Function over form

Many ready mix suppliers in Dubai are also using superplasticisers to help lengthen the lifespan of concrete.

There are additives that increase the plasticity or fluidity of the material to which they are added.

Superplasticisers for cement soften the mix before it hardens, increasing its workability or reducing water.

In ancient times, the Romans used blood as a superplasticiser for their cement mixes, but nowadays cutting edge chemical mixes are used.

They are commonly manufactured from lignosulfonates, a by-product of the paper industry.

And more recently, they have been made from sulfonated naphthalene or polycarboxylate.

When mixing these, the amount of superplasticiser used in the mix is critical.

Usually, it is about one to two per cent. But if too much is used it could have a retarding effect, meaning the cement will take longer to harden.

During the placement of fresh concrete, Sharma insists it is vital to keep the temperature as low as possible - a difficult task in the region.

He says placement temperature should be no higher than 32C.

"This is achieved by using ice in the form of flakes together with the use of chilled water at the readymix batching plants," he says.

But even before any concrete can be poured, there is the challenge of transporting the material from plant to site.

With summer temperatures sometimes exceeding 50C, if concrete trucks are held up in traffic this will affect the workability of concrete, which is measured in slump temps.

In the Gulf winter, when the temperature averages around 25C, a batch of concrete may be sent from the plant with a 180mm slump.

By the time it has reached the site, after an hour for example, the slump will be around 150mm.

But an hour on the road during the summer could lead to the slump falling from 180mm to 120mm.

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