Suitable plaster for copper pipes?

[Steve]

Hi

The hot water pipes from my back boiler pass through a wall into a bedroom. There's a big gap around the pipes and a CORGI chap has told me it's unsafe as gases could potentially get into the bedroom.

I'd like to fill in the hole with plaster but I'm worried that some types may contain substances which could corrode the copper (as with cement). I don't want to sleeve the pipes as at least one gets very hot and a (plastic) sleeve might therefore deteriorate over time.

Can anyone tell me a 'safe' plaster to use (or ones to avoid)?

Many thanks,

Steve

[daddyfreddy]

I don't believe plaster causes any reaction with copper.

[The Natural Philosopher]

expanding foam, and use decorators caulk to get a paintable finish.

[Nigel Molesworth]

It will crack out again. Use expanding foam.

[Steve]