Is it possible to make concrete with less cement without losing quality or strength?

I absolutely agree with Mr. Jetley.

ECMAPLAST100

Water Reducing & Plasticising Admixture Increases Slump/Workability at Low dosage, Improves Strength, Makes Cement savings possible.

There is the possibility that concrete sampling is not the same  for each samples so the compressive  test results are not uniform.

yes, there are additives that improve the strength , by making a perfect surrounding so all the cement hydrates, so it is possible to use less cement. These additives also can make you use sea sand and even seawater.