"・RAAC soaks up water like a sponge and increases the load on the building if it is exposed to rainwater.

・Stress tests showed it becomes 25% weaker when wet.

・And analysis under a microscope showed that cracks can appear around the steel rods running through the RAAC"

"To make matters worse, these problems aren't really apparent until the material breaks."

Experts warn RAAC concrete affects thousands of UK buildings(BBC)
https://www.bbc.com/news/science-environment-66733888