaches at least the same strengths as tricalcium silicate. The clinker is predominantly exists ß-modification without sufficient introduction of other ions. At room temperature, ß-S2S stable in thermodynamics is more stable hydraulically. Modification less goes active in other forms. Switching to other shapes may occur with insufficient introduction of other ions in the lattice, particularly alkalis and can also occur during slow process comprises ohlazhdeniya.Belit..Dvuhkaltsievy silicate C2S, which contains the same tricalcium silicate oxides. Dicalcium silicate melt at a temperature of occurrence exists mainly in the solid state, in a high lime clinker standard (CN) in a small amount of its contents. C2S strength growth is slow, but after prolonged hydration of belite strength reaches at least the same as the strengths of tricalcium silicate. The clinker exists mainly ß-modification without sufficient introduction of alien ions at room temperature C2S stable and thermodynamically more stable than hydraulically, however, this modification is inactive. The conversion can be carried out introducing other ions, in particular alkali and more rapid cooling process. The clinker costave dicalcium silicate crystals form round, seen in the electron microscope brown crystals with cross-hatching of the plates. Dicalcium silicate is formed in most cases cells (clusters), since there is a local shortage of CaO. This is due to insufficient mixing of the raw meal and heterogeneity. When lime standard (CN) <100 in the clinker produced dicalcium silicate and tricalcium silicate.

Phase alyuminata Melkozernistye aluminate phase and ferrite phase is often summarized as "intermediate material" or "the bulk" of cement clinker. Both are formed by cooling the clinker from its liquid phase (melt), and marked so as the melt phase. aluminate (C3A) phase also contains other ions, particularly alkali (Na2O, K2O), which can be introduced in an amount of more than 5%. Phase composition Na2O · 8CaO · 3A12O3 and K2O · 8CaO · 3A12O3 known. As part of the clinker phase aluminate and ferrite phase must be distinguished only at normal and slow cooling of the clinker, as they are very finely crystallized. Ideomorfichesky aluminate exists in gradually cooled clinker in long, gray colored prisms or needles (Figure 1.2). aluminate phase has a high activity of hydration. It can even significantly improve the introduction of alkaline reaction in the early phase (5-15 min.). Nevertheless, the following reaction that starts after 2-4 hours. Considerably slows alkalis [4, 27,31].Faza ferritaFerritovaya phase has a certain composition, but a mixed crystal series, shorting links C2A (existing only in extreme conditions) and C2F: C2A ····· C6A2F ····· C4AF ····· C6AF2 ····· C2F. The composition of the ferrite phase is determined by the iron. Often he meets an aluminum proportion of the raw meal, about C4AF formula, which is consistent with the existing mineral in nature brownmillerite. The general formula of the mixed crystal series C2 (A, F). Also in the ferrite phase includes other ions. Magnesium causes gray cement color; clean C4AF brown, saturated the MgO C4AF opposite - gray-green. Ferrite phase hydrates with water is slower than the aluminate phase. Its reactivity of the less significant than the Fe2O3 content above [4, 5, 25, 133]. The polished sections of clinker ferrite phase appears in etching as the purple matrix, which includes other phases