Concrete spalling doesn't require fire at all. Ask any Civil Engineer (I'm not actually Chartered). I trained as a Civ Eng in Plymouth (Devon, UK) and obvious

Concrete spalling doesn't require fire at all. Ask any Civil Engineer (I'm not actually Chartered). I trained as a Civ Eng in Plymouth (Devon, UK) and obviously ended up in IT (22 years as MD of an IT firm). It's quite wet, windy and the air is pretty salty in Plimuff. All of those factors scream: Bad for conc. if you don't allow for them. Also, steel is well known to get quite unhappy in the presence of salty water, if it isn't cared for properly. Concrete cancer is another exciting opportunity to contend with in the face of ... conditions. Concrete is a marvellous material, it really is but it is a sodding complicated matrix of variously graded (sizes) stones (aggregate) and particular sands bound up in the cement plus some admixtures (stuff added for various reasons). The cement alone is properly complicated - clinker and that. When you mix the stuff up and pour it, it's a chemical reaction that happens and not simply drying. That's why it works underwater - what you are worrying about underwater is avoiding the finer materials being carried off before the stuff sets. In the air, you worry more about temperature effects on setting and wind causing the surface to dry too fast. The reaction is caused by water, so if the surface dries out, the reaction doesn't happen and you get ... spalling later in life. I hope that the studies quoted in court relating to conc spalling, describe the precise conditions that the stuff was poured in. Care will be taken over the effects of admixtures and the temperatures, weather and other conditions that affect setting and curing of conc. Was gap grading of the agg. a factor perhaps? What is the agg. composition anyway, let alone its size distribution? I could go on a lot, lot more and I'm not even close to being an expert. I can pour a decent 3-2-1 mix and expect it to do the job at home. My little DIY conc related projects tend to work rather well - my garden is quite challenging topographically. I hope I'm getting across that concrete is rather complicated. It's not a simple material just as balsa and elm are both "wood" but have very, very different properties.