oa Civil Engineering = Siviele Ingenieurswese - Some aspects of the effect of micaceous sand on concrete
Mica is generally known to be a deleterious substance in aggregates used for the manufacture of concrete. In regions where micaceous aggregates are the only materials available they have nevertheless been used extensively for this purpose. There is thus a discrepancy between the engineer's distrust of a material regarded as deleterious and an impressive record of successful use of this material. An investigation was carried out by the National Building Research Institute to determine the effect of mica contained in the fine aggregate upon the workability, compressive strength and drying shrinkage of concrete made with such an aggregate. It was found that the effects depend much more on the nature of the micaceous particles than on their quantity. Mica in the form of biotite caused only small effects, whereas the presence of muscovite profoundly changed the concrete-making properties of a fine aggregate.
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