This appears to be a rare proper use of machine-learning tech.

No, they did not ask ChatGPT to whip them up a concrete mix. They (in co-operation with engineers) trained a mathematical model specifically for the task of predicting the performance of concrete mixes, in order to narrow down the number of mixes to do (time-intensive) real-world testing on. With a focus on also predicting the carbon-emission impact of the mixes.

This is the kind of technology we need more of. Not LLM slop.