An expert has appeared on Channel 4 News explaining the important differences between Raac and standard concrete.Source: Channel 4 News
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00:00 schools even in the last couple of days? Even today, yes. But you've not found any that are
00:04 down? Luckily I haven't found anything so far in London. Now you've brought some of this rack
00:08 concrete in with you, could you explain what's wrong with it? Well the variation from what we
00:13 would call conventional reinforced concrete, rack concrete as you can see has no aggregate so it's
00:18 a lot weaker and the the main concern is we have a hidden defect here. Here you can see quite
00:25 clearly where a reinforcing bar was adjacent to this area. This can corrode with no outward signs,
00:31 you'd normally get a crack in conventional concrete would give us an idea what's going on.
00:35 Here you don't get anything. So you'd never tell? So you never tell. What you have to do,
00:40 you'd have to undertake non-destructive testing which we could determine this. But that's the
00:47 second stage. The first stage is what I believe has happened in the schools so far is they've
00:51 identified right concrete.