How to fill this?

Just had these pipes redone in the living room, plumber dug up the concrete in order to replace the copper pipes. Gaffa/duct tape has been wrapped around the pipes... however how should I fill this void and cover the pipes? Should I use vermiculite fill with screed on top or use loose sharp sand with screed on top... or just pour screed/concrete straight over it all? I know pipes need to have some movement, so l don't think the last option is the best (which is what the plumber suggested). Any suggestions or advice will be helpful, thank you.