Concrete future - Concrete Mix Design, Quality Control and Specification - page 289

13.2.5 Water/cement and binder ratios
Globally there is still great confusion on what cement is. Are we talking about
Portland cement/OPC or the 27 binders listed in the prescriptive EN 197?
So how can we prescribe w/c ratios when the word cement itself is not
clear? In Europe, when fly ash mixed with CEM I up to 35% by the cement
producer, it is considered 100% cement and when mixed by the concrete
producer it only counts for 40% as a binder. Is this what we need for our
low-carbon-era concrete?
Looking at only the two mixes that both used 165 liters of water plus
good PCE admixtures, would result in the following:

WCR (EN197) WBR NL WBR ES+DE+ Water/powder ratio

SCC prec.
C56/65

0.92 0.45 0.92 0.29

RMC C20/25 2.43 0.78 2.43 0.48

The water/powder ratio, not the w/c ratio or w/cm ratio explains the high
strength.

13.2.6 Plan of action
Regulations
What kind of cars would we have if the steel industry had designed them?
Do you think we would be able to build the Pantheon in Rome under pres-
ent EN 197 and EN 206 national versions? Present regulations are restrict-
ing the use of low carbon binders by the concrete producer and discourage
young people to work in this profession. On the other hand, we need cred-
ibility in the eyes of the customer so a verification methodology that allows
a relative fast uptake of innovations seems to be the solution.
Although w/c ratio (or w/cm ratio) has done a job avoiding disasters in
an uneducated setting, it would make sense to introduce the water/pow-
der ratio as a guideline for concrete mix design only, where the powder
component is all materials less than 125 microns. These examples high-
light the fact that performance specification of properties must be allowed
to take precedence over prescriptive requirements, which stifle innovation
and the use of more environmentally friendly mixtures. Fortunately, more
engineers and contractors are abandoning 28-day strength as mandatory in
favor of environmental friendlier pozzolans such as fly ash.
As a first step, a producer should be free to use any SCM specified in
the EN 197 to produce an “equal rights concrete” whether blended by the
cement company or added separately at the batch plant. If the concrete