hi,fellas,i'm repairing a concrete ceiling this week, where chunks have come out & the resi bars are showing. i got all the rust of the bars & they have had 2 coats of hammerite redoxide. will bonding adhere to it? also i've scrapped off the original tight coat of bonding & skim which had blown. will i need to pva the smooth parts of the concrete ceiling & also the parts where chunks of concrete have come out? cheers