Round silica sand producers

The particle shape of sands produced by crushing dense limestones tends to be angular and cubical. This is satisfactory from the viewpoint of the properties of the hardened mortar, but tends to produce a somewhat harsher and less workable fresh mortar than many naturally occurring silica sands, which generally have a more rounded shape. 

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. 

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