Extraction methods clinker

Concerning portland cement, the free lime is the phase most sensitive to moisture uptake (Dubina et al. 2011) see Table 1.1. As the water sorption starts at such a low relative humidity, the transformation of calcium oxide to portlandite cannot really be avoided in practise. Thus, the determination of free lime in clinkers and cements by quantitative XRD should always be verified by other methods, e.g. the extraction method of Franke (1941). From the cement clinker phases the orthorhombic C3A phase is the most sensitive to moisture. The prehydrated surfaces retard further hydration of the clinker grains (Dubina et al. 2011). Calcium silicates and calcium sulfates are involved as well in the prehydration process, as they may take up moisture already at quite low relative humidity. 

Quantitative data on the rate of consumption of pfa are few and somewhat variable. Those based on differences between the CH contents of pure Portland and pfa cements are suspect, because the calculation involves the effects of pfa substitution both on the rate of consumption of the clinker phases and on the compositions of the products, which are not fully understood. Unreacted pfa has been directly determined by dissolution of the other phases with HCl (C43) or with salicylic acid in methanol followed by HCl (T44), chemical separation of the residual pfa followed by QXDA determination of its content of crystalline phases (D12) and a trimethylsily-lation method (U19). A method based on EDTA extraction was found unsatisfactory (L46). 

XRD (Cu Ka) data for (A) raw Portland cement clinker, (B) Residue 1 from which most of the C3S has been removed and (C) Residue 2 from which C3S and C2S have been removed. Silicate phase extraction was conducted using a salicylic acid methanol (SAM) mixture using the method described by Taylor." In Residue 2 the presence of the alkali sulfate phases [denoted Arc for arcanite K2SO4 and Ap for aphthitalite K3Na(S04)2] is clearly evident. Notably, the material used in these plots was derived from a different cement plant to the one illustrated in Figure 10. 

C this phase decomposes [40]. At higher content of spurrite the expansive properties of clinker are reduced. The amormt of C4A3S in clinker can be determined by XRD or by chemical method. This method consists in the extraction of the other clinker components with the solution of maleic acid in methanol and subsequent with the ammonium chloride water solution [107]. 

The results of microscopy by the Ono method are considered an important part of the data base in a computerized multivariate analysis conducted routinely for cement quality control in plants of the Onoda Cement Company in Japan (Aizawa, 1985). Microscopical data are said to be helpful in making frequent adjustments in kiln parameters, clinker silo operation, and adjustment of cement fineness. The continually updated analysis involves the following process variables burning zone temperature, kiln outlet clinker temperature, secondary air temperature, extraction air temperature, kiln rotation torque, nitrous oxide, percent clinker passing the 5-mm screen, and liter weight. In some Japanese cement plants, clinkers are recycled until the microscopical targets have been met, according to Uchikawa (1992). 

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