Alite color

Aliphatic solvents, alkyllithium compounds and, 14 250-251 Aliphatic sulfonates, 26 145 Aliquot samples, 13 413-415 analysis of, 13 416 Aliskren, 5 158 Alitame, 12 42 24 232 Alite, phase in Portland cement clinker, 5 471, 472t, 473t Alitretinoin, 25 790 Alizarin, color of, 7 331 Alizarin derivatives, 9 337 Alizarin pure Blue B, 4 361t Alkadienes, metathesis of, 26 923 Alkali/alkaline-earth cation recognition,... 

C. Nital is perhaps the most common etchant and stain for silicates and improves with age. Nital is 1.5 mL of nitric acid (HNO ) in 100 mL of ethyl, methyl, isopropyl, or amyl alcohol. The author routinely uses asolution of 1 mL of HNOj and 99 mL of anhydrous isopropyl alcohol. The solution quickly reacts in 6 to 10 seconds with alite and belite. At a 0.05% dilution the reaction time is 20 to 40 seconds. Ono (1995) relates alite reactivity to color produced with 0.2% nital. Depending on the relative reactivity of silicates, alite normally turns blue to green, belite is brown to blue—both silicates showing details of internal structure. Nital superimposed on a 20-second potassium hydroxide etch turns C3A light brown and colors the silicates. 

F. Maleic acid attacks alite and belite at about equal rates and a little faster than salicylic acid. When followed by NH NOj, it does not give color distinction to alite and belite. 

G. Ammonium chloride (saturated, aqueous) colors a hexagonal section of alite (perpendicular to the threefold crystallographic axis) light yellow. The slender hexagonal section of alite (parallel to the caxis) is colored blue. Zoned crystals in the slender hexagonal section show light-blue cores and dark-blue rims. Ono (1995) recommends an... 

Dorn and Adams (1983) have described the various etch rates of alite and belite in relation to hydraulic activity. A blue color on alite after a 15-second nital etch was said to represent an active alite. 

Photograph 3-2 Blue coloration on alite with an otherwise uniform tan color on alite crystals. Possible explanations include differences in crystallographic orientation, chemical composition, structural state (for example, monoclinic versus triclinic), or perhaps combinations of these. (S A6612)... 

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. 

Select a bright alite crystal (one that exhibits the maximum interference color in cross polarized light) and rotate the microscope stage so that the crystal is at its extinction position (dark). 

Insert the gypsum accessory plate (wavelength = 530 nanometers). The interference color of the alite crystal will be first order red (530 nanom eters), as seen on the Chart. 

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

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. 

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. 

Colorless belite, according to Lee (1983), can occur as very small inclusions in alite and contains very little impurity. Large-crystal, ringlike belite nests (from coarse alkali feldspar) are also colorless because of iron-oxide deficiency. These occurrences of belite, therefore, do not reflect the cooling rate. Consequently, Ono (1978) recommends color observation of roughly 20 pm belite crystals in order to judge the cooling rate. 

Prismatic alite round belite light-colored, highly reflective intermediate material dark prismatic aluminate Typical clinker from small kiln (4.5x170m) (Kolenova, 1974)... 

Overall increase in crystal size alite more than belite, which tends toward yellow color Lowering of feed to speed ratio, thinning clinker bed depth as burning zone moves uphill (Rader, 1985)... 

Disappearance of ferrite phase, iron transformed to metallic state, clinker color changes to white, alite decomposition structures vanish Extreme reducing conditions (Woermann, 1960)... 

Photograph 7-37 Bimodal belite in laboratory-burned clinker made from a raw feed containing coarse quartz sand. Large nest of tightly packed belite crystals and much smaller crystals showing wide lamellae. Note gradational color response in nital etch of nest. 55% of the alite crystals were said to be greater than 75 pm. 

Photograph 7-45 Blue, amoeboid belite in a coarsely crystalline, matrix-rich clinker. Amoeboid belite crystals seem to be most common in clinkers burned at a high temperature. Angular, tan alite. Other clinkers in this section contained alite that produced a blue color. (S A6665)... 

Image analysis and description of its methodological problems, discussed in papers by Marten, Strunge, and Knbfel (1994), Theisen (1997), and Anwander (1998), are quite instructive. These authors recommend the use of HF vapor as an etchant and real color processing to determine phase percentages (alite, belite, and matrix). Research by the present writer suggests the feasibility of the technique. 

Unlike ordinary Portland clinker, alite-fluoroaluminate clinker is brownish in color, rather than dark gray. It typically possesses a very low porosity, and the alite and behte crystals that are present are distinctly smaller than those in ordinary Portland clinker. Only some of the fluorine is in the CjjA2.Cap2 phase the rest is incorporated into alite (Odler and Abdul-Maula, 1980). 

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