Can concrete sand be used for mortar?
No. The maximum particle size for concrete sand is 3/16 to 1/4 inch. This is too big for most mortar joints. Also, the needed fines have been washed out of concrete sand. This makes concrete sand both harsher and coarser than sand specified in ASTM C 144 "Standard Specification for Aggregate for Masonry Mortar." The Brick Industry Association in Technical Note 8A recommends some modifications to the ASTM C 144 gradation limits. Both of these gradations are significantly finer than concrete sand.