DH (chem prof) was telling me it's nigh on impossible to properly assess the structural integrity of RAAC. With regular reinforced concrete there are clear visible signs before it fails. As it corrodes the steel rods rust and swell, causing the concrete to bend and crack, and you can calculate from that how corroded your reinforcements are and if/when it will fail. With RAAC that initial corrosion swelling can be absorbed by the aeriation, with no visual signs that it's failing. And if cracks do appear, they can't be used to accurately measure the internal corrosion. It's pretty much guess work.
As demonstrated by the fact the one that failed over the summer had been cleared as safe.