Haveth we any commitment to the Paris accord?
To set the record straight, it is portland cement that binds the sand and aggregate in concrete. Concrete is nown to presstitutes as cement
Pozzolan provides an alternative for the Portland process. Use of fly-ash in modern mixtures is an attempt to gain attributes of volcanic ash as applied in Roman cement, which is very resistant to salt water.
https://www.history.com/news/the-secrets-of-ancient-roman-concrete