Reactivity of Ultrafine Powders Produced from Siliceous Rocks


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Title: Reactivity of Ultrafine Powders Produced from Siliceous Rocks

Author(s): K. M. Alexander

Publication: Journal Proceedings

Volume: 57

Issue: 11

Appears on pages(s): 557-570

Keywords: none

Date: 11/1/1960

Siliceous materials such as quartz and basic or devitrified volcanic rocks, which are not likely sources of active pozzolan, become high1 reactive when ground to ultra-fine powders.If grindingi is sufficiently prolonged an upper limit of activity is attained, beyond which continued increase in surface area does not produce any further general increase in pozzolanic reactivity. With widely different types of siliceous material the upperlimit of pozzolanic reactivity attained at very high surface areas tends to be the same in all cases, regardless of whether the mineral powders would be classed as pozzolanic, weakly pozzolanic, or nonpozzolanic when ground to the usual fineness specified for pozzolans. These observations can be explained by the prssence of a disturbed layer of highly reactive material which is formed on the surface of siliceous mineral particles as a result of prolonged grinding.