11 February 2016

Concrete admixtures for industrial concrete floors

What are concrete admixtures?

Concrete admixtures are chemicals added to a concrete mix before it is poured into place. Admixtures change how the concrete will behave during the pour and the curing process, or give the concrete certain properties (eg, waterproofing).

What different concrete admixtures are available?

Admixtures are chosen based on the job they need to do, and typically this is one or more of the following:

Reducing the water needed in the concrete mix – “water reducing admixtures” or “superplasticizers” / “plasticizers”
Reducing the curing time of the concrete once it is in situ – “accelerating admixtures”
Making the concrete resistant to something – eg, a waterproofing admixture.

Water reducing admixtures / superplasticizers / plasticizers

Reducing the amount of water in a concrete mix has several advantages, the main one being that higher concrete strength can be achieved if less water is used relative to the amount of cement in the mix.

But less water in the mix also means the concrete can become difficult to work with. These admixtures allow the amount of water to be reduced, and at the same time provide the extra lubrication the mix needs for the concrete to stay workable.

Less water also means that using these concrete admixtures can help to speed up the curing time, and build early strength. So it’s helpful to consider using one of these admixtures if you are working on a project where there is time pressure.

The difference between a plasticizer and a superplasticizer relates to the amount of water which can be omitted from the concrete mix. A superplasticizer allows more water to be omitted.

Our products: Roc MA Fluid, Roc Fluid, Roc PO Fluid

Accelerating admixtures

Concrete pours during the winter, and in some countries, can be marred by weather which is too cold to allow the concrete to cure. In some instances this can stop work altogether – not a profitable situation for a specialist flooring contractor.
An accelerating admixture is formulated to speed up the setting time of the concrete and build early strength, so concrete pours can often still happen in cold conditions.

Our product: Roc NC Accelerator

Waterproofing admixtures, or oil resistant admixtures

As the name suggests, waterproofing admixtures add waterproofing qualities to the concrete mix. This means that water leaks and spillages are less likely to permeate into the concrete, or pass through it – important where there is a risk of water ingress which could infiltrate neighbouring areas, or affect the longevity and structure of the concrete itself.

Admixtures are also available which resist other risks in a similar way – for example, oil resistant admixtures, fuel resistant admixtures and mineral resistant admixtures. These admixtures will be suitable for specialist environments such as service stations, or ports.

Our product: Roc HP, Roc PO Fluid

Can different concrete admixtures be used together?

In some cases, yes, although only one superplasticizer can be used in a concrete mix.

Using an admixture affects the design of the concrete mix, and has significant impact on the early performance of the slab. Also, because the water content in the slab is affected, there may be implications if you intend to use a dry-shake surface hardener which depends on bleed water. So it is important to take all factors into account, and consider the full impact when choosing a concrete admixture.