M Sand is manufactured sand made from a rock which is used for producing the aggregates at crusher plants.
To the best of my knowledge, it is produced by crushing 10mm aggregates and removing the dust from it via dust collectors or by washing.
If that rock aggregates can be used in a concrete, M sand can also be used in a concrete.
If you had a doubt that, M sand contains chloride, you can test it in your nearest laboratory as its a rock and properties of rock are not constant, they do vary belt to belt, place to place.