The composition of the raw meal. Equations 5-9
In practice, the composition is characterized by raw materials (also part of PZ clinker) in most cases by the ratio of oxide (so-called modules). They set out certain chemical analyzes oxides. Lime standard (KSt or as it is accepted in Kazakhstan KN saturation ratio) in the majority of cases, is used to calculate the optimum lime component. The high lime component (CaO) allows the formation of rich lime silicate clinker phases during its firing. They are used for quality assurance with regard to the development of high strength cement. CaO content must be agreed with the content of other oxides - SiO2, A12O3, Fe2O3. If there is an excess of CaO (lime CaOsvob free), it can lead to later reaction with water, formation of Ca (OH) 2, and the increase in volume of the cement stone destruction. The optimum proportion of lime should be high, but not be too high. Lime Standard (KN) is used to accurately establish the optimal proportion of lime. It is expressed in the feed (or clinker) shows the available CaO proportion in percent that can bind in the firing process with the existing oxides SiO2, A12O3, Fe2O3 phase in the clinker; those. It expresses actually contained in the raw material or a mixture of CaO in the clinker,% of CaO to the amount that can be caused in the process of clinker burning and cooling.
equation 5
Silicate module characterizes the ratio of silica to the sum of aluminum and iron oxides. With the increase in clinker silicate module increases the content of minerals - silicates alite and belite. Clinker phase with alumina and iron oxide are fusible. The production value of the silicate cements module clinker SMlezhit generally between 1.6 and 4.1 [24], most often, and most favorably between 2.3 and 2.8 [4]. Low modulus silicate leads to easier calcined clinker simultaneously also to accelerate the formation of clinker in the kiln.
Alumina Module (GM, p Alumina Module) - is the ratio of alumina to iron oxide:
equation 6
Alumina module GM characterized clinker melt, since both exist oxide melt formation at a temperature almost entirely in the liquid phase. When aluminum modulus of 1.4 to 1.6 the maximum mass of the melt is formed at a low temperature. When GM <0,638 C3A mineral is formed. Cements with a low C3A exhibit particularly high resistance to the aggressive action of sulphate attack. The cement manufacturing GM value lies between 1.4 and 3.7 [24], in most cases between 1.8 and 2.8 at special cements GM can be reduced to 0.4 [4].
Cement clinker contains some 2% of alkali (Na2O + K2O), an average of about 1%. They are mostly made of raw clay component of the mixture. alkali content is indicated generally as Na2O equivalent [M .-%], and is calculated as follows:
Na2O equivalent [M .-%] = 0,658 K2O [M .-%] + Na2O [M .-%]
equation 7
Further characterization of clinker (SG). In addition, the cement clinker contains up to 2% SO3 (as sulfate). Sulfates arise from the oxidation of sulfur that fall within the furnace with raw material and fuel. When firing sulfate binds with alkalis. The compound to alkali sulfate is designated as (SG).
equation 8
It indicates the percentage of participation in the alkalis, which exists on the basis of the calculation as sulfate alkali. Alkali sulfate by 100% means that all the alkali clinker exist entirely as sulfate. When firing sulfate (SG> 100%) of sulfur is not connected polnostyuK2SO4, Na2SO4, K2SO4 · 2CaSO4 and / or CaSO4 forms as anhydrite. If sulfate firing occurred <100%, the excess alkali can be introduced into the clinker phases [20, 21,22].
Different proportion of alkali is reflected particularly strongly in the aluminate activity. By adding alkali slight (about 0.5%) increased the activity of hydraulic clinker in comparison with non-subsidized aluminate. When subsidized alkali in 1.0% hardly affect the hydraulic activity and if they contain> 1,5% hydraulic activity decreases. Table 1.4 covers the field and averages modules German cement clinkers.
Table - modules in the German Portland cement clinker
Показатель |
Max. |
Средний |
Min. |
KSt |
104,1 |
97,1 |
90,5 |
SM |
4,1 |
2,5 |
1,6 |
TM |
3,7 |
2,3 |
1,4 |
SG |
188,5 |
80,1 |
34,8 |