Belite Color

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

Kawamura and Mizukami (1969), while investigating the relation between raw feed containing various particle sizes and different Blaines of quartz and feldspar, described belite rings. Ono (1995) stated that belite rings with diameters of 300- to 600-pm develop from coarse silicates (quartz, feldspar, and shale), forming large Type I crystals (40 to 60 pm) which are colorless even in slowly cooled clinkers. 

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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. 

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

Certain observationalproblems can skew belite color data and complicate the interpretation of cooling rate, and the following comments are reproduced almost verbatim from Campbell (1994b) ... 

Tiny belite crystals formed as a surficial decomposition of the alite during slow cooling have always been clear in the writer s observations secondary belite (formed out of the matrix during cooling) is also clear, perhaps because these crystals have little to exsolve. Research is needed on this point. Amoeboid crystals are rarely colored dendritic crystals have never been observed to be colored in the writer s experience. Ono s belite color interpretation seems most applicable to properly formed crystals. 

Boundary-line colors refers to colors falling between the major categories of clear, pale yellow, yellow, and amber. In other words, pale yellow to one observer is obviously yellow to another, even when each person is being as objective as possible. The problem is not unique to cement microsco-pists. An attempt at a photographic belite color standard is presented in this book. 

For details of crystal counting to determine belite color percentages and a discussion of some of the problems involving color observations, see Campbell (1994) and parts of Chapter 6. Alkali sulfate, epezite, periclase, some free lime, and ofher phases are present in the residue. 

Campbell, D.H., "A Summary of Ono s Method for Cement Quality Control with Emphasis on Belite Color," Petrography of Cementitious Materials, ASTM STP1215, S.M. DeHayes and D.S. Stark, eds., American Society for Testing and Materials, Philadelphia, 1994b, pp.13-25. 

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