Is joint sand suitable against weeds?

For permeable paving, one usually uses 1-3mm grit; compared to that, this will definitely infiltrate much worse.

Yes, we currently also have that in the joints since we have sealed all surfaces with cobblestone paving. The only thing we’ve noticed so far is that this 1-3mm grit is quickly washed out of the joints by heavy rain. We haven’t really had any problems with weeds themselves yet. Occasionally a small one appears, but it just pulls out easily :) My question was generally about other joint materials. Specifically regarding their infiltration performance.