Rawl plug and screw a 75mm wall without it splitting

[perky416]

Evening all.
I have to drill and rawl plug an old 75mm block wall to fit a door lining. If looks like dense concrete block however when cut the dust is pretty much black so im not too sure what it actually is.
The last time i tried to rawl plug 75mm block it split when driving the screw in (tbf they were aerated blocks), i cant get replacement blocks so would rather not have them split and bodge a repair.

There are no screw holes in the blocks from the previous lining, they appear to have what i can only describe as a "tongue and groove" style edging where they fit together so im assuming the "groove" was filled mortar and the door lining was screwed into this. I could dry pack the "groove" and do the same however im not confident it will stand the test of time.

Does anybody have any recommendations how to rawplug the block without splitting it?

I was thinking about maybe using 8mm or 10mm rawl plugs with a 5mm dia screw to limit the expansion.

Many thanks.

 

[Harry Bloomfield]

It sounds like it is 'cinder block' or breeze block. Drill something like 12mm holes where you need the fixings, then completely fill the holes with car body filler. You can then either drill a smaller pilot hole down the centre of that once it has gone off, so your screw is a reasonably tight fit in it without a plug - or you can grease a screw and push it into the still soft body filler to around the correct depth, wait until it is more or less set, then take the screw out.

 

[perky416]

Fantastic idea thanks!
I actually have a resin at home designed for that very thing.