What are the implications of specifying low carbon concrete?

@Ross One challenge with I’ve seen in the Canadian market is that suppliers do not share the ingredients of a mix design as the data is proprietary in Canada. This makes understanding the true carbon impact of a mix design difficult as for instance a 500 lbs cement + 100 lbs fly ash mix and a 550 lbs cement + 110 lbs fly ash mix are both 20% SCM mix designs but with different carbon footprints.