Seems logical--I might try something similar when I cold-steep my dark grains (or cap a mash) in order to keep the pH at ideal levels.
Yes...seems logical, but without experimental testing it's only just a hypothesis.
The brewing spreadsheet assumes that only 50% of the chalk is effective. Without data, what level of effectiveness should you presume? Baking soda and pickling lime are clearly superior because they readily dissolve.
I tried this prior to hearing about the better effectiveness of baking soda or pickling lime. I'd hate to guess at what effectiveness it might have, as I'm certian I'd be way off.
Plus, I've long felt that chalk has a flavor/mouthfeel impact that works well with some beer styles, dry stout in particular. So I've often added some, but normally only a third to a half of what calculations suggested.
But, the only sure way to find out if there's truth to that idea is a blind triangle taste test...who knows, I may be wasting my time by adding it.