Alite thickness

SEM examination. A layer of apparently structureless material built up to a thickness of 5 pm in 30 min, together with cryptocrystalline CH this later shrank, and acicular outgrowths were formed. The product layer contained aluminium, and had thus formed in part from the surrounding alite. 

The thickness, X, is determined by rolling the crystal, or it can be approximated by other techniques as previously described. Alite birefringence is calculated as follows ... 

The problem of measurement of crystal thickness (t) for the determination of alite birefringence in powder mounts has been the subject of much discussion. Prout (oral communication, 1984) finds that the thick ness can be approximated by the equation (length + width)/2, giving a reasonable apparent birefringence. 

The factor of 0.75 in the denominator of Eq. 7 for alite birefringence was statistically derived to account for deviations between true and observed birefrin gences of an alite crystal in which the X vibration direction is not exactly parallel to the microscope stage and the Y and Z directionsarenotpreciselyknown. In order to minimize this deviation, which lessens the birefringence, a crystal thickness-to particle width ra tio of 3/4 is assumed (Ono, letter, 1978). The clinker particle, in this case, was illustrated to contain only part of an alite crystal. 

Determination of alite birefringence in powder mount is subject to an error of approximately 0.0006 and that a petrographers rule of crystal width being equal to 4/3 crystal thickness is not valid as a short cut. 

Alite birefringence determined in thin section, using quartz as an internal thickness standard, is a suitable method. However, a correlation with burning temperature was not evident. 

Belite nest with dense, thick layer of alite with very porous outermost zones Typical in dust formation (Fundal, 1980)... 

Extremely large and thick alite (100-200 pm) Contamination ofconsiderable amounts of Na O, K O, and SO3 in clinker (Ono, Hidaka, and Shirasaka, 1969)... 

Photograph 7-18 Clinker thin section (approximately 15 pm thick) showing relatively large angular alite smaller, round belite and normal ferrite with its short slender intersecting crystals, between which the aluminate occurs (not visible at this magnification). (S A6638)... 

Separation of matrix phases, ferrite and aluminate, but without typical eutectic intergrowths content of free lime high alite coated with thin ferrite seam, then by thick belite cover Reducing conditions, quenched, lab experiment melt rich in silica, poor in lime resorption of belite which was prevented by quick cooling (Woermann, 1960)... 

Photograph 7-68 Ultrathin section, approximately 10 pm thick, showing tan to beige aluminate (C3A) crystals comprising most of the matrix in this clinker. Round belite crystals, angular alite crystals. (S A6686)... 

For powder samples, an example of unreacted alite is shown. The anhydrous powder was mixed with a hard polishing resin and left to harden. Semicircular discs, 3 mm in diameter, were cut from the blocks of embedded sample. The discs were mechanically polished on the two sides to reach 20-50 pm in thickness. Then some areas ( windows ) containing the grain edges were thinned down by FIB. This method allows a precise selection of the grain, and several samples can be produced on one semidisc. There is no need for transferring samples inside the FIB, which reduces the time for preparation. 

XRE gives the total amount without differentiating between the amounts in exsolved regions and in solid solution in alite. The microscopy techniques permit the selection of regions without clusters. With SEM techniques, because of the large interaction volume, subsurface clusters not visible from the surface may be included, but the relatively large distance between exsolved regions makes this unlikely. The STEM technique allows a localised analysis of the composition, since the interaction volume is small because of the small thickness of the sample. Table 8.1 compares the results obtained with the different techniques to the calculated amount of each element from the synthesis recipe. 

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