Alite crystal size

The subject of clinker grindability also has microscopical aspects and the most complete literature survey, to date, is that of Hills (1995) who enumerated most of the prevailing agreed-upon relations (such as decreasing alite crystal size increasing grindability). Other variables on which the interpretations were not as clear cut (such as percent liquid phase) were also listed. 

Alite—crystal size, optics, zoning, fringing, habit, crystal form ... 

A partial least-square regression analysis was applied by Svinning and Bremseth (1993) on alite crystal size and various process parameters, showing that alite size accounted for only approximately 40% of the total variance and that an increase in the >60-pm crystals occurred with decreasing secondary air temperature measured in the cooler. Statistical analyses of this type, in the present writer s opinion, are greatly needed in our industry to decipher relative importance of the many kinds of measurements. 

Photograph 7-7 Variation in alite crystal sizes clusters of small crystals (14 pm), noncluster crystals (38 pm). Round belite crystals in nest in upper center. High maximum temperature, long burning time, moderately slow heating rate, quickly cooled, 42 MPa. Gas-fired, dry-process kiln, 770 tons/day. (S A6627)... 

Decrease in alite crystal size Increase in feed rate (Jany, 1986)... 

Decrease in range of alite crystal sizes Increase in burning temperature, decrease in burning time (Butt, Timashev, and Starke, 1973)... 

Photograph 7-26 Experimental laboratory burn with raw mix containing quartz (44-75 pm) as a silica source. Average alite crystal size = 44 pm. 1000°C for 30 min, 1425°C for 10 min. Very rapid temperature change. Note abundant free lime inclusions in alite. Clinker courtesy of Joe Garcia, Capitol Cement, San Antonio, Texas. (S A6646)... 

Higher burning temperature required for adequate combination increase in alite crystal size Coarse raw feed (Long, 1982a)... 

Zivanovic (1995) presented a description of clinkers made with silica fume, instead of quartz sand, as the primary silica component in the raw feed. The silica fume made up approximately 3.0 percent of the feed. Alite crystal size was reported to be from 50 to 200 pm and belite grains were said to be rounded and between 50 and 60 pm. No mention of belite nests was made. The cements made with silica fume or tuff and a particular marl, compared to other cements not made with these materials, did not require as much grinding and produced higher 28-day mortar strengths. 

Efch reactivity variations (specify etch and length of time). Crystal morphology crystal surface characteristics (depth of alteration) internal structure tendency for coarse cannibalism (masses greater than 5 times the average alite crystal size) inclusions. Size and abundance variations within and between clinkers. 

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