Increasing available area of a solid will increase effective concentration?
The concentration of solid in itself is always the same, like m3wolf said in the comments (unless the solid is not pure, which is not relevant anyway, because grinding wouldn't change that either). So no, you can't change the effective concentration this way.

If anything, you will have higher surface area and hence higher overall rate of reaction (or dissolution, if the reaction happens in the solution and not on the surface, and thus has to be preceded by dissolution). In this manner, you will get the same yield, but in less time.

Secondary effects can eventually change your yield in an unpredictable way, as likely down as up.