I suggest you go and re-read the announcement, ill break it down...

I suggest you go and re-read the announcement, ill break it down for you.
The ready mix supplier has an existing mix design where they have replaced some of the opc with slag.
The existing mix design was cheap but had problems with strength therefore was only sold when a weak or standard mix was needed.
They've done extensive testing with edencrete pz and worked out a way to add edencrete pz, more slag and reduce the opc content even further.
This new mix has resulted in a higher strength grade than the original mix design and made it cheaper.

Assumptions
This new mix design will replace the old mix design for standard strength concrete (think 20Mpa)
This new mix design may replace a higher grade concrete (think 25Mpa)

These concrete grades are generally the most used in my opinion.
Thoughts?