Alite birefringence

Retardation (delta) is the distance that the slow light ray lags behind the fast ray and is directly related to crystal birefringence and thickness. In other words. 

To measure alite birefringence using a Senarmont compensator and the upper element of the substage condensor, Ono recommends the following steps  

Measure and record the crystal width (W) in pm using the calibrated, graduated eyepiece scale. 

In cross-polarized light, rotate the stage 45 from crystal extinction (darkness) as illustrated in Photograph 6-2. For crystals that exhibit a strongly wavy (undulatory) extinction, birefringence data may be questionable. Therefore, crystals with uniform or nearly uniform extinction are sought. 

Insert the Senarmont compensator, properly oriented so that the darkness of the background results in cross-polarized light. Place a green filter in the path of the incoming light. The green filter facilitates observation of the alite crystal compensation point determined in the next step. 

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An extraction of the matrix phases with a warm KOH-sugar solution concentrates the silicates for easy determination of alite birefringence and belite color. Details are given in Chapter 11. 

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 ... 

As in the estimation of alite birefringence, one should eliminate the extremely large and the very... 

For example, assume the following data alite size (AS) 50 im (slow heating rate), alite birefringence (AB)... 

Ono stated (letter, 1977) that an alite birefringence slightly higher than 0.007 could be written 0.007 and ranked as good a birefringence slightly lower than 0.008 may be written as 0.008 and ranked as excellent. ... 

AB = alite birefringence BS = belite size BC = belite color... 

Using alite birefringence and belite size, Ueda and Suzuki (1985) were able to monitor the variable calorific value of coals and make adjustments in the kiln conditions to maintain clinker quality. 

According to Ono, Kawamura, and Soda (1968), alite birefringence is a function of maximum temperature in the kiln load the higher the temperature, the larger the birefringence. Birefringence in Ono s method is measured on alite crystals in clinker particles mounted in RI oil and observed in transmitted, polarized light. 

Pennell (1987) discussed the differences between alite birefringences determined with thin sections (the present author s data) and powder mounts, illustrating the fact that the latter determination was not accurate, but concluding that the values may be tolerable for correlation purposes. 

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. 

A different interpretation of alite has been given by Fundal (1982), who stated that alite crystals are twinned individuals of a lower symmetry which imitate a higher symmetry (a mimetic relationship). The monoclinic form of alite was said to have an index of refraction of 1.72 and a birefringence of approximately 0.0050. Tri clinic alite was reported to be polysynthetically twinned in a fused clinker and have a birefringence of 0.0020. Alite birefringence, however, exhibits two average val ues in Fundal s Table 1 (1982) 0.0043 (monoclinic) and... 

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. 

In response to Fundal (1982), Lee (1983) pointed out the bimodality of alite birefringence determined by Maki and Kato (1982), who demonstrated relationships with magnesium oxide content in the crystal. Lee restated the conclusion by Maki and Kato that the M, (monoclinic) phase appears pseudotrigonal in an X-ray powder-diffraction pattern. Lee believed that Fundal s comparison of alite compositional and optical data with a tectosilicate solid-solution series, such as plagio... 

Mor and Perez (1994) presented a critical evaluation of Ono s method (powder mount only) using laboratory heating stages, concluding that the alite size and alite birefringence did not correlate. Correlation was said to be much better with regard to belite size and color. The correspondence between laboratory and industrial kiln microscopy was seriously questioned and differences in environmental conditions, mainly atmospheric composition, were alleged to be responsible. 

Increase in alite and belite sizes, deformed belite, low alite birefringence Dusty, oxidizing divergent flame (Campbell and Weiss, 1987)... 

Alite birefringence = 0.005 to 0.006 M3 form, MgO-rich (Maki and Goto, 1982)... 

Alite birefringence = 0.0026 Tj variety, formed during 120-minute firing (Maki, Haba, and Takahashi, 1983)... 

Pennell, J.F., "Alite Birefringence Measurement- Some Problems and Possible Solutions," Proceedings of the 9th International Conference on Cement Microscopy, International Cement Microscopy Association, Reno, Nevada, 1987, pp. 1-15. 

Stark, 0.,AnAltemative Procedurefor Measuring Alite Birefringence, Research Development Serial No. 1206, Portland Cement Association, Skokie, Illinois, 1980,8 pp. 

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