On my slab porch out front, I placed some randomly positioned/broken
up slate tiles in mortar and once it dries will need to fill the gaps.
normally you'd use grout, but the gaps are big - some 3 inches... what
can I use to fill them? has to be something that hardens that I can
seal - if I just throw sand or pebbles down, rain will leak through
and dissolve the mortar. do they make grout specifically for large
gaps? should I use cement or something?