Concrete future - Concrete Mix Design, Quality Control and Specification - page 286

higher quality. It can then provide a higher financial return for the supplier.
More important, the people involved in the process at all levels have also
to be better trained.
Since strength and durability do depend on reactivity, particle packing
and adhesion especially of the fine particles, one has to learn to work with
many different ingredients that are available at a reasonable cost and travel
distance. Depending on the location, different supplementary cementing
materials (SCMs) are available. Particle size engineering, especially of all
the fines <125 µm with the objective to reduce the water demand of the
mix, is becoming a key discipline.
SCMs play a key role in sustainability since most of them have much
lower embodied energy and emissions. They also play different roles in
reactivity, packing, and adhesion resulting in different strength develop-
ment and durability. However, obtaining these attractive SCMs is often
a local problem since they derive often as secondary products from other
industries. New ones such as APReM (activated paper recycled minerals),
rice husk ash (RHA), and SUCABM (sugar cane bagasse minerals) should
be further industrially produced with proper quality control.
Also more choice of different fractions and better shapes of the aggre-
gates will reduce the volume of the more expensive higher environmental
impact paste.
Using the water/powder ratio as a guideline for mix design is replacing
the water/cement ratio (w/c). The interpretation on what cement means is
different from country to country and depends on different regulations.
This has resulted in different calculated w/c or w/cm ratios depending on
the treatment of different SCMs in different countries. Obviously such
bureaucracy has little to do with technology.
13.2.1 Binders
Besides SCMs, both those recognised as ingredients of standardised
composite blended cements and other more exotic ones, there are now
many different new non-Portland clinker binders under development. Of
all these, at the writing of the topic, the family of alkali activated binders
that include geopolymers seem to have gained the most credibility. The
environmental impact of these binders versus clinker will depend on the
sources of materials. Testing of materials that have a different rheology is
being addressed by the RILEM.
13.2.2 From prescription to performance
Not how but what concrete has been produced is of importance. One could
question what kind of automobiles we would have if the steel industry
would have designed them. Is the steel content relevant to the performance