October 22, 2008

Letter to the Editor

Standards, regulations discourage use of supplementary cementitious materials

To the editor,
Although initially lagging behind in the use of fly-ash when compared with Europe, Canada is now more advanced in allowing up to 50 per cent fly ash, but standards and regulations are still discouraging the proper use of supplementary cementitious materials (SCM) on an equal footing in general.

In Europe, the cement industry can add up to 35 per cent fly ash with Portland cement, but the concrete producer can calculate such an amount only for 40 per cent as a binder!

Such standards neither stimulate the use of environmental friendly materials, nor does it teach the concrete producer to make more flexibly tailor-made concrete.

If one looks at strength development in a more custom oriented way, such as for infrastructure longer then 28 days, one can increase the fly ash content even further.

Also natural puzzolans from volcanic sources should be investigated.

In certain parts of the world there is an abundance of this material, used by the Romans.

Ground granulated blast furnace slag (GGBS) is hard to come by since it needs integrated steel mills, not present at the North American West Coast, although shipping it in from Asia would make sense. However, there is ample good cristaline limestone available which can be ground to powder, Calcium Carbonate Fines (CCF), often finer then Portland cement.

The cement industry in Europe can use up to 35 per cent to mix with Portland cement, however, the use by the concrete producer of this interesting SCM is not encouraged by restrictive standards.

We have to move now from volume oriented unsustainable prescription concrete towards quality sustainable performance concrete.

It is not how we make things, but what we have made. Quality is another way to make money then pushing volumes common in the construction industry. If we would have asked the steel industry to design a safe car, we would all be driving in tanks.

A modern ready mix concrete plant (in the Netherlands) has four silos, a high grade very-reactive Portland cement, fly-ash, GGBS and CCF.

It also has a good selection of liquid admixtures and in the future a special dosage of low volume powder admixtures. Just look at the great evolution we made with moving the refractory concrete towards high tech.

Boudewijn Piscaer
Univerde Agencies SARL
Amsterdam

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