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Effect of mica particles on the strength (especially for plaster work)

In india -Delhi the sand available is Fine Jamuna. In the Sand mica particles are found Pl. tell,what will be the affect of mica particles on the strength especially for plaster work. Can we measure the quanity of the mica particles? (Question asked by Mr Sanjay Kumar Deedwania)

Mica being flaky & laminated affects strength & durability of mortar /concrete in the same way as other such particles do. The effect on workability & strength is more for leaner mixes.

In Indian river sands, mica content could be as high as 12%. The problem is further aggravated if the sand is of finer variety (Ganges sand could have fineness modulus as low as 0.6) .

Muscovite variety of mica is more harmful than the mica biotite variety. Jamuna sand is mainly biotite with small percentage of muscovite particles; whereas Ganga sand is mainly muscovite with small percentage of biotite particles;

Indian Standards do not prescribe any test for measuring the quantity of mica. You can, however, measure the mica content by Floatation/Density separation method or the Wind blowing method; former being more accurate.”