I'd just shove a load of mortor in the gaps, paint over it with masonary paint and forget about it.
@mustardbeak started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
I'd just shove a load of mortor in the gaps, paint over it with masonary paint and forget about it.