Improve Workability Without Losing Strength? NZ
Improve Workability Without Losing Strength?

Improve Workability Without Losing Strength?

What's the secret?

Words by MARKHAM

The flow, or workability, or ‘rheology’ of the concrete mix, is an important part of the smooth production process.

Too stiff?

A stronger mix may be stiffer, but it will be more difficult to handle. A stiffer mix can be challenging to place, particularly in irregular or confined areas, and the working time frame is reduced.

Cementitious or crystalline additives may contribute to stiffness, by taking up free moisture before placement.

Too fluid?

Obviously, water is an integral part of mixing, placing and curing concrete, and the proportion of water available will affect the flow.

You may be tempted to add water to improve flow. This ‘water of convenience’ will contribute to increased porosity as it bleeds and evaporates, resulting in weaker concrete.

How to strike a balance?

We need to have the maximum possible moisture available for the flow of the concrete – without adding excess. Yes, this is achievable.
It’s important that the moisture isn’t ‘sucked up’ prematurely by dry or crystalline admixtures – these will contribute to stiffness and awkward placement.

The answer is found in hydrogel technology. By introducing catalytic silica with the mix water, a hydrogel formation is commenced, which is still in flux at the time of pour. The rheology of the mix is greatly improved, making placement easier.

Once the concrete is placed, the hydrogel formed in the concrete has even more benefits:
1. Enhanced hydration – for improved curing, reduced shrinkage cracking, and lower heat of hydration.
2. Sealing the concrete porosity – effectively waterproofing the concrete from the inside out.
3. Self-healing: the hydrogel provides ‘stimulated autogenous healing’, boosting the concrete’s own strength and chemistry.

A side note on slump testing

‘Slump’ is the expression for the rigidity of the uncured concrete. A slump test involves a conical mould filled with uncured concrete, which is then released onto a flat surface. The distance the mix sags indicates its slump. Stiff concrete has lower slump; fluid concrete has a higher slump.


Using concrete hydrogel admixtures is a win for the placement team, improving the workability of the mix.

It is a win for the construction and design teams, providing waterproofing and reduced shrinkage cracking.

It is a win for the owners and users of the structure as the long-term durability is enhanced, reducing later maintenance issues.

Why not try hydrogel admixture in your next project?
Prove the benefits for your own team, and for your customer!
Reach out to the friendly Markham team for more information!

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