Reinforced-Autoclaved-Aerated-Concrete (RAAC) is very much in the news in the UK. More than a hundred schools have been forced to close because of the risk of classrooms collapsing. I’m a retired civil engineer and have designed and built numerous concrete structures. Even I had to look RAAC up. I could tell you what it is, but I’ll let Artificial Intelligence do that. Here’s what ChatGBT has to say.
RAAC concrete is a lightweight, precast, foam-based material that is made by mixing cement, sand, lime, water, and an expanding agent. The mixture is then poured into moulds and subjected to high-pressure steam curing, resulting in a cellular structure with numerous air pockets. These air pockets make RAAC concrete significantly lighter than traditional concrete, while still maintaining its strength and durability.
One of the most notable benefits of RAAC concrete is its excellent thermal insulation properties. The air pockets within the material act as insulating agents, reducing heat transfer and making buildings more energy-efficient. This characteristic not only helps to lower heating and cooling costs but also provides a comfortable environment for occupants. Additionally, the high thermal mass of RAAC concrete allows for better temperature regulation, reducing the need for mechanical heating and cooling systems.
Another advantage of RAAC concrete is its remarkable fire resistance. Due to its cellular structure, RAAC concrete has a high fire rating and is able to withstand extreme temperatures for a longer duration compared to traditional concrete. This makes it an ideal choice for fire-resistant walls and structures, enhancing the safety of buildings and potentially reducing fire-related casualties.
Me again! RAAC has some benefits, notably it’s cheaper. But it’s not as durable. RAAC’s cellular structure can allow water to get in and the reinforcement to rust. Sadly government procurement decisions are often made on cost rather than longevity. Why should a minster worry about what happens thirty years later? That’ll be another minister’s problem.
You may note that AI didn’t tell me anything about the current problems with RAAC affecting schools. It does a remarkable job of writing like a human, but fact checking leaves a lot to be desired.