I have some of this stuff:
https://www.wickes.co.uk/Sika-Bond-SBR%2B-Waterproof-Bonding-Agent-and-Mortar-Admixture---5L/p/133789
Some time in the next few weeks I intend to replace the badly rusting and fragmenting metal frames that my septic tank covers sit on, so once I've chipped away all...